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 "dir.h"
  24
  25 static char *diff_gui_tool;
  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, "diff.guitool")) {
  36                 diff_gui_tool = xstrdup(value);
  37                 return 0;
  38         }
  39
  40         if (!strcmp(var, "difftool.trustexitcode")) {
  41                 trust_exit_code = git_config_bool(var, value);
  42                 return 0;
  43         }
  44
  45         return git_default_config(var, value, cb);
  46 }
  47
  48 static int print_tool_help(void)
  49 {
  50         const char *argv[] = { "mergetool", "--tool-help=diff", NULL };
  51         return run_command_v_opt(argv, RUN_GIT_CMD);
  52 }
  53
  54 static int parse_index_info(char *p, int *mode1, int *mode2,
  55                             struct object_id *oid1, struct object_id *oid2,
  56                             char *status)
  57 {
  58         if (*p != ':')
  59                 return error("expected ':', got '%c'", *p);
  60         *mode1 = (int)strtol(p + 1, &p, 8);
  61         if (*p != ' ')
  62                 return error("expected ' ', got '%c'", *p);
  63         *mode2 = (int)strtol(p + 1, &p, 8);
  64         if (*p != ' ')
  65                 return error("expected ' ', got '%c'", *p);
  66         if (get_oid_hex(++p, oid1))
  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         if (get_oid_hex(++p, oid2))
  72                 return error("expected object ID, got '%s'", p + 1);
  73         p += GIT_SHA1_HEXSZ;
  74         if (*p != ' ')
  75                 return error("expected ' ', got '%c'", *p);
  76         *status = *++p;
  77         if (!*status)
  78                 return error("missing status");
  79         if (p[1] && !isdigit(p[1]))
  80                 return error("unexpected trailer: '%s'", p + 1);
  81         return 0;
  82 }
  83
  84 /*
  85  * Remove any trailing slash from $workdir
  86  * before starting to avoid double slashes in symlink targets.
  87  */
  88 static void add_path(struct strbuf *buf, size_t base_len, const char *path)
  89 {
  90         strbuf_setlen(buf, base_len);
  91         if (buf->len && buf->buf[buf->len - 1] != '/')
  92                 strbuf_addch(buf, '/');
  93         strbuf_addstr(buf, path);
  94 }
  95
  96 /*
  97  * Determine whether we can simply reuse the file in the worktree.
  98  */
  99 static int use_wt_file(const char *workdir, const char *name,
 100                        struct object_id *oid)
 101 {
 102         struct strbuf buf = STRBUF_INIT;
 103         struct stat st;
 104         int use = 0;
 105
 106         strbuf_addstr(&buf, workdir);
 107         add_path(&buf, buf.len, name);
 108
 109         if (!lstat(buf.buf, &st) && !S_ISLNK(st.st_mode)) {
 110                 struct object_id wt_oid;
 111                 int fd = open(buf.buf, O_RDONLY);
 112
 113                 if (fd >= 0 &&
 114                     !index_fd(&wt_oid, fd, &st, OBJ_BLOB, name, 0)) {
 115                         if (is_null_oid(oid)) {
 116                                 oidcpy(oid, &wt_oid);
 117                                 use = 1;
 118                         } else if (!oidcmp(oid, &wt_oid))
 119                                 use = 1;
 120                 }
 121         }
 122
 123         strbuf_release(&buf);
 124
 125         return use;
 126 }
 127
 128 struct working_tree_entry {
 129         struct hashmap_entry entry;
 130         char path[FLEX_ARRAY];
 131 };
 132
 133 static int working_tree_entry_cmp(const void *unused_cmp_data,
 134                                   const void *entry,
 135                                   const void *entry_or_key,
 136                                   const void *unused_keydata)
 137 {
 138         const struct working_tree_entry *a = entry;
 139         const struct working_tree_entry *b = entry_or_key;
 140         return strcmp(a->path, b->path);
 141 }
 142
 143 /*
 144  * The `left` and `right` entries hold paths for the symlinks hashmap,
 145  * and a SHA-1 surrounded by brief text for submodules.
