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 #define USE_THE_INDEX_COMPATIBILITY_MACROS
  15 #include "cache.h"
  16 #include "config.h"
  17 #include "builtin.h"
  18 #include "run-command.h"
  19 #include "exec-cmd.h"
  20 #include "parse-options.h"
  21 #include "argv-array.h"
  22 #include "strbuf.h"
  23 #include "lockfile.h"
  24 #include "object-store.h"
  25 #include "dir.h"
  26
  27 static int trust_exit_code;
  28
  29 static const char *const builtin_difftool_usage[] = {
  30         N_("git difftool [<options>] [<commit> [<commit>]] [--] [<path>...]"),
  31         NULL
  32 };
  33
  34 static int difftool_config(const char *var, const char *value, void *cb)
  35 {
  36         if (!strcmp(var, "difftool.trustexitcode")) {
  37                 trust_exit_code = git_config_bool(var, value);
  38                 return 0;
  39         }
  40
  41         return git_default_config(var, value, cb);
  42 }
  43
  44 static int print_tool_help(void)
  45 {
  46         const char *argv[] = { "mergetool", "--tool-help=diff", NULL };
  47         return run_command_v_opt(argv, RUN_GIT_CMD);
  48 }
  49
  50 static int parse_index_info(char *p, int *mode1, int *mode2,
  51                             struct object_id *oid1, struct object_id *oid2,
  52                             char *status)
  53 {
  54         if (*p != ':')
  55                 return error("expected ':', got '%c'", *p);
  56         *mode1 = (int)strtol(p + 1, &p, 8);
  57         if (*p != ' ')
  58                 return error("expected ' ', got '%c'", *p);
  59         *mode2 = (int)strtol(p + 1, &p, 8);
  60         if (*p != ' ')
  61                 return error("expected ' ', got '%c'", *p);
  62         if (parse_oid_hex(++p, oid1, (const char **)&p))
  63                 return error("expected object ID, got '%s'", p);
  64         if (*p != ' ')
  65                 return error("expected ' ', got '%c'", *p);
  66         if (parse_oid_hex(++p, oid2, (const char **)&p))
  67                 return error("expected object ID, got '%s'", p);
  68         if (*p != ' ')
  69                 return error("expected ' ', got '%c'", *p);
  70         *status = *++p;
  71         if (!*status)
  72                 return error("missing status");
  73         if (p[1] && !isdigit(p[1]))
  74                 return error("unexpected trailer: '%s'", p + 1);
  75         return 0;
  76 }
  77
  78 /*
  79  * Remove any trailing slash from $workdir
  80  * before starting to avoid double slashes in symlink targets.
  81  */
  82 static void add_path(struct strbuf *buf, size_t base_len, const char *path)
  83 {
  84         strbuf_setlen(buf, base_len);
  85         if (buf->len && buf->buf[buf->len - 1] != '/')
  86                 strbuf_addch(buf, '/');
  87         strbuf_addstr(buf, path);
  88 }
  89
  90 /*
  91  * Determine whether we can simply reuse the file in the worktree.
