git.oblomov.eu Git - git/blob - builtin/difftool.c

   1 /*
   2  * "git difftool" builtin command
   3  *
   4  * This is a wrapper around the GIT_EXTERNAL_DIFF-compatible
   5  * git-difftool--helper script.
   6  *
   7  * This script exports GIT_EXTERNAL_DIFF and GIT_PAGER for use by git.
   8  * The GIT_DIFF* variables are exported for use by git-difftool--helper.
   9  *
  10  * Any arguments that are unknown to this script are forwarded to 'git diff'.
  11  *
  12  * Copyright (C) 2016 Johannes Schindelin
  13  */
  14 #include "cache.h"
  15 #include "config.h"
  16 #include "builtin.h"
  17 #include "run-command.h"
  18 #include "exec-cmd.h"
  19 #include "parse-options.h"
  20 #include "argv-array.h"
  21 #include "strbuf.h"
  22 #include "lockfile.h"
  23 #include "object-store.h"
  24 #include "dir.h"
  25
  26 static int trust_exit_code;
  27
  28 static const char *const builtin_difftool_usage[] = {
  29         N_("git difftool [<options>] [<commit> [<commit>]] [--] [<path>...]"),
  30         NULL
  31 };
  32
  33 static int difftool_config(const char *var, const char *value, void *cb)
  34 {
  35         if (!strcmp(var, "difftool.trustexitcode")) {
  36                 trust_exit_code = git_config_bool(var, value);
  37                 return 0;
  38         }
  39
  40         return git_default_config(var, value, cb);
  41 }
  42
  43 static int print_tool_help(void)
  44 {
  45         const char *argv[] = { "mergetool", "--tool-help=diff", NULL };
  46         return run_command_v_opt(argv, RUN_GIT_CMD);
  47 }
  48
  49 static int parse_index_info(char *p, int *mode1, int *mode2,
  50                             struct object_id *oid1, struct object_id *oid2,
  51                             char *status)
  52 {
  53         if (*p != ':')
  54                 return error("expected ':', got '%c'", *p);
  55         *mode1 = (int)strtol(p + 1, &p, 8);
  56         if (*p != ' ')
  57                 return error("expected ' ', got '%c'", *p);
  58         *mode2 = (int)strtol(p + 1, &p, 8);
  59         if (*p != ' ')
  60                 return error("expected ' ', got '%c'", *p);
  61         if (get_oid_hex(++p, oid1))
  62                 return error("expected object ID, got '%s'", p + 1);
  63         p += GIT_SHA1_HEXSZ;
  64         if (*p != ' ')
  65                 return error("expected ' ', got '%c'", *p);
  66         if (get_oid_hex(++p, oid2))
  67                 return error("expected object ID, got '%s'", p + 1);
  68         p += GIT_SHA1_HEXSZ;
  69         if (*p != ' ')
  70                 return error("expected ' ', got '%c'", *p);
  71         *status = *++p;
  72         if (!*status)
  73                 return error("missing status");
  74         if (p[1] && !isdigit(p[1]))
  75                 return error("unexpected trailer: '%s'", p + 1);
  76         return 0;
  77 }
  78
  79 /*
  80  * Remove any trailing slash from $workdir
  81  * before starting to avoid double slashes in symlink targets.
  82  */
  83 static void add_path(struct strbuf *buf, size_t base_len, const char *path)
  84 {
  85         strbuf_setlen(buf, base_len);
  86         if (buf->len && buf->buf[buf->len - 1] != '/')
  87                 strbuf_addch(buf, '/');
  88         strbuf_addstr(buf, path);
  89 }
  90
  91 /*
  92  * Determine whether we can simply reuse the file in the worktree.
