Add support for an info version of the user manual

[git] / builtin-blame.c

/*
 * Pickaxe
 *
 * Copyright (c) 2006, Junio C Hamano
 */

#include "cache.h"
#include "builtin.h"
#include "blob.h"
#include "commit.h"
#include "tag.h"
#include "tree-walk.h"
#include "diff.h"
#include "diffcore.h"
#include "revision.h"
#include "quote.h"
#include "xdiff-interface.h"
#include "cache-tree.h"
#include "path-list.h"
#include "mailmap.h"

static char blame_usage[] =
"git-blame [-c] [-b] [-l] [--root] [-t] [-f] [-n] [-s] [-p] [-w] [-L n,m] [-S <revs-file>] [-M] [-C] [-C] [--contents <filename>] [--incremental] [commit] [--] file\n"
"  -c                  Use the same output mode as git-annotate (Default: off)\n"
"  -b                  Show blank SHA-1 for boundary commits (Default: off)\n"
"  -l                  Show long commit SHA1 (Default: off)\n"
"  --root              Do not treat root commits as boundaries (Default: off)\n"
"  -t                  Show raw timestamp (Default: off)\n"
"  -f, --show-name     Show original filename (Default: auto)\n"
"  -n, --show-number   Show original linenumber (Default: off)\n"
"  -s                  Suppress author name and timestamp (Default: off)\n"
"  -p, --porcelain     Show in a format designed for machine consumption\n"
"  -w                  Ignore whitespace differences\n"
"  -L n,m              Process only line range n,m, counting from 1\n"
"  -M, -C              Find line movements within and across files\n"
"  --incremental       Show blame entries as we find them, incrementally\n"
"  --contents file     Use <file>'s contents as the final image\n"
"  -S revs-file        Use revisions from revs-file instead of calling git-rev-list\n";

static int longest_file;
static int longest_author;
static int max_orig_digits;
static int max_digits;
static int max_score_digits;
static int show_root;
static int blank_boundary;
static int incremental;
static int cmd_is_annotate;
static int xdl_opts = XDF_NEED_MINIMAL;
static struct path_list mailmap;

#ifndef DEBUG
#define DEBUG 0
#endif

/* stats */
static int num_read_blob;
static int num_get_patch;
static int num_commits;

#define PICKAXE_BLAME_MOVE              01
#define PICKAXE_BLAME_COPY              02
#define PICKAXE_BLAME_COPY_HARDER       04
#define PICKAXE_BLAME_COPY_HARDEST      010

/*
 * blame for a blame_entry with score lower than these thresholds
 * is not passed to the parent using move/copy logic.
 */
static unsigned blame_move_score;
static unsigned blame_copy_score;
#define BLAME_DEFAULT_MOVE_SCORE        20
#define BLAME_DEFAULT_COPY_SCORE        40

/* bits #0..7 in revision.h, #8..11 used for merge_bases() in commit.c */
#define METAINFO_SHOWN          (1u<<12)
#define MORE_THAN_ONE_PATH      (1u<<13)

/*
 * One blob in a commit that is being suspected
 */
struct origin {
        int refcnt;
        struct commit *commit;
        mmfile_t file;
        unsigned char blob_sha1[20];
        char path[FLEX_ARRAY];
};

/*
 * Given an origin, prepare mmfile_t structure to be used by the
 * diff machinery
 */
static char *fill_origin_blob(struct origin *o, mmfile_t *file)
{
        if (!o->file.ptr) {
                enum object_type type;
                num_read_blob++;
                file->ptr = read_sha1_file(o->blob_sha1, &type,
                                           (unsigned long *)(&(file->size)));
                o->file = *file;
        }
        else
                *file = o->file;
        return file->ptr;
}

/*
 * Origin is refcounted and usually we keep the blob contents to be
 * reused.
 */
static inline struct origin *origin_incref(struct origin *o)
{
        if (o)
                o->refcnt++;
        return o;
}

static void origin_decref(struct origin *o)
{
        if (o && --o->refcnt <= 0) {
                if (o->file.ptr)
                        free(o->file.ptr);
                memset(o, 0, sizeof(*o));
                free(o);
        }
}

/*
 * Each group of lines is described by a blame_entry; it can be split
 * as we pass blame to the parents.  They form a linked list in the
 * scoreboard structure, sorted by the target line number.
 */
struct blame_entry {
        struct blame_entry *prev;
        struct blame_entry *next;

        /* the first line of this group in the final image;
         * internally all line numbers are 0 based.
         */
        int lno;

        /* how many lines this group has */
        int num_lines;

        /* the commit that introduced this group into the final image */
        struct origin *suspect;

        /* true if the suspect is truly guilty; false while we have not
         * checked if the group came from one of its parents.
         */
        char guilty;

        /* the line number of the first line of this group in the
         * suspect's file; internally all line numbers are 0 based.
         */
        int s_lno;

        /* how significant this entry is -- cached to avoid
         * scanning the lines over and over.
         */
        unsigned score;
};

/*
 * The current state of the blame assignment.
 */
struct scoreboard {
        /* the final commit (i.e. where we started digging from) */
        struct commit *final;

        const char *path;

        /*
         * The contents in the final image.
         * Used by many functions to obtain contents of the nth line,
         * indexed with scoreboard.lineno[blame_entry.lno].
         */
        const char *final_buf;
        unsigned long final_buf_size;

        /* linked list of blames */
        struct blame_entry *ent;

        /* look-up a line in the final buffer */
        int num_lines;
        int *lineno;
};

static inline int same_suspect(struct origin *a, struct origin *b)
{
        if (a == b)
                return 1;
        if (a->commit != b->commit)
                return 0;
        return !strcmp(a->path, b->path);
}

static void sanity_check_refcnt(struct scoreboard *);

/*
 * If two blame entries that are next to each other came from
 * contiguous lines in the same origin (i.e. <commit, path> pair),
 * merge them together.
 */
static void coalesce(struct scoreboard *sb)
{
        struct blame_entry *ent, *next;

        for (ent = sb->ent; ent && (next = ent->next); ent = next) {
                if (same_suspect(ent->suspect, next->suspect) &&
                    ent->guilty == next->guilty &&
                    ent->s_lno + ent->num_lines == next->s_lno) {
                        ent->num_lines += next->num_lines;
                        ent->next = next->next;
                        if (ent->next)
                                ent->next->prev = ent;
                        origin_decref(next->suspect);
                        free(next);
                        ent->score = 0;
                        next = ent; /* again */
                }
        }

        if (DEBUG) /* sanity */
                sanity_check_refcnt(sb);
}

/*
 * Given a commit and a path in it, create a new origin structure.
 * The callers that add blame to the scoreboard should use
 * get_origin() to obtain shared, refcounted copy instead of calling
 * this function directly.
 */
static struct origin *make_origin(struct commit *commit, const char *path)
{
        struct origin *o;
        o = xcalloc(1, sizeof(*o) + strlen(path) + 1);
        o->commit = commit;
        o->refcnt = 1;
        strcpy(o->path, path);
        return o;
}

/*
 * Locate an existing origin or create a new one.
 */
static struct origin *get_origin(struct scoreboard *sb,
                                 struct commit *commit,
                                 const char *path)
{
        struct blame_entry *e;

        for (e = sb->ent; e; e = e->next) {
                if (e->suspect->commit == commit &&
                    !strcmp(e->suspect->path, path))
                        return origin_incref(e->suspect);
        }
        return make_origin(commit, path);
}

/*
 * Fill the blob_sha1 field of an origin if it hasn't, so that later
 * call to fill_origin_blob() can use it to locate the data.  blob_sha1
 * for an origin is also used to pass the blame for the entire file to
 * the parent to detect the case where a child's blob is identical to
 * that of its parent's.
 */
static int fill_blob_sha1(struct origin *origin)
{
        unsigned mode;

        if (!is_null_sha1(origin->blob_sha1))
                return 0;
        if (get_tree_entry(origin->commit->object.sha1,
                           origin->path,
                           origin->blob_sha1, &mode))
                goto error_out;
        if (sha1_object_info(origin->blob_sha1, NULL) != OBJ_BLOB)
                goto error_out;
        return 0;
 error_out:
        hashclr(origin->blob_sha1);
        return -1;
}

/*
 * We have an origin -- check if the same path exists in the
 * parent and return an origin structure to represent it.
 */
static struct origin *find_origin(struct scoreboard *sb,
                                  struct commit *parent,
                                  struct origin *origin)
{
        struct origin *porigin = NULL;
        struct diff_options diff_opts;
        const char *paths[2];

        if (parent->util) {
                /*
                 * Each commit object can cache one origin in that
                 * commit.  This is a freestanding copy of origin and
                 * not refcounted.
                 */
                struct origin *cached = parent->util;
                if (!strcmp(cached->path, origin->path)) {
                        /*
                         * The same path between origin and its parent
                         * without renaming -- the most common case.
                         */
                        porigin = get_origin(sb, parent, cached->path);

                        /*
                         * If the origin was newly created (i.e. get_origin
                         * would call make_origin if none is found in the
                         * scoreboard), it does not know the blob_sha1,
                         * so copy it.  Otherwise porigin was in the
                         * scoreboard and already knows blob_sha1.
                         */
                        if (porigin->refcnt == 1)
                                hashcpy(porigin->blob_sha1, cached->blob_sha1);
                        return porigin;
                }
                /* otherwise it was not very useful; free it */
                free(parent->util);
                parent->util = NULL;
        }