  92  */
  93 static int use_wt_file(const char *workdir, const char *name,
  94                        struct object_id *oid)
  95 {
  96         struct strbuf buf = STRBUF_INIT;
  97         struct stat st;
  98         int use = 0;
  99
 100         strbuf_addstr(&buf, workdir);
 101         add_path(&buf, buf.len, name);
 102
 103         if (!lstat(buf.buf, &st) && !S_ISLNK(st.st_mode)) {
 104                 struct object_id wt_oid;
 105                 int fd = open(buf.buf, O_RDONLY);
 106
 107                 if (fd >= 0 &&
 108                     !index_fd(&the_index, &wt_oid, fd, &st, OBJ_BLOB, name, 0)) {
 109                         if (is_null_oid(oid)) {
 110                                 oidcpy(oid, &wt_oid);
 111                                 use = 1;
 112                         } else if (oideq(oid, &wt_oid))
 113                                 use = 1;
 114                 }
 115         }
 116
 117         strbuf_release(&buf);
 118
 119         return use;
 120 }
 121
 122 struct working_tree_entry {
 123         struct hashmap_entry entry;
 124         char path[FLEX_ARRAY];
 125 };
 126
 127 static int working_tree_entry_cmp(const void *unused_cmp_data,
 128                                   const void *entry,
 129                                   const void *entry_or_key,
 130                                   const void *unused_keydata)
 131 {
 132         const struct working_tree_entry *a = entry;
 133         const struct working_tree_entry *b = entry_or_key;
 134         return strcmp(a->path, b->path);
 135 }
 136
 137 /*
 138  * The `left` and `right` entries hold paths for the symlinks hashmap,
 139  * and a SHA-1 surrounded by brief text for submodules.
 140  */
 141 struct pair_entry {
 142         struct hashmap_entry entry;
 143         char left[PATH_MAX], right[PATH_MAX];
 144         const char path[FLEX_ARRAY];
 145 };
 146
 147 static int pair_cmp(const void *unused_cmp_data,
 148                     const void *entry,
 149                     const void *entry_or_key,
 150                     const void *unused_keydata)
 151 {
 152         const struct pair_entry *a = entry;
 153         const struct pair_entry *b = entry_or_key;
 154
 155         return strcmp(a->path, b->path);
 156 }
 157
 158 static void add_left_or_right(struct hashmap *map, const char *path,
 159                               const char *content, int is_right)
 160 {
 161         struct pair_entry *e, *existing;
 162
 163         FLEX_ALLOC_STR(e, path, path);
 164         hashmap_entry_init(e, strhash(path));
 165         existing = hashmap_get(map, e, NULL);
 166         if (existing) {
 167                 free(e);
 168                 e = existing;
 169         } else {
 170                 e->left[0] = e->right[0] = '\0';
 171                 hashmap_add(map, e);
 172         }
 173         strlcpy(is_right ? e->right : e->left, content, PATH_MAX);
 174 }
 175
 176 struct path_entry {
 177         struct hashmap_entry entry;
 178         char path[FLEX_ARRAY];
 179 };
 180
 181 static int path_entry_cmp(const void *unused_cmp_data,
 182                           const void *entry,
 183                           const void *entry_or_key,
 184                           const void *key)
 185 {
 186         const struct path_entry *a = entry;
 187         const struct path_entry *b = entry_or_key;
 188
 189         return strcmp(a->path, key ? key : b->path);
 190 }
 191
 192 static void changed_files(struct hashmap *result, const char *index_path,
 193                           const char *workdir)
 194 {
 195         struct child_process update_index = CHILD_PROCESS_INIT;
 196         struct child_process diff_files = CHILD_PROCESS_INIT;
 197         struct strbuf index_env = STRBUF_INIT, buf = STRBUF_INIT;
 198         const char *git_dir = absolute_path(get_git_dir()), *env[] = {