 146  */
 147 struct pair_entry {
 148         struct hashmap_entry entry;
 149         char left[PATH_MAX], right[PATH_MAX];
 150         const char path[FLEX_ARRAY];
 151 };
 152
 153 static int pair_cmp(const void *unused_cmp_data,
 154                     const void *entry,
 155                     const void *entry_or_key,
 156                     const void *unused_keydata)
 157 {
 158         const struct pair_entry *a = entry;
 159         const struct pair_entry *b = entry_or_key;
 160
 161         return strcmp(a->path, b->path);
 162 }
 163
 164 static void add_left_or_right(struct hashmap *map, const char *path,
 165                               const char *content, int is_right)
 166 {
 167         struct pair_entry *e, *existing;
 168
 169         FLEX_ALLOC_STR(e, path, path);
 170         hashmap_entry_init(e, strhash(path));
 171         existing = hashmap_get(map, e, NULL);
 172         if (existing) {
 173                 free(e);
 174                 e = existing;
 175         } else {
 176                 e->left[0] = e->right[0] = '\0';
 177                 hashmap_add(map, e);
 178         }
 179         strlcpy(is_right ? e->right : e->left, content, PATH_MAX);
 180 }
 181
 182 struct path_entry {
 183         struct hashmap_entry entry;
 184         char path[FLEX_ARRAY];
 185 };
 186
 187 static int path_entry_cmp(const void *unused_cmp_data,
 188                           const void *entry,
 189                           const void *entry_or_key,
 190                           const void *key)
 191 {
 192         const struct path_entry *a = entry;
 193         const struct path_entry *b = entry_or_key;
 194
 195         return strcmp(a->path, key ? key : b->path);
 196 }
 197
 198 static void changed_files(struct hashmap *result, const char *index_path,
 199                           const char *workdir)
 200 {
 201         struct child_process update_index = CHILD_PROCESS_INIT;
 202         struct child_process diff_files = CHILD_PROCESS_INIT;
 203         struct strbuf index_env = STRBUF_INIT, buf = STRBUF_INIT;
 204         const char *git_dir = absolute_path(get_git_dir()), *env[] = {
 205                 NULL, NULL
 206         };
 207         FILE *fp;
 208
 209         strbuf_addf(&index_env, "GIT_INDEX_FILE=%s", index_path);
 210         env[0] = index_env.buf;
 211
 212         argv_array_pushl(&update_index.args,
 213                          "--git-dir", git_dir, "--work-tree", workdir,
 214                          "update-index", "--really-refresh", "-q",
 215                          "--unmerged", NULL);
 216         update_index.no_stdin = 1;
 217         update_index.no_stdout = 1;
 218         update_index.no_stderr = 1;
 219         update_index.git_cmd = 1;
 220         update_index.use_shell = 0;
 221         update_index.clean_on_exit = 1;
 222         update_index.dir = workdir;
 223         update_index.env = env;
 224         /* Ignore any errors of update-index */
 225         run_command(&update_index);
 226
 227         argv_array_pushl(&diff_files.args,
 228                          "--git-dir", git_dir, "--work-tree", workdir,
 229                          "diff-files", "--name-only", "-z", NULL);
 230         diff_files.no_stdin = 1;
 231         diff_files.git_cmd = 1;
 232         diff_files.use_shell = 0;
 233         diff_files.clean_on_exit = 1;
 234         diff_files.out = -1;
 235         diff_files.dir = workdir;
 236         diff_files.env = env;
 237         if (start_command(&diff_files))
 238                 die("could not obtain raw diff");
 239         fp = xfdopen(diff_files.out, "r");
 240         while (!strbuf_getline_nul(&buf, fp)) {
 241                 struct path_entry *entry;
 242                 FLEX_ALLOC_STR(entry, path, buf.buf);
 243                 hashmap_entry_init(entry, strhash(buf.buf));
 244                 hashmap_add(result, entry);
 245         }
 246         fclose(fp);
 247         if (finish_command(&diff_files))
 248                 die("diff-files did not exit properly");
 249         strbuf_release(&index_env);
 250         strbuf_release(&buf);
 251 }
 252
 253 static NORETURN void exit_cleanup(const char *tmpdir, int exit_code)
 254 {
 255         struct strbuf buf = STRBUF_INIT;
 256         strbuf_addstr(&buf, tmpdir);
 257         remove_dir_recursively(&buf, 0);
 258         if (exit_code)
 259                 warning(_("failed: %d"), exit_code);
 260         exit(exit_code);
 261 }
 262
 263 static int ensure_leading_directories(char *path)
 264 {
 265         switch (safe_create_leading_directories(path)) {
 266                 case SCLD_OK:
 267                 case SCLD_EXISTS:
 268                         return 0;
 269                 default:
 270                         return error(_("could not create leading directories "
 271                                        "of '%s'"), path);
 272         }
 273 }
 274
 275 /*
 276  * Unconditional writing of a plain regular file is what
 277  * "git difftool --dir-diff" wants to do for symlinks.  We are preparing two
 278  * temporary directories to be fed to a Git-unaware tool that knows how to
 279  * show a diff of two directories (e.g. "diff -r A B").
