Merge branch 'ae/pack-autothread'

[git] / builtin-apply.c

/*
 * apply.c
 *
 * Copyright (C) Linus Torvalds, 2005
 *
 * This applies patches on top of some (arbitrary) version of the SCM.
 *
 */
#include "cache.h"
#include "cache-tree.h"
#include "quote.h"
#include "blob.h"
#include "delta.h"
#include "builtin.h"

/*
 *  --check turns on checking that the working tree matches the
 *    files that are being modified, but doesn't apply the patch
 *  --stat does just a diffstat, and doesn't actually apply
 *  --numstat does numeric diffstat, and doesn't actually apply
 *  --index-info shows the old and new index info for paths if available.
 *  --index updates the cache as well.
 *  --cached updates only the cache without ever touching the working tree.
 */
static const char *prefix;
static int prefix_length = -1;
static int newfd = -1;

static int unidiff_zero;
static int p_value = 1;
static int p_value_known;
static int check_index;
static int update_index;
static int cached;
static int diffstat;
static int numstat;
static int summary;
static int check;
static int apply = 1;
static int apply_in_reverse;
static int apply_with_reject;
static int apply_verbosely;
static int no_add;
static const char *fake_ancestor;
static int line_termination = '\n';
static unsigned long p_context = ULONG_MAX;
static const char apply_usage[] =
"git-apply [--stat] [--numstat] [--summary] [--check] [--index] [--cached] [--apply] [--no-add] [--index-info] [--allow-binary-replacement] [--reverse] [--reject] [--verbose] [-z] [-pNUM] [-CNUM] [--whitespace=<nowarn|warn|fix|error|error-all>] <patch>...";

static enum ws_error_action {
        nowarn_ws_error,
        warn_on_ws_error,
        die_on_ws_error,
        correct_ws_error,
} ws_error_action = warn_on_ws_error;
static int whitespace_error;
static int squelch_whitespace_errors = 5;
static int applied_after_fixing_ws;
static const char *patch_input_file;

static void parse_whitespace_option(const char *option)
{
        if (!option) {
                ws_error_action = warn_on_ws_error;
                return;
        }
        if (!strcmp(option, "warn")) {
                ws_error_action = warn_on_ws_error;
                return;
        }
        if (!strcmp(option, "nowarn")) {
                ws_error_action = nowarn_ws_error;
                return;
        }
        if (!strcmp(option, "error")) {
                ws_error_action = die_on_ws_error;
                return;
        }
        if (!strcmp(option, "error-all")) {
                ws_error_action = die_on_ws_error;
                squelch_whitespace_errors = 0;
                return;
        }
        if (!strcmp(option, "strip") || !strcmp(option, "fix")) {
                ws_error_action = correct_ws_error;
                return;
        }
        die("unrecognized whitespace option '%s'", option);
}

static void set_default_whitespace_mode(const char *whitespace_option)
{
        if (!whitespace_option && !apply_default_whitespace)
                ws_error_action = (apply ? warn_on_ws_error : nowarn_ws_error);
}

/*
 * For "diff-stat" like behaviour, we keep track of the biggest change
 * we've seen, and the longest filename. That allows us to do simple
 * scaling.
 */
static int max_change, max_len;

/*
 * Various "current state", notably line numbers and what
 * file (and how) we're patching right now.. The "is_xxxx"
 * things are flags, where -1 means "don't know yet".
 */
static int linenr = 1;

/*
 * This represents one "hunk" from a patch, starting with
 * "@@ -oldpos,oldlines +newpos,newlines @@" marker.  The
 * patch text is pointed at by patch, and its byte length
 * is stored in size.  leading and trailing are the number
 * of context lines.
 */
struct fragment {
        unsigned long leading, trailing;
        unsigned long oldpos, oldlines;
        unsigned long newpos, newlines;
        const char *patch;
        int size;
        int rejected;
        struct fragment *next;
};

/*
 * When dealing with a binary patch, we reuse "leading" field
 * to store the type of the binary hunk, either deflated "delta"
 * or deflated "literal".
 */
#define binary_patch_method leading
#define BINARY_DELTA_DEFLATED   1
#define BINARY_LITERAL_DEFLATED 2

/*
 * This represents a "patch" to a file, both metainfo changes
 * such as creation/deletion, filemode and content changes represented
 * as a series of fragments.
 */
struct patch {
        char *new_name, *old_name, *def_name;
        unsigned int old_mode, new_mode;
        int is_new, is_delete;  /* -1 = unknown, 0 = false, 1 = true */
        int rejected;
        unsigned ws_rule;
        unsigned long deflate_origlen;
        int lines_added, lines_deleted;
        int score;
        unsigned int is_toplevel_relative:1;
        unsigned int inaccurate_eof:1;
        unsigned int is_binary:1;
        unsigned int is_copy:1;
        unsigned int is_rename:1;
        struct fragment *fragments;
        char *result;
        size_t resultsize;
        char old_sha1_prefix[41];
        char new_sha1_prefix[41];
        struct patch *next;
};

/*
 * A line in a file, len-bytes long (includes the terminating LF,
 * except for an incomplete line at the end if the file ends with
 * one), and its contents hashes to 'hash'.
 */
struct line {
        size_t len;
        unsigned hash : 24;
        unsigned flag : 8;
#define LINE_COMMON     1
};

/*
 * This represents a "file", which is an array of "lines".
 */
struct image {
        char *buf;
        size_t len;
        size_t nr;
        size_t alloc;
        struct line *line_allocated;
        struct line *line;
};

static uint32_t hash_line(const char *cp, size_t len)
{
        size_t i;
        uint32_t h;
        for (i = 0, h = 0; i < len; i++) {
                if (!isspace(cp[i])) {
                        h = h * 3 + (cp[i] & 0xff);
                }
        }
        return h;
}

static void add_line_info(struct image *img, const char *bol, size_t len, unsigned flag)
{
        ALLOC_GROW(img->line_allocated, img->nr + 1, img->alloc);
        img->line_allocated[img->nr].len = len;
        img->line_allocated[img->nr].hash = hash_line(bol, len);
        img->line_allocated[img->nr].flag = flag;
        img->nr++;
}

static void prepare_image(struct image *image, char *buf, size_t len,
                          int prepare_linetable)
{
        const char *cp, *ep;

        memset(image, 0, sizeof(*image));
        image->buf = buf;
        image->len = len;

        if (!prepare_linetable)
                return;

        ep = image->buf + image->len;
        cp = image->buf;
        while (cp < ep) {
                const char *next;
                for (next = cp; next < ep && *next != '\n'; next++)
                        ;
                if (next < ep)
                        next++;
                add_line_info(image, cp, next - cp, 0);
                cp = next;
        }
        image->line = image->line_allocated;
}

static void clear_image(struct image *image)
{
        free(image->buf);
        image->buf = NULL;
        image->len = 0;
}

static void say_patch_name(FILE *output, const char *pre,
                           struct patch *patch, const char *post)
{
        fputs(pre, output);
        if (patch->old_name && patch->new_name &&
            strcmp(patch->old_name, patch->new_name)) {
                quote_c_style(patch->old_name, NULL, output, 0);
                fputs(" => ", output);
                quote_c_style(patch->new_name, NULL, output, 0);
        } else {
                const char *n = patch->new_name;
                if (!n)
                        n = patch->old_name;
                quote_c_style(n, NULL, output, 0);
        }
        fputs(post, output);
}

#define CHUNKSIZE (8192)
#define SLOP (16)

static void read_patch_file(struct strbuf *sb, int fd)
{
        if (strbuf_read(sb, fd, 0) < 0)
                die("git-apply: read returned %s", strerror(errno));

        /*
         * Make sure that we have some slop in the buffer
         * so that we can do speculative "memcmp" etc, and
         * see to it that it is NUL-filled.
         */
        strbuf_grow(sb, SLOP);
        memset(sb->buf + sb->len, 0, SLOP);
}

static unsigned long linelen(const char *buffer, unsigned long size)
{
        unsigned long len = 0;
        while (size--) {
                len++;
                if (*buffer++ == '\n')
                        break;
        }
        return len;
}

static int is_dev_null(const char *str)
{
        return !memcmp("/dev/null", str, 9) && isspace(str[9]);
}

#define TERM_SPACE      1
#define TERM_TAB        2

static int name_terminate(const char *name, int namelen, int c, int terminate)
{
        if (c == ' ' && !(terminate & TERM_SPACE))
                return 0;
        if (c == '\t' && !(terminate & TERM_TAB))
                return 0;

        return 1;
}

static char *find_name(const char *line, char *def, int p_value, int terminate)
{
        int len;
        const char *start = line;

        if (*line == '"') {
                struct strbuf name;

                /*
                 * Proposed "new-style" GNU patch/diff format; see
                 * http://marc.theaimsgroup.com/?l=git&m=112927316408690&w=2
                 */
                strbuf_init(&name, 0);
                if (!unquote_c_style(&name, line, NULL)) {
                        char *cp;

                        for (cp = name.buf; p_value; p_value--) {
                                cp = strchr(cp, '/');
                                if (!cp)
                                        break;
                                cp++;
                        }
                        if (cp) {
                                /* name can later be freed, so we need
                                 * to memmove, not just return cp
                                 */
                                strbuf_remove(&name, 0, cp - name.buf);
                                free(def);
                                return strbuf_detach(&name, NULL);
                        }
                }
                strbuf_release(&name);
        }

        for (;;) {
                char c = *line;

                if (isspace(c)) {
                        if (c == '\n')
                                break;
                        if (name_terminate(start, line-start, c, terminate))
                                break;
                }
                line++;
                if (c == '/' && !--p_value)
                        start = line;
        }
        if (!start)
                return def;
        len = line - start;
        if (!len)
                return def;

        /*
         * Generally we prefer the shorter name, especially
         * if the other one is just a variation of that with
         * something else tacked on to the end (ie "file.orig"
         * or "file~").
         */
        if (def) {
                int deflen = strlen(def);
                if (deflen < len && !strncmp(start, def, deflen))
                        return def;
                free(def);
        }

        return xmemdupz(start, len);
}

static int count_slashes(const char *cp)
{
        int cnt = 0;
        char ch;

        while ((ch = *cp++))
                if (ch == '/')
                        cnt++;
        return cnt;
}

/*
 * Given the string after "--- " or "+++ ", guess the appropriate
 * p_value for the given patch.
 */
static int guess_p_value(const char *nameline)
{
        char *name, *cp;
        int val = -1;

        if (is_dev_null(nameline))
                return -1;
        name = find_name(nameline, NULL, 0, TERM_SPACE | TERM_TAB);
        if (!name)
                return -1;
        cp = strchr(name, '/');
        if (!cp)
                val = 0;
        else if (prefix) {
                /*
                 * Does it begin with "a/$our-prefix" and such?  Then this is
                 * very likely to apply to our directory.
                 */
                if (!strncmp(name, prefix, prefix_length))
                        val = count_slashes(prefix);
                else {
                        cp++;
                        if (!strncmp(cp, prefix, prefix_length))
                                val = count_slashes(prefix) + 1;
                }
        }
        free(name);
        return val;
}