  93  */
  94 static int use_wt_file(const char *workdir, const char *name,
  95                        struct object_id *oid)
  96 {
  97         struct strbuf buf = STRBUF_INIT;
  98         struct stat st;
  99         int use = 0;
 100
 101         strbuf_addstr(&buf, workdir);
 102         add_path(&buf, buf.len, name);
 103
 104         if (!lstat(buf.buf, &st) && !S_ISLNK(st.st_mode)) {
 105                 struct object_id wt_oid;
 106                 int fd = open(buf.buf, O_RDONLY);
 107
 108                 if (fd >= 0 &&
 109                     !index_fd(&the_index, &wt_oid, fd, &st, OBJ_BLOB, name, 0)) {
 110                         if (is_null_oid(oid)) {
 111                                 oidcpy(oid, &wt_oid);
 112                                 use = 1;
 113                         } else if (oideq(oid, &wt_oid))
 114                                 use = 1;
 115                 }
 116         }
 117
 118         strbuf_release(&buf);
 119
 120         return use;
 121 }
 122
 123 struct working_tree_entry {
 124         struct hashmap_entry entry;
 125         char path[FLEX_ARRAY];
 126 };
 127
 128 static int working_tree_entry_cmp(const void *unused_cmp_data,
 129                                   const void *entry,
 130                                   const void *entry_or_key,
 131                                   const void *unused_keydata)
 132 {
 133         const struct working_tree_entry *a = entry;
 134         const struct working_tree_entry *b = entry_or_key;
 135         return strcmp(a->path, b->path);
 136 }
 137
 138 /*
 139  * The `left` and `right` entries hold paths for the symlinks hashmap,
 140  * and a SHA-1 surrounded by brief text for submodules.
 141  */
 142 struct pair_entry {
 143         struct hashmap_entry entry;
 144         char left[PATH_MAX], right[PATH_MAX];
 145         const char path[FLEX_ARRAY];
 146 };
 147
 148 static int pair_cmp(const void *unused_cmp_data,
 149                     const void *entry,
 150                     const void *entry_or_key,
 151                     const void *unused_keydata)
 152 {
 153         const struct pair_entry *a = entry;
 154         const struct pair_entry *b = entry_or_key;
 155
 156         return strcmp(a->path, b->path);
 157 }
 158
 159 static void add_left_or_right(struct hashmap *map, const char *path,
 160                               const char *content, int is_right)
 161 {
 162         struct pair_entry *e, *existing;
 163
 164         FLEX_ALLOC_STR(e, path, path);
 165         hashmap_entry_init(e, strhash(path));
 166         existing = hashmap_get(map, e, NULL);
 167         if (existing) {
 168                 free(e);
 169                 e = existing;
 170         } else {
 171                 e->left[0] = e->right[0] = '\0';
 172                 hashmap_add(map, e);
 173         }
 174         strlcpy(is_right ? e->right : e->left, content, PATH_MAX);
 175 }
 176
 177 struct path_entry {
 178         struct hashmap_entry entry;
 179         char path[FLEX_ARRAY];
 180 };
 181
 182 static int path_entry_cmp(const void *unused_cmp_data,
 183                           const void *entry,
 184                           const void *entry_or_key,
 185                           const void *key)
 186 {
 187         const struct path_entry *a = entry;
 188         const struct path_entry *b = entry_or_key;
 189
 190         return strcmp(a->path, key ? key : b->path);
 191 }
 192
 193 static void changed_files(struct hashmap *result, const char *index_path,
 194                           const char *workdir)
 195 {
 196         struct child_process update_index = CHILD_PROCESS_INIT;
 197         struct child_process diff_files = CHILD_PROCESS_INIT;
 198         struct strbuf index_env = STRBUF_INIT, buf = STRBUF_INIT;
 199         const char *git_dir = absolute_path(get_git_dir()), *env[] = {