 280  *
 281  * Because the tool is Git-unaware, if a symbolic link appears in either of
 282  * these temporary directories, it will try to dereference and show the
 283  * difference of the target of the symbolic link, which is not what we want,
 284  * as the goal of the dir-diff mode is to produce an output that is logically
 285  * equivalent to what "git diff" produces.
 286  *
 287  * Most importantly, we want to get textual comparison of the result of the
 288  * readlink(2).  get_symlink() provides that---it returns the contents of
 289  * the symlink that gets written to a regular file to force the external tool
 290  * to compare the readlink(2) result as text, even on a filesystem that is
 291  * capable of doing a symbolic link.
 292  */
 293 static char *get_symlink(const struct object_id *oid, const char *path)
 294 {
 295         char *data;
 296         if (is_null_oid(oid)) {
 297                 /* The symlink is unknown to Git so read from the filesystem */
 298                 struct strbuf link = STRBUF_INIT;
 299                 if (has_symlinks) {
 300                         if (strbuf_readlink(&link, path, strlen(path)))
 301                                 die(_("could not read symlink %s"), path);
 302                 } else if (strbuf_read_file(&link, path, 128))
 303                         die(_("could not read symlink file %s"), path);
 304
 305                 data = strbuf_detach(&link, NULL);
 306         } else {
 307                 enum object_type type;
 308                 unsigned long size;
 309                 data = read_sha1_file(oid->hash, &type, &size);
 310                 if (!data)
 311                         die(_("could not read object %s for symlink %s"),
 312                                 oid_to_hex(oid), path);
 313         }
 314
 315         return data;
 316 }
 317
 318 static int checkout_path(unsigned mode, struct object_id *oid,
 319                          const char *path, const struct checkout *state)
 320 {
 321         struct cache_entry *ce;
 322         int ret;
 323
 324         ce = make_cache_entry(mode, oid->hash, path, 0, 0);
 325         ret = checkout_entry(ce, state, NULL);
 326
 327         free(ce);
 328         return ret;
 329 }
 330
 331 static int run_dir_diff(const char *extcmd, int symlinks, const char *prefix,
 332                         int argc, const char **argv)
 333 {
 334         char tmpdir[PATH_MAX];
 335         struct strbuf info = STRBUF_INIT, lpath = STRBUF_INIT;
 336         struct strbuf rpath = STRBUF_INIT, buf = STRBUF_INIT;
 337         struct strbuf ldir = STRBUF_INIT, rdir = STRBUF_INIT;
 338         struct strbuf wtdir = STRBUF_INIT;
 339         char *lbase_dir, *rbase_dir;
 340         size_t ldir_len, rdir_len, wtdir_len;
 341         const char *workdir, *tmp;
 342         int ret = 0, i;
 343         FILE *fp;
 344         struct hashmap working_tree_dups, submodules, symlinks2;
 345         struct hashmap_iter iter;
 346         struct pair_entry *entry;
 347         struct index_state wtindex;
 348         struct checkout lstate, rstate;
 349         int rc, flags = RUN_GIT_CMD, err = 0;
 350         struct child_process child = CHILD_PROCESS_INIT;
 351         const char *helper_argv[] = { "difftool--helper", NULL, NULL, NULL };
 352         struct hashmap wt_modified, tmp_modified;
 353         int indices_loaded = 0;
 354
 355         workdir = get_git_work_tree();
 356
 357         /* Setup temp directories */
 358         tmp = getenv("TMPDIR");
 359         xsnprintf(tmpdir, sizeof(tmpdir), "%s/git-difftool.XXXXXX", tmp ? tmp : "/tmp");
 360         if (!mkdtemp(tmpdir))
 361                 return error("could not create '%s'", tmpdir);
 362         strbuf_addf(&ldir, "%s/left/", tmpdir);
 363         strbuf_addf(&rdir, "%s/right/", tmpdir);
 364         strbuf_addstr(&wtdir, workdir);
 365         if (!wtdir.len || !is_dir_sep(wtdir.buf[wtdir.len - 1]))
 366                 strbuf_addch(&wtdir, '/');
 367         mkdir(ldir.buf, 0700);
 368         mkdir(rdir.buf, 0700);
 369
 370         memset(&wtindex, 0, sizeof(wtindex));
 371
 372         memset(&lstate, 0, sizeof(lstate));
 373         lstate.base_dir = lbase_dir = xstrdup(ldir.buf);
 374         lstate.base_dir_len = ldir.len;
 375         lstate.force = 1;
 376         memset(&rstate, 0, sizeof(rstate));
 377         rstate.base_dir = rbase_dir = xstrdup(rdir.buf);
 378         rstate.base_dir_len = rdir.len;
 379         rstate.force = 1;
 380
 381         ldir_len = ldir.len;
 382         rdir_len = rdir.len;
 383         wtdir_len = wtdir.len;
 384
 385         hashmap_init(&working_tree_dups, working_tree_entry_cmp, NULL, 0);
 386         hashmap_init(&submodules, pair_cmp, NULL, 0);
 387         hashmap_init(&symlinks2, pair_cmp, NULL, 0);
 388
 389         child.no_stdin = 1;