/*
 * Get the name etc info from the --/+++ lines of a traditional patch header
 *
 * FIXME! The end-of-filename heuristics are kind of screwy. For existing
 * files, we can happily check the index for a match, but for creating a
 * new file we should try to match whatever "patch" does. I have no idea.
 */
static void parse_traditional_patch(const char *first, const char *second, struct patch *patch)
{
        char *name;

        first += 4;     /* skip "--- " */
        second += 4;    /* skip "+++ " */
        if (!p_value_known) {
                int p, q;
                p = guess_p_value(first);
                q = guess_p_value(second);
                if (p < 0) p = q;
                if (0 <= p && p == q) {
                        p_value = p;
                        p_value_known = 1;
                }
        }
        if (is_dev_null(first)) {
                patch->is_new = 1;
                patch->is_delete = 0;
                name = find_name(second, NULL, p_value, TERM_SPACE | TERM_TAB);
                patch->new_name = name;
        } else if (is_dev_null(second)) {
                patch->is_new = 0;
                patch->is_delete = 1;
                name = find_name(first, NULL, p_value, TERM_SPACE | TERM_TAB);
                patch->old_name = name;
        } else {
                name = find_name(first, NULL, p_value, TERM_SPACE | TERM_TAB);
                name = find_name(second, name, p_value, TERM_SPACE | TERM_TAB);
                patch->old_name = patch->new_name = name;
        }
        if (!name)
                die("unable to find filename in patch at line %d", linenr);
}

static int gitdiff_hdrend(const char *line, struct patch *patch)
{
        return -1;
}

/*
 * We're anal about diff header consistency, to make
 * sure that we don't end up having strange ambiguous
 * patches floating around.
 *
 * As a result, gitdiff_{old|new}name() will check
 * their names against any previous information, just
 * to make sure..
 */
static char *gitdiff_verify_name(const char *line, int isnull, char *orig_name, const char *oldnew)
{
        if (!orig_name && !isnull)
                return find_name(line, NULL, p_value, TERM_TAB);

        if (orig_name) {
                int len;
                const char *name;
                char *another;
                name = orig_name;
                len = strlen(name);
                if (isnull)
                        die("git-apply: bad git-diff - expected /dev/null, got %s on line %d", name, linenr);
                another = find_name(line, NULL, p_value, TERM_TAB);
                if (!another || memcmp(another, name, len))
                        die("git-apply: bad git-diff - inconsistent %s filename on line %d", oldnew, linenr);
                free(another);
                return orig_name;
        }
        else {
                /* expect "/dev/null" */
                if (memcmp("/dev/null", line, 9) || line[9] != '\n')
                        die("git-apply: bad git-diff - expected /dev/null on line %d", linenr);
                return NULL;
        }
}

static int gitdiff_oldname(const char *line, struct patch *patch)
{
        patch->old_name = gitdiff_verify_name(line, patch->is_new, patch->old_name, "old");
        return 0;
}

static int gitdiff_newname(const char *line, struct patch *patch)
{
        patch->new_name = gitdiff_verify_name(line, patch->is_delete, patch->new_name, "new");
        return 0;
}

static int gitdiff_oldmode(const char *line, struct patch *patch)
{
        patch->old_mode = strtoul(line, NULL, 8);
        return 0;
}

static int gitdiff_newmode(const char *line, struct patch *patch)
{
        patch->new_mode = strtoul(line, NULL, 8);
        return 0;
}

static int gitdiff_delete(const char *line, struct patch *patch)
{
        patch->is_delete = 1;
        patch->old_name = patch->def_name;
        return gitdiff_oldmode(line, patch);
}

static int gitdiff_newfile(const char *line, struct patch *patch)
{
        patch->is_new = 1;
        patch->new_name = patch->def_name;
        return gitdiff_newmode(line, patch);
}

static int gitdiff_copysrc(const char *line, struct patch *patch)
{
        patch->is_copy = 1;
        patch->old_name = find_name(line, NULL, 0, 0);
        return 0;
}

static int gitdiff_copydst(const char *line, struct patch *patch)
{
        patch->is_copy = 1;
        patch->new_name = find_name(line, NULL, 0, 0);
        return 0;
}

static int gitdiff_renamesrc(const char *line, struct patch *patch)
{
        patch->is_rename = 1;
        patch->old_name = find_name(line, NULL, 0, 0);
        return 0;
}

static int gitdiff_renamedst(const char *line, struct patch *patch)
{
        patch->is_rename = 1;
        patch->new_name = find_name(line, NULL, 0, 0);
        return 0;
}

static int gitdiff_similarity(const char *line, struct patch *patch)
{
        if ((patch->score = strtoul(line, NULL, 10)) == ULONG_MAX)
                patch->score = 0;
        return 0;
}

static int gitdiff_dissimilarity(const char *line, struct patch *patch)
{
        if ((patch->score = strtoul(line, NULL, 10)) == ULONG_MAX)
                patch->score = 0;
        return 0;
}

static int gitdiff_index(const char *line, struct patch *patch)
{
        /*
         * index line is N hexadecimal, "..", N hexadecimal,
         * and optional space with octal mode.
         */
        const char *ptr, *eol;
        int len;

        ptr = strchr(line, '.');
        if (!ptr || ptr[1] != '.' || 40 < ptr - line)
                return 0;
        len = ptr - line;
        memcpy(patch->old_sha1_prefix, line, len);
        patch->old_sha1_prefix[len] = 0;

        line = ptr + 2;
        ptr = strchr(line, ' ');
        eol = strchr(line, '\n');

        if (!ptr || eol < ptr)
                ptr = eol;
        len = ptr - line;

        if (40 < len)
                return 0;
        memcpy(patch->new_sha1_prefix, line, len);
        patch->new_sha1_prefix[len] = 0;
        if (*ptr == ' ')
                patch->new_mode = patch->old_mode = strtoul(ptr+1, NULL, 8);
        return 0;
}

/*
 * This is normal for a diff that doesn't change anything: we'll fall through
 * into the next diff. Tell the parser to break out.
 */
static int gitdiff_unrecognized(const char *line, struct patch *patch)
{
        return -1;
}

static const char *stop_at_slash(const char *line, int llen)
{
        int i;

        for (i = 0; i < llen; i++) {
                int ch = line[i];
                if (ch == '/')
                        return line + i;
        }
        return NULL;
}

/*
 * This is to extract the same name that appears on "diff --git"
 * line.  We do not find and return anything if it is a rename
 * patch, and it is OK because we will find the name elsewhere.
 * We need to reliably find name only when it is mode-change only,
 * creation or deletion of an empty file.  In any of these cases,
 * both sides are the same name under a/ and b/ respectively.
 */
static char *git_header_name(char *line, int llen)
{
        const char *name;
        const char *second = NULL;
        size_t len;

        line += strlen("diff --git ");
        llen -= strlen("diff --git ");

        if (*line == '"') {
                const char *cp;
                struct strbuf first;
                struct strbuf sp;

                strbuf_init(&first, 0);
                strbuf_init(&sp, 0);

                if (unquote_c_style(&first, line, &second))
                        goto free_and_fail1;

                /* advance to the first slash */
                cp = stop_at_slash(first.buf, first.len);
                /* we do not accept absolute paths */
                if (!cp || cp == first.buf)
                        goto free_and_fail1;
                strbuf_remove(&first, 0, cp + 1 - first.buf);

                /*
                 * second points at one past closing dq of name.
                 * find the second name.
                 */
                while ((second < line + llen) && isspace(*second))
                        second++;

                if (line + llen <= second)
                        goto free_and_fail1;
                if (*second == '"') {
                        if (unquote_c_style(&sp, second, NULL))
                                goto free_and_fail1;
                        cp = stop_at_slash(sp.buf, sp.len);
                        if (!cp || cp == sp.buf)
                                goto free_and_fail1;
                        /* They must match, otherwise ignore */
                        if (strcmp(cp + 1, first.buf))
                                goto free_and_fail1;
                        strbuf_release(&sp);
                        return strbuf_detach(&first, NULL);
                }

                /* unquoted second */
                cp = stop_at_slash(second, line + llen - second);
                if (!cp || cp == second)
                        goto free_and_fail1;
                cp++;
                if (line + llen - cp != first.len + 1 ||
                    memcmp(first.buf, cp, first.len))
                        goto free_and_fail1;
                return strbuf_detach(&first, NULL);

        free_and_fail1:
                strbuf_release(&first);
                strbuf_release(&sp);
                return NULL;
        }

        /* unquoted first name */
        name = stop_at_slash(line, llen);
        if (!name || name == line)
                return NULL;
        name++;

        /*
         * since the first name is unquoted, a dq if exists must be
         * the beginning of the second name.
         */
        for (second = name; second < line + llen; second++) {
                if (*second == '"') {
                        struct strbuf sp;
                        const char *np;

                        strbuf_init(&sp, 0);
                        if (unquote_c_style(&sp, second, NULL))
                                goto free_and_fail2;

                        np = stop_at_slash(sp.buf, sp.len);
                        if (!np || np == sp.buf)
                                goto free_and_fail2;
                        np++;

                        len = sp.buf + sp.len - np;
                        if (len < second - name &&
                            !strncmp(np, name, len) &&
                            isspace(name[len])) {
                                /* Good */
                                strbuf_remove(&sp, 0, np - sp.buf);
                                return strbuf_detach(&sp, NULL);
                        }

                free_and_fail2:
                        strbuf_release(&sp);
                        return NULL;
                }
        }

        /*
         * Accept a name only if it shows up twice, exactly the same
         * form.
         */
        for (len = 0 ; ; len++) {
                switch (name[len]) {
                default:
                        continue;
                case '\n':
                        return NULL;
                case '\t': case ' ':
                        second = name+len;
                        for (;;) {
                                char c = *second++;
                                if (c == '\n')
                                        return NULL;
                                if (c == '/')
                                        break;
                        }
                        if (second[len] == '\n' && !memcmp(name, second, len)) {
                                return xmemdupz(name, len);
                        }
                }
        }
}

/* Verify that we recognize the lines following a git header */
static int parse_git_header(char *line, int len, unsigned int size, struct patch *patch)
{
        unsigned long offset;

        /* A git diff has explicit new/delete information, so we don't guess */
        patch->is_new = 0;
        patch->is_delete = 0;

        /*
         * Some things may not have the old name in the
         * rest of the headers anywhere (pure mode changes,
         * or removing or adding empty files), so we get
         * the default name from the header.
         */
        patch->def_name = git_header_name(line, len);

        line += len;
        size -= len;
        linenr++;
        for (offset = len ; size > 0 ; offset += len, size -= len, line += len, linenr++) {
                static const struct opentry {
                        const char *str;
                        int (*fn)(const char *, struct patch *);
                } optable[] = {
                        { "@@ -", gitdiff_hdrend },
                        { "--- ", gitdiff_oldname },
                        { "+++ ", gitdiff_newname },
                        { "old mode ", gitdiff_oldmode },
                        { "new mode ", gitdiff_newmode },
                        { "deleted file mode ", gitdiff_delete },
                        { "new file mode ", gitdiff_newfile },
                        { "copy from ", gitdiff_copysrc },
                        { "copy to ", gitdiff_copydst },
                        { "rename old ", gitdiff_renamesrc },
                        { "rename new ", gitdiff_renamedst },
                        { "rename from ", gitdiff_renamesrc },
                        { "rename to ", gitdiff_renamedst },
                        { "similarity index ", gitdiff_similarity },
                        { "dissimilarity index ", gitdiff_dissimilarity },
                        { "index ", gitdiff_index },
                        { "", gitdiff_unrecognized },
                };
                int i;

                len = linelen(line, size);
                if (!len || line[len-1] != '\n')
                        break;
                for (i = 0; i < ARRAY_SIZE(optable); i++) {
                        const struct opentry *p = optable + i;
                        int oplen = strlen(p->str);
                        if (len < oplen || memcmp(p->str, line, oplen))
                                continue;
                        if (p->fn(line + oplen, patch) < 0)
                                return offset;
                        break;
                }
        }

        return offset;
}

static int parse_num(const char *line, unsigned long *p)
{
        char *ptr;

        if (!isdigit(*line))
                return 0;
        *p = strtoul(line, &ptr, 10);
        return ptr - line;
}

static int parse_range(const char *line, int len, int offset, const char *expect,
                       unsigned long *p1, unsigned long *p2)
{
        int digits, ex;

        if (offset < 0 || offset >= len)
                return -1;
        line += offset;
        len -= offset;

        digits = parse_num(line, p1);
        if (!digits)
                return -1;

        offset += digits;
        line += digits;
        len -= digits;