 199                 NULL, NULL
 200         };
 201         FILE *fp;
 202
 203         strbuf_addf(&index_env, "GIT_INDEX_FILE=%s", index_path);
 204         env[0] = index_env.buf;
 205
 206         argv_array_pushl(&update_index.args,
 207                          "--git-dir", git_dir, "--work-tree", workdir,
 208                          "update-index", "--really-refresh", "-q",
 209                          "--unmerged", NULL);
 210         update_index.no_stdin = 1;
 211         update_index.no_stdout = 1;
 212         update_index.no_stderr = 1;
 213         update_index.git_cmd = 1;
 214         update_index.use_shell = 0;
 215         update_index.clean_on_exit = 1;
 216         update_index.dir = workdir;
 217         update_index.env = env;
 218         /* Ignore any errors of update-index */
 219         run_command(&update_index);
 220
 221         argv_array_pushl(&diff_files.args,
 222                          "--git-dir", git_dir, "--work-tree", workdir,
 223                          "diff-files", "--name-only", "-z", NULL);
 224         diff_files.no_stdin = 1;
 225         diff_files.git_cmd = 1;
 226         diff_files.use_shell = 0;
 227         diff_files.clean_on_exit = 1;
 228         diff_files.out = -1;
 229         diff_files.dir = workdir;
 230         diff_files.env = env;
 231         if (start_command(&diff_files))
 232                 die("could not obtain raw diff");
 233         fp = xfdopen(diff_files.out, "r");
 234         while (!strbuf_getline_nul(&buf, fp)) {
 235                 struct path_entry *entry;
 236                 FLEX_ALLOC_STR(entry, path, buf.buf);
 237                 hashmap_entry_init(entry, strhash(buf.buf));
 238                 hashmap_add(result, entry);
 239         }
 240         fclose(fp);
 241         if (finish_command(&diff_files))
 242                 die("diff-files did not exit properly");
 243         strbuf_release(&index_env);
 244         strbuf_release(&buf);
 245 }
 246
 247 static NORETURN void exit_cleanup(const char *tmpdir, int exit_code)
 248 {
 249         struct strbuf buf = STRBUF_INIT;
 250         strbuf_addstr(&buf, tmpdir);
 251         remove_dir_recursively(&buf, 0);
 252         if (exit_code)
 253                 warning(_("failed: %d"), exit_code);
 254         exit(exit_code);
 255 }
 256
 257 static int ensure_leading_directories(char *path)
 258 {
 259         switch (safe_create_leading_directories(path)) {
 260                 case SCLD_OK:
 261                 case SCLD_EXISTS:
 262                         return 0;
 263                 default:
 264                         return error(_("could not create leading directories "
 265                                        "of '%s'"), path);
 266         }
 267 }
 268
 269 /*
 270  * Unconditional writing of a plain regular file is what
 271  * "git difftool --dir-diff" wants to do for symlinks.  We are preparing two
 272  * temporary directories to be fed to a Git-unaware tool that knows how to
 273  * show a diff of two directories (e.g. "diff -r A B").
 274  *
 275  * Because the tool is Git-unaware, if a symbolic link appears in either of
 276  * these temporary directories, it will try to dereference and show the
 277  * difference of the target of the symbolic link, which is not what we want,
 278  * as the goal of the dir-diff mode is to produce an output that is logically
 279  * equivalent to what "git diff" produces.
 280  *
 281  * Most importantly, we want to get textual comparison of the result of the
 282  * readlink(2).  get_symlink() provides that---it returns the contents of
 283  * the symlink that gets written to a regular file to force the external tool
 284  * to compare the readlink(2) result as text, even on a filesystem that is
 285  * capable of doing a symbolic link.