        /* See if the origin->path is different between parent
         * and origin first.  Most of the time they are the
         * same and diff-tree is fairly efficient about this.
         */
        diff_setup(&diff_opts);
        diff_opts.recursive = 1;
        diff_opts.detect_rename = 0;
        diff_opts.output_format = DIFF_FORMAT_NO_OUTPUT;
        paths[0] = origin->path;
        paths[1] = NULL;

        diff_tree_setup_paths(paths, &diff_opts);
        if (diff_setup_done(&diff_opts) < 0)
                die("diff-setup");

        if (is_null_sha1(origin->commit->object.sha1))
                do_diff_cache(parent->tree->object.sha1, &diff_opts);
        else
                diff_tree_sha1(parent->tree->object.sha1,
                               origin->commit->tree->object.sha1,
                               "", &diff_opts);
        diffcore_std(&diff_opts);

        /* It is either one entry that says "modified", or "created",
         * or nothing.
         */
        if (!diff_queued_diff.nr) {
                /* The path is the same as parent */
                porigin = get_origin(sb, parent, origin->path);
                hashcpy(porigin->blob_sha1, origin->blob_sha1);
        }
        else if (diff_queued_diff.nr != 1)
                die("internal error in blame::find_origin");
        else {
                struct diff_filepair *p = diff_queued_diff.queue[0];
                switch (p->status) {
                default:
                        die("internal error in blame::find_origin (%c)",
                            p->status);
                case 'M':
                        porigin = get_origin(sb, parent, origin->path);
                        hashcpy(porigin->blob_sha1, p->one->sha1);
                        break;
                case 'A':
                case 'T':
                        /* Did not exist in parent, or type changed */
                        break;
                }
        }
        diff_flush(&diff_opts);
        if (porigin) {
                /*
                 * Create a freestanding copy that is not part of
                 * the refcounted origin found in the scoreboard, and
                 * cache it in the commit.
                 */
                struct origin *cached;

                cached = make_origin(porigin->commit, porigin->path);
                hashcpy(cached->blob_sha1, porigin->blob_sha1);
                parent->util = cached;
        }
        return porigin;
}

/*
 * We have an origin -- find the path that corresponds to it in its
 * parent and return an origin structure to represent it.
 */
static struct origin *find_rename(struct scoreboard *sb,
                                  struct commit *parent,
                                  struct origin *origin)
{
        struct origin *porigin = NULL;
        struct diff_options diff_opts;
        int i;
        const char *paths[2];

        diff_setup(&diff_opts);
        diff_opts.recursive = 1;
        diff_opts.detect_rename = DIFF_DETECT_RENAME;
        diff_opts.output_format = DIFF_FORMAT_NO_OUTPUT;
        diff_opts.single_follow = origin->path;
        paths[0] = NULL;
        diff_tree_setup_paths(paths, &diff_opts);
        if (diff_setup_done(&diff_opts) < 0)
                die("diff-setup");

        if (is_null_sha1(origin->commit->object.sha1))
                do_diff_cache(parent->tree->object.sha1, &diff_opts);
        else
                diff_tree_sha1(parent->tree->object.sha1,
                               origin->commit->tree->object.sha1,
                               "", &diff_opts);
        diffcore_std(&diff_opts);

        for (i = 0; i < diff_queued_diff.nr; i++) {
                struct diff_filepair *p = diff_queued_diff.queue[i];
                if ((p->status == 'R' || p->status == 'C') &&
                    !strcmp(p->two->path, origin->path)) {
                        porigin = get_origin(sb, parent, p->one->path);
                        hashcpy(porigin->blob_sha1, p->one->sha1);
                        break;
                }
        }
        diff_flush(&diff_opts);
        return porigin;
}

/*
 * Parsing of patch chunks...
 */
struct chunk {
        /* line number in postimage; up to but not including this
         * line is the same as preimage
         */
        int same;

        /* preimage line number after this chunk */
        int p_next;

        /* postimage line number after this chunk */
        int t_next;
};

struct patch {
        struct chunk *chunks;
        int num;
};

struct blame_diff_state {
        struct xdiff_emit_state xm;
        struct patch *ret;
        unsigned hunk_post_context;
        unsigned hunk_in_pre_context : 1;
};

static void process_u_diff(void *state_, char *line, unsigned long len)
{
        struct blame_diff_state *state = state_;
        struct chunk *chunk;
        int off1, off2, len1, len2, num;

        num = state->ret->num;
        if (len < 4 || line[0] != '@' || line[1] != '@') {
                if (state->hunk_in_pre_context && line[0] == ' ')
                        state->ret->chunks[num - 1].same++;
                else {
                        state->hunk_in_pre_context = 0;
                        if (line[0] == ' ')
                                state->hunk_post_context++;
                        else
                                state->hunk_post_context = 0;
                }
                return;
        }

        if (num && state->hunk_post_context) {
                chunk = &state->ret->chunks[num - 1];
                chunk->p_next -= state->hunk_post_context;
                chunk->t_next -= state->hunk_post_context;
        }
        state->ret->num = ++num;
        state->ret->chunks = xrealloc(state->ret->chunks,
                                      sizeof(struct chunk) * num);
        chunk = &state->ret->chunks[num - 1];
        if (parse_hunk_header(line, len, &off1, &len1, &off2, &len2)) {
                state->ret->num--;
                return;
        }

        /* Line numbers in patch output are one based. */
        off1--;
        off2--;

        chunk->same = len2 ? off2 : (off2 + 1);

        chunk->p_next = off1 + (len1 ? len1 : 1);
        chunk->t_next = chunk->same + len2;
        state->hunk_in_pre_context = 1;
        state->hunk_post_context = 0;
}

static struct patch *compare_buffer(mmfile_t *file_p, mmfile_t *file_o,
                                    int context)
{
        struct blame_diff_state state;
        xpparam_t xpp;
        xdemitconf_t xecfg;
        xdemitcb_t ecb;

        xpp.flags = xdl_opts;
        memset(&xecfg, 0, sizeof(xecfg));
        xecfg.ctxlen = context;
        ecb.outf = xdiff_outf;
        ecb.priv = &state;
        memset(&state, 0, sizeof(state));
        state.xm.consume = process_u_diff;
        state.ret = xmalloc(sizeof(struct patch));
        state.ret->chunks = NULL;
        state.ret->num = 0;

        xdl_diff(file_p, file_o, &xpp, &xecfg, &ecb);

        if (state.ret->num) {
                struct chunk *chunk;
                chunk = &state.ret->chunks[state.ret->num - 1];
                chunk->p_next -= state.hunk_post_context;
                chunk->t_next -= state.hunk_post_context;
        }
        return state.ret;
}

/*
 * Run diff between two origins and grab the patch output, so that
 * we can pass blame for lines origin is currently suspected for
 * to its parent.
 */
static struct patch *get_patch(struct origin *parent, struct origin *origin)
{
        mmfile_t file_p, file_o;
        struct patch *patch;

        fill_origin_blob(parent, &file_p);
        fill_origin_blob(origin, &file_o);
        if (!file_p.ptr || !file_o.ptr)
                return NULL;
        patch = compare_buffer(&file_p, &file_o, 0);
        num_get_patch++;
        return patch;
}

static void free_patch(struct patch *p)
{
        free(p->chunks);
        free(p);
}

/*
 * Link in a new blame entry to the scoreboard.  Entries that cover the
 * same line range have been removed from the scoreboard previously.
 */
static void add_blame_entry(struct scoreboard *sb, struct blame_entry *e)
{
        struct blame_entry *ent, *prev = NULL;

        origin_incref(e->suspect);

        for (ent = sb->ent; ent && ent->lno < e->lno; ent = ent->next)
                prev = ent;

        /* prev, if not NULL, is the last one that is below e */
        e->prev = prev;
        if (prev) {
                e->next = prev->next;
                prev->next = e;
        }
        else {
                e->next = sb->ent;
                sb->ent = e;
        }
        if (e->next)
                e->next->prev = e;
}

/*
 * src typically is on-stack; we want to copy the information in it to
 * an malloced blame_entry that is already on the linked list of the
 * scoreboard.  The origin of dst loses a refcnt while the origin of src
 * gains one.
 */
static void dup_entry(struct blame_entry *dst, struct blame_entry *src)
{
        struct blame_entry *p, *n;

        p = dst->prev;
        n = dst->next;
        origin_incref(src->suspect);
        origin_decref(dst->suspect);
        memcpy(dst, src, sizeof(*src));
        dst->prev = p;
        dst->next = n;
        dst->score = 0;
}

static const char *nth_line(struct scoreboard *sb, int lno)
{
        return sb->final_buf + sb->lineno[lno];
}