        *p2 = 1;
        if (*line == ',') {
                digits = parse_num(line+1, p2);
                if (!digits)
                        return -1;

                offset += digits+1;
                line += digits+1;
                len -= digits+1;
        }

        ex = strlen(expect);
        if (ex > len)
                return -1;
        if (memcmp(line, expect, ex))
                return -1;

        return offset + ex;
}

/*
 * Parse a unified diff fragment header of the
 * form "@@ -a,b +c,d @@"
 */
static int parse_fragment_header(char *line, int len, struct fragment *fragment)
{
        int offset;

        if (!len || line[len-1] != '\n')
                return -1;

        /* Figure out the number of lines in a fragment */
        offset = parse_range(line, len, 4, " +", &fragment->oldpos, &fragment->oldlines);
        offset = parse_range(line, len, offset, " @@", &fragment->newpos, &fragment->newlines);

        return offset;
}

static int find_header(char *line, unsigned long size, int *hdrsize, struct patch *patch)
{
        unsigned long offset, len;

        patch->is_toplevel_relative = 0;
        patch->is_rename = patch->is_copy = 0;
        patch->is_new = patch->is_delete = -1;
        patch->old_mode = patch->new_mode = 0;
        patch->old_name = patch->new_name = NULL;
        for (offset = 0; size > 0; offset += len, size -= len, line += len, linenr++) {
                unsigned long nextlen;

                len = linelen(line, size);
                if (!len)
                        break;

                /* Testing this early allows us to take a few shortcuts.. */
                if (len < 6)
                        continue;

                /*
                 * Make sure we don't find any unconnected patch fragments.
                 * That's a sign that we didn't find a header, and that a
                 * patch has become corrupted/broken up.
                 */
                if (!memcmp("@@ -", line, 4)) {
                        struct fragment dummy;
                        if (parse_fragment_header(line, len, &dummy) < 0)
                                continue;
                        die("patch fragment without header at line %d: %.*s",
                            linenr, (int)len-1, line);
                }

                if (size < len + 6)
                        break;

                /*
                 * Git patch? It might not have a real patch, just a rename
                 * or mode change, so we handle that specially
                 */
                if (!memcmp("diff --git ", line, 11)) {
                        int git_hdr_len = parse_git_header(line, len, size, patch);
                        if (git_hdr_len <= len)
                                continue;
                        if (!patch->old_name && !patch->new_name) {
                                if (!patch->def_name)
                                        die("git diff header lacks filename information (line %d)", linenr);
                                patch->old_name = patch->new_name = patch->def_name;
                        }
                        patch->is_toplevel_relative = 1;
                        *hdrsize = git_hdr_len;
                        return offset;
                }

                /* --- followed by +++ ? */
                if (memcmp("--- ", line,  4) || memcmp("+++ ", line + len, 4))
                        continue;

                /*
                 * We only accept unified patches, so we want it to
                 * at least have "@@ -a,b +c,d @@\n", which is 14 chars
                 * minimum ("@@ -0,0 +1 @@\n" is the shortest).
                 */
                nextlen = linelen(line + len, size - len);
                if (size < nextlen + 14 || memcmp("@@ -", line + len + nextlen, 4))
                        continue;

                /* Ok, we'll consider it a patch */
                parse_traditional_patch(line, line+len, patch);
                *hdrsize = len + nextlen;
                linenr += 2;
                return offset;
        }
        return -1;
}

static void check_whitespace(const char *line, int len, unsigned ws_rule)
{
        char *err;
        unsigned result = check_and_emit_line(line + 1, len - 1, ws_rule,
            NULL, NULL, NULL, NULL);
        if (!result)
                return;

        whitespace_error++;
        if (squelch_whitespace_errors &&
            squelch_whitespace_errors < whitespace_error)
                ;
        else {
                err = whitespace_error_string(result);
                fprintf(stderr, "%s:%d: %s.\n%.*s\n",
                     patch_input_file, linenr, err, len - 2, line + 1);
                free(err);
        }
}

/*
 * Parse a unified diff. Note that this really needs to parse each
 * fragment separately, since the only way to know the difference
 * between a "---" that is part of a patch, and a "---" that starts
 * the next patch is to look at the line counts..
 */
static int parse_fragment(char *line, unsigned long size,
                          struct patch *patch, struct fragment *fragment)
{
        int added, deleted;
        int len = linelen(line, size), offset;
        unsigned long oldlines, newlines;
        unsigned long leading, trailing;

        offset = parse_fragment_header(line, len, fragment);
        if (offset < 0)
                return -1;
        oldlines = fragment->oldlines;
        newlines = fragment->newlines;
        leading = 0;
        trailing = 0;

        /* Parse the thing.. */
        line += len;
        size -= len;
        linenr++;
        added = deleted = 0;
        for (offset = len;
             0 < size;
             offset += len, size -= len, line += len, linenr++) {
                if (!oldlines && !newlines)
                        break;
                len = linelen(line, size);
                if (!len || line[len-1] != '\n')
                        return -1;
                switch (*line) {
                default:
                        return -1;
                case '\n': /* newer GNU diff, an empty context line */
                case ' ':
                        oldlines--;
                        newlines--;
                        if (!deleted && !added)
                                leading++;
                        trailing++;
                        break;
                case '-':
                        if (apply_in_reverse &&
                            ws_error_action != nowarn_ws_error)
                                check_whitespace(line, len, patch->ws_rule);
                        deleted++;
                        oldlines--;
                        trailing = 0;
                        break;
                case '+':
                        if (!apply_in_reverse &&
                            ws_error_action != nowarn_ws_error)
                                check_whitespace(line, len, patch->ws_rule);
                        added++;
                        newlines--;
                        trailing = 0;
                        break;

                /*
                 * We allow "\ No newline at end of file". Depending
                 * on locale settings when the patch was produced we
                 * don't know what this line looks like. The only
                 * thing we do know is that it begins with "\ ".
                 * Checking for 12 is just for sanity check -- any
                 * l10n of "\ No newline..." is at least that long.
                 */
                case '\\':
                        if (len < 12 || memcmp(line, "\\ ", 2))
                                return -1;
                        break;
                }
        }
        if (oldlines || newlines)
                return -1;
        fragment->leading = leading;
        fragment->trailing = trailing;

        /*
         * If a fragment ends with an incomplete line, we failed to include
         * it in the above loop because we hit oldlines == newlines == 0
         * before seeing it.
         */
        if (12 < size && !memcmp(line, "\\ ", 2))
                offset += linelen(line, size);

        patch->lines_added += added;
        patch->lines_deleted += deleted;

        if (0 < patch->is_new && oldlines)
                return error("new file depends on old contents");
        if (0 < patch->is_delete && newlines)
                return error("deleted file still has contents");
        return offset;
}

static int parse_single_patch(char *line, unsigned long size, struct patch *patch)
{
        unsigned long offset = 0;
        unsigned long oldlines = 0, newlines = 0, context = 0;
        struct fragment **fragp = &patch->fragments;

        while (size > 4 && !memcmp(line, "@@ -", 4)) {
                struct fragment *fragment;
                int len;

                fragment = xcalloc(1, sizeof(*fragment));
                len = parse_fragment(line, size, patch, fragment);
                if (len <= 0)
                        die("corrupt patch at line %d", linenr);
                fragment->patch = line;
                fragment->size = len;
                oldlines += fragment->oldlines;
                newlines += fragment->newlines;
                context += fragment->leading + fragment->trailing;

                *fragp = fragment;
                fragp = &fragment->next;

                offset += len;
                line += len;
                size -= len;
        }

        /*
         * If something was removed (i.e. we have old-lines) it cannot
         * be creation, and if something was added it cannot be
         * deletion.  However, the reverse is not true; --unified=0
         * patches that only add are not necessarily creation even
         * though they do not have any old lines, and ones that only
         * delete are not necessarily deletion.
         *
         * Unfortunately, a real creation/deletion patch do _not_ have
         * any context line by definition, so we cannot safely tell it
         * apart with --unified=0 insanity.  At least if the patch has
         * more than one hunk it is not creation or deletion.
         */
        if (patch->is_new < 0 &&
            (oldlines || (patch->fragments && patch->fragments->next)))
                patch->is_new = 0;
        if (patch->is_delete < 0 &&
            (newlines || (patch->fragments && patch->fragments->next)))
                patch->is_delete = 0;
        if (!unidiff_zero || context) {
                /* If the user says the patch is not generated with
                 * --unified=0, or if we have seen context lines,
                 * then not having oldlines means the patch is creation,
                 * and not having newlines means the patch is deletion.
                 */
                if (patch->is_new < 0 && !oldlines) {
                        patch->is_new = 1;
                        patch->old_name = NULL;
                }
                if (patch->is_delete < 0 && !newlines) {
                        patch->is_delete = 1;
                        patch->new_name = NULL;
                }
        }

        if (0 < patch->is_new && oldlines)
                die("new file %s depends on old contents", patch->new_name);
        if (0 < patch->is_delete && newlines)
                die("deleted file %s still has contents", patch->old_name);
        if (!patch->is_delete && !newlines && context)
                fprintf(stderr, "** warning: file %s becomes empty but "
                        "is not deleted\n", patch->new_name);

        return offset;
}

static inline int metadata_changes(struct patch *patch)
{
        return  patch->is_rename > 0 ||
                patch->is_copy > 0 ||
                patch->is_new > 0 ||
                patch->is_delete ||
                (patch->old_mode && patch->new_mode &&
                 patch->old_mode != patch->new_mode);
}

static char *inflate_it(const void *data, unsigned long size,
                        unsigned long inflated_size)
{
        z_stream stream;
        void *out;
        int st;

        memset(&stream, 0, sizeof(stream));

        stream.next_in = (unsigned char *)data;
        stream.avail_in = size;
        stream.next_out = out = xmalloc(inflated_size);
        stream.avail_out = inflated_size;
        inflateInit(&stream);
        st = inflate(&stream, Z_FINISH);
        if ((st != Z_STREAM_END) || stream.total_out != inflated_size) {
                free(out);
                return NULL;
        }
        return out;
}

static struct fragment *parse_binary_hunk(char **buf_p,
                                          unsigned long *sz_p,
                                          int *status_p,
                                          int *used_p)
{
        /*
         * Expect a line that begins with binary patch method ("literal"
         * or "delta"), followed by the length of data before deflating.
         * a sequence of 'length-byte' followed by base-85 encoded data
         * should follow, terminated by a newline.
         *
         * Each 5-byte sequence of base-85 encodes up to 4 bytes,
         * and we would limit the patch line to 66 characters,
         * so one line can fit up to 13 groups that would decode
         * to 52 bytes max.  The length byte 'A'-'Z' corresponds
         * to 1-26 bytes, and 'a'-'z' corresponds to 27-52 bytes.
         */
        int llen, used;
        unsigned long size = *sz_p;
        char *buffer = *buf_p;
        int patch_method;
        unsigned long origlen;
        char *data = NULL;
        int hunk_size = 0;
        struct fragment *frag;

        llen = linelen(buffer, size);
        used = llen;