 390         child.git_cmd = 1;
 391         child.use_shell = 0;
 392         child.clean_on_exit = 1;
 393         child.dir = prefix;
 394         child.out = -1;
 395         argv_array_pushl(&child.args, "diff", "--raw", "--no-abbrev", "-z",
 396                          NULL);
 397         for (i = 0; i < argc; i++)
 398                 argv_array_push(&child.args, argv[i]);
 399         if (start_command(&child))
 400                 die("could not obtain raw diff");
 401         fp = xfdopen(child.out, "r");
 402
 403         /* Build index info for left and right sides of the diff */
 404         i = 0;
 405         while (!strbuf_getline_nul(&info, fp)) {
 406                 int lmode, rmode;
 407                 struct object_id loid, roid;
 408                 char status;
 409                 const char *src_path, *dst_path;
 410
 411                 if (starts_with(info.buf, "::"))
 412                         die(N_("combined diff formats('-c' and '--cc') are "
 413                                "not supported in\n"
 414                                "directory diff mode('-d' and '--dir-diff')."));
 415
 416                 if (parse_index_info(info.buf, &lmode, &rmode, &loid, &roid,
 417                                      &status))
 418                         break;
 419                 if (strbuf_getline_nul(&lpath, fp))
 420                         break;
 421                 src_path = lpath.buf;
 422
 423                 i++;
 424                 if (status != 'C' && status != 'R') {
 425                         dst_path = src_path;
 426                 } else {
 427                         if (strbuf_getline_nul(&rpath, fp))
 428                                 break;
 429                         dst_path = rpath.buf;
 430                 }
 431
 432                 if (S_ISGITLINK(lmode) || S_ISGITLINK(rmode)) {
 433                         strbuf_reset(&buf);
 434                         strbuf_addf(&buf, "Subproject commit %s",
 435                                     oid_to_hex(&loid));
 436                         add_left_or_right(&submodules, src_path, buf.buf, 0);
 437                         strbuf_reset(&buf);
 438                         strbuf_addf(&buf, "Subproject commit %s",
 439                                     oid_to_hex(&roid));
 440                         if (!oidcmp(&loid, &roid))
 441                                 strbuf_addstr(&buf, "-dirty");
 442                         add_left_or_right(&submodules, dst_path, buf.buf, 1);
 443                         continue;
 444                 }
 445
 446                 if (S_ISLNK(lmode)) {
 447                         char *content = get_symlink(&loid, src_path);
 448                         add_left_or_right(&symlinks2, src_path, content, 0);
 449                         free(content);
 450                 }
 451
 452                 if (S_ISLNK(rmode)) {
 453                         char *content = get_symlink(&roid, dst_path);
 454                         add_left_or_right(&symlinks2, dst_path, content, 1);
 455                         free(content);
 456                 }
 457
 458                 if (lmode && status != 'C') {
 459                         if (checkout_path(lmode, &loid, src_path, &lstate)) {
 460                                 ret = error("could not write '%s'", src_path);
 461                                 goto finish;
 462                         }
 463                 }
 464
 465                 if (rmode && !S_ISLNK(rmode)) {
 466                         struct working_tree_entry *entry;
 467
 468                         /* Avoid duplicate working_tree entries */
 469                         FLEX_ALLOC_STR(entry, path, dst_path);
 470                         hashmap_entry_init(entry, strhash(dst_path));
 471                         if (hashmap_get(&working_tree_dups, entry, NULL)) {
 472                                 free(entry);
 473                                 continue;
 474                         }
 475                         hashmap_add(&working_tree_dups, entry);
 476
 477                         if (!use_wt_file(workdir, dst_path, &roid)) {
 478                                 if (checkout_path(rmode, &roid, dst_path,
 479                                                   &rstate)) {
 480                                         ret = error("could not write '%s'",
 481                                                     dst_path);
 482                                         goto finish;
 483                                 }
 484                         } else if (!is_null_oid(&roid)) {
 485                                 /*
 486                                  * Changes in the working tree need special
 487                                  * treatment since they are not part of the
 488                                  * index.