 286  */
 287 static char *get_symlink(const struct object_id *oid, const char *path)
 288 {
 289         char *data;
 290         if (is_null_oid(oid)) {
 291                 /* The symlink is unknown to Git so read from the filesystem */
 292                 struct strbuf link = STRBUF_INIT;
 293                 if (has_symlinks) {
 294                         if (strbuf_readlink(&link, path, strlen(path)))
 295                                 die(_("could not read symlink %s"), path);
 296                 } else if (strbuf_read_file(&link, path, 128))
 297                         die(_("could not read symlink file %s"), path);
 298
 299                 data = strbuf_detach(&link, NULL);
 300         } else {
 301                 enum object_type type;
 302                 unsigned long size;
 303                 data = read_object_file(oid, &type, &size);
 304                 if (!data)
 305                         die(_("could not read object %s for symlink %s"),
 306                                 oid_to_hex(oid), path);
 307         }
 308
 309         return data;
 310 }
 311
 312 static int checkout_path(unsigned mode, struct object_id *oid,
 313                          const char *path, const struct checkout *state)
 314 {
 315         struct cache_entry *ce;
 316         int ret;
 317
 318         ce = make_transient_cache_entry(mode, oid, path, 0);
 319         ret = checkout_entry(ce, state, NULL, NULL);
 320
 321         discard_cache_entry(ce);
 322         return ret;
 323 }
 324
 325 static int run_dir_diff(const char *extcmd, int symlinks, const char *prefix,
 326                         int argc, const char **argv)
 327 {
 328         char tmpdir[PATH_MAX];
 329         struct strbuf info = STRBUF_INIT, lpath = STRBUF_INIT;
 330         struct strbuf rpath = STRBUF_INIT, buf = STRBUF_INIT;
 331         struct strbuf ldir = STRBUF_INIT, rdir = STRBUF_INIT;
 332         struct strbuf wtdir = STRBUF_INIT;
 333         char *lbase_dir, *rbase_dir;
 334         size_t ldir_len, rdir_len, wtdir_len;
 335         const char *workdir, *tmp;
 336         int ret = 0, i;
 337         FILE *fp;
 338         struct hashmap working_tree_dups, submodules, symlinks2;
 339         struct hashmap_iter iter;
 340         struct pair_entry *entry;
 341         struct index_state wtindex;
 342         struct checkout lstate, rstate;
 343         int rc, flags = RUN_GIT_CMD, err = 0;
 344         struct child_process child = CHILD_PROCESS_INIT;
 345         const char *helper_argv[] = { "difftool--helper", NULL, NULL, NULL };
 346         struct hashmap wt_modified, tmp_modified;
 347         int indices_loaded = 0;
 348
 349         workdir = get_git_work_tree();
 350
 351         /* Setup temp directories */
 352         tmp = getenv("TMPDIR");
 353         xsnprintf(tmpdir, sizeof(tmpdir), "%s/git-difftool.XXXXXX", tmp ? tmp : "/tmp");
 354         if (!mkdtemp(tmpdir))
 355                 return error("could not create '%s'", tmpdir);
 356         strbuf_addf(&ldir, "%s/left/", tmpdir);
 357         strbuf_addf(&rdir, "%s/right/", tmpdir);
 358         strbuf_addstr(&wtdir, workdir);
 359         if (!wtdir.len || !is_dir_sep(wtdir.buf[wtdir.len - 1]))
 360                 strbuf_addch(&wtdir, '/');
 361         mkdir(ldir.buf, 0700);
 362         mkdir(rdir.buf, 0700);
 363
 364         memset(&wtindex, 0, sizeof(wtindex));
 365
 366         memset(&lstate, 0, sizeof(lstate));
 367         lstate.base_dir = lbase_dir = xstrdup(ldir.buf);
 368         lstate.base_dir_len = ldir.len;
 369         lstate.force = 1;
 370         memset(&rstate, 0, sizeof(rstate));
 371         rstate.base_dir = rbase_dir = xstrdup(rdir.buf);
 372         rstate.base_dir_len = rdir.len;
 373         rstate.force = 1;
 374
 375         ldir_len = ldir.len;
 376         rdir_len = rdir.len;
 377         wtdir_len = wtdir.len;
 378
 379         hashmap_init(&working_tree_dups, working_tree_entry_cmp, NULL, 0);
 380         hashmap_init(&submodules, pair_cmp, NULL, 0);
 381         hashmap_init(&symlinks2, pair_cmp, NULL, 0);
 382
 383         child.no_stdin = 1;
 384         child.git_cmd = 1;
 385         child.use_shell = 0;
 386         child.clean_on_exit = 1;
 387         child.dir = prefix;
 388         child.out = -1;
 389         argv_array_pushl(&child.args, "diff", "--raw", "--no-abbrev", "-z",
 390                          NULL);
 391         for (i = 0; i < argc; i++)
 392                 argv_array_push(&child.args, argv[i]);