        *status_p = 0;

        if (!prefixcmp(buffer, "delta ")) {
                patch_method = BINARY_DELTA_DEFLATED;
                origlen = strtoul(buffer + 6, NULL, 10);
        }
        else if (!prefixcmp(buffer, "literal ")) {
                patch_method = BINARY_LITERAL_DEFLATED;
                origlen = strtoul(buffer + 8, NULL, 10);
        }
        else
                return NULL;

        linenr++;
        buffer += llen;
        while (1) {
                int byte_length, max_byte_length, newsize;
                llen = linelen(buffer, size);
                used += llen;
                linenr++;
                if (llen == 1) {
                        /* consume the blank line */
                        buffer++;
                        size--;
                        break;
                }
                /*
                 * Minimum line is "A00000\n" which is 7-byte long,
                 * and the line length must be multiple of 5 plus 2.
                 */
                if ((llen < 7) || (llen-2) % 5)
                        goto corrupt;
                max_byte_length = (llen - 2) / 5 * 4;
                byte_length = *buffer;
                if ('A' <= byte_length && byte_length <= 'Z')
                        byte_length = byte_length - 'A' + 1;
                else if ('a' <= byte_length && byte_length <= 'z')
                        byte_length = byte_length - 'a' + 27;
                else
                        goto corrupt;
                /* if the input length was not multiple of 4, we would
                 * have filler at the end but the filler should never
                 * exceed 3 bytes
                 */
                if (max_byte_length < byte_length ||
                    byte_length <= max_byte_length - 4)
                        goto corrupt;
                newsize = hunk_size + byte_length;
                data = xrealloc(data, newsize);
                if (decode_85(data + hunk_size, buffer + 1, byte_length))
                        goto corrupt;
                hunk_size = newsize;
                buffer += llen;
                size -= llen;
        }

        frag = xcalloc(1, sizeof(*frag));
        frag->patch = inflate_it(data, hunk_size, origlen);
        if (!frag->patch)
                goto corrupt;
        free(data);
        frag->size = origlen;
        *buf_p = buffer;
        *sz_p = size;
        *used_p = used;
        frag->binary_patch_method = patch_method;
        return frag;

 corrupt:
        free(data);
        *status_p = -1;
        error("corrupt binary patch at line %d: %.*s",
              linenr-1, llen-1, buffer);
        return NULL;
}

static int parse_binary(char *buffer, unsigned long size, struct patch *patch)
{
        /*
         * We have read "GIT binary patch\n"; what follows is a line
         * that says the patch method (currently, either "literal" or
         * "delta") and the length of data before deflating; a
         * sequence of 'length-byte' followed by base-85 encoded data
         * follows.
         *
         * When a binary patch is reversible, there is another binary
         * hunk in the same format, starting with patch method (either
         * "literal" or "delta") with the length of data, and a sequence
         * of length-byte + base-85 encoded data, terminated with another
         * empty line.  This data, when applied to the postimage, produces
         * the preimage.
         */
        struct fragment *forward;
        struct fragment *reverse;
        int status;
        int used, used_1;

        forward = parse_binary_hunk(&buffer, &size, &status, &used);
        if (!forward && !status)
                /* there has to be one hunk (forward hunk) */
                return error("unrecognized binary patch at line %d", linenr-1);
        if (status)
                /* otherwise we already gave an error message */
                return status;

        reverse = parse_binary_hunk(&buffer, &size, &status, &used_1);
        if (reverse)
                used += used_1;
        else if (status) {
                /*
                 * Not having reverse hunk is not an error, but having
                 * a corrupt reverse hunk is.
                 */
                free((void*) forward->patch);
                free(forward);
                return status;
        }
        forward->next = reverse;
        patch->fragments = forward;
        patch->is_binary = 1;
        return used;
}

static int parse_chunk(char *buffer, unsigned long size, struct patch *patch)
{
        int hdrsize, patchsize;
        int offset = find_header(buffer, size, &hdrsize, patch);

        if (offset < 0)
                return offset;

        patch->ws_rule = whitespace_rule(patch->new_name
                                         ? patch->new_name
                                         : patch->old_name);

        patchsize = parse_single_patch(buffer + offset + hdrsize,
                                       size - offset - hdrsize, patch);

        if (!patchsize) {
                static const char *binhdr[] = {
                        "Binary files ",
                        "Files ",
                        NULL,
                };
                static const char git_binary[] = "GIT binary patch\n";
                int i;
                int hd = hdrsize + offset;
                unsigned long llen = linelen(buffer + hd, size - hd);

                if (llen == sizeof(git_binary) - 1 &&
                    !memcmp(git_binary, buffer + hd, llen)) {
                        int used;
                        linenr++;
                        used = parse_binary(buffer + hd + llen,
                                            size - hd - llen, patch);
                        if (used)
                                patchsize = used + llen;
                        else
                                patchsize = 0;
                }
                else if (!memcmp(" differ\n", buffer + hd + llen - 8, 8)) {
                        for (i = 0; binhdr[i]; i++) {
                                int len = strlen(binhdr[i]);
                                if (len < size - hd &&
                                    !memcmp(binhdr[i], buffer + hd, len)) {
                                        linenr++;
                                        patch->is_binary = 1;
                                        patchsize = llen;
                                        break;
                                }
                        }
                }

                /* Empty patch cannot be applied if it is a text patch
                 * without metadata change.  A binary patch appears
                 * empty to us here.
                 */
                if ((apply || check) &&
                    (!patch->is_binary && !metadata_changes(patch)))
                        die("patch with only garbage at line %d", linenr);
        }

        return offset + hdrsize + patchsize;
}

#define swap(a,b) myswap((a),(b),sizeof(a))

#define myswap(a, b, size) do {         \
        unsigned char mytmp[size];      \
        memcpy(mytmp, &a, size);                \
        memcpy(&a, &b, size);           \
        memcpy(&b, mytmp, size);                \
} while (0)

static void reverse_patches(struct patch *p)
{
        for (; p; p = p->next) {
                struct fragment *frag = p->fragments;

                swap(p->new_name, p->old_name);
                swap(p->new_mode, p->old_mode);
                swap(p->is_new, p->is_delete);
                swap(p->lines_added, p->lines_deleted);
                swap(p->old_sha1_prefix, p->new_sha1_prefix);

                for (; frag; frag = frag->next) {
                        swap(frag->newpos, frag->oldpos);
                        swap(frag->newlines, frag->oldlines);
                }
        }
}

static const char pluses[] =
"++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++";
static const char minuses[]=
"----------------------------------------------------------------------";

static void show_stats(struct patch *patch)
{
        struct strbuf qname;
        char *cp = patch->new_name ? patch->new_name : patch->old_name;
        int max, add, del;

        strbuf_init(&qname, 0);
        quote_c_style(cp, &qname, NULL, 0);

        /*
         * "scale" the filename
         */
        max = max_len;
        if (max > 50)
                max = 50;

        if (qname.len > max) {
                cp = strchr(qname.buf + qname.len + 3 - max, '/');
                if (!cp)
                        cp = qname.buf + qname.len + 3 - max;
                strbuf_splice(&qname, 0, cp - qname.buf, "...", 3);
        }

        if (patch->is_binary) {
                printf(" %-*s |  Bin\n", max, qname.buf);
                strbuf_release(&qname);
                return;
        }

        printf(" %-*s |", max, qname.buf);
        strbuf_release(&qname);

        /*
         * scale the add/delete
         */
        max = max + max_change > 70 ? 70 - max : max_change;
        add = patch->lines_added;
        del = patch->lines_deleted;

        if (max_change > 0) {
                int total = ((add + del) * max + max_change / 2) / max_change;
                add = (add * max + max_change / 2) / max_change;
                del = total - add;
        }
        printf("%5d %.*s%.*s\n", patch->lines_added + patch->lines_deleted,
                add, pluses, del, minuses);
}

static int read_old_data(struct stat *st, const char *path, struct strbuf *buf)
{
        switch (st->st_mode & S_IFMT) {
        case S_IFLNK:
                strbuf_grow(buf, st->st_size);
                if (readlink(path, buf->buf, st->st_size) != st->st_size)
                        return -1;
                strbuf_setlen(buf, st->st_size);
                return 0;
        case S_IFREG:
                if (strbuf_read_file(buf, path, st->st_size) != st->st_size)
                        return error("unable to open or read %s", path);
                convert_to_git(path, buf->buf, buf->len, buf, 0);
                return 0;
        default:
                return -1;
        }
}

static void update_pre_post_images(struct image *preimage,
                                   struct image *postimage,
                                   char *buf,
                                   size_t len)
{
        int i, ctx;
        char *new, *old, *fixed;
        struct image fixed_preimage;

        /*
         * Update the preimage with whitespace fixes.  Note that we
         * are not losing preimage->buf -- apply_one_fragment() will
         * free "oldlines".
         */
        prepare_image(&fixed_preimage, buf, len, 1);
        assert(fixed_preimage.nr == preimage->nr);
        for (i = 0; i < preimage->nr; i++)
                fixed_preimage.line[i].flag = preimage->line[i].flag;
        free(preimage->line_allocated);
        *preimage = fixed_preimage;

        /*
         * Adjust the common context lines in postimage, in place.
         * This is possible because whitespace fixing does not make
         * the string grow.
         */
        new = old = postimage->buf;
        fixed = preimage->buf;
        for (i = ctx = 0; i < postimage->nr; i++) {
                size_t len = postimage->line[i].len;
                if (!(postimage->line[i].flag & LINE_COMMON)) {
                        /* an added line -- no counterparts in preimage */
                        memmove(new, old, len);
                        old += len;
                        new += len;
                        continue;
                }

                /* a common context -- skip it in the original postimage */
                old += len;

                /* and find the corresponding one in the fixed preimage */
                while (ctx < preimage->nr &&
                       !(preimage->line[ctx].flag & LINE_COMMON)) {
                        fixed += preimage->line[ctx].len;
                        ctx++;
                }
                if (preimage->nr <= ctx)
                        die("oops");

                /* and copy it in, while fixing the line length */
                len = preimage->line[ctx].len;
                memcpy(new, fixed, len);
                new += len;
                fixed += len;
                postimage->line[i].len = len;
                ctx++;
        }

        /* Fix the length of the whole thing */
        postimage->len = new - postimage->buf;
}

static int match_fragment(struct image *img,
                          struct image *preimage,
                          struct image *postimage,
                          unsigned long try,
                          int try_lno,
                          unsigned ws_rule,
                          int match_beginning, int match_end)
{
        int i;
        char *fixed_buf, *buf, *orig, *target;

        if (preimage->nr + try_lno > img->nr)
                return 0;

        if (match_beginning && try_lno)
                return 0;

        if (match_end && preimage->nr + try_lno != img->nr)
                return 0;

        /* Quick hash check */
        for (i = 0; i < preimage->nr; i++)
                if (preimage->line[i].hash != img->line[try_lno + i].hash)
                        return 0;

