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 "strvec.h"
  22 #include "strbuf.h"
  23 #include "lockfile.h"
  24 #include "object-store.h"
  25 #include "dir.h"
  26 #include "entry.h"
  27
  28 static int trust_exit_code;
  29
  30 static const char *const builtin_difftool_usage[] = {
  31         N_("git difftool [<options>] [<commit> [<commit>]] [--] [<path>...]"),
  32         NULL
  33 };
  34
  35 static int difftool_config(const char *var, const char *value, void *cb)
  36 {
  37         if (!strcmp(var, "difftool.trustexitcode")) {
  38                 trust_exit_code = git_config_bool(var, value);
  39                 return 0;
  40         }
  41
  42         return git_default_config(var, value, cb);
  43 }
  44
  45 static int print_tool_help(void)
  46 {
  47         const char *argv[] = { "mergetool", "--tool-help=diff", NULL };
  48         return run_command_v_opt(argv, RUN_GIT_CMD);
  49 }
  50
  51 static int parse_index_info(char *p, int *mode1, int *mode2,
  52                             struct object_id *oid1, struct object_id *oid2,
  53                             char *status)
  54 {
  55         if (*p != ':')
  56                 return error("expected ':', got '%c'", *p);
  57         *mode1 = (int)strtol(p + 1, &p, 8);
  58         if (*p != ' ')
  59                 return error("expected ' ', got '%c'", *p);
  60         *mode2 = (int)strtol(p + 1, &p, 8);
  61         if (*p != ' ')
  62                 return error("expected ' ', got '%c'", *p);
  63         if (parse_oid_hex(++p, oid1, (const char **)&p))
  64                 return error("expected object ID, got '%s'", p);
  65         if (*p != ' ')
  66                 return error("expected ' ', got '%c'", *p);
  67         if (parse_oid_hex(++p, oid2, (const char **)&p))
  68                 return error("expected object ID, got '%s'", p);
  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 struct hashmap_entry *eptr,
 130                                   const struct hashmap_entry *entry_or_key,
 131                                   const void *unused_keydata)
 132 {
 133         const struct working_tree_entry *a, *b;
 134
 135         a = container_of(eptr, const struct working_tree_entry, entry);
 136         b = container_of(entry_or_key, const struct working_tree_entry, entry);
 137
 138         return strcmp(a->path, b->path);
 139 }
 140
 141 /*
 142  * The `left` and `right` entries hold paths for the symlinks hashmap,
 143  * and a SHA-1 surrounded by brief text for submodules.
 144  */
 145 struct pair_entry {
 146         struct hashmap_entry entry;
 147         char left[PATH_MAX], right[PATH_MAX];
 148         const char path[FLEX_ARRAY];
 149 };
 150
 151 static int pair_cmp(const void *unused_cmp_data,
 152                     const struct hashmap_entry *eptr,
 153                     const struct hashmap_entry *entry_or_key,
 154                     const void *unused_keydata)
 155 {
 156         const struct pair_entry *a, *b;
 157
 158         a = container_of(eptr, const struct pair_entry, entry);
 159         b = container_of(entry_or_key, const struct pair_entry, entry);
 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->entry, strhash(path));
 171         existing = hashmap_get_entry(map, e, entry, 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->entry);
 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 struct hashmap_entry *eptr,
 189                           const struct hashmap_entry *entry_or_key,
 190                           const void *key)
 191 {
 192         const struct path_entry *a, *b;
 193
 194         a = container_of(eptr, const struct path_entry, entry);
 195         b = container_of(entry_or_key, const struct path_entry, entry);
 196
 197         return strcmp(a->path, key ? key : b->path);
 198 }
 199
 200 static void changed_files(struct hashmap *result, const char *index_path,
 201                           const char *workdir)
 202 {
 203         struct child_process update_index = CHILD_PROCESS_INIT;
 204         struct child_process diff_files = CHILD_PROCESS_INIT;
 205         struct strbuf index_env = STRBUF_INIT, buf = STRBUF_INIT;
 206         const char *git_dir = absolute_path(get_git_dir()), *env[] = {
 207                 NULL, NULL
 208         };
 209         FILE *fp;
 210
 211         strbuf_addf(&index_env, "GIT_INDEX_FILE=%s", index_path);
 212         env[0] = index_env.buf;
 213
 214         strvec_pushl(&update_index.args,
 215                      "--git-dir", git_dir, "--work-tree", workdir,
 216                      "update-index", "--really-refresh", "-q",
 217                      "--unmerged", NULL);
 218         update_index.no_stdin = 1;
 219         update_index.no_stdout = 1;
 220         update_index.no_stderr = 1;
 221         update_index.git_cmd = 1;
 222         update_index.use_shell = 0;
 223         update_index.clean_on_exit = 1;
 224         update_index.dir = workdir;
 225         update_index.env = env;