 393         if (start_command(&child))
 394                 die("could not obtain raw diff");
 395         fp = xfdopen(child.out, "r");
 396
 397         /* Build index info for left and right sides of the diff */
 398         i = 0;
 399         while (!strbuf_getline_nul(&info, fp)) {
 400                 int lmode, rmode;
 401                 struct object_id loid, roid;
 402                 char status;
 403                 const char *src_path, *dst_path;
 404
 405                 if (starts_with(info.buf, "::"))
 406                         die(N_("combined diff formats('-c' and '--cc') are "
 407                                "not supported in\n"
 408                                "directory diff mode('-d' and '--dir-diff')."));
 409
 410                 if (parse_index_info(info.buf, &lmode, &rmode, &loid, &roid,
 411                                      &status))
 412                         break;
 413                 if (strbuf_getline_nul(&lpath, fp))
 414                         break;
 415                 src_path = lpath.buf;
 416
 417                 i++;
 418                 if (status != 'C' && status != 'R') {
 419                         dst_path = src_path;
 420                 } else {
 421                         if (strbuf_getline_nul(&rpath, fp))
 422                                 break;
 423                         dst_path = rpath.buf;
 424                 }
 425
 426                 if (S_ISGITLINK(lmode) || S_ISGITLINK(rmode)) {
 427                         strbuf_reset(&buf);
 428                         strbuf_addf(&buf, "Subproject commit %s",
 429                                     oid_to_hex(&loid));
 430                         add_left_or_right(&submodules, src_path, buf.buf, 0);
 431                         strbuf_reset(&buf);
 432                         strbuf_addf(&buf, "Subproject commit %s",
 433                                     oid_to_hex(&roid));
 434                         if (oideq(&loid, &roid))
 435                                 strbuf_addstr(&buf, "-dirty");
 436                         add_left_or_right(&submodules, dst_path, buf.buf, 1);
 437                         continue;
 438                 }
 439
 440                 if (S_ISLNK(lmode)) {
 441                         char *content = get_symlink(&loid, src_path);
 442                         add_left_or_right(&symlinks2, src_path, content, 0);
 443                         free(content);
 444                 }
 445
 446                 if (S_ISLNK(rmode)) {
 447                         char *content = get_symlink(&roid, dst_path);
 448                         add_left_or_right(&symlinks2, dst_path, content, 1);
 449                         free(content);
 450                 }
 451
 452                 if (lmode && status != 'C') {
 453                         if (checkout_path(lmode, &loid, src_path, &lstate)) {
 454                                 ret = error("could not write '%s'", src_path);
 455                                 goto finish;
 456                         }
 457                 }
 458
 459                 if (rmode && !S_ISLNK(rmode)) {
 460                         struct working_tree_entry *entry;
 461
 462                         /* Avoid duplicate working_tree entries */
 463                         FLEX_ALLOC_STR(entry, path, dst_path);
 464                         hashmap_entry_init(entry, strhash(dst_path));
 465                         if (hashmap_get(&working_tree_dups, entry, NULL)) {
 466                                 free(entry);
 467                                 continue;
 468                         }
 469                         hashmap_add(&working_tree_dups, entry);
 470
 471                         if (!use_wt_file(workdir, dst_path, &roid)) {
 472                                 if (checkout_path(rmode, &roid, dst_path,
 473                                                   &rstate)) {
 474                                         ret = error("could not write '%s'",
 475                                                     dst_path);
 476                                         goto finish;
 477                                 }
 478                         } else if (!is_null_oid(&roid)) {
 479                                 /*
 480                                  * Changes in the working tree need special
 481                                  * treatment since they are not part of the
 482                                  * index.