        /*
         * Do we have an exact match?  If we were told to match
         * at the end, size must be exactly at try+fragsize,
         * otherwise try+fragsize must be still within the preimage,
         * and either case, the old piece should match the preimage
         * exactly.
         */
        if ((match_end
             ? (try + preimage->len == img->len)
             : (try + preimage->len <= img->len)) &&
            !memcmp(img->buf + try, preimage->buf, preimage->len))
                return 1;

        if (ws_error_action != correct_ws_error)
                return 0;

        /*
         * The hunk does not apply byte-by-byte, but the hash says
         * it might with whitespace fuzz.
         */
        fixed_buf = xmalloc(preimage->len + 1);
        buf = fixed_buf;
        orig = preimage->buf;
        target = img->buf + try;
        for (i = 0; i < preimage->nr; i++) {
                size_t fixlen; /* length after fixing the preimage */
                size_t oldlen = preimage->line[i].len;
                size_t tgtlen = img->line[try_lno + i].len;
                size_t tgtfixlen; /* length after fixing the target line */
                char tgtfixbuf[1024], *tgtfix;
                int match;

                /* Try fixing the line in the preimage */
                fixlen = ws_fix_copy(buf, orig, oldlen, ws_rule, NULL);

                /* Try fixing the line in the target */
                if (sizeof(tgtfixbuf) < tgtlen)
                        tgtfix = tgtfixbuf;
                else
                        tgtfix = xmalloc(tgtlen);
                tgtfixlen = ws_fix_copy(tgtfix, target, tgtlen, ws_rule, NULL);

                /*
                 * If they match, either the preimage was based on
                 * a version before our tree fixed whitespace breakage,
                 * or we are lacking a whitespace-fix patch the tree
                 * the preimage was based on already had (i.e. target
                 * has whitespace breakage, the preimage doesn't).
                 * In either case, we are fixing the whitespace breakages
                 * so we might as well take the fix together with their
                 * real change.
                 */
                match = (tgtfixlen == fixlen && !memcmp(tgtfix, buf, fixlen));

                if (tgtfix != tgtfixbuf)
                        free(tgtfix);
                if (!match)
                        goto unmatch_exit;

                orig += oldlen;
                buf += fixlen;
                target += tgtlen;
        }

        /*
         * Yes, the preimage is based on an older version that still
         * has whitespace breakages unfixed, and fixing them makes the
         * hunk match.  Update the context lines in the postimage.
         */
        update_pre_post_images(preimage, postimage,
                               fixed_buf, buf - fixed_buf);
        return 1;

 unmatch_exit:
        free(fixed_buf);
        return 0;
}

static int find_pos(struct image *img,
                    struct image *preimage,
                    struct image *postimage,
                    int line,
                    unsigned ws_rule,
                    int match_beginning, int match_end)
{
        int i;
        unsigned long backwards, forwards, try;
        int backwards_lno, forwards_lno, try_lno;

        if (preimage->nr > img->nr)
                return -1;

        /*
         * If match_begining or match_end is specified, there is no
         * point starting from a wrong line that will never match and
         * wander around and wait for a match at the specified end.
         */
        if (match_beginning)
                line = 0;
        else if (match_end)
                line = img->nr - preimage->nr;

        if (line > img->nr)
                line = img->nr;

        try = 0;
        for (i = 0; i < line; i++)
                try += img->line[i].len;

        /*
         * There's probably some smart way to do this, but I'll leave
         * that to the smart and beautiful people. I'm simple and stupid.
         */
        backwards = try;
        backwards_lno = line;
        forwards = try;
        forwards_lno = line;
        try_lno = line;

        for (i = 0; ; i++) {
                if (match_fragment(img, preimage, postimage,
                                   try, try_lno, ws_rule,
                                   match_beginning, match_end))
                        return try_lno;

        again:
                if (backwards_lno == 0 && forwards_lno == img->nr)
                        break;

                if (i & 1) {
                        if (backwards_lno == 0) {
                                i++;
                                goto again;
                        }
                        backwards_lno--;
                        backwards -= img->line[backwards_lno].len;
                        try = backwards;
                        try_lno = backwards_lno;
                } else {
                        if (forwards_lno == img->nr) {
                                i++;
                                goto again;
                        }
                        forwards += img->line[forwards_lno].len;
                        forwards_lno++;
                        try = forwards;
                        try_lno = forwards_lno;
                }

        }
        return -1;
}

static void remove_first_line(struct image *img)
{
        img->buf += img->line[0].len;
        img->len -= img->line[0].len;
        img->line++;
        img->nr--;
}

static void remove_last_line(struct image *img)
{
        img->len -= img->line[--img->nr].len;
}

static void update_image(struct image *img,
                         int applied_pos,
                         struct image *preimage,
                         struct image *postimage)
{
        /*
         * remove the copy of preimage at offset in img
         * and replace it with postimage
         */
        int i, nr;
        size_t remove_count, insert_count, applied_at = 0;
        char *result;

        for (i = 0; i < applied_pos; i++)
                applied_at += img->line[i].len;

        remove_count = 0;
        for (i = 0; i < preimage->nr; i++)
                remove_count += img->line[applied_pos + i].len;
        insert_count = postimage->len;

        /* Adjust the contents */
        result = xmalloc(img->len + insert_count - remove_count + 1);
        memcpy(result, img->buf, applied_at);
        memcpy(result + applied_at, postimage->buf, postimage->len);
        memcpy(result + applied_at + postimage->len,
               img->buf + (applied_at + remove_count),
               img->len - (applied_at + remove_count));
        free(img->buf);
        img->buf = result;
        img->len += insert_count - remove_count;
        result[img->len] = '\0';

        /* Adjust the line table */
        nr = img->nr + postimage->nr - preimage->nr;
        if (preimage->nr < postimage->nr) {
                /*
                 * NOTE: this knows that we never call remove_first_line()
                 * on anything other than pre/post image.
                 */
                img->line = xrealloc(img->line, nr * sizeof(*img->line));
                img->line_allocated = img->line;
        }
        if (preimage->nr != postimage->nr)
                memmove(img->line + applied_pos + postimage->nr,
                        img->line + applied_pos + preimage->nr,
                        (img->nr - (applied_pos + preimage->nr)) *
                        sizeof(*img->line));
        memcpy(img->line + applied_pos,
               postimage->line,
               postimage->nr * sizeof(*img->line));
        img->nr = nr;
}

static int apply_one_fragment(struct image *img, struct fragment *frag,
                              int inaccurate_eof, unsigned ws_rule)
{
        int match_beginning, match_end;
        const char *patch = frag->patch;
        int size = frag->size;
        char *old, *new, *oldlines, *newlines;
        int new_blank_lines_at_end = 0;
        unsigned long leading, trailing;
        int pos, applied_pos;
        struct image preimage;
        struct image postimage;

        memset(&preimage, 0, sizeof(preimage));
        memset(&postimage, 0, sizeof(postimage));
        oldlines = xmalloc(size);
        newlines = xmalloc(size);

        old = oldlines;
        new = newlines;
        while (size > 0) {
                char first;
                int len = linelen(patch, size);
                int plen, added;
                int added_blank_line = 0;

                if (!len)
                        break;

                /*
                 * "plen" is how much of the line we should use for
                 * the actual patch data. Normally we just remove the
                 * first character on the line, but if the line is
                 * followed by "\ No newline", then we also remove the
                 * last one (which is the newline, of course).
                 */
                plen = len - 1;
                if (len < size && patch[len] == '\\')
                        plen--;
                first = *patch;
                if (apply_in_reverse) {
                        if (first == '-')
                                first = '+';
                        else if (first == '+')
                                first = '-';
                }

                switch (first) {
                case '\n':
                        /* Newer GNU diff, empty context line */
                        if (plen < 0)
                                /* ... followed by '\No newline'; nothing */
                                break;
                        *old++ = '\n';
                        *new++ = '\n';
                        add_line_info(&preimage, "\n", 1, LINE_COMMON);
                        add_line_info(&postimage, "\n", 1, LINE_COMMON);
                        break;
                case ' ':
                case '-':
                        memcpy(old, patch + 1, plen);
                        add_line_info(&preimage, old, plen,
                                      (first == ' ' ? LINE_COMMON : 0));
                        old += plen;
                        if (first == '-')
                                break;
                /* Fall-through for ' ' */
                case '+':
                        /* --no-add does not add new lines */
                        if (first == '+' && no_add)
                                break;

                        if (first != '+' ||
                            !whitespace_error ||
                            ws_error_action != correct_ws_error) {
                                memcpy(new, patch + 1, plen);
                                added = plen;
                        }
                        else {
                                added = ws_fix_copy(new, patch + 1, plen, ws_rule, &applied_after_fixing_ws);
                        }
                        add_line_info(&postimage, new, added,
                                      (first == '+' ? 0 : LINE_COMMON));
                        new += added;
                        if (first == '+' &&
                            added == 1 && new[-1] == '\n')
                                added_blank_line = 1;
                        break;
                case '@': case '\\':
                        /* Ignore it, we already handled it */
                        break;
                default:
                        if (apply_verbosely)
                                error("invalid start of line: '%c'", first);
                        return -1;
                }
                if (added_blank_line)
                        new_blank_lines_at_end++;
                else
                        new_blank_lines_at_end = 0;
                patch += len;
                size -= len;
        }
        if (inaccurate_eof &&
            old > oldlines && old[-1] == '\n' &&
            new > newlines && new[-1] == '\n') {
                old--;
                new--;
        }

        leading = frag->leading;
        trailing = frag->trailing;

        /*
         * If we don't have any leading/trailing data in the patch,
         * we want it to match at the beginning/end of the file.
         *
         * But that would break if the patch is generated with
         * --unified=0; sane people wouldn't do that to cause us
         * trouble, but we try to please not so sane ones as well.
         */
        if (unidiff_zero) {
                match_beginning = (!leading && !frag->oldpos);
                match_end = 0;
        }
        else {
                match_beginning = !leading && (frag->oldpos == 1);
                match_end = !trailing;
        }

        pos = frag->newpos ? (frag->newpos - 1) : 0;
        preimage.buf = oldlines;
        preimage.len = old - oldlines;
        postimage.buf = newlines;
        postimage.len = new - newlines;
        preimage.line = preimage.line_allocated;
        postimage.line = postimage.line_allocated;

        for (;;) {

                applied_pos = find_pos(img, &preimage, &postimage, pos,
                                       ws_rule, match_beginning, match_end);

                if (applied_pos >= 0)
                        break;

                /* Am I at my context limits? */
                if ((leading <= p_context) && (trailing <= p_context))
                        break;
                if (match_beginning || match_end) {
                        match_beginning = match_end = 0;
                        continue;
                }

                /*
                 * Reduce the number of context lines; reduce both
                 * leading and trailing if they are equal otherwise
                 * just reduce the larger context.
                 */
                if (leading >= trailing) {
                        remove_first_line(&preimage);
                        remove_first_line(&postimage);
                        pos--;
                        leading--;
                }
                if (trailing > leading) {
                        remove_last_line(&preimage);
                        remove_last_line(&postimage);
                        trailing--;
                }
        }

        if (applied_pos >= 0) {
                if (ws_error_action == correct_ws_error &&
                    new_blank_lines_at_end &&
                    postimage.nr + applied_pos == img->nr) {
                        /*
                         * If the patch application adds blank lines
                         * at the end, and if the patch applies at the
                         * end of the image, remove those added blank
                         * lines.
                         */
                        while (new_blank_lines_at_end--)
                                remove_last_line(&postimage);
                }