 226         /* Ignore any errors of update-index */
 227         run_command(&update_index);
 228
 229         strvec_pushl(&diff_files.args,
 230                      "--git-dir", git_dir, "--work-tree", workdir,
 231                      "diff-files", "--name-only", "-z", NULL);
 232         diff_files.no_stdin = 1;
 233         diff_files.git_cmd = 1;
 234         diff_files.use_shell = 0;
 235         diff_files.clean_on_exit = 1;
 236         diff_files.out = -1;
 237         diff_files.dir = workdir;
 238         diff_files.env = env;
 239         if (start_command(&diff_files))
 240                 die("could not obtain raw diff");
 241         fp = xfdopen(diff_files.out, "r");
 242         while (!strbuf_getline_nul(&buf, fp)) {
 243                 struct path_entry *entry;
 244                 FLEX_ALLOC_STR(entry, path, buf.buf);
 245                 hashmap_entry_init(&entry->entry, strhash(buf.buf));
 246                 hashmap_add(result, &entry->entry);
 247         }
 248         fclose(fp);
 249         if (finish_command(&diff_files))
 250                 die("diff-files did not exit properly");
 251         strbuf_release(&index_env);
 252         strbuf_release(&buf);
 253 }
 254
 255 static NORETURN void exit_cleanup(const char *tmpdir, int exit_code)
 256 {
 257         struct strbuf buf = STRBUF_INIT;
 258         strbuf_addstr(&buf, tmpdir);
 259         remove_dir_recursively(&buf, 0);
 260         if (exit_code)
 261                 warning(_("failed: %d"), exit_code);
 262         exit(exit_code);
 263 }
 264
 265 static int ensure_leading_directories(char *path)
 266 {
 267         switch (safe_create_leading_directories(path)) {
 268                 case SCLD_OK:
 269                 case SCLD_EXISTS:
 270                         return 0;
 271                 default:
 272                         return error(_("could not create leading directories "
 273                                        "of '%s'"), path);
 274         }
 275 }
 276
 277 /*
 278  * Unconditional writing of a plain regular file is what
 279  * "git difftool --dir-diff" wants to do for symlinks.  We are preparing two
 280  * temporary directories to be fed to a Git-unaware tool that knows how to
 281  * show a diff of two directories (e.g. "diff -r A B").
 282  *
 283  * Because the tool is Git-unaware, if a symbolic link appears in either of
 284  * these temporary directories, it will try to dereference and show the
 285  * difference of the target of the symbolic link, which is not what we want,
 286  * as the goal of the dir-diff mode is to produce an output that is logically
 287  * equivalent to what "git diff" produces.
 288  *
 289  * Most importantly, we want to get textual comparison of the result of the
 290  * readlink(2).  get_symlink() provides that---it returns the contents of
 291  * the symlink that gets written to a regular file to force the external tool
 292  * to compare the readlink(2) result as text, even on a filesystem that is
 293  * capable of doing a symbolic link.
 294  */
 295 static char *get_symlink(const struct object_id *oid, const char *path)
 296 {
 297         char *data;
 298         if (is_null_oid(oid)) {
 299                 /* The symlink is unknown to Git so read from the filesystem */
 300                 struct strbuf link = STRBUF_INIT;
 301                 if (has_symlinks) {
 302                         if (strbuf_readlink(&link, path, strlen(path)))
 303                                 die(_("could not read symlink %s"), path);
 304                 } else if (strbuf_read_file(&link, path, 128))
 305                         die(_("could not read symlink file %s"), path);
 306
 307                 data = strbuf_detach(&link, NULL);
 308         } else {
 309                 enum object_type type;
 310                 unsigned long size;
 311                 data = read_object_file(oid, &type, &size);
 312                 if (!data)
 313                         die(_("could not read object %s for symlink %s"),
 314                                 oid_to_hex(oid), path);
 315         }
 316
 317         return data;
 318 }
 319
 320 static int checkout_path(unsigned mode, struct object_id *oid,
 321                          const char *path, const struct checkout *state)
 322 {
 323         struct cache_entry *ce;
 324         int ret;
 325
 326         ce = make_transient_cache_entry(mode, oid, path, 0, NULL);
 327         ret = checkout_entry(ce, state, NULL, NULL);
 328
 329         discard_cache_entry(ce);
 330         return ret;
 331 }
 332
 333 static int run_dir_diff(const char *extcmd, int symlinks, const char *prefix,
 334                         struct child_process *child)
 335 {
 336         char tmpdir[PATH_MAX];
 337         struct strbuf info = STRBUF_INIT, lpath = STRBUF_INIT;
 338         struct strbuf rpath = STRBUF_INIT, buf = STRBUF_INIT;
 339         struct strbuf ldir = STRBUF_INIT, rdir = STRBUF_INIT;
 340         struct strbuf wtdir = STRBUF_