 200                 NULL, NULL
 201         };
 202         FILE *fp;
 203
 204         strbuf_addf(&index_env, "GIT_INDEX_FILE=%s", index_path);
 205         env[0] = index_env.buf;
 206
 207         argv_array_pushl(&update_index.args,
 208                          "--git-dir", git_dir, "--work-tree", workdir,
 209                          "update-index", "--really-refresh", "-q",
 210                          "--unmerged", NULL);
 211         update_index.no_stdin = 1;
 212         update_index.no_stdout = 1;
 213         update_index.no_stderr = 1;
 214         update_index.git_cmd = 1;
 215         update_index.use_shell = 0;
 216         update_index.clean_on_exit = 1;
 217         update_index.dir = workdir;
 218         update_index.env = env;
 219         /* Ignore any errors of update-index */
 220         run_command(&update_index);
 221
 222         argv_array_pushl(&diff_files.args,
 223                          "--git-dir", git_dir, "--work-tree", workdir,
 224                          "diff-files", "--name-only", "-z", NULL);
 225         diff_files.no_stdin = 1;
 226         diff_files.git_cmd = 1;
 227         diff_files.use_shell = 0;
 228         diff_files.clean_on_exit = 1;
 229         diff_files.out = -1;
 230         diff_files.dir = workdir;
 231         diff_files.env = env;
 232         if (start_command(&diff_files))
 233                 die("could not obtain raw diff");
 234         fp = xfdopen(diff_files.out, "r");
 235         while (!strbuf_getline_nul(&buf, fp)) {
 236                 struct path_entry *entry;
 237                 FLEX_ALLOC_STR(entry, path, buf.buf);
 238                 hashmap_entry_init(entry, strhash(buf.buf));
 239                 hashmap_add(result, entry);
 240         }
 241         fclose(fp);
 242         if (finish_command(&diff_files))
 243                 die("diff-files did not exit properly");
 244         strbuf_release(&index_env);
 245         strbuf_release(&buf);
 246 }
 247
 248 static NORETURN void exit_cleanup(const char *tmpdir, int exit_code)
 249 {
 250         struct strbuf buf = STRBUF_INIT;
 251         strbuf_addstr(&buf, tmpdir);
 252         remove_dir_recursively(&buf, 0);
 253         if (exit_code)
 254                 warning(_("failed: %d"), exit_code);
 255         exit(exit_code);
 256 }
 257
 258 static int ensure_leading_directories(char *path)
 259 {
 260         switch (safe_create_leading_directories(path)) {
 261                 case SCLD_OK:
 262                 case SCLD_EXISTS:
 263                         return 0;
 264                 default:
 265                         return error(_("could not create leading directories "
 266                                        "of '%s'"), path);
 267         }
 268 }
 269
 270 /*
 271  * Unconditional writing of a plain regular file is what
 272  * "git difftool --dir-diff" wants to do for symlinks.  We are preparing two
 273  * temporary directories to be fed to a Git-unaware tool that knows how to
 274  * show a diff of two directories (e.g. "diff -r A B").
 275  *
 276  * Because the tool is Git-unaware, if a symbolic link appears in either of
 277  * these temporary directories, it will try to dereference and show the
 278  * difference of the target of the symbolic link, which is not what we want,
 279  * as the goal of the dir-diff mode is to produce an output that is logically
 280  * equivalent to what "git diff" produces.
 281  *
 282  * Most importantly, we want to get textual comparison of the result of the
 283  * readlink(2).  get_symlink() provides that---it returns the contents of
 284  * the symlink that gets written to a regular file to force the external tool
 285  * to compare the readlink(2) result as text, even on a filesystem that is
 286  * capable of doing a symbolic link.