                /*
                 * Warn if it was necessary to reduce the number
                 * of context lines.
                 */
                if ((leading != frag->leading) ||
                    (trailing != frag->trailing))
                        fprintf(stderr, "Context reduced to (%ld/%ld)"
                                " to apply fragment at %d\n",
                                leading, trailing, applied_pos+1);
                update_image(img, applied_pos, &preimage, &postimage);
        } else {
                if (apply_verbosely)
                        error("while searching for:\n%.*s",
                              (int)(old - oldlines), oldlines);
        }

        free(oldlines);
        free(newlines);
        free(preimage.line_allocated);
        free(postimage.line_allocated);

        return (applied_pos < 0);
}

static int apply_binary_fragment(struct image *img, struct patch *patch)
{
        struct fragment *fragment = patch->fragments;
        unsigned long len;
        void *dst;

        /* Binary patch is irreversible without the optional second hunk */
        if (apply_in_reverse) {
                if (!fragment->next)
                        return error("cannot reverse-apply a binary patch "
                                     "without the reverse hunk to '%s'",
                                     patch->new_name
                                     ? patch->new_name : patch->old_name);
                fragment = fragment->next;
        }
        switch (fragment->binary_patch_method) {
        case BINARY_DELTA_DEFLATED:
                dst = patch_delta(img->buf, img->len, fragment->patch,
                                  fragment->size, &len);
                if (!dst)
                        return -1;
                clear_image(img);
                img->buf = dst;
                img->len = len;
                return 0;
        case BINARY_LITERAL_DEFLATED:
                clear_image(img);
                img->len = fragment->size;
                img->buf = xmalloc(img->len+1);
                memcpy(img->buf, fragment->patch, img->len);
                img->buf[img->len] = '\0';
                return 0;
        }
        return -1;
}

static int apply_binary(struct image *img, struct patch *patch)
{
        const char *name = patch->old_name ? patch->old_name : patch->new_name;
        unsigned char sha1[20];

        /*
         * For safety, we require patch index line to contain
         * full 40-byte textual SHA1 for old and new, at least for now.
         */
        if (strlen(patch->old_sha1_prefix) != 40 ||
            strlen(patch->new_sha1_prefix) != 40 ||
            get_sha1_hex(patch->old_sha1_prefix, sha1) ||
            get_sha1_hex(patch->new_sha1_prefix, sha1))
                return error("cannot apply binary patch to '%s' "
                             "without full index line", name);

        if (patch->old_name) {
                /*
                 * See if the old one matches what the patch
                 * applies to.
                 */
                hash_sha1_file(img->buf, img->len, blob_type, sha1);
                if (strcmp(sha1_to_hex(sha1), patch->old_sha1_prefix))
                        return error("the patch applies to '%s' (%s), "
                                     "which does not match the "
                                     "current contents.",
                                     name, sha1_to_hex(sha1));
        }
        else {
                /* Otherwise, the old one must be empty. */
                if (img->len)
                        return error("the patch applies to an empty "
                                     "'%s' but it is not empty", name);
        }

        get_sha1_hex(patch->new_sha1_prefix, sha1);
        if (is_null_sha1(sha1)) {
                clear_image(img);
                return 0; /* deletion patch */
        }

        if (has_sha1_file(sha1)) {
                /* We already have the postimage */
                enum object_type type;
                unsigned long size;
                char *result;

                result = read_sha1_file(sha1, &type, &size);
                if (!result)
                        return error("the necessary postimage %s for "
                                     "'%s' cannot be read",
                                     patch->new_sha1_prefix, name);
                clear_image(img);
                img->buf = result;
                img->len = size;
        } else {
                /*
                 * We have verified buf matches the preimage;
                 * apply the patch data to it, which is stored
                 * in the patch->fragments->{patch,size}.
                 */
                if (apply_binary_fragment(img, patch))
                        return error("binary patch does not apply to '%s'",
                                     name);

                /* verify that the result matches */
                hash_sha1_file(img->buf, img->len, blob_type, sha1);
                if (strcmp(sha1_to_hex(sha1), patch->new_sha1_prefix))
                        return error("binary patch to '%s' creates incorrect result (expecting %s, got %s)",
                                name, patch->new_sha1_prefix, sha1_to_hex(sha1));
        }

        return 0;
}

static int apply_fragments(struct image *img, struct patch *patch)
{
        struct fragment *frag = patch->fragments;
        const char *name = patch->old_name ? patch->old_name : patch->new_name;
        unsigned ws_rule = patch->ws_rule;
        unsigned inaccurate_eof = patch->inaccurate_eof;

        if (patch->is_binary)
                return apply_binary(img, patch);

        while (frag) {
                if (apply_one_fragment(img, frag, inaccurate_eof, ws_rule)) {
                        error("patch failed: %s:%ld", name, frag->oldpos);
                        if (!apply_with_reject)
                                return -1;
                        frag->rejected = 1;
                }
                frag = frag->next;
        }
        return 0;
}

static int read_file_or_gitlink(struct cache_entry *ce, struct strbuf *buf)
{
        if (!ce)
                return 0;

        if (S_ISGITLINK(ce->ce_mode)) {
                strbuf_grow(buf, 100);
                strbuf_addf(buf, "Subproject commit %s\n", sha1_to_hex(ce->sha1));
        } else {
                enum object_type type;
                unsigned long sz;
                char *result;

                result = read_sha1_file(ce->sha1, &type, &sz);
                if (!result)
                        return -1;
                /* XXX read_sha1_file NUL-terminates */
                strbuf_attach(buf, result, sz, sz + 1);
        }
        return 0;
}

static int apply_data(struct patch *patch, struct stat *st, struct cache_entry *ce)
{
        struct strbuf buf;
        struct image image;
        size_t len;
        char *img;

        strbuf_init(&buf, 0);
        if (cached) {
                if (read_file_or_gitlink(ce, &buf))
                        return error("read of %s failed", patch->old_name);
        } else if (patch->old_name) {
                if (S_ISGITLINK(patch->old_mode)) {
                        if (ce) {
                                read_file_or_gitlink(ce, &buf);
                        } else {
                                /*
                                 * There is no way to apply subproject
                                 * patch without looking at the index.
                                 */
                                patch->fragments = NULL;
                        }
                } else {
                        if (read_old_data(st, patch->old_name, &buf))
                                return error("read of %s failed", patch->old_name);
                }
        }

        img = strbuf_detach(&buf, &len);
        prepare_image(&image, img, len, !patch->is_binary);

        if (apply_fragments(&image, patch) < 0)
                return -1; /* note with --reject this succeeds. */
        patch->result = image.buf;
        patch->resultsize = image.len;
        free(image.line_allocated);

        if (0 < patch->is_delete && patch->resultsize)
                return error("removal patch leaves file contents");

        return 0;
}

static int check_to_create_blob(const char *new_name, int ok_if_exists)
{
        struct stat nst;
        if (!lstat(new_name, &nst)) {
                if (S_ISDIR(nst.st_mode) || ok_if_exists)
                        return 0;
                /*
                 * A leading component of new_name might be a symlink
                 * that is going to be removed with this patch, but
                 * still pointing at somewhere that has the path.
                 * In such a case, path "new_name" does not exist as
                 * far as git is concerned.
                 */
                if (has_symlink_leading_path(new_name, NULL))
                        return 0;

                return error("%s: already exists in working directory", new_name);
        }
        else if ((errno != ENOENT) && (errno != ENOTDIR))
                return error("%s: %s", new_name, strerror(errno));
        return 0;
}

static int verify_index_match(struct cache_entry *ce, struct stat *st)
{
        if (S_ISGITLINK(ce->ce_mode)) {
                if (!S_ISDIR(st->st_mode))
                        return -1;
                return 0;
        }
        return ce_match_stat(ce, st, CE_MATCH_IGNORE_VALID);
}

static int check_patch(struct patch *patch, struct patch *prev_patch)
{
        struct stat st;
        const char *old_name = patch->old_name;
        const char *new_name = patch->new_name;
        const char *name = old_name ? old_name : new_name;
        struct cache_entry *ce = NULL;
        int ok_if_exists;

        patch->rejected = 1; /* we will drop this after we succeed */

        /*
         * Make sure that we do not have local modifications from the
         * index when we are looking at the index.  Also make sure
         * we have the preimage file to be patched in the work tree,
         * unless --cached, which tells git to apply only in the index.
         */
        if (old_name) {
                int stat_ret = 0;
                unsigned st_mode = 0;

                if (!cached)
                        stat_ret = lstat(old_name, &st);
                if (check_index) {
                        int pos = cache_name_pos(old_name, strlen(old_name));
                        if (pos < 0)
                                return error("%s: does not exist in index",
                                             old_name);
                        ce = active_cache[pos];
                        if (stat_ret < 0) {
                                struct checkout costate;
                                if (errno != ENOENT)
                                        return error("%s: %s", old_name,
                                                     strerror(errno));
                                /* checkout */
                                costate.base_dir = "";
                                costate.base_dir_len = 0;
                                costate.force = 0;
                                costate.quiet = 0;
                                costate.not_new = 0;
                                costate.refresh_cache = 1;
                                if (checkout_entry(ce,
                                                   &costate,
                                                   NULL) ||
                                    lstat(old_name, &st))
                                        return -1;
                        }
                        if (!cached && verify_index_match(ce, &st))
                                return error("%s: does not match index",
                                             old_name);
                        if (cached)
                                st_mode = ce->ce_mode;
                } else if (stat_ret < 0)
                        return error("%s: %s", old_name, strerror(errno));

                if (!cached)
                        st_mode = ce_mode_from_stat(ce, st.st_mode);

                if (patch->is_new < 0)
                        patch->is_new = 0;
                if (!patch->old_mode)
                        patch->old_mode = st_mode;
                if ((st_mode ^ patch->old_mode) & S_IFMT)
                        return error("%s: wrong type", old_name);
                if (st_mode != patch->old_mode)
                        fprintf(stderr, "warning: %s has type %o, expected %o\n",
                                old_name, st_mode, patch->old_mode);
        }

        if (new_name && prev_patch && 0 < prev_patch->is_delete &&
            !strcmp(prev_patch->old_name, new_name))
                /*
                 * A type-change diff is always split into a patch to
                 * delete old, immediately followed by a patch to
                 * create new (see diff.c::run_diff()); in such a case
                 * it is Ok that the entry to be deleted by the
                 * previous patch is still in the working tree and in
                 * the index.
                 */
                ok_if_exists = 1;
        else
                ok_if_exists = 0;

        if (new_name &&
            ((0 < patch->is_new) | (0 < patch->is_rename) | patch->is_copy)) {
                if (check_index &&
                    cache_name_pos(new_name, strlen(new_name)) >= 0 &&
                    !ok_if_exists)
                        return error("%s: already exists in index", new_name);
                if (!cached) {
                        int err = check_to_create_blob(new_name, ok_if_exists);
                        if (err)
                                return err;
                }
                if (!patch->new_mode) {
                        if (0 < patch->is_new)
                                patch->new_mode = S_IFREG | 0644;
                        else
                                patch->new_mode = patch->old_mode;
                }
        }

        if (new_name && old_name) {
                int same = !strcmp(old_name, new_name);
                if (!patch->new_mode)
                        patch->new_mode = patch->old_mode;
                if ((patch->old_mode ^ patch->new_mode) & S_IFMT)
                        return error("new mode (%o) of %s does not match old mode (%o)%s%s",
                                patch->new_mode, new_name, patch->old_mode,
                                same ? "" : " of ", same ? "" : old_name);
        }

        if (apply_data(patch, &st, ce) < 0)
                return error("%s: patch does not apply", name);
        patch->rejected = 0;
        return 0;
}

static int check_patch_list(struct patch *patch)
{
        struct patch *prev_patch = NULL;
        int err = 0;

        for (prev_patch = NULL; patch ; patch = patch->next) {
                if (apply_verbosely)
                        say_patch_name(stderr,
                                       "Checking patch ", patch, "...\n");
                err |= check_patch(patch, prev_patch);
                prev_patch = patch;
        }
        return err;
}