 483                                  */
 484                                 struct cache_entry *ce2 =
 485                                         make_cache_entry(&wtindex, rmode, &roid,
 486                                                          dst_path, 0, 0);
 487
 488                                 add_index_entry(&wtindex, ce2,
 489                                                 ADD_CACHE_JUST_APPEND);
 490
 491                                 add_path(&rdir, rdir_len, dst_path);
 492                                 if (ensure_leading_directories(rdir.buf)) {
 493                                         ret = error("could not create "
 494                                                     "directory for '%s'",
 495                                                     dst_path);
 496                                         goto finish;
 497                                 }
 498                                 add_path(&wtdir, wtdir_len, dst_path);
 499                                 if (symlinks) {
 500                                         if (symlink(wtdir.buf, rdir.buf)) {
 501                                                 ret = error_errno("could not symlink '%s' to '%s'", wtdir.buf, rdir.buf);
 502                                                 goto finish;
 503                                         }
 504                                 } else {
 505                                         struct stat st;
 506                                         if (stat(wtdir.buf, &st))
 507                                                 st.st_mode = 0644;
 508                                         if (copy_file(rdir.buf, wtdir.buf,
 509                                                       st.st_mode)) {
 510                                                 ret = error("could not copy '%s' to '%s'", wtdir.buf, rdir.buf);
 511                                                 goto finish;
 512                                         }
 513                                 }
 514                         }
 515                 }
 516         }
 517
 518         fclose(fp);
 519         fp = NULL;
 520         if (finish_command(&child)) {
 521                 ret = error("error occurred running diff --raw");
 522                 goto finish;
 523         }
 524
 525         if (!i)
 526                 goto finish;
 527
 528         /*
 529          * Changes to submodules require special treatment.This loop writes a
 530          * temporary file to both the left and right directories to show the
 531          * change in the recorded SHA1 for the submodule.
 532          */
 533         hashmap_iter_init(&submodules, &iter);
 534         while ((entry = hashmap_iter_next(&iter))) {
 535                 if (*entry->left) {
 536                         add_path(&ldir, ldir_len, entry->path);
 537                         ensure_leading_directories(ldir.buf);
 538                         write_file(ldir.buf, "%s", entry->left);
 539                 }
 540                 if (*entry->right) {
 541                         add_path(&rdir, rdir_len, entry->path);
 542                         ensure_leading_directories(rdir.buf);
 543                         write_file(rdir.buf, "%s", entry->right);
 544                 }
 545         }
 546
 547         /*
 548          * Symbolic links require special treatment.The standard "git diff"
 549          * shows only the link itself, not the contents of the link target.
 550          * This loop replicates that behavior.
 551          */
 552         hashmap_iter_init(&symlinks2, &iter);
 553         while ((entry = hashmap_iter_next(&iter))) {
 554                 if (*entry->left) {
 555                         add_path(&ldir, ldir_len, entry->path);
 556                         ensure_leading_directories(ldir.buf);
 557                         write_file(ldir.buf, "%s", entry->left);
 558                 }
 559                 if (*entry->right) {
 560                         add_path(&rdir, rdir_len, entry->path);
 561                         ensure_leading_directories(rdir.buf);
 562                         write_file(rdir.buf, "%s", entry->right);
 563                 }
 564         }
 565
 566         strbuf_release(&buf);
 567
 568         strbuf_setlen(&ldir, ldir_len);
 569         helper_argv[1] = ldir.buf;
 570         strbuf_setlen(&rdir, rdir_len);
 571         helper_argv[2] = rdir.buf;
 572
 573         if (extcmd) {
 574                 helper_argv[0] = extcmd;
 575                 flags = 0;
 576         } else
 577                 setenv("GIT_DIFFTOOL_DIRDIFF", "true", 1);
 578         rc = run_command_v_opt(helper_argv, flags);
 579
 580         /*
 581          * If the diff includes working copy files and those
 582          * files were modified during the diff, then the changes
 583          * should be copied back to the working tree.
 584          * Do not copy back files when symlinks are used and the
 585          * external tool did not replace the original link with a file.
 586          *
 587          * These hashes are loaded lazily since they aren't needed
 588          * in the common case of --symlinks and the difftool updating
 589          * files through the symlink.