 489                                  */
 490                                 struct cache_entry *ce2 =
 491                                         make_cache_entry(rmode, roid.hash,
 492                                                          dst_path, 0, 0);
 493
 494                                 add_index_entry(&wtindex, ce2,
 495                                                 ADD_CACHE_JUST_APPEND);
 496
 497                                 add_path(&rdir, rdir_len, dst_path);
 498                                 if (ensure_leading_directories(rdir.buf)) {
 499                                         ret = error("could not create "
 500                                                     "directory for '%s'",
 501                                                     dst_path);
 502                                         goto finish;
 503                                 }
 504                                 add_path(&wtdir, wtdir_len, dst_path);
 505                                 if (symlinks) {
 506                                         if (symlink(wtdir.buf, rdir.buf)) {
 507                                                 ret = error_errno("could not symlink '%s' to '%s'", wtdir.buf, rdir.buf);
 508                                                 goto finish;
 509                                         }
 510                                 } else {
 511                                         struct stat st;
 512                                         if (stat(wtdir.buf, &st))
 513                                                 st.st_mode = 0644;
 514                                         if (copy_file(rdir.buf, wtdir.buf,
 515                                                       st.st_mode)) {
 516                                                 ret = error("could not copy '%s' to '%s'", wtdir.buf, rdir.buf);
 517                                                 goto finish;
 518                                         }
 519                                 }
 520                         }
 521                 }
 522         }
 523
 524         fclose(fp);
 525         fp = NULL;
 526         if (finish_command(&child)) {
 527                 ret = error("error occurred running diff --raw");
 528                 goto finish;
 529         }
 530
 531         if (!i)
 532                 goto finish;
 533
 534         /*
 535          * Changes to submodules require special treatment.This loop writes a
 536          * temporary file to both the left and right directories to show the
 537          * change in the recorded SHA1 for the submodule.
 538          */
 539         hashmap_iter_init(&submodules, &iter);
 540         while ((entry = hashmap_iter_next(&iter))) {
 541                 if (*entry->left) {
 542                         add_path(&ldir, ldir_len, entry->path);
 543                         ensure_leading_directories(ldir.buf);
 544                         write_file(ldir.buf, "%s", entry->left);
 545                 }
 546                 if (*entry->right) {
 547                         add_path(&rdir, rdir_len, entry->path);
 548                         ensure_leading_directories(rdir.buf);
 549                         write_file(rdir.buf, "%s", entry->right);
 550                 }
 551         }
 552
 553         /*
 554          * Symbolic links require special treatment.The standard "git diff"
 555          * shows only the link itself, not the contents of the link target.
 556          * This loop replicates that behavior.
 557          */
 558         hashmap_iter_init(&symlinks2, &iter);
 559         while ((entry = hashmap_iter_next(&iter))) {
 560                 if (*entry->left) {
 561                         add_path(&ldir, ldir_len, entry->path);
 562                         ensure_leading_directories(ldir.buf);
 563                         write_file(ldir.buf, "%s", entry->left);
 564                 }
 565                 if (*entry->right) {
 566                         add_path(&rdir, rdir_len, entry->path);
 567                         ensure_leading_directories(rdir.buf);
 568                         write_file(rdir.buf, "%s", entry->right);
 569                 }
 570         }
 571
 572         strbuf_release(&buf);
 573
 574         strbuf_setlen(&ldir, ldir_len);
 575         helper_argv[1] = ldir.buf;
 576         strbuf_setlen(&rdir, rdir_len);
 577         helper_argv[2] = rdir.buf;
 578
 579         if (extcmd) {
 580                 helper_argv[0] = extcmd;
 581                 flags = 0;
 582         } else
 583                 setenv("GIT_DIFFTOOL_DIRDIFF", "true", 1);
 584         rc = run_command_v_opt(helper_argv, flags);
 585
 586         /*
 587          * If the diff includes working copy files and those
 588          * files were modified during the diff, then the changes
 589          * should be copied back to the working tree.