/*
 * It is known that lines between tlno to same came from parent, and e
 * has an overlap with that range.  it also is known that parent's
 * line plno corresponds to e's line tlno.
 *
 *                <---- e ----->
 *                   <------>
 *                   <------------>
 *             <------------>
 *             <------------------>
 *
 * Split e into potentially three parts; before this chunk, the chunk
 * to be blamed for the parent, and after that portion.
 */
static void split_overlap(struct blame_entry *split,
                          struct blame_entry *e,
                          int tlno, int plno, int same,
                          struct origin *parent)
{
        int chunk_end_lno;
        memset(split, 0, sizeof(struct blame_entry [3]));

        if (e->s_lno < tlno) {
                /* there is a pre-chunk part not blamed on parent */
                split[0].suspect = origin_incref(e->suspect);
                split[0].lno = e->lno;
                split[0].s_lno = e->s_lno;
                split[0].num_lines = tlno - e->s_lno;
                split[1].lno = e->lno + tlno - e->s_lno;
                split[1].s_lno = plno;
        }
        else {
                split[1].lno = e->lno;
                split[1].s_lno = plno + (e->s_lno - tlno);
        }

        if (same < e->s_lno + e->num_lines) {
                /* there is a post-chunk part not blamed on parent */
                split[2].suspect = origin_incref(e->suspect);
                split[2].lno = e->lno + (same - e->s_lno);
                split[2].s_lno = e->s_lno + (same - e->s_lno);
                split[2].num_lines = e->s_lno + e->num_lines - same;
                chunk_end_lno = split[2].lno;
        }
        else
                chunk_end_lno = e->lno + e->num_lines;
        split[1].num_lines = chunk_end_lno - split[1].lno;

        /*
         * if it turns out there is nothing to blame the parent for,
         * forget about the splitting.  !split[1].suspect signals this.
         */
        if (split[1].num_lines < 1)
                return;
        split[1].suspect = origin_incref(parent);
}

/*
 * split_overlap() divided an existing blame e into up to three parts
 * in split.  Adjust the linked list of blames in the scoreboard to
 * reflect the split.
 */
static void split_blame(struct scoreboard *sb,
                        struct blame_entry *split,
                        struct blame_entry *e)
{
        struct blame_entry *new_entry;

        if (split[0].suspect && split[2].suspect) {
                /* The first part (reuse storage for the existing entry e) */
                dup_entry(e, &split[0]);

                /* The last part -- me */
                new_entry = xmalloc(sizeof(*new_entry));
                memcpy(new_entry, &(split[2]), sizeof(struct blame_entry));
                add_blame_entry(sb, new_entry);

                /* ... and the middle part -- parent */
                new_entry = xmalloc(sizeof(*new_entry));
                memcpy(new_entry, &(split[1]), sizeof(struct blame_entry));
                add_blame_entry(sb, new_entry);
        }
        else if (!split[0].suspect && !split[2].suspect)
                /*
                 * The parent covers the entire area; reuse storage for
                 * e and replace it with the parent.
                 */
                dup_entry(e, &split[1]);
        else if (split[0].suspect) {
                /* me and then parent */
                dup_entry(e, &split[0]);

                new_entry = xmalloc(sizeof(*new_entry));
                memcpy(new_entry, &(split[1]), sizeof(struct blame_entry));
                add_blame_entry(sb, new_entry);
        }
        else {
                /* parent and then me */
                dup_entry(e, &split[1]);

                new_entry = xmalloc(sizeof(*new_entry));
                memcpy(new_entry, &(split[2]), sizeof(struct blame_entry));
                add_blame_entry(sb, new_entry);
        }

        if (DEBUG) { /* sanity */
                struct blame_entry *ent;
                int lno = sb->ent->lno, corrupt = 0;

                for (ent = sb->ent; ent; ent = ent->next) {
                        if (lno != ent->lno)
                                corrupt = 1;
                        if (ent->s_lno < 0)
                                corrupt = 1;
                        lno += ent->num_lines;
                }
                if (corrupt) {
                        lno = sb->ent->lno;
                        for (ent = sb->ent; ent; ent = ent->next) {
                                printf("L %8d l %8d n %8d\n",
                                       lno, ent->lno, ent->num_lines);
                                lno = ent->lno + ent->num_lines;
                        }
                        die("oops");
                }
        }
}

/*
 * After splitting the blame, the origins used by the
 * on-stack blame_entry should lose one refcnt each.
 */
static void decref_split(struct blame_entry *split)
{
        int i;

        for (i = 0; i < 3; i++)
                origin_decref(split[i].suspect);
}

/*
 * Helper for blame_chunk().  blame_entry e is known to overlap with
 * the patch hunk; split it and pass blame to the parent.
 */
static void blame_overlap(struct scoreboard *sb, struct blame_entry *e,
                          int tlno, int plno, int same,
                          struct origin *parent)
{
        struct blame_entry split[3];

        split_overlap(split, e, tlno, plno, same, parent);
        if (split[1].suspect)
                split_blame(sb, split, e);
        decref_split(split);
}

/*
 * Find the line number of the last line the target is suspected for.
 */
static int find_last_in_target(struct scoreboard *sb, struct origin *target)
{
        struct blame_entry *e;
        int last_in_target = -1;

        for (e = sb->ent; e; e = e->next) {
                if (e->guilty || !same_suspect(e->suspect, target))
                        continue;
                if (last_in_target < e->s_lno + e->num_lines)
                        last_in_target = e->s_lno + e->num_lines;
        }
        return last_in_target;
}

/*
 * Process one hunk from the patch between the current suspect for
 * blame_entry e and its parent.  Find and split the overlap, and
 * pass blame to the overlapping part to the parent.
 */
static void blame_chunk(struct scoreboard *sb,
                        int tlno, int plno, int same,
                        struct origin *target, struct origin *parent)
{
        struct blame_entry *e;

        for (e = sb->ent; e; e = e->next) {
                if (e->guilty || !same_suspect(e->suspect, target))
                        continue;
                if (same <= e->s_lno)
                        continue;
                if (tlno < e->s_lno + e->num_lines)
                        blame_overlap(sb, e, tlno, plno, same, parent);
        }
}

/*
 * We are looking at the origin 'target' and aiming to pass blame
 * for the lines it is suspected to its parent.  Run diff to find
 * which lines came from parent and pass blame for them.
 */
static int pass_blame_to_parent(struct scoreboard *sb,
                                struct origin *target,
                                struct origin *parent)
{
        int i, last_in_target, plno, tlno;
        struct patch *patch;

        last_in_target = find_last_in_target(sb, target);
        if (last_in_target < 0)
                return 1; /* nothing remains for this target */

        patch = get_patch(parent, target);
        plno = tlno = 0;
        for (i = 0; i < patch->num; i++) {
                struct chunk *chunk = &patch->chunks[i];

                blame_chunk(sb, tlno, plno, chunk->same, target, parent);
                plno = chunk->p_next;
                tlno = chunk->t_next;
        }
        /* The rest (i.e. anything after tlno) are the same as the parent */
        blame_chunk(sb, tlno, plno, last_in_target, target, parent);

        free_patch(patch);
        return 0;
}

/*
 * The lines in blame_entry after splitting blames many times can become
 * very small and trivial, and at some point it becomes pointless to
 * blame the parents.  E.g. "\t\t}\n\t}\n\n" appears everywhere in any
 * ordinary C program, and it is not worth to say it was copied from
 * totally unrelated file in the parent.
 *
 * Compute how trivial the lines in the blame_entry are.
 */
static unsigned ent_score(struct scoreboard *sb, struct blame_entry *e)
{
        unsigned score;
        const char *cp, *ep;

        if (e->score)
                return e->score;

        score = 1;
        cp = nth_line(sb, e->lno);
        ep = nth_line(sb, e->lno + e->num_lines);
        while (cp < ep) {
                unsigned ch = *((unsigned char *)cp);
                if (isalnum(ch))
                        score++;
                cp++;
        }
        e->score = score;
        return score;
}

/*
 * best_so_far[] and this[] are both a split of an existing blame_entry
 * that passes blame to the parent.  Maintain best_so_far the best split
 * so far, by comparing this and best_so_far and copying this into
 * bst_so_far as needed.
 */
static void copy_split_if_better(struct scoreboard *sb,
                                 struct blame_entry *best_so_far,
                                 struct blame_entry *this)
{
        int i;

        if (!this[1].suspect)
                return;
        if (best_so_far[1].suspect) {
                if (ent_score(sb, &this[1]) < ent_score(sb, &best_so_far[1]))
                        return;
        }

        for (i = 0; i < 3; i++)
                origin_incref(this[i].suspect);
        decref_split(best_so_far);
        memcpy(best_so_far, this, sizeof(struct blame_entry [3]));
}

/*
 * We are looking at a part of the final image represented by
 * ent (tlno and same are offset by ent->s_lno).
 * tlno is where we are looking at in the final image.
 * up to (but not including) same match preimage.
 * plno is where we are looking at in the preimage.
 *
 * <-------------- final image ---------------------->
 *       <------ent------>
 *         ^tlno ^same
 *    <---------preimage----->
 *         ^plno
 *
 * All line numbers are 0-based.
 */
static void handle_split(struct scoreboard *sb,
                         struct blame_entry *ent,
                         int tlno, int plno, int same,
                         struct origin *parent,
                         struct blame_entry *split)
{
        if (ent->num_lines <= tlno)
                return;
        if (tlno < same) {
                struct blame_entry this[3];
                tlno += ent->s_lno;
                same += ent->s_lno;
                split_overlap(this, ent, tlno, plno, same, parent);
                copy_split_if_better(sb, split, this);
                decref_split(this);
        }
}