 287  */
 288 static char *get_symlink(const struct object_id *oid, const char *path)
 289 {
 290         char *data;
 291         if (is_null_oid(oid)) {
 292                 /* The symlink is unknown to Git so read from the filesystem */
 293                 struct strbuf link = STRBUF_INIT;
 294                 if (has_symlinks) {
 295                         if (strbuf_readlink(&link, path, strlen(path)))
 296                                 die(_("could not read symlink %s"), path);
 297                 } else if (strbuf_read_file(&link, path, 128))
 298                         die(_("could not read symlink file %s"), path);
 299
 300                 data = strbuf_detach(&link, NULL);
 301         } else {
 302                 enum object_type type;
 303                 unsigned long size;
 304                 data = read_object_file(oid, &type, &size);
 305                 if (!data)
 306                         die(_("could not read object %s for symlink %s"),
 307                                 oid_to_hex(oid), path);
 308         }
 309
 310         return data;
 311 }
 312
 313 static int checkout_path(unsigned mode, struct object_id *oid,
 314                          const char *path, const struct checkout *state)
 315 {
 316         struct cache_entry *ce;
 317         int ret;
 318
 319         ce = make_transient_cache_entry(mode, oid, path, 0);
 320         ret = checkout_entry(ce, state, NULL);
 321
 322         discard_cache_entry(ce);
 323         return ret;
 324 }
 325
 326 static int run_dir_diff(const char *extcmd, int symlinks, const char *prefix,
 327                         int argc, const char **argv)
 328 {
 329         char tmpdir[PATH_MAX];
 330         struct strbuf info = STRBUF_INIT, lpath = STRBUF_INIT;
 331         struct strbuf rpath = STRBUF_INIT, buf = STRBUF_INIT;
 332         struct strbuf ldir = STRBUF_INIT, rdir = STRBUF_INIT;
 333         struct strbuf wtdir = STRBUF_INIT;
 334         char *lbase_dir, *rbase_dir;
 335         size_t ldir_len, rdir_len, wtdir_len;
 336         const char *workdir, *tmp;
 337         int ret = 0, i;
 338         FILE *fp;
 339         struct hashmap working_tree_dups, submodules, symlinks2;
 340         struct hashmap_iter iter;
 341         struct pair_entry *entry;
 342         struct index_state wtindex;
 343         struct checkout lstate, rstate;
 344         int rc, flags = RUN_GIT_CMD, err = 0;
 345         struct child_process child = CHILD_PROCESS_INIT;
 346         const char *helper_argv[] = { "difftool--helper", NULL, NULL, NULL };
 347         struct hashmap wt_modified, tmp_modified;
 348         int indices_loaded = 0;
 349
 350         workdir = get_git_work_tree();
 351
 352         /* Setup temp directories */
 353         tmp = getenv("TMPDIR");
 354         xsnprintf(tmpdir, sizeof(tmpdir), "%s/git-difftool.XXXXXX", tmp ? tmp : "/tmp");
 355         if (!mkdtemp(tmpdir))
 356                 return error("could not create '%s'", tmpdir);
 357         strbuf_addf(&ldir, "%s/left/", tmpdir);
 358         strbuf_addf(&rdir, "%s/right/", tmpdir);
 359         strbuf_addstr(&wtdir, workdir);
 360         if (!wtdir.len || !is_dir_sep(wtdir.buf[wtdir.len - 1]))
 361                 strbuf_addch(&wtdir, '/');
 362         mkdir(ldir.buf, 0700);
 363         mkdir(rdir.buf, 0700);
 364
 365         memset(&wtindex, 0, sizeof(wtindex));
 366
 367         memset(&lstate, 0, sizeof(lstate));
 368         lstate.base_dir = lbase_dir = xstrdup(ldir.buf);
 369         lstate.base_dir_len = ldir.len;
 370         lstate.force = 1;
 371         memset(&rstate, 0, sizeof(rstate));
 372         rstate.base_dir = rbase_dir = xstrdup(rdir.buf);
 373         rstate.base_dir_len = rdir.len;
 374         rstate.force = 1;
 375
 376         ldir_len = ldir.len;
 377         rdir_len = rdir.len;
 378         wtdir_len = wtdir.len;
 379
 380         hashmap_init(&working_tree_dups, working_tree_entry_cmp, NULL, 0);
 381         hashmap_init(&submodules, pair_cmp, NULL, 0);
 382         hashmap_init(&symlinks2, pair_cmp, NULL, 0);
 383
 384         child.no_stdin = 1;
 385         child.git_cmd = 1;
 386         child.use_shell = 0;
 387         child.clean_on_exit = 1;
 388         child.dir = prefix;
 389         child.out = -1;
 390         argv_array_pushl(&child.args, "diff", "--raw", "--no-abbrev", "-z",
 391                          NULL);
 392         for (i = 0; i < argc; i++)
 393                 argv_array_push(&child.args, argv[i]);