/* This function tries to read the sha1 from the current index */
static int get_current_sha1(const char *path, unsigned char *sha1)
{
        int pos;

        if (read_cache() < 0)
                return -1;
        pos = cache_name_pos(path, strlen(path));
        if (pos < 0)
                return -1;
        hashcpy(sha1, active_cache[pos]->sha1);
        return 0;
}

/* Build an index that contains the just the files needed for a 3way merge */
static void build_fake_ancestor(struct patch *list, const char *filename)
{
        struct patch *patch;
        struct index_state result = { 0 };
        int fd;

        /* Once we start supporting the reverse patch, it may be
         * worth showing the new sha1 prefix, but until then...
         */
        for (patch = list; patch; patch = patch->next) {
                const unsigned char *sha1_ptr;
                unsigned char sha1[20];
                struct cache_entry *ce;
                const char *name;

                name = patch->old_name ? patch->old_name : patch->new_name;
                if (0 < patch->is_new)
                        continue;
                else if (get_sha1(patch->old_sha1_prefix, sha1))
                        /* git diff has no index line for mode/type changes */
                        if (!patch->lines_added && !patch->lines_deleted) {
                                if (get_current_sha1(patch->new_name, sha1) ||
                                    get_current_sha1(patch->old_name, sha1))
                                        die("mode change for %s, which is not "
                                                "in current HEAD", name);
                                sha1_ptr = sha1;
                        } else
                                die("sha1 information is lacking or useless "
                                        "(%s).", name);
                else
                        sha1_ptr = sha1;

                ce = make_cache_entry(patch->old_mode, sha1_ptr, name, 0, 0);
                if (add_index_entry(&result, ce, ADD_CACHE_OK_TO_ADD))
                        die ("Could not add %s to temporary index", name);
        }

        fd = open(filename, O_WRONLY | O_CREAT, 0666);
        if (fd < 0 || write_index(&result, fd) || close(fd))
                die ("Could not write temporary index to %s", filename);

        discard_index(&result);
}

static void stat_patch_list(struct patch *patch)
{
        int files, adds, dels;

        for (files = adds = dels = 0 ; patch ; patch = patch->next) {
                files++;
                adds += patch->lines_added;
                dels += patch->lines_deleted;
                show_stats(patch);
        }

        printf(" %d files changed, %d insertions(+), %d deletions(-)\n", files, adds, dels);
}

static void numstat_patch_list(struct patch *patch)
{
        for ( ; patch; patch = patch->next) {
                const char *name;
                name = patch->new_name ? patch->new_name : patch->old_name;
                if (patch->is_binary)
                        printf("-\t-\t");
                else
                        printf("%d\t%d\t", patch->lines_added, patch->lines_deleted);
                write_name_quoted(name, stdout, line_termination);
        }
}

static void show_file_mode_name(const char *newdelete, unsigned int mode, const char *name)
{
        if (mode)
                printf(" %s mode %06o %s\n", newdelete, mode, name);
        else
                printf(" %s %s\n", newdelete, name);
}

static void show_mode_change(struct patch *p, int show_name)
{
        if (p->old_mode && p->new_mode && p->old_mode != p->new_mode) {
                if (show_name)
                        printf(" mode change %06o => %06o %s\n",
                               p->old_mode, p->new_mode, p->new_name);
                else
                        printf(" mode change %06o => %06o\n",
                               p->old_mode, p->new_mode);
        }
}

static void show_rename_copy(struct patch *p)
{
        const char *renamecopy = p->is_rename ? "rename" : "copy";
        const char *old, *new;

        /* Find common prefix */
        old = p->old_name;
        new = p->new_name;
        while (1) {
                const char *slash_old, *slash_new;
                slash_old = strchr(old, '/');
                slash_new = strchr(new, '/');
                if (!slash_old ||
                    !slash_new ||
                    slash_old - old != slash_new - new ||
                    memcmp(old, new, slash_new - new))
                        break;
                old = slash_old + 1;
                new = slash_new + 1;
        }
        /* p->old_name thru old is the common prefix, and old and new
         * through the end of names are renames
         */
        if (old != p->old_name)
                printf(" %s %.*s{%s => %s} (%d%%)\n", renamecopy,
                       (int)(old - p->old_name), p->old_name,
                       old, new, p->score);
        else
                printf(" %s %s => %s (%d%%)\n", renamecopy,
                       p->old_name, p->new_name, p->score);
        show_mode_change(p, 0);
}

static void summary_patch_list(struct patch *patch)
{
        struct patch *p;

        for (p = patch; p; p = p->next) {
                if (p->is_new)
                        show_file_mode_name("create", p->new_mode, p->new_name);
                else if (p->is_delete)
                        show_file_mode_name("delete", p->old_mode, p->old_name);
                else {
                        if (p->is_rename || p->is_copy)
                                show_rename_copy(p);
                        else {
                                if (p->score) {
                                        printf(" rewrite %s (%d%%)\n",
                                               p->new_name, p->score);
                                        show_mode_change(p, 0);
                                }
                                else
                                        show_mode_change(p, 1);
                        }
                }
        }
}

static void patch_stats(struct patch *patch)
{
        int lines = patch->lines_added + patch->lines_deleted;

        if (lines > max_change)
                max_change = lines;
        if (patch->old_name) {
                int len = quote_c_style(patch->old_name, NULL, NULL, 0);
                if (!len)
                        len = strlen(patch->old_name);
                if (len > max_len)
                        max_len = len;
        }
        if (patch->new_name) {
                int len = quote_c_style(patch->new_name, NULL, NULL, 0);
                if (!len)
                        len = strlen(patch->new_name);
                if (len > max_len)
                        max_len = len;
        }
}

static void remove_file(struct patch *patch, int rmdir_empty)
{
        if (update_index) {
                if (remove_file_from_cache(patch->old_name) < 0)
                        die("unable to remove %s from index", patch->old_name);
        }
        if (!cached) {
                if (S_ISGITLINK(patch->old_mode)) {
                        if (rmdir(patch->old_name))
                                warning("unable to remove submodule %s",
                                        patch->old_name);
                } else if (!unlink(patch->old_name) && rmdir_empty) {
                        char *name = xstrdup(patch->old_name);
                        char *end = strrchr(name, '/');
                        while (end) {
                                *end = 0;
                                if (rmdir(name))
                                        break;
                                end = strrchr(name, '/');
                        }
                        free(name);
                }
        }
}

static void add_index_file(const char *path, unsigned mode, void *buf, unsigned long size)
{
        struct stat st;
        struct cache_entry *ce;
        int namelen = strlen(path);
        unsigned ce_size = cache_entry_size(namelen);

        if (!update_index)
                return;

        ce = xcalloc(1, ce_size);
        memcpy(ce->name, path, namelen);
        ce->ce_mode = create_ce_mode(mode);
        ce->ce_flags = namelen;
        if (S_ISGITLINK(mode)) {
                const char *s = buf;

                if (get_sha1_hex(s + strlen("Subproject commit "), ce->sha1))
                        die("corrupt patch for subproject %s", path);
        } else {
                if (!cached) {
                        if (lstat(path, &st) < 0)
                                die("unable to stat newly created file %s",
                                    path);
                        fill_stat_cache_info(ce, &st);
                }
                if (write_sha1_file(buf, size, blob_type, ce->sha1) < 0)
                        die("unable to create backing store for newly created file %s", path);
        }
        if (add_cache_entry(ce, ADD_CACHE_OK_TO_ADD) < 0)
                die("unable to add cache entry for %s", path);
}

static int try_create_file(const char *path, unsigned int mode, const char *buf, unsigned long size)
{
        int fd;
        struct strbuf nbuf;

        if (S_ISGITLINK(mode)) {
                struct stat st;
                if (!lstat(path, &st) && S_ISDIR(st.st_mode))
                        return 0;
                return mkdir(path, 0777);
        }

        if (has_symlinks && S_ISLNK(mode))
                /* Although buf:size is counted string, it also is NUL
                 * terminated.
                 */
                return symlink(buf, path);

        fd = open(path, O_CREAT | O_EXCL | O_WRONLY, (mode & 0100) ? 0777 : 0666);
        if (fd < 0)
                return -1;

        strbuf_init(&nbuf, 0);
        if (convert_to_working_tree(path, buf, size, &nbuf)) {
                size = nbuf.len;
                buf  = nbuf.buf;
        }
        write_or_die(fd, buf, size);
        strbuf_release(&nbuf);

        if (close(fd) < 0)
                die("closing file %s: %s", path, strerror(errno));
        return 0;
}

/*
 * We optimistically assume that the directories exist,
 * which is true 99% of the time anyway. If they don't,
 * we create them and try again.
 */
static void create_one_file(char *path, unsigned mode, const char *buf, unsigned long size)
{
        if (cached)
                return;
        if (!try_create_file(path, mode, buf, size))
                return;

        if (errno == ENOENT) {
                if (safe_create_leading_directories(path))
                        return;
                if (!try_create_file(path, mode, buf, size))
                        return;
        }

        if (errno == EEXIST || errno == EACCES) {
                /* We may be trying to create a file where a directory
                 * used to be.
                 */
                struct stat st;
                if (!lstat(path, &st) && (!S_ISDIR(st.st_mode) || !rmdir(path)))
                        errno = EEXIST;
        }

        if (errno == EEXIST) {
                unsigned int nr = getpid();

                for (;;) {
                        const char *newpath;
                        newpath = mkpath("%s~%u", path, nr);
                        if (!try_create_file(newpath, mode, buf, size)) {
                                if (!rename(newpath, path))
                                        return;
                                unlink(newpath);
                                break;
                        }
                        if (errno != EEXIST)
                                break;
                        ++nr;
                }
        }
        die("unable to write file %s mode %o", path, mode);
}

static void create_file(struct patch *patch)
{
        char *path = patch->new_name;
        unsigned mode = patch->new_mode;
        unsigned long size = patch->resultsize;
        char *buf = patch->result;

        if (!mode)
                mode = S_IFREG | 0644;
        create_one_file(path, mode, buf, size);
        add_index_file(path, mode, buf, size);
}

/* phase zero is to remove, phase one is to create */
static void write_out_one_result(struct patch *patch, int phase)
{
        if (patch->is_delete > 0) {
                if (phase == 0)
                        remove_file(patch, 1);
                return;
        }
        if (patch->is_new > 0 || patch->is_copy) {
                if (phase == 1)
                        create_file(patch);
                return;
        }
        /*
         * Rename or modification boils down to the same
         * thing: remove the old, write the new
         */
        if (phase == 0)
                remove_file(patch, patch->is_rename);
        if (phase == 1)
                create_file(patch);
}

static int write_out_one_reject(struct patch *patch)
{
        FILE *rej;
        char namebuf[PATH_MAX];
        struct fragment *frag;
        int cnt = 0;

        for (cnt = 0, frag = patch->fragments; frag; frag = frag->next) {
                if (!frag->rejected)
                        continue;
                cnt++;
        }

        if (!cnt) {
                if (apply_verbosely)
                        say_patch_name(stderr,
                                       "Applied patch ", patch, " cleanly.\n");
                return 0;
        }