/*
 * Find the lines from parent that are the same as ent so that
 * we can pass blames to it.  file_p has the blob contents for
 * the parent.
 */
static void find_copy_in_blob(struct scoreboard *sb,
                              struct blame_entry *ent,
                              struct origin *parent,
                              struct blame_entry *split,
                              mmfile_t *file_p)
{
        const char *cp;
        int cnt;
        mmfile_t file_o;
        struct patch *patch;
        int i, plno, tlno;

        /*
         * Prepare mmfile that contains only the lines in ent.
         */
        cp = nth_line(sb, ent->lno);
        file_o.ptr = (char*) cp;
        cnt = ent->num_lines;

        while (cnt && cp < sb->final_buf + sb->final_buf_size) {
                if (*cp++ == '\n')
                        cnt--;
        }
        file_o.size = cp - file_o.ptr;

        patch = compare_buffer(file_p, &file_o, 1);

        /*
         * file_o is a part of final image we are annotating.
         * file_p partially may match that image.
         */
        memset(split, 0, sizeof(struct blame_entry [3]));
        plno = tlno = 0;
        for (i = 0; i < patch->num; i++) {
                struct chunk *chunk = &patch->chunks[i];

                handle_split(sb, ent, tlno, plno, chunk->same, parent, split);
                plno = chunk->p_next;
                tlno = chunk->t_next;
        }
        /* remainder, if any, all match the preimage */
        handle_split(sb, ent, tlno, plno, ent->num_lines, parent, split);
        free_patch(patch);
}

/*
 * See if lines currently target is suspected for can be attributed to
 * parent.
 */
static int find_move_in_parent(struct scoreboard *sb,
                               struct origin *target,
                               struct origin *parent)
{
        int last_in_target, made_progress;
        struct blame_entry *e, split[3];
        mmfile_t file_p;

        last_in_target = find_last_in_target(sb, target);
        if (last_in_target < 0)
                return 1; /* nothing remains for this target */

        fill_origin_blob(parent, &file_p);
        if (!file_p.ptr)
                return 0;

        made_progress = 1;
        while (made_progress) {
                made_progress = 0;
                for (e = sb->ent; e; e = e->next) {
                        if (e->guilty || !same_suspect(e->suspect, target))
                                continue;
                        find_copy_in_blob(sb, e, parent, split, &file_p);
                        if (split[1].suspect &&
                            blame_move_score < ent_score(sb, &split[1])) {
                                split_blame(sb, split, e);
                                made_progress = 1;
                        }
                        decref_split(split);
                }
        }
        return 0;
}

struct blame_list {
        struct blame_entry *ent;
        struct blame_entry split[3];
};

/*
 * Count the number of entries the target is suspected for,
 * and prepare a list of entry and the best split.
 */
static struct blame_list *setup_blame_list(struct scoreboard *sb,
                                           struct origin *target,
                                           int *num_ents_p)
{
        struct blame_entry *e;
        int num_ents, i;
        struct blame_list *blame_list = NULL;

        for (e = sb->ent, num_ents = 0; e; e = e->next)
                if (!e->guilty && same_suspect(e->suspect, target))
                        num_ents++;
        if (num_ents) {
                blame_list = xcalloc(num_ents, sizeof(struct blame_list));
                for (e = sb->ent, i = 0; e; e = e->next)
                        if (!e->guilty && same_suspect(e->suspect, target))
                                blame_list[i++].ent = e;
        }
        *num_ents_p = num_ents;
        return blame_list;
}

/*
 * For lines target is suspected for, see if we can find code movement
 * across file boundary from the parent commit.  porigin is the path
 * in the parent we already tried.
 */
static int find_copy_in_parent(struct scoreboard *sb,
                               struct origin *target,
                               struct commit *parent,
                               struct origin *porigin,
                               int opt)
{
        struct diff_options diff_opts;
        const char *paths[1];
        int i, j;
        int retval;
        struct blame_list *blame_list;
        int num_ents;

        blame_list = setup_blame_list(sb, target, &num_ents);
        if (!blame_list)
                return 1; /* nothing remains for this target */

        diff_setup(&diff_opts);
        diff_opts.recursive = 1;
        diff_opts.output_format = DIFF_FORMAT_NO_OUTPUT;

        paths[0] = NULL;
        diff_tree_setup_paths(paths, &diff_opts);
        if (diff_setup_done(&diff_opts) < 0)
                die("diff-setup");

        /* Try "find copies harder" on new path if requested;
         * we do not want to use diffcore_rename() actually to
         * match things up; find_copies_harder is set only to
         * force diff_tree_sha1() to feed all filepairs to diff_queue,
         * and this code needs to be after diff_setup_done(), which
         * usually makes find-copies-harder imply copy detection.
         */
        if ((opt & PICKAXE_BLAME_COPY_HARDEST)
            || ((opt & PICKAXE_BLAME_COPY_HARDER)
                && (!porigin || strcmp(target->path, porigin->path))))
                diff_opts.find_copies_harder = 1;

        if (is_null_sha1(target->commit->object.sha1))
                do_diff_cache(parent->tree->object.sha1, &diff_opts);
        else
                diff_tree_sha1(parent->tree->object.sha1,
                               target->commit->tree->object.sha1,
                               "", &diff_opts);

        if (!diff_opts.find_copies_harder)
                diffcore_std(&diff_opts);

        retval = 0;
        while (1) {
                int made_progress = 0;

                for (i = 0; i < diff_queued_diff.nr; i++) {
                        struct diff_filepair *p = diff_queued_diff.queue[i];
                        struct origin *norigin;
                        mmfile_t file_p;
                        struct blame_entry this[3];

                        if (!DIFF_FILE_VALID(p->one))
                                continue; /* does not exist in parent */
                        if (porigin && !strcmp(p->one->path, porigin->path))
                                /* find_move already dealt with this path */
                                continue;

                        norigin = get_origin(sb, parent, p->one->path);
                        hashcpy(norigin->blob_sha1, p->one->sha1);
                        fill_origin_blob(norigin, &file_p);
                        if (!file_p.ptr)
                                continue;

                        for (j = 0; j < num_ents; j++) {
                                find_copy_in_blob(sb, blame_list[j].ent,
                                                  norigin, this, &file_p);
                                copy_split_if_better(sb, blame_list[j].split,
                                                     this);
                                decref_split(this);
                        }
                        origin_decref(norigin);
                }

                for (j = 0; j < num_ents; j++) {
                        struct blame_entry *split = blame_list[j].split;
                        if (split[1].suspect &&
                            blame_copy_score < ent_score(sb, &split[1])) {
                                split_blame(sb, split, blame_list[j].ent);
                                made_progress = 1;
                        }
                        decref_split(split);
                }
                free(blame_list);

                if (!made_progress)
                        break;
                blame_list = setup_blame_list(sb, target, &num_ents);
                if (!blame_list) {
                        retval = 1;
                        break;
                }
        }
        diff_flush(&diff_opts);

        return retval;
}

/*
 * The blobs of origin and porigin exactly match, so everything
 * origin is suspected for can be blamed on the parent.
 */
static void pass_whole_blame(struct scoreboard *sb,
                             struct origin *origin, struct origin *porigin)
{
        struct blame_entry *e;

        if (!porigin->file.ptr && origin->file.ptr) {
                /* Steal its file */
                porigin->file = origin->file;
                origin->file.ptr = NULL;
        }
        for (e = sb->ent; e; e = e->next) {
                if (!same_suspect(e->suspect, origin))
                        continue;
                origin_incref(porigin);
                origin_decref(e->suspect);
                e->suspect = porigin;
        }
}

#define MAXPARENT 16

static void pass_blame(struct scoreboard *sb, struct origin *origin, int opt)
{
        int i, pass;
        struct commit *commit = origin->commit;
        struct commit_list *parent;
        struct origin *parent_origin[MAXPARENT], *porigin;

        memset(parent_origin, 0, sizeof(parent_origin));

        /* The first pass looks for unrenamed path to optimize for
         * common cases, then we look for renames in the second pass.
         */
        for (pass = 0; pass < 2; pass++) {
                struct origin *(*find)(struct scoreboard *,
                                       struct commit *, struct origin *);
                find = pass ? find_rename : find_origin;

                for (i = 0, parent = commit->parents;
                     i < MAXPARENT && parent;
                     parent = parent->next, i++) {
                        struct commit *p = parent->item;
                        int j, same;

                        if (parent_origin[i])
                                continue;
                        if (parse_commit(p))
                                continue;
                        porigin = find(sb, p, origin);
                        if (!porigin)
                                continue;
                        if (!hashcmp(porigin->blob_sha1, origin->blob_sha1)) {
                                pass_whole_blame(sb, origin, porigin);
                                origin_decref(porigin);
                                goto finish;
                        }
                        for (j = same = 0; j < i; j++)
                                if (parent_origin[j] &&
                                    !hashcmp(parent_origin[j]->blob_sha1,
                                             porigin->blob_sha1)) {
                                        same = 1;
                                        break;
                                }
                        if (!same)
                                parent_origin[i] = porigin;
                        else
                                origin_decref(porigin);
                }
        }

        num_commits++;
        for (i = 0, parent = commit->parents;
             i < MAXPARENT && parent;
             parent = parent->next, i++) {
                struct origin *porigin = parent_origin[i];
                if (!porigin)
                        continue;
                if (pass_blame_to_parent(sb, origin, porigin))
                        goto finish;
        }