 394         if (start_command(&child))
 395                 die("could not obtain raw diff");
 396         fp = xfdopen(child.out, "r");
 397
 398         /* Build index info for left and right sides of the diff */
 399         i = 0;
 400         while (!strbuf_getline_nul(&info, fp)) {
 401                 int lmode, rmode;
 402                 struct object_id loid, roid;
 403                 char status;
 404                 const char *src_path, *dst_path;
 405
 406                 if (starts_with(info.buf, "::"))
 407                         die(N_("combined diff formats('-c' and '--cc') are "
 408                                "not supported in\n"
 409                                "directory diff mode('-d' and '--dir-diff')."));
 410
 411                 if (parse_index_info(info.buf, &lmode, &rmode, &loid, &roid,
 412                                      &status))
 413                         break;
 414                 if (strbuf_getline_nul(&lpath, fp))
 415                         break;
 416                 src_path = lpath.buf;
 417
 418                 i++;
 419                 if (status != 'C' && status != 'R') {
 420                         dst_path = src_path;
 421                 } else {
 422                         if (strbuf_getline_nul(&rpath, fp))
 423                                 break;
 424                         dst_path = rpath.buf;
 425                 }
 426
 427                 if (S_ISGITLINK(lmode) || S_ISGITLINK(rmode)) {
 428                         strbuf_reset(&buf);
 429                         strbuf_addf(&buf, "Subproject commit %s",
 430                                     oid_to_hex(&loid));
 431                         add_left_or_right(&submodules, src_path, buf.buf, 0);
 432                         strbuf_reset(&buf);
 433                         strbuf_addf(&buf, "Subproject commit %s",
 434                                     oid_to_hex(&roid));
 435                         if (oideq(&loid, &roid))
 436                                 strbuf_addstr(&buf, "-dirty");
 437                         add_left_or_right(&submodules, dst_path, buf.buf, 1);
 438                         continue;
 439                 }
 440
 441                 if (S_ISLNK(lmode)) {
 442                         char *content = get_symlink(&loid, src_path);
 443                         add_left_or_right(&symlinks2, src_path, content, 0);
 444                         free(content);
 445                 }
 446
 447                 if (S_ISLNK(rmode)) {
 448                         char *content = get_symlink(&roid, dst_path);
 449                         add_left_or_right(&symlinks2, dst_path, content, 1);
 450                         free(content);
 451                 }
 452
 453                 if (lmode && status != 'C') {
 454                         if (checkout_path(lmode, &loid, src_path, &lstate)) {
 455                                 ret = error("could not write '%s'", src_path);
 456                                 goto finish;
 457                         }
 458                 }
 459
 460                 if (rmode && !S_ISLNK(rmode)) {
 461                         struct working_tree_entry *entry;
 462
 463                         /* Avoid duplicate working_tree entries */
 464                         FLEX_ALLOC_STR(entry, path, dst_path);
 465                         hashmap_entry_init(entry, strhash(dst_path));
 466                         if (hashmap_get(&working_tree_dups, entry, NULL)) {
 467                                 free(entry);
 468                                 continue;
 469                         }
 470                         hashmap_add(&working_tree_dups, entry);
 471
 472                         if (!use_wt_file(workdir, dst_path, &roid)) {
 473                                 if (checkout_path(rmode, &roid, dst_path,
 474                                                   &rstate)) {
 475                                         ret = error("could not write '%s'",
 476                                                     dst_path);
 477                                         goto finish;
 478                                 }
 479                         } else if (!is_null_oid(&roid)) {
 480                                 /*
 481                                  * Changes in the working tree need special
 482                                  * treatment since they are not part of the
 483                                  * index.