 590          */
 591         hashmap_init(&wt_modified, path_entry_cmp, NULL, wtindex.cache_nr);
 592         hashmap_init(&tmp_modified, path_entry_cmp, NULL, wtindex.cache_nr);
 593
 594         for (i = 0; i < wtindex.cache_nr; i++) {
 595                 struct hashmap_entry dummy;
 596                 const char *name = wtindex.cache[i]->name;
 597                 struct stat st;
 598
 599                 add_path(&rdir, rdir_len, name);
 600                 if (lstat(rdir.buf, &st))
 601                         continue;
 602
 603                 if ((symlinks && S_ISLNK(st.st_mode)) || !S_ISREG(st.st_mode))
 604                         continue;
 605
 606                 if (!indices_loaded) {
 607                         struct lock_file lock = LOCK_INIT;
 608                         strbuf_reset(&buf);
 609                         strbuf_addf(&buf, "%s/wtindex", tmpdir);
 610                         if (hold_lock_file_for_update(&lock, buf.buf, 0) < 0 ||
 611                             write_locked_index(&wtindex, &lock, COMMIT_LOCK)) {
 612                                 ret = error("could not write %s", buf.buf);
 613                                 goto finish;
 614                         }
 615                         changed_files(&wt_modified, buf.buf, workdir);
 616                         strbuf_setlen(&rdir, rdir_len);
 617                         changed_files(&tmp_modified, buf.buf, rdir.buf);
 618                         add_path(&rdir, rdir_len, name);
 619                         indices_loaded = 1;
 620                 }
 621
 622                 hashmap_entry_init(&dummy, strhash(name));
 623                 if (hashmap_get(&tmp_modified, &dummy, name)) {
 624                         add_path(&wtdir, wtdir_len, name);
 625                         if (hashmap_get(&wt_modified, &dummy, name)) {
 626                                 warning(_("both files modified: '%s' and '%s'."),
 627                                         wtdir.buf, rdir.buf);
 628                                 warning(_("working tree file has been left."));
 629                                 warning("%s", "");
 630                                 err = 1;
 631                         } else if (unlink(wtdir.buf) ||
 632                                    copy_file(wtdir.buf, rdir.buf, st.st_mode))
 633                                 warning_errno(_("could not copy '%s' to '%s'"),
 634                                               rdir.buf, wtdir.buf);
 635                 }
 636         }
 637
 638         if (err) {
 639                 warning(_("temporary files exist in '%s'."), tmpdir);
 640                 warning(_("you may want to cleanup or recover these."));
 641                 exit(1);
 642         } else
 643                 exit_cleanup(tmpdir, rc);
 644
 645 finish:
 646         if (fp)
 647                 fclose(fp);
 648
 649         free(lbase_dir);
 650         free(rbase_dir);
 651         strbuf_release(&ldir);
 652         strbuf_release(&rdir);
 653         strbuf_release(&wtdir);
 654         strbuf_release(&buf);
 655
 656         return ret;
 657 }
 658
 659 static int run_file_diff(int prompt, const char *prefix,
 660                          int argc, const char **argv)
 661 {
 662         struct argv_array args = ARGV_ARRAY_INIT;
 663         const char *env[] = {
 664                 "GIT_PAGER=", "GIT_EXTERNAL_DIFF=git-difftool--helper", NULL,
 665                 NULL
 666         };
 667         int ret = 0, i;
 668
 669         if (prompt > 0)
 670                 env[2] = "GIT_DIFFTOOL_PROMPT=true";
 671         else if (!prompt)
 672                 env[2] = "GIT_DIFFTOOL_NO_PROMPT=true";
 673
 674
 675         argv_array_push(&args, "diff");
 676         for (i = 0; i < argc; i++)
 677                 argv_array_push(&args, argv[i]);