        /* This should not happen, because a removal patch that leaves
         * contents are marked "rejected" at the patch level.
         */
        if (!patch->new_name)
                die("internal error");

        /* Say this even without --verbose */
        say_patch_name(stderr, "Applying patch ", patch, " with");
        fprintf(stderr, " %d rejects...\n", cnt);

        cnt = strlen(patch->new_name);
        if (ARRAY_SIZE(namebuf) <= cnt + 5) {
                cnt = ARRAY_SIZE(namebuf) - 5;
                fprintf(stderr,
                        "warning: truncating .rej filename to %.*s.rej",
                        cnt - 1, patch->new_name);
        }
        memcpy(namebuf, patch->new_name, cnt);
        memcpy(namebuf + cnt, ".rej", 5);

        rej = fopen(namebuf, "w");
        if (!rej)
                return error("cannot open %s: %s", namebuf, strerror(errno));

        /* Normal git tools never deal with .rej, so do not pretend
         * this is a git patch by saying --git nor give extended
         * headers.  While at it, maybe please "kompare" that wants
         * the trailing TAB and some garbage at the end of line ;-).
         */
        fprintf(rej, "diff a/%s b/%s\t(rejected hunks)\n",
                patch->new_name, patch->new_name);
        for (cnt = 1, frag = patch->fragments;
             frag;
             cnt++, frag = frag->next) {
                if (!frag->rejected) {
                        fprintf(stderr, "Hunk #%d applied cleanly.\n", cnt);
                        continue;
                }
                fprintf(stderr, "Rejected hunk #%d.\n", cnt);
                fprintf(rej, "%.*s", frag->size, frag->patch);
                if (frag->patch[frag->size-1] != '\n')
                        fputc('\n', rej);
        }
        fclose(rej);
        return -1;
}

static int write_out_results(struct patch *list, int skipped_patch)
{
        int phase;
        int errs = 0;
        struct patch *l;

        if (!list && !skipped_patch)
                return error("No changes");

        for (phase = 0; phase < 2; phase++) {
                l = list;
                while (l) {
                        if (l->rejected)
                                errs = 1;
                        else {
                                write_out_one_result(l, phase);
                                if (phase == 1 && write_out_one_reject(l))
                                        errs = 1;
                        }
                        l = l->next;
                }
        }
        return errs;
}

static struct lock_file lock_file;

static struct excludes {
        struct excludes *next;
        const char *path;
} *excludes;

static int use_patch(struct patch *p)
{
        const char *pathname = p->new_name ? p->new_name : p->old_name;
        struct excludes *x = excludes;
        while (x) {
                if (fnmatch(x->path, pathname, 0) == 0)
                        return 0;
                x = x->next;
        }
        if (0 < prefix_length) {
                int pathlen = strlen(pathname);
                if (pathlen <= prefix_length ||
                    memcmp(prefix, pathname, prefix_length))
                        return 0;
        }
        return 1;
}

static void prefix_one(char **name)
{
        char *old_name = *name;
        if (!old_name)
                return;
        *name = xstrdup(prefix_filename(prefix, prefix_length, *name));
        free(old_name);
}

static void prefix_patches(struct patch *p)
{
        if (!prefix || p->is_toplevel_relative)
                return;
        for ( ; p; p = p->next) {
                if (p->new_name == p->old_name) {
                        char *prefixed = p->new_name;
                        prefix_one(&prefixed);
                        p->new_name = p->old_name = prefixed;
                }
                else {
                        prefix_one(&p->new_name);
                        prefix_one(&p->old_name);
                }
        }
}

static int apply_patch(int fd, const char *filename, int inaccurate_eof)
{
        size_t offset;
        struct strbuf buf;
        struct patch *list = NULL, **listp = &list;
        int skipped_patch = 0;

        strbuf_init(&buf, 0);
        patch_input_file = filename;
        read_patch_file(&buf, fd);
        offset = 0;
        while (offset < buf.len) {
                struct patch *patch;
                int nr;

                patch = xcalloc(1, sizeof(*patch));
                patch->inaccurate_eof = inaccurate_eof;
                nr = parse_chunk(buf.buf + offset, buf.len - offset, patch);
                if (nr < 0)
                        break;
                if (apply_in_reverse)
                        reverse_patches(patch);
                if (prefix)
                        prefix_patches(patch);
                if (use_patch(patch)) {
                        patch_stats(patch);
                        *listp = patch;
                        listp = &patch->next;
                }
                else {
                        /* perhaps free it a bit better? */
                        free(patch);
                        skipped_patch++;
                }
                offset += nr;
        }

        if (whitespace_error && (ws_error_action == die_on_ws_error))
                apply = 0;

        update_index = check_index && apply;
        if (update_index && newfd < 0)
                newfd = hold_locked_index(&lock_file, 1);

        if (check_index) {
                if (read_cache() < 0)
                        die("unable to read index file");
        }

        if ((check || apply) &&
            check_patch_list(list) < 0 &&
            !apply_with_reject)
                exit(1);

        if (apply && write_out_results(list, skipped_patch))
                exit(1);

        if (fake_ancestor)
                build_fake_ancestor(list, fake_ancestor);

        if (diffstat)
                stat_patch_list(list);

        if (numstat)
                numstat_patch_list(list);

        if (summary)
                summary_patch_list(list);

        strbuf_release(&buf);
        return 0;
}

static int git_apply_config(const char *var, const char *value)
{
        if (!strcmp(var, "apply.whitespace")) {
                if (!value)
                        return config_error_nonbool(var);
                apply_default_whitespace = xstrdup(value);
                return 0;
        }
        return git_default_config(var, value);
}


int cmd_apply(int argc, const char **argv, const char *unused_prefix)
{
        int i;
        int read_stdin = 1;
        int inaccurate_eof = 0;
        int errs = 0;
        int is_not_gitdir = 0;

        const char *whitespace_option = NULL;

        prefix = setup_git_directory_gently(&is_not_gitdir);
        prefix_length = prefix ? strlen(prefix) : 0;
        git_config(git_apply_config);
        if (apply_default_whitespace)
                parse_whitespace_option(apply_default_whitespace);

        for (i = 1; i < argc; i++) {
                const char *arg = argv[i];
                char *end;
                int fd;

                if (!strcmp(arg, "-")) {
                        errs |= apply_patch(0, "<stdin>", inaccurate_eof);
                        read_stdin = 0;
                        continue;
                }
                if (!prefixcmp(arg, "--exclude=")) {
                        struct excludes *x = xmalloc(sizeof(*x));
                        x->path = arg + 10;
                        x->next = excludes;
                        excludes = x;
                        continue;
                }
                if (!prefixcmp(arg, "-p")) {
                        p_value = atoi(arg + 2);
                        p_value_known = 1;
                        continue;
                }
                if (!strcmp(arg, "--no-add")) {
                        no_add = 1;
                        continue;
                }
                if (!strcmp(arg, "--stat")) {
                        apply = 0;
                        diffstat = 1;
                        continue;
                }
                if (!strcmp(arg, "--allow-binary-replacement") ||
                    !strcmp(arg, "--binary")) {
                        continue; /* now no-op */
                }
                if (!strcmp(arg, "--numstat")) {
                        apply = 0;
                        numstat = 1;
                        continue;
                }
                if (!strcmp(arg, "--summary")) {
                        apply = 0;
                        summary = 1;
                        continue;
                }
                if (!strcmp(arg, "--check")) {
                        apply = 0;
                        check = 1;
                        continue;
                }
                if (!strcmp(arg, "--index")) {
                        if (is_not_gitdir)
                                die("--index outside a repository");
                        check_index = 1;
                        continue;
                }
                if (!strcmp(arg, "--cached")) {
                        if (is_not_gitdir)
                                die("--cached outside a repository");
                        check_index = 1;
                        cached = 1;
                        continue;
                }
                if (!strcmp(arg, "--apply")) {
                        apply = 1;
                        continue;
                }
                if (!strcmp(arg, "--build-fake-ancestor")) {
                        apply = 0;
                        if (++i >= argc)
                                die ("need a filename");
                        fake_ancestor = argv[i];
                        continue;
                }
                if (!strcmp(arg, "-z")) {
                        line_termination = 0;
                        continue;
                }
                if (!prefixcmp(arg, "-C")) {
                        p_context = strtoul(arg + 2, &end, 0);
                        if (*end != '\0')
                                die("unrecognized context count '%s'", arg + 2);
                        continue;
                }
                if (!prefixcmp(arg, "--whitespace=")) {
                        whitespace_option = arg + 13;
                        parse_whitespace_option(arg + 13);
                        continue;
                }
                if (!strcmp(arg, "-R") || !strcmp(arg, "--reverse")) {
                        apply_in_reverse = 1;
                        continue;
                }
                if (!strcmp(arg, "--unidiff-zero")) {
                        unidiff_zero = 1;
                        continue;
                }
                if (!strcmp(arg, "--reject")) {
                        apply = apply_with_reject = apply_verbosely = 1;
                        continue;
                }
                if (!strcmp(arg, "-v") || !strcmp(arg, "--verbose")) {
                        apply_verbosely = 1;
                        continue;
                }
                if (!strcmp(arg, "--inaccurate-eof")) {
                        inaccurate_eof = 1;
                        continue;
                }
                if (0 < prefix_length)
                        arg = prefix_filename(prefix, prefix_length, arg);

                fd = open(arg, O_RDONLY);
                if (fd < 0)
                        usage(apply_usage);
                read_stdin = 0;
                set_default_whitespace_mode(whitespace_option);
                errs |= apply_patch(fd, arg, inaccurate_eof);
                close(fd);
        }
        set_default_whitespace_mode(whitespace_option);
        if (read_stdin)
                errs |= apply_patch(0, "<stdin>", inaccurate_eof);
        if (whitespace_error) {
                if (squelch_whitespace_errors &&
                    squelch_whitespace_errors < whitespace_error) {
                        int squelched =
                                whitespace_error - squelch_whitespace_errors;
                        fprintf(stderr, "warning: squelched %d "
                                "whitespace error%s\n",
                                squelched,
                                squelched == 1 ? "" : "s");
                }
                if (ws_error_action == die_on_ws_error)
                        die("%d line%s add%s whitespace errors.",
                            whitespace_error,
                            whitespace_error == 1 ? "" : "s",
                            whitespace_error == 1 ? "s" : "");
                if (applied_after_fixing_ws && apply)
                        fprintf(stderr, "warning: %d line%s applied after"
                                " fixing whitespace errors.\n",
                                applied_after_fixing_ws,
                                applied_after_fixing_ws == 1 ? "" : "s");
                else if (whitespace_error)
                        fprintf(stderr, "warning: %d line%s add%s whitespace errors.\n",
                                whitespace_error,
                                whitespace_error == 1 ? "" : "s",
                                whitespace_error == 1 ? "s" : "");
        }

        if (update_index) {
                if (write_cache(newfd, active_cache, active_nr) ||
                    commit_locked_index(&lock_file))
                        die("Unable to write new index file");
        }

        return !!errs;
}