 484                                  */
 485                                 struct cache_entry *ce2 =
 486                                         make_cache_entry(&wtindex, rmode, &roid,
 487                                                          dst_path, 0, 0);
 488
 489                                 add_index_entry(&wtindex, ce2,
 490                                                 ADD_CACHE_JUST_APPEND);
 491
 492                                 add_path(&rdir, rdir_len, dst_path);
 493                                 if (ensure_leading_directories(rdir.buf)) {
 494                                         ret = error("could not create "
 495                                                     "directory for '%s'",
 496                                                     dst_path);
 497                                         goto finish;
 498                                 }
 499                                 add_path(&wtdir, wtdir_len, dst_path);
 500                                 if (symlinks) {
 501                                         if (symlink(wtdir.buf, rdir.buf)) {
 502                                                 ret = error_errno("could not symlink '%s' to '%s'", wtdir.buf, rdir.buf);
 503                                                 goto finish;
 504                                         }
 505                                 } else {
 506                                         struct stat st;
 507                                         if (stat(wtdir.buf, &st))
 508                                                 st.st_mode = 0644;
 509                                         if (copy_file(rdir.buf, wtdir.buf,
 510                                                       st.st_mode)) {
 511                                                 ret = error("could not copy '%s' to '%s'", wtdir.buf, rdir.buf);
 512                                                 goto finish;
 513                                         }
 514                                 }
 515                         }
 516                 }
 517         }
 518
 519         fclose(fp);
 520         fp = NULL;
 521         if (finish_command(&child)) {
 522                 ret = error("error occurred running diff --raw");
 523                 goto finish;
 524         }
 525
 526         if (!i)
 527                 goto finish;
 528
 529         /*
 530          * Changes to submodules require special treatment.This loop writes a
 531          * temporary file to both the left and right directories to show the
 532          * change in the recorded SHA1 for the submodule.
 533          */
 534         hashmap_iter_init(&submodules, &iter);
 535         while ((entry = hashmap_iter_next(&iter))) {
 536                 if (*entry->left) {
 537                         add_path(&ldir, ldir_len, entry->path);
 538                         ensure_leading_directories(ldir.buf);
 539                         write_file(ldir.buf, "%s", entry->left);
 540                 }
 541                 if (*entry->right) {
 542                         add_path(&rdir, rdir_len, entry->path);
 543                         ensure_leading_directories(rdir.buf);
 544                         write_file(rdir.buf, "%s", entry->right);
 545                 }
 546         }
 547
 548         /*
 549          * Symbolic links require special treatment.The standard "git diff"
 550          * shows only the link itself, not the contents of the link target.
 551          * This loop replicates that behavior.
 552          */
 553         hashmap_iter_init(&symlinks2, &iter);
 554         while ((entry = hashmap_iter_next(&iter))) {
 555                 if (*entry->left) {
 556                         add_path(&ldir, ldir_len, entry->path);
 557                         ensure_leading_directories(ldir.buf);
 558                         write_file(ldir.buf, "%s", entry->left);
 559                 }
 560                 if (*entry->right) {
 561                         add_path(&rdir, rdir_len, entry->path);
 562                         ensure_leading_directories(rdir.buf);
 563                         write_file(rdir.buf, "%s", entry->right);
 564                 }
 565         }
 566
 567         strbuf_release(&buf);
 568
 569         strbuf_setlen(&ldir, ldir_len);
 570         helper_argv[1] = ldir.buf;
 571         strbuf_setlen(&rdir, rdir_len);
 572         helper_argv[2] = rdir.buf;
 573
 574         if (extcmd) {
 575                 helper_argv[0] = extcmd;
 576                 flags = 0;
 577         } else
 578                 setenv("GIT_DIFFTOOL_DIRDIFF", "true", 1);
 579         rc = run_command_v_opt(helper_argv, flags);
 580
 581         /*
 582          * If the diff includes working copy files and those
 583          * files were modified during the diff, then the changes
 584          * should be copied back to the working tree.
 585          * Do not copy back files when symlinks are used and the
 586          * external tool did not replace the original link with a file.