        /*
         * Optionally find moves in parents' files.
         */
        if (opt & PICKAXE_BLAME_MOVE)
                for (i = 0, parent = commit->parents;
                     i < MAXPARENT && parent;
                     parent = parent->next, i++) {
                        struct origin *porigin = parent_origin[i];
                        if (!porigin)
                                continue;
                        if (find_move_in_parent(sb, origin, porigin))
                                goto finish;
                }

        /*
         * Optionally find copies from parents' files.
         */
        if (opt & PICKAXE_BLAME_COPY)
                for (i = 0, parent = commit->parents;
                     i < MAXPARENT && parent;
                     parent = parent->next, i++) {
                        struct origin *porigin = parent_origin[i];
                        if (find_copy_in_parent(sb, origin, parent->item,
                                                porigin, opt))
                                goto finish;
                }

 finish:
        for (i = 0; i < MAXPARENT; i++)
                origin_decref(parent_origin[i]);
}

/*
 * Information on commits, used for output.
 */
struct commit_info
{
        const char *author;
        const char *author_mail;
        unsigned long author_time;
        const char *author_tz;

        /* filled only when asked for details */
        const char *committer;
        const char *committer_mail;
        unsigned long committer_time;
        const char *committer_tz;

        const char *summary;
};

/*
 * Parse author/committer line in the commit object buffer
 */
static void get_ac_line(const char *inbuf, const char *what,
                        int bufsz, char *person, const char **mail,
                        unsigned long *time, const char **tz)
{
        int len, tzlen, maillen;
        char *tmp, *endp, *timepos;

        tmp = strstr(inbuf, what);
        if (!tmp)
                goto error_out;
        tmp += strlen(what);
        endp = strchr(tmp, '\n');
        if (!endp)
                len = strlen(tmp);
        else
                len = endp - tmp;
        if (bufsz <= len) {
        error_out:
                /* Ugh */
                *mail = *tz = "(unknown)";
                *time = 0;
                return;
        }
        memcpy(person, tmp, len);

        tmp = person;
        tmp += len;
        *tmp = 0;
        while (*tmp != ' ')
                tmp--;
        *tz = tmp+1;
        tzlen = (person+len)-(tmp+1);

        *tmp = 0;
        while (*tmp != ' ')
                tmp--;
        *time = strtoul(tmp, NULL, 10);
        timepos = tmp;

        *tmp = 0;
        while (*tmp != ' ')
                tmp--;
        *mail = tmp + 1;
        *tmp = 0;
        maillen = timepos - tmp;

        if (!mailmap.nr)
                return;

        /*
         * mailmap expansion may make the name longer.
         * make room by pushing stuff down.
         */
        tmp = person + bufsz - (tzlen + 1);
        memmove(tmp, *tz, tzlen);
        tmp[tzlen] = 0;
        *tz = tmp;

        tmp = tmp - (maillen + 1);
        memmove(tmp, *mail, maillen);
        tmp[maillen] = 0;
        *mail = tmp;

        /*
         * Now, convert e-mail using mailmap
         */
        map_email(&mailmap, tmp + 1, person, tmp-person-1);
}

static void get_commit_info(struct commit *commit,
                            struct commit_info *ret,
                            int detailed)
{
        int len;
        char *tmp, *endp;
        static char author_buf[1024];
        static char committer_buf[1024];
        static char summary_buf[1024];

        /*
         * We've operated without save_commit_buffer, so
         * we now need to populate them for output.
         */
        if (!commit->buffer) {
                enum object_type type;
                unsigned long size;
                commit->buffer =
                        read_sha1_file(commit->object.sha1, &type, &size);
        }
        ret->author = author_buf;
        get_ac_line(commit->buffer, "\nauthor ",
                    sizeof(author_buf), author_buf, &ret->author_mail,
                    &ret->author_time, &ret->author_tz);

        if (!detailed)
                return;

        ret->committer = committer_buf;
        get_ac_line(commit->buffer, "\ncommitter ",
                    sizeof(committer_buf), committer_buf, &ret->committer_mail,
                    &ret->committer_time, &ret->committer_tz);

        ret->summary = summary_buf;
        tmp = strstr(commit->buffer, "\n\n");
        if (!tmp) {
        error_out:
                sprintf(summary_buf, "(%s)", sha1_to_hex(commit->object.sha1));
                return;
        }
        tmp += 2;
        endp = strchr(tmp, '\n');
        if (!endp)
                endp = tmp + strlen(tmp);
        len = endp - tmp;
        if (len >= sizeof(summary_buf) || len == 0)
                goto error_out;
        memcpy(summary_buf, tmp, len);
        summary_buf[len] = 0;
}

/*
 * To allow LF and other nonportable characters in pathnames,
 * they are c-style quoted as needed.
 */
static void write_filename_info(const char *path)
{
        printf("filename ");
        write_name_quoted(NULL, 0, path, 1, stdout);
        putchar('\n');
}

/*
 * The blame_entry is found to be guilty for the range.  Mark it
 * as such, and show it in incremental output.
 */
static void found_guilty_entry(struct blame_entry *ent)
{
        if (ent->guilty)
                return;
        ent->guilty = 1;
        if (incremental) {
                struct origin *suspect = ent->suspect;

                printf("%s %d %d %d\n",
                       sha1_to_hex(suspect->commit->object.sha1),
                       ent->s_lno + 1, ent->lno + 1, ent->num_lines);
                if (!(suspect->commit->object.flags & METAINFO_SHOWN)) {
                        struct commit_info ci;
                        suspect->commit->object.flags |= METAINFO_SHOWN;
                        get_commit_info(suspect->commit, &ci, 1);
                        printf("author %s\n", ci.author);
                        printf("author-mail %s\n", ci.author_mail);
                        printf("author-time %lu\n", ci.author_time);
                        printf("author-tz %s\n", ci.author_tz);
                        printf("committer %s\n", ci.committer);
                        printf("committer-mail %s\n", ci.committer_mail);
                        printf("committer-time %lu\n", ci.committer_time);
                        printf("committer-tz %s\n", ci.committer_tz);
                        printf("summary %s\n", ci.summary);
                        if (suspect->commit->object.flags & UNINTERESTING)
                                printf("boundary\n");
                }
                write_filename_info(suspect->path);
                maybe_flush_or_die(stdout, "stdout");
        }
}

/*
 * The main loop -- while the scoreboard has lines whose true origin
 * is still unknown, pick one blame_entry, and allow its current
 * suspect to pass blames to its parents.
 */
static void assign_blame(struct scoreboard *sb, struct rev_info *revs, int opt)
{
        while (1) {
                struct blame_entry *ent;
                struct commit *commit;
                struct origin *suspect = NULL;

                /* find one suspect to break down */
                for (ent = sb->ent; !suspect && ent; ent = ent->next)
                        if (!ent->guilty)
                                suspect = ent->suspect;
                if (!suspect)
                        return; /* all done */

                /*
                 * We will use this suspect later in the loop,
                 * so hold onto it in the meantime.
                 */
                origin_incref(suspect);
                commit = suspect->commit;
                if (!commit->object.parsed)
                        parse_commit(commit);
                if (!(commit->object.flags & UNINTERESTING) &&
                    !(revs->max_age != -1 && commit->date < revs->max_age))
                        pass_blame(sb, suspect, opt);
                else {
                        commit->object.flags |= UNINTERESTING;
                        if (commit->object.parsed)
                                mark_parents_uninteresting(commit);
                }
                /* treat root commit as boundary */
                if (!commit->parents && !show_root)
                        commit->object.flags |= UNINTERESTING;

                /* Take responsibility for the remaining entries */
                for (ent = sb->ent; ent; ent = ent->next)
                        if (same_suspect(ent->suspect, suspect))
                                found_guilty_entry(ent);
                origin_decref(suspect);

                if (DEBUG) /* sanity */
                        sanity_check_refcnt(sb);
        }
}

static const char *format_time(unsigned long time, const char *tz_str,
                               int show_raw_time)
{
        static char time_buf[128];
        time_t t = time;
        int minutes, tz;
        struct tm *tm;

        if (show_raw_time) {
                sprintf(time_buf, "%lu %s", time, tz_str);
                return time_buf;
        }

        tz = atoi(tz_str);
        minutes = tz < 0 ? -tz : tz;
        minutes = (minutes / 100)*60 + (minutes % 100);
        minutes = tz < 0 ? -minutes : minutes;
        t = time + minutes * 60;
        tm = gmtime(&t);

        strftime(time_buf, sizeof(time_buf), "%Y-%m-%d %H:%M:%S ", tm);
        strcat(time_buf, tz_str);
        return time_buf;
}