 678         ret = run_command_v_opt_cd_env(args.argv, RUN_GIT_CMD, prefix, env);
 679         exit(ret);
 680 }
 681
 682 int cmd_difftool(int argc, const char **argv, const char *prefix)
 683 {
 684         int use_gui_tool = 0, dir_diff = 0, prompt = -1, symlinks = 0,
 685             tool_help = 0, no_index = 0;
 686         static char *difftool_cmd = NULL, *extcmd = NULL;
 687         struct option builtin_difftool_options[] = {
 688                 OPT_BOOL('g', "gui", &use_gui_tool,
 689                          N_("use `diff.guitool` instead of `diff.tool`")),
 690                 OPT_BOOL('d', "dir-diff", &dir_diff,
 691                          N_("perform a full-directory diff")),
 692                 OPT_SET_INT_F('y', "no-prompt", &prompt,
 693                         N_("do not prompt before launching a diff tool"),
 694                         0, PARSE_OPT_NONEG),
 695                 OPT_SET_INT_F(0, "prompt", &prompt, NULL,
 696                         1, PARSE_OPT_NONEG | PARSE_OPT_HIDDEN),
 697                 OPT_BOOL(0, "symlinks", &symlinks,
 698                          N_("use symlinks in dir-diff mode")),
 699                 OPT_STRING('t', "tool", &difftool_cmd, N_("tool"),
 700                            N_("use the specified diff tool")),
 701                 OPT_BOOL(0, "tool-help", &tool_help,
 702                          N_("print a list of diff tools that may be used with "
 703                             "`--tool`")),
 704                 OPT_BOOL(0, "trust-exit-code", &trust_exit_code,
 705                          N_("make 'git-difftool' exit when an invoked diff "
 706                             "tool returns a non - zero exit code")),
 707                 OPT_STRING('x', "extcmd", &extcmd, N_("command"),
 708                            N_("specify a custom command for viewing diffs")),
 709                 OPT_ARGUMENT("no-index", &no_index, N_("passed to `diff`")),
 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         if (!no_index && !startup_info->have_repository)
 724                 die(_("difftool requires worktree or --no-index"));
 725
 726         if (!no_index){
 727                 setup_work_tree();
 728                 setenv(GIT_DIR_ENVIRONMENT, absolute_path(get_git_dir()), 1);
 729                 setenv(GIT_WORK_TREE_ENVIRONMENT, absolute_path(get_git_work_tree()), 1);
 730         } else if (dir_diff)
 731                 die(_("--dir-diff is incompatible with --no-index"));
 732
 733         if (use_gui_tool + !!difftool_cmd + !!extcmd > 1)
 734                 die(_("--gui, --tool and --extcmd are mutually exclusive"));
 735
 736         if (use_gui_tool)
 737                 setenv("GIT_MERGETOOL_GUI", "true", 1);
 738         else if (difftool_cmd) {
 739                 if (*difftool_cmd)
 740                         setenv("GIT_DIFF_TOOL", difftool_cmd, 1);
 741                 else
 742                         die(_("no <tool> given for --tool=<tool>"));
 743         }
 744
 745         if (extcmd) {
 746                 if (*extcmd)
 747                         setenv("GIT_DIFFTOOL_EXTCMD", extcmd, 1);
 748                 else
 749                         die(_("no <cmd> given for --extcmd=<cmd>"));
 750         }
 751
 752         setenv("GIT_DIFFTOOL_TRUST_EXIT_CODE",
 753                trust_exit_code ? "true" : "false", 1);
 754
 755         /*
 756          * In directory diff mode, 'git-difftool--helper' is called once
 757          * to compare the a / b directories. In file diff mode, 'git diff'
 758          * will invoke a separate instance of 'git-difftool--helper' for
 759          * each file that changed.
 760          */
 761         if (dir_diff)
 762                 return run_dir_diff(extcmd, symlinks, prefix, argc, argv);
 763         return run_file_diff(prompt, prefix, argc, argv);
 764 }