 590          * Do not copy back files when symlinks are used and the
 591          * external tool did not replace the original link with a file.
 592          *
 593          * These hashes are loaded lazily since they aren't needed
 594          * in the common case of --symlinks and the difftool updating
 595          * files through the symlink.
 596          */
 597         hashmap_init(&wt_modified, path_entry_cmp, NULL, wtindex.cache_nr);
 598         hashmap_init(&tmp_modified, path_entry_cmp, NULL, wtindex.cache_nr);
 599
 600         for (i = 0; i < wtindex.cache_nr; i++) {
 601                 struct hashmap_entry dummy;
 602                 const char *name = wtindex.cache[i]->name;
 603                 struct stat st;
 604
 605                 add_path(&rdir, rdir_len, name);
 606                 if (lstat(rdir.buf, &st))
 607                         continue;
 608
 609                 if ((symlinks && S_ISLNK(st.st_mode)) || !S_ISREG(st.st_mode))
 610                         continue;
 611
 612                 if (!indices_loaded) {
 613                         static struct lock_file lock;
 614                         strbuf_reset(&buf);
 615                         strbuf_addf(&buf, "%s/wtindex", tmpdir);
 616                         if (hold_lock_file_for_update(&lock, buf.buf, 0) < 0 ||
 617                             write_locked_index(&wtindex, &lock, COMMIT_LOCK)) {
 618                                 ret = error("could not write %s", buf.buf);
 619                                 goto finish;
 620                         }
 621                         changed_files(&wt_modified, buf.buf, workdir);
 622                         strbuf_setlen(&rdir, rdir_len);
 623                         changed_files(&tmp_modified, buf.buf, rdir.buf);
 624                         add_path(&rdir, rdir_len, name);
 625                         indices_loaded = 1;
 626                 }
 627
 628                 hashmap_entry_init(&dummy, strhash(name));
 629                 if (hashmap_get(&tmp_modified, &dummy, name)) {
 630                         add_path(&wtdir, wtdir_len, name);
 631                         if (hashmap_get(&wt_modified, &dummy, name)) {
 632                                 warning(_("both files modified: '%s' and '%s'."),
 633                                         wtdir.buf, rdir.buf);
 634                                 warning(_("working tree file has been left."));
 635                                 warning("%s", "");
 636                                 err = 1;
 637                         } else if (unlink(wtdir.buf) ||
 638                                    copy_file(wtdir.buf, rdir.buf, st.st_mode))
 639                                 warning_errno(_("could not copy '%s' to '%s'"),
 640                                               rdir.buf, wtdir.buf);
 641                 }
 642         }
 643
 644         if (err) {
 645                 warning(_("temporary files exist in '%s'."), tmpdir);
 646                 warning(_("you may want to cleanup or recover these."));
 647                 exit(1);
 648         } else
 649                 exit_cleanup(tmpdir, rc);
 650
 651 finish:
 652         if (fp)
 653                 fclose(fp);
 654
 655         free(lbase_dir);
 656         free(rbase_dir);
 657         strbuf_release(&ldir);
 658         strbuf_release(&rdir);
 659         strbuf_release(&wtdir);
 660         strbuf_release(&buf);
 661
 662         return ret;
 663 }
 664
 665 static int run_file_diff(int prompt, const char *prefix,
 666                          int argc, const char **argv)
 667 {
 668         struct argv_array args = ARGV_ARRAY_INIT;
 669         const char *env[] = {
 670                 "GIT_PAGER=", "GIT_EXTERNAL_DIFF=git-difftool--helper", NULL,
 671                 NULL
 672         };
 673         int ret = 0, i;
 674
 675         if (prompt > 0)
 676                 env[2] = "GIT_DIFFTOOL_PROMPT=true";
 677         else if (!prompt)
 678                 env[2] = "GIT_DIFFTOOL_NO_PROMPT=true";