#define OUTPUT_ANNOTATE_COMPAT  001
#define OUTPUT_LONG_OBJECT_NAME 002
#define OUTPUT_RAW_TIMESTAMP    004
#define OUTPUT_PORCELAIN        010
#define OUTPUT_SHOW_NAME        020
#define OUTPUT_SHOW_NUMBER      040
#define OUTPUT_SHOW_SCORE      0100
#define OUTPUT_NO_AUTHOR       0200

static void emit_porcelain(struct scoreboard *sb, struct blame_entry *ent)
{
        int cnt;
        const char *cp;
        struct origin *suspect = ent->suspect;
        char hex[41];

        strcpy(hex, sha1_to_hex(suspect->commit->object.sha1));
        printf("%s%c%d %d %d\n",
               hex,
               ent->guilty ? ' ' : '*', // purely for debugging
               ent->s_lno + 1,
               ent->lno + 1,
               ent->num_lines);
        if (!(suspect->commit->object.flags & METAINFO_SHOWN)) {
                struct commit_info ci;
                suspect->commit->object.flags |= METAINFO_SHOWN;
                get_commit_info(suspect->commit, &ci, 1);
                printf("author %s\n", ci.author);
                printf("author-mail %s\n", ci.author_mail);
                printf("author-time %lu\n", ci.author_time);
                printf("author-tz %s\n", ci.author_tz);
                printf("committer %s\n", ci.committer);
                printf("committer-mail %s\n", ci.committer_mail);
                printf("committer-time %lu\n", ci.committer_time);
                printf("committer-tz %s\n", ci.committer_tz);
                write_filename_info(suspect->path);
                printf("summary %s\n", ci.summary);
                if (suspect->commit->object.flags & UNINTERESTING)
                        printf("boundary\n");
        }
        else if (suspect->commit->object.flags & MORE_THAN_ONE_PATH)
                write_filename_info(suspect->path);

        cp = nth_line(sb, ent->lno);
        for (cnt = 0; cnt < ent->num_lines; cnt++) {
                char ch;
                if (cnt)
                        printf("%s %d %d\n", hex,
                               ent->s_lno + 1 + cnt,
                               ent->lno + 1 + cnt);
                putchar('\t');
                do {
                        ch = *cp++;
                        putchar(ch);
                } while (ch != '\n' &&
                         cp < sb->final_buf + sb->final_buf_size);
        }
}

static void emit_other(struct scoreboard *sb, struct blame_entry *ent, int opt)
{
        int cnt;
        const char *cp;
        struct origin *suspect = ent->suspect;
        struct commit_info ci;
        char hex[41];
        int show_raw_time = !!(opt & OUTPUT_RAW_TIMESTAMP);

        get_commit_info(suspect->commit, &ci, 1);
        strcpy(hex, sha1_to_hex(suspect->commit->object.sha1));

        cp = nth_line(sb, ent->lno);
        for (cnt = 0; cnt < ent->num_lines; cnt++) {
                char ch;
                int length = (opt & OUTPUT_LONG_OBJECT_NAME) ? 40 : 8;

                if (suspect->commit->object.flags & UNINTERESTING) {
                        if (blank_boundary)
                                memset(hex, ' ', length);
                        else if (!cmd_is_annotate) {
                                length--;
                                putchar('^');
                        }
                }

                printf("%.*s", length, hex);
                if (opt & OUTPUT_ANNOTATE_COMPAT)
                        printf("\t(%10s\t%10s\t%d)", ci.author,
                               format_time(ci.author_time, ci.author_tz,
                                           show_raw_time),
                               ent->lno + 1 + cnt);
                else {
                        if (opt & OUTPUT_SHOW_SCORE)
                                printf(" %*d %02d",
                                       max_score_digits, ent->score,
                                       ent->suspect->refcnt);
                        if (opt & OUTPUT_SHOW_NAME)
                                printf(" %-*.*s", longest_file, longest_file,
                                       suspect->path);
                        if (opt & OUTPUT_SHOW_NUMBER)
                                printf(" %*d", max_orig_digits,
                                       ent->s_lno + 1 + cnt);

                        if (!(opt & OUTPUT_NO_AUTHOR))
                                printf(" (%-*.*s %10s",
                                       longest_author, longest_author,
                                       ci.author,
                                       format_time(ci.author_time,
                                                   ci.author_tz,
                                                   show_raw_time));
                        printf(" %*d) ",
                               max_digits, ent->lno + 1 + cnt);
                }
                do {
                        ch = *cp++;
                        putchar(ch);
                } while (ch != '\n' &&
                         cp < sb->final_buf + sb->final_buf_size);
        }
}

static void output(struct scoreboard *sb, int option)
{
        struct blame_entry *ent;

        if (option & OUTPUT_PORCELAIN) {
                for (ent = sb->ent; ent; ent = ent->next) {
                        struct blame_entry *oth;
                        struct origin *suspect = ent->suspect;
                        struct commit *commit = suspect->commit;
                        if (commit->object.flags & MORE_THAN_ONE_PATH)
                                continue;
                        for (oth = ent->next; oth; oth = oth->next) {
                                if ((oth->suspect->commit != commit) ||
                                    !strcmp(oth->suspect->path, suspect->path))
                                        continue;
                                commit->object.flags |= MORE_THAN_ONE_PATH;
                                break;
                        }
                }
        }

        for (ent = sb->ent; ent; ent = ent->next) {
                if (option & OUTPUT_PORCELAIN)
                        emit_porcelain(sb, ent);
                else {
                        emit_other(sb, ent, option);
                }
        }
}

/*
 * To allow quick access to the contents of nth line in the
 * final image, prepare an index in the scoreboard.
 */
static int prepare_lines(struct scoreboard *sb)
{
        const char *buf = sb->final_buf;
        unsigned long len = sb->final_buf_size;
        int num = 0, incomplete = 0, bol = 1;

        if (len && buf[len-1] != '\n')
                incomplete++; /* incomplete line at the end */
        while (len--) {
                if (bol) {
                        sb->lineno = xrealloc(sb->lineno,
                                              sizeof(int* ) * (num + 1));
                        sb->lineno[num] = buf - sb->final_buf;
                        bol = 0;
                }
                if (*buf++ == '\n') {
                        num++;
                        bol = 1;
                }
        }
        sb->lineno = xrealloc(sb->lineno,
                              sizeof(int* ) * (num + incomplete + 1));
        sb->lineno[num + incomplete] = buf - sb->final_buf;
        sb->num_lines = num + incomplete;
        return sb->num_lines;
}

/*
 * Add phony grafts for use with -S; this is primarily to
 * support git-cvsserver that wants to give a linear history
 * to its clients.
 */
static int read_ancestry(const char *graft_file)
{
        FILE *fp = fopen(graft_file, "r");
        char buf[1024];
        if (!fp)
                return -1;
        while (fgets(buf, sizeof(buf), fp)) {
                /* The format is just "Commit Parent1 Parent2 ...\n" */
                int len = strlen(buf);
                struct commit_graft *graft = read_graft_line(buf, len);
                if (graft)
                        register_commit_graft(graft, 0);
        }
        fclose(fp);
        return 0;
}

/*
 * How many columns do we need to show line numbers in decimal?
 */
static int lineno_width(int lines)
{
        int i, width;

        for (width = 1, i = 10; i <= lines + 1; width++)
                i *= 10;
        return width;
}

/*
 * How many columns do we need to show line numbers, authors,
 * and filenames?
 */
static void find_alignment(struct scoreboard *sb, int *option)
{
        int longest_src_lines = 0;
        int longest_dst_lines = 0;
        unsigned largest_score = 0;
        struct blame_entry *e;

        for (e = sb->ent; e; e = e->next) {
                struct origin *suspect = e->suspect;
                struct commit_info ci;
                int num;

                if (strcmp(suspect->path, sb->path))
                        *option |= OUTPUT_SHOW_NAME;
                num = strlen(suspect->path);
                if (longest_file < num)
                        longest_file = num;
                if (!(suspect->commit->object.flags & METAINFO_SHOWN)) {
                        suspect->commit->object.flags |= METAINFO_SHOWN;
                        get_commit_info(suspect->commit, &ci, 1);
                        num = strlen(ci.author);
                        if (longest_author < num)
                                longest_author = num;
                }
                num = e->s_lno + e->num_lines;
                if (longest_src_lines < num)
                        longest_src_lines = num;
                num = e->lno + e->num_lines;
                if (longest_dst_lines < num)
                        longest_dst_lines = num;
                if (largest_score < ent_score(sb, e))
                        largest_score = ent_score(sb, e);
        }
        max_orig_digits = lineno_width(longest_src_lines);
        max_digits = lineno_width(longest_dst_lines);
        max_score_digits = lineno_width(largest_score);
}

/*
 * For debugging -- origin is refcounted, and this asserts that
 * we do not underflow.
 */
static void sanity_check_refcnt(struct scoreboard *sb)
{
        int baa = 0;
        struct blame_entry *ent;

        for (ent = sb->ent; ent; ent = ent->next) {
                /* Nobody should have zero or negative refcnt */
                if (ent->suspect->refcnt <= 0) {
                        fprintf(stderr, "%s in %s has negative refcnt %d\n",
                                ent->suspect->path,
                                sha1_to_hex(ent->suspect->commit->object.sha1),
                                ent->suspect->refcnt);
                        baa = 1;
                }
        }
        for (ent = sb->ent; ent; ent = ent->next) {
                /* Mark the ones that haven't been checked */
                if (0 < ent->suspect->refcnt)
                        ent->suspect->refcnt = -ent->suspect->refcnt;
        }
        for (ent = sb->ent; ent; ent = ent->next) {
                /*
                 * ... then pick each and see if they have the the
                 * correct refcnt.
                 */
                int found;
                struct blame_entry *e;
                struct origin *suspect = ent->suspect;

                if (0 < suspect->refcnt)
                        continue;
                suspect->refcnt = -suspect->refcnt; /* Unmark */
                for (found = 0, e = sb->ent; e; e = e->next) {
                        if (e->suspect != suspect)
                                continue;
                        found++;
                }
                if (suspect->refcnt != found) {
                        fprintf(stderr, "%s in %s has refcnt %d, not %d\n",
                                ent->suspect->path,
                                sha1_to_hex(ent->suspect->commit->object.sha1),
                                ent->suspect->refcnt, found);
                        baa = 2;
                }
        }
        if (baa) {
                int opt = 0160;
                find_alignment(sb, &opt);
                output(sb, opt);
                die("Baa %d!", baa);
        }
}