 587          *
 588          * These hashes are loaded lazily since they aren't needed
 589          * in the common case of --symlinks and the difftool updating
 590          * files through the symlink.
 591          */
 592         hashmap_init(&wt_modified, path_entry_cmp, NULL, wtindex.cache_nr);
 593         hashmap_init(&tmp_modified, path_entry_cmp, NULL, wtindex.cache_nr);
 594
 595         for (i = 0; i < wtindex.cache_nr; i++) {
 596                 struct hashmap_entry dummy;
 597                 const char *name = wtindex.cache[i]->name;
 598                 struct stat st;
 599
 600                 add_path(&rdir, rdir_len, name);
 601                 if (lstat(rdir.buf, &st))
 602                         continue;
 603
 604                 if ((symlinks && S_ISLNK(st.st_mode)) || !S_ISREG(st.st_mode))
 605                         continue;
 606
 607                 if (!indices_loaded) {
 608                         struct lock_file lock = LOCK_INIT;
 609                         strbuf_reset(&buf);
 610                         strbuf_addf(&buf, "%s/wtindex", tmpdir);
 611                         if (hold_lock_file_for_update(&lock, buf.buf, 0) < 0 ||
 612                             write_locked_index(&wtindex, &lock, COMMIT_LOCK)) {
 613                                 ret = error("could not write %s", buf.buf);
 614                                 goto finish;
 615                         }
 616                         changed_files(&wt_modified, buf.buf, workdir);
 617                         strbuf_setlen(&rdir, rdir_len);
 618                         changed_files(&tmp_modified, buf.buf, rdir.buf);
 619                         add_path(&rdir, rdir_len, name);
 620                         indices_loaded = 1;
 621                 }
 622
 623                 hashmap_entry_init(&dummy, strhash(name));
 624                 if (hashmap_get(&tmp_modified, &dummy, name)) {
 625                         add_path(&wtdir, wtdir_len, name);
 626                         if (hashmap_get(&wt_modified, &dummy, name)) {
 627                                 warning(_("both files modified: '%s' and '%s'."),
 628                                         wtdir.buf, rdir.buf);
 629                                 warning(_("working tree file has been left."));
 630                                 warning("%s", "");
 631                                 err = 1;
 632                         } else if (unlink(wtdir.buf) ||
 633                                    copy_file(wtdir.buf, rdir.buf, st.st_mode))
 634                                 warning_errno(_("could not copy '%s' to '%s'"),
 635                                               rdir.buf, wtdir.buf);
 636                 }
 637         }
 638
 639         if (err) {
 640                 warning(_("temporary files exist in '%s'."), tmpdir);
 641                 warning(_("you may want to cleanup or recover these."));
 642                 exit(1);
 643         } else
 644                 exit_cleanup(tmpdir, rc);
 645
 646 finish:
 647         if (fp)
 648                 fclose(fp);
 649
 650         free(lbase_dir);
 651         free(rbase_dir);
 652         strbuf_release(&ldir);
 653         strbuf_release(&rdir);
 654         strbuf_release(&wtdir);
 655         strbuf_release(&buf);
 656
 657         return ret;
 658 }
 659
 660 static int run_file_diff(int prompt, const char *prefix,
 661                          int argc, const char **argv)
 662 {
 663         struct argv_array args = ARGV_ARRAY_INIT;
 664         const char *env[] = {
 665                 "GIT_PAGER=", "GIT_EXTERNAL_DIFF=git-difftool--helper", NULL,
 666                 NULL
 667         };
 668         int ret = 0, i;
 669
 670         if (prompt > 0)
 671                 env[2] = "GIT_DIFFTOOL_PROMPT=true";
 672         else if (!prompt)
 673                 env[2] = "GIT_DIFFTOOL_NO_PROMPT=true";
 674
 675
 676         argv_array_push(&args, "diff");
 677         for (i = 0; i < argc; i++)