 679
 680
 681         argv_array_push(&args, "diff");
 682         for (i = 0; i < argc; i++)
 683                 argv_array_push(&args, argv[i]);
 684         ret = run_command_v_opt_cd_env(args.argv, RUN_GIT_CMD, prefix, env);
 685         exit(ret);
 686 }
 687
 688 int cmd_difftool(int argc, const char **argv, const char *prefix)
 689 {
 690         int use_gui_tool = 0, dir_diff = 0, prompt = -1, symlinks = 0,
 691             tool_help = 0;
 692         static char *difftool_cmd = NULL, *extcmd = NULL;
 693         struct option builtin_difftool_options[] = {
 694                 OPT_BOOL('g', "gui", &use_gui_tool,
 695                          N_("use `diff.guitool` instead of `diff.tool`")),
 696                 OPT_BOOL('d', "dir-diff", &dir_diff,
 697                          N_("perform a full-directory diff")),
 698                 { OPTION_SET_INT, 'y', "no-prompt", &prompt, NULL,
 699                         N_("do not prompt before launching a diff tool"),
 700                         PARSE_OPT_NOARG | PARSE_OPT_NONEG, NULL, 0},
 701                 { OPTION_SET_INT, 0, "prompt", &prompt, NULL, NULL,
 702                         PARSE_OPT_NOARG | PARSE_OPT_NONEG | PARSE_OPT_HIDDEN,
 703                         NULL, 1 },
 704                 OPT_BOOL(0, "symlinks", &symlinks,
 705                          N_("use symlinks in dir-diff mode")),
 706                 OPT_STRING('t', "tool", &difftool_cmd, N_("<tool>"),
 707                            N_("use the specified diff tool")),
 708                 OPT_BOOL(0, "tool-help", &tool_help,
 709                          N_("print a list of diff tools that may be used with "
 710                             "`--tool`")),
 711                 OPT_BOOL(0, "trust-exit-code", &trust_exit_code,
 712                          N_("make 'git-difftool' exit when an invoked diff "
 713                             "tool returns a non - zero exit code")),
 714                 OPT_STRING('x', "extcmd", &extcmd, N_("<command>"),
 715                            N_("specify a custom command for viewing diffs")),
 716                 OPT_END()
 717         };
 718
 719         git_config(difftool_config, NULL);
 720         symlinks = has_symlinks;
 721
 722         argc = parse_options(argc, argv, prefix, builtin_difftool_options,
 723                              builtin_difftool_usage, PARSE_OPT_KEEP_UNKNOWN |
 724                              PARSE_OPT_KEEP_DASHDASH);
 725
 726         if (tool_help)
 727                 return print_tool_help();
 728
 729         /* NEEDSWORK: once we no longer spawn anything, remove this */
 730         setenv(GIT_DIR_ENVIRONMENT, absolute_path(get_git_dir()), 1);
 731         setenv(GIT_WORK_TREE_ENVIRONMENT, absolute_path(get_git_work_tree()), 1);
 732
 733         if (use_gui_tool && diff_gui_tool && *diff_gui_tool)
 734                 setenv("GIT_DIFF_TOOL", diff_gui_tool, 1);
 735         else if (difftool_cmd) {
 736                 if (*difftool_cmd)
 737                         setenv("GIT_DIFF_TOOL", difftool_cmd, 1);
 738                 else
 739                         die(_("no <tool> given for --tool=<tool>"));
 740         }
 741
 742         if (extcmd) {
 743                 if (*extcmd)
 744                         setenv("GIT_DIFFTOOL_EXTCMD", extcmd, 1);
 745                 else
 746                         die(_("no <cmd> given for --extcmd=<cmd>"));
 747         }
 748
 749         setenv("GIT_DIFFTOOL_TRUST_EXIT_CODE",
 750                trust_exit_code ? "true" : "false", 1);
 751
 752         /*
 753          * In directory diff mode, 'git-difftool--helper' is called once
 754          * to compare the a / b directories. In file diff mode, 'git diff'
 755          * will invoke a separate instance of 'git-difftool--helper' for
 756          * each file that changed.
 757          */
 758         if (dir_diff)
 759                 return run_dir_diff(extcmd, symlinks, prefix, argc, argv);
 760         return run_file_diff(prompt, prefix, argc, argv);
 761 }