/*
 * Used for the command line parsing; check if the path exists
 * in the working tree.
 */
static int has_path_in_work_tree(const char *path)
{
        struct stat st;
        return !lstat(path, &st);
}

static unsigned parse_score(const char *arg)
{
        char *end;
        unsigned long score = strtoul(arg, &end, 10);
        if (*end)
                return 0;
        return score;
}

static const char *add_prefix(const char *prefix, const char *path)
{
        if (!prefix || !prefix[0])
                return path;
        return prefix_path(prefix, strlen(prefix), path);
}

/*
 * Parsing of (comma separated) one item in the -L option
 */
static const char *parse_loc(const char *spec,
                             struct scoreboard *sb, long lno,
                             long begin, long *ret)
{
        char *term;
        const char *line;
        long num;
        int reg_error;
        regex_t regexp;
        regmatch_t match[1];

        /* Allow "-L <something>,+20" to mean starting at <something>
         * for 20 lines, or "-L <something>,-5" for 5 lines ending at
         * <something>.
         */
        if (1 < begin && (spec[0] == '+' || spec[0] == '-')) {
                num = strtol(spec + 1, &term, 10);
                if (term != spec + 1) {
                        if (spec[0] == '-')
                                num = 0 - num;
                        if (0 < num)
                                *ret = begin + num - 2;
                        else if (!num)
                                *ret = begin;
                        else
                                *ret = begin + num;
                        return term;
                }
                return spec;
        }
        num = strtol(spec, &term, 10);
        if (term != spec) {
                *ret = num;
                return term;
        }
        if (spec[0] != '/')
                return spec;

        /* it could be a regexp of form /.../ */
        for (term = (char*) spec + 1; *term && *term != '/'; term++) {
                if (*term == '\\')
                        term++;
        }
        if (*term != '/')
                return spec;

        /* try [spec+1 .. term-1] as regexp */
        *term = 0;
        begin--; /* input is in human terms */
        line = nth_line(sb, begin);

        if (!(reg_error = regcomp(&regexp, spec + 1, REG_NEWLINE)) &&
            !(reg_error = regexec(&regexp, line, 1, match, 0))) {
                const char *cp = line + match[0].rm_so;
                const char *nline;

                while (begin++ < lno) {
                        nline = nth_line(sb, begin);
                        if (line <= cp && cp < nline)
                                break;
                        line = nline;
                }
                *ret = begin;
                regfree(&regexp);
                *term++ = '/';
                return term;
        }
        else {
                char errbuf[1024];
                regerror(reg_error, &regexp, errbuf, 1024);
                die("-L parameter '%s': %s", spec + 1, errbuf);
        }
}

/*
 * Parsing of -L option
 */
static void prepare_blame_range(struct scoreboard *sb,
                                const char *bottomtop,
                                long lno,
                                long *bottom, long *top)
{
        const char *term;

        term = parse_loc(bottomtop, sb, lno, 1, bottom);
        if (*term == ',') {
                term = parse_loc(term + 1, sb, lno, *bottom + 1, top);
                if (*term)
                        usage(blame_usage);
        }
        if (*term)
                usage(blame_usage);
}

static int git_blame_config(const char *var, const char *value)
{
        if (!strcmp(var, "blame.showroot")) {
                show_root = git_config_bool(var, value);
                return 0;
        }
        if (!strcmp(var, "blame.blankboundary")) {
                blank_boundary = git_config_bool(var, value);
                return 0;
        }
        return git_default_config(var, value);
}

static struct commit *fake_working_tree_commit(const char *path, const char *contents_from)
{
        struct commit *commit;
        struct origin *origin;
        unsigned char head_sha1[20];
        char *buf;
        const char *ident;
        int fd;
        time_t now;
        unsigned long fin_size;
        int size, len;
        struct cache_entry *ce;
        unsigned mode;

        if (get_sha1("HEAD", head_sha1))
                die("No such ref: HEAD");

        time(&now);
        commit = xcalloc(1, sizeof(*commit));
        commit->parents = xcalloc(1, sizeof(*commit->parents));
        commit->parents->item = lookup_commit_reference(head_sha1);
        commit->object.parsed = 1;
        commit->date = now;
        commit->object.type = OBJ_COMMIT;

        origin = make_origin(commit, path);

        if (!contents_from || strcmp("-", contents_from)) {
                struct stat st;
                const char *read_from;

                if (contents_from) {
                        if (stat(contents_from, &st) < 0)
                                die("Cannot stat %s", contents_from);
                        read_from = contents_from;
                }
                else {
                        if (lstat(path, &st) < 0)
                                die("Cannot lstat %s", path);
                        read_from = path;
                }
                fin_size = xsize_t(st.st_size);
                buf = xmalloc(fin_size+1);
                mode = canon_mode(st.st_mode);
                switch (st.st_mode & S_IFMT) {
                case S_IFREG:
                        fd = open(read_from, O_RDONLY);
                        if (fd < 0)
                                die("cannot open %s", read_from);
                        if (read_in_full(fd, buf, fin_size) != fin_size)
                                die("cannot read %s", read_from);
                        break;
                case S_IFLNK:
                        if (readlink(read_from, buf, fin_size+1) != fin_size)
                                die("cannot readlink %s", read_from);
                        break;
                default:
                        die("unsupported file type %s", read_from);
                }
        }
        else {
                /* Reading from stdin */
                contents_from = "standard input";
                buf = NULL;
                fin_size = 0;
                mode = 0;
                while (1) {
                        ssize_t cnt = 8192;
                        buf = xrealloc(buf, fin_size + cnt);
                        cnt = xread(0, buf + fin_size, cnt);
                        if (cnt < 0)
                                die("read error %s from stdin",
                                    strerror(errno));
                        if (!cnt)
                                break;
                        fin_size += cnt;
                }
                buf = xrealloc(buf, fin_size + 1);
        }
        buf[fin_size] = 0;
        origin->file.ptr = buf;
        origin->file.size = fin_size;
        pretend_sha1_file(buf, fin_size, OBJ_BLOB, origin->blob_sha1);
        commit->util = origin;

        /*
         * Read the current index, replace the path entry with
         * origin->blob_sha1 without mucking with its mode or type
         * bits; we are not going to write this index out -- we just
         * want to run "diff-index --cached".
         */
        discard_cache();
        read_cache();

        len = strlen(path);
        if (!mode) {
                int pos = cache_name_pos(path, len);
                if (0 <= pos)
                        mode = ntohl(active_cache[pos]->ce_mode);
                else
                        /* Let's not bother reading from HEAD tree */
                        mode = S_IFREG | 0644;
        }
        size = cache_entry_size(len);
        ce = xcalloc(1, size);
        hashcpy(ce->sha1, origin->blob_sha1);
        memcpy(ce->name, path, len);
        ce->ce_flags = create_ce_flags(len, 0);
        ce->ce_mode = create_ce_mode(mode);
        add_cache_entry(ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);

        /*
         * We are not going to write this out, so this does not matter
         * right now, but someday we might optimize diff-index --cached
         * with cache-tree information.
         */
        cache_tree_invalidate_path(active_cache_tree, path);

        commit->buffer = xmalloc(400);
        ident = fmt_ident("Not Committed Yet", "not.committed.yet", NULL, 0);
        snprintf(commit->buffer, 400,
                "tree 0000000000000000000000000000000000000000\n"
                "parent %s\n"
                "author %s\n"
                "committer %s\n\n"
                "Version of %s from %s\n",
                sha1_to_hex(head_sha1),
                ident, ident, path, contents_from ? contents_from : path);
        return commit;
}

int cmd_blame(int argc, const char **argv, const char *prefix)
{
        struct rev_info revs;
        const char *path;
        struct scoreboard sb;
        struct origin *o;
        struct blame_entry *ent;
        int i, seen_dashdash, unk, opt;
        long bottom, top, lno;
        int output_option = 0;
        int show_stats = 0;
        const char *revs_file = NULL;
        const char *final_commit_name = NULL;
        enum object_type type;
        const char *bottomtop = NULL;
        const char *contents_from = NULL;

        cmd_is_annotate = !strcmp(argv[0], "annotate");

        git_config(git_blame_config);
        save_commit_buffer = 0;