 678                 argv_array_push(&args, argv[i]);
 679         ret = run_command_v_opt_cd_env(args.argv, RUN_GIT_CMD, prefix, env);
 680         exit(ret);
 681 }
 682
 683 int cmd_difftool(int argc, const char **argv, const char *prefix)
 684 {
 685         int use_gui_tool = 0, dir_diff = 0, prompt = -1, symlinks = 0,
 686             tool_help = 0;
 687         static char *difftool_cmd = NULL, *extcmd = NULL;
 688         struct option builtin_difftool_options[] = {
 689                 OPT_BOOL('g', "gui", &use_gui_tool,
 690                          N_("use `diff.guitool` instead of `diff.tool`")),
 691                 OPT_BOOL('d', "dir-diff", &dir_diff,
 692                          N_("perform a full-directory diff")),
 693                 OPT_SET_INT_F('y', "no-prompt", &prompt,
 694                         N_("do not prompt before launching a diff tool"),
 695                         0, PARSE_OPT_NONEG),
 696                 OPT_SET_INT_F(0, "prompt", &prompt, NULL,
 697                         1, PARSE_OPT_NONEG | PARSE_OPT_HIDDEN),
 698                 OPT_BOOL(0, "symlinks", &symlinks,
 699                          N_("use symlinks in dir-diff mode")),
 700                 OPT_STRING('t', "tool", &difftool_cmd, N_("tool"),
 701                            N_("use the specified diff tool")),
 702                 OPT_BOOL(0, "tool-help", &tool_help,
 703                          N_("print a list of diff tools that may be used with "
 704                             "`--tool`")),
 705                 OPT_BOOL(0, "trust-exit-code", &trust_exit_code,
 706                          N_("make 'git-difftool' exit when an invoked diff "
 707                             "tool returns a non - zero exit code")),
 708                 OPT_STRING('x', "extcmd", &extcmd, N_("command"),
 709                            N_("specify a custom command for viewing diffs")),
 710                 OPT_END()
 711         };
 712
 713         git_config(difftool_config, NULL);
 714         symlinks = has_symlinks;
 715
 716         argc = parse_options(argc, argv, prefix, builtin_difftool_options,
 717                              builtin_difftool_usage, PARSE_OPT_KEEP_UNKNOWN |
 718                              PARSE_OPT_KEEP_DASHDASH);
 719
 720         if (tool_help)
 721                 return print_tool_help();
 722
 723         /* NEEDSWORK: once we no longer spawn anything, remove this */
 724         setenv(GIT_DIR_ENVIRONMENT, absolute_path(get_git_dir()), 1);
 725         setenv(GIT_WORK_TREE_ENVIRONMENT, absolute_path(get_git_work_tree()), 1);
 726
 727         if (use_gui_tool + !!difftool_cmd + !!extcmd > 1)
 728                 die(_("--gui, --tool and --extcmd are mutually exclusive"));
 729
 730         if (use_gui_tool)
 731                 setenv("GIT_MERGETOOL_GUI", "true", 1);
 732         else if (difftool_cmd) {
 733                 if (*difftool_cmd)
 734                         setenv("GIT_DIFF_TOOL", difftool_cmd, 1);
 735                 else
 736                         die(_("no <tool> given for --tool=<tool>"));
 737         }
 738
 739         if (extcmd) {
 740                 if (*extcmd)
 741                         setenv("GIT_DIFFTOOL_EXTCMD", extcmd, 1);
 742                 else
 743                         die(_("no <cmd> given for --extcmd=<cmd>"));
 744         }
 745
 746         setenv("GIT_DIFFTOOL_TRUST_EXIT_CODE",
 747                trust_exit_code ? "true" : "false", 1);
 748
 749         /*
 750          * In directory diff mode, 'git-difftool--helper' is called once
 751          * to compare the a / b directories. In file diff mode, 'git diff'
 752          * will invoke a separate instance of 'git-difftool--helper' for
 753          * each file that changed.
 754          */
 755         if (dir_diff)
 756                 return run_dir_diff(extcmd, symlinks, prefix, argc, argv);
 757         return run_file_diff(prompt, prefix, argc, argv);
 758 }