        opt = 0;
        seen_dashdash = 0;
        for (unk = i = 1; i < argc; i++) {
                const char *arg = argv[i];
                if (*arg != '-')
                        break;
                else if (!strcmp("-b", arg))
                        blank_boundary = 1;
                else if (!strcmp("--root", arg))
                        show_root = 1;
                else if (!strcmp(arg, "--show-stats"))
                        show_stats = 1;
                else if (!strcmp("-c", arg))
                        output_option |= OUTPUT_ANNOTATE_COMPAT;
                else if (!strcmp("-t", arg))
                        output_option |= OUTPUT_RAW_TIMESTAMP;
                else if (!strcmp("-l", arg))
                        output_option |= OUTPUT_LONG_OBJECT_NAME;
                else if (!strcmp("-s", arg))
                        output_option |= OUTPUT_NO_AUTHOR;
                else if (!strcmp("-w", arg))
                        xdl_opts |= XDF_IGNORE_WHITESPACE;
                else if (!strcmp("-S", arg) && ++i < argc)
                        revs_file = argv[i];
                else if (!prefixcmp(arg, "-M")) {
                        opt |= PICKAXE_BLAME_MOVE;
                        blame_move_score = parse_score(arg+2);
                }
                else if (!prefixcmp(arg, "-C")) {
                        /*
                         * -C enables copy from removed files;
                         * -C -C enables copy from existing files, but only
                         *       when blaming a new file;
                         * -C -C -C enables copy from existing files for
                         *          everybody
                         */
                        if (opt & PICKAXE_BLAME_COPY_HARDER)
                                opt |= PICKAXE_BLAME_COPY_HARDEST;
                        if (opt & PICKAXE_BLAME_COPY)
                                opt |= PICKAXE_BLAME_COPY_HARDER;
                        opt |= PICKAXE_BLAME_COPY | PICKAXE_BLAME_MOVE;
                        blame_copy_score = parse_score(arg+2);
                }
                else if (!prefixcmp(arg, "-L")) {
                        if (!arg[2]) {
                                if (++i >= argc)
                                        usage(blame_usage);
                                arg = argv[i];
                        }
                        else
                                arg += 2;
                        if (bottomtop)
                                die("More than one '-L n,m' option given");
                        bottomtop = arg;
                }
                else if (!strcmp("--contents", arg)) {
                        if (++i >= argc)
                                usage(blame_usage);
                        contents_from = argv[i];
                }
                else if (!strcmp("--incremental", arg))
                        incremental = 1;
                else if (!strcmp("--score-debug", arg))
                        output_option |= OUTPUT_SHOW_SCORE;
                else if (!strcmp("-f", arg) ||
                         !strcmp("--show-name", arg))
                        output_option |= OUTPUT_SHOW_NAME;
                else if (!strcmp("-n", arg) ||
                         !strcmp("--show-number", arg))
                        output_option |= OUTPUT_SHOW_NUMBER;
                else if (!strcmp("-p", arg) ||
                         !strcmp("--porcelain", arg))
                        output_option |= OUTPUT_PORCELAIN;
                else if (!strcmp("--", arg)) {
                        seen_dashdash = 1;
                        i++;
                        break;
                }
                else
                        argv[unk++] = arg;
        }

        if (!incremental)
                setup_pager();

        if (!blame_move_score)
                blame_move_score = BLAME_DEFAULT_MOVE_SCORE;
        if (!blame_copy_score)
                blame_copy_score = BLAME_DEFAULT_COPY_SCORE;

        /*
         * We have collected options unknown to us in argv[1..unk]
         * which are to be passed to revision machinery if we are
         * going to do the "bottom" processing.
         *
         * The remaining are:
         *
         * (1) if seen_dashdash, its either
         *     "-options -- <path>" or
         *     "-options -- <path> <rev>".
         *     but the latter is allowed only if there is no
         *     options that we passed to revision machinery.
         *
         * (2) otherwise, we may have "--" somewhere later and
         *     might be looking at the first one of multiple 'rev'
         *     parameters (e.g. " master ^next ^maint -- path").
         *     See if there is a dashdash first, and give the
         *     arguments before that to revision machinery.
         *     After that there must be one 'path'.
         *
         * (3) otherwise, its one of the three:
         *     "-options <path> <rev>"
         *     "-options <rev> <path>"
         *     "-options <path>"
         *     but again the first one is allowed only if
         *     there is no options that we passed to revision
         *     machinery.
         */

        if (seen_dashdash) {
                /* (1) */
                if (argc <= i)
                        usage(blame_usage);
                path = add_prefix(prefix, argv[i]);
                if (i + 1 == argc - 1) {
                        if (unk != 1)
                                usage(blame_usage);
                        argv[unk++] = argv[i + 1];
                }
                else if (i + 1 != argc)
                        /* garbage at end */
                        usage(blame_usage);
        }
        else {
                int j;
                for (j = i; !seen_dashdash && j < argc; j++)
                        if (!strcmp(argv[j], "--"))
                                seen_dashdash = j;
                if (seen_dashdash) {
                        /* (2) */
                        if (seen_dashdash + 1 != argc - 1)
                                usage(blame_usage);
                        path = add_prefix(prefix, argv[seen_dashdash + 1]);
                        for (j = i; j < seen_dashdash; j++)
                                argv[unk++] = argv[j];
                }
                else {
                        /* (3) */
                        if (argc <= i)
                                usage(blame_usage);
                        path = add_prefix(prefix, argv[i]);
                        if (i + 1 == argc - 1) {
                                final_commit_name = argv[i + 1];

                                /* if (unk == 1) we could be getting
                                 * old-style
                                 */
                                if (unk == 1 && !has_path_in_work_tree(path)) {
                                        path = add_prefix(prefix, argv[i + 1]);
                                        final_commit_name = argv[i];
                                }
                        }
                        else if (i != argc - 1)
                                usage(blame_usage); /* garbage at end */

                        if (!has_path_in_work_tree(path))
                                die("cannot stat path %s: %s",
                                    path, strerror(errno));
                }
        }

        if (final_commit_name)
                argv[unk++] = final_commit_name;

        /*
         * Now we got rev and path.  We do not want the path pruning
         * but we may want "bottom" processing.
         */
        argv[unk++] = "--"; /* terminate the rev name */
        argv[unk] = NULL;

        init_revisions(&revs, NULL);
        setup_revisions(unk, argv, &revs, NULL);
        memset(&sb, 0, sizeof(sb));

        /*
         * There must be one and only one positive commit in the
         * revs->pending array.
         */
        for (i = 0; i < revs.pending.nr; i++) {
                struct object *obj = revs.pending.objects[i].item;
                if (obj->flags & UNINTERESTING)
                        continue;
                while (obj->type == OBJ_TAG)
                        obj = deref_tag(obj, NULL, 0);
                if (obj->type != OBJ_COMMIT)
                        die("Non commit %s?",
                            revs.pending.objects[i].name);
                if (sb.final)
                        die("More than one commit to dig from %s and %s?",
                            revs.pending.objects[i].name,
                            final_commit_name);
                sb.final = (struct commit *) obj;
                final_commit_name = revs.pending.objects[i].name;
        }

        if (!sb.final) {
                /*
                 * "--not A B -- path" without anything positive;
                 * do not default to HEAD, but use the working tree
                 * or "--contents".
                 */
                sb.final = fake_working_tree_commit(path, contents_from);
                add_pending_object(&revs, &(sb.final->object), ":");
        }
        else if (contents_from)
                die("Cannot use --contents with final commit object name");

        /*
         * If we have bottom, this will mark the ancestors of the
         * bottom commits we would reach while traversing as
         * uninteresting.
         */
        prepare_revision_walk(&revs);

        if (is_null_sha1(sb.final->object.sha1)) {
                char *buf;
                o = sb.final->util;
                buf = xmalloc(o->file.size + 1);
                memcpy(buf, o->file.ptr, o->file.size + 1);
                sb.final_buf = buf;
                sb.final_buf_size = o->file.size;
        }
        else {
                o = get_origin(&sb, sb.final, path);
                if (fill_blob_sha1(o))
                        die("no such path %s in %s", path, final_commit_name);

                sb.final_buf = read_sha1_file(o->blob_sha1, &type,
                                              &sb.final_buf_size);
        }
        num_read_blob++;
        lno = prepare_lines(&sb);

        bottom = top = 0;
        if (bottomtop)
                prepare_blame_range(&sb, bottomtop, lno, &bottom, &top);
        if (bottom && top && top < bottom) {
                long tmp;
                tmp = top; top = bottom; bottom = tmp;
        }
        if (bottom < 1)
                bottom = 1;
        if (top < 1)
                top = lno;
        bottom--;
        if (lno < top)
                die("file %s has only %lu lines", path, lno);

        ent = xcalloc(1, sizeof(*ent));
        ent->lno = bottom;
        ent->num_lines = top - bottom;
        ent->suspect = o;
        ent->s_lno = bottom;

        sb.ent = ent;
        sb.path = path;

        if (revs_file && read_ancestry(revs_file))
                die("reading graft file %s failed: %s",
                    revs_file, strerror(errno));

        read_mailmap(&mailmap, ".mailmap", NULL);

        assign_blame(&sb, &revs, opt);

        if (incremental)
                return 0;

        coalesce(&sb);

        if (!(output_option & OUTPUT_PORCELAIN))
                find_alignment(&sb, &output_option);

        output(&sb, output_option);
        free((void *)sb.final_buf);
        for (ent = sb.ent; ent; ) {
                struct blame_entry *e = ent->next;
                free(ent);
                ent = e;
        }

        if (show_stats) {
                printf("num read blob: %d\n", num_read_blob);
                printf("num get patch: %d\n", num_get_patch);
                printf("num commits: %d\n", num_commits);
        }
        return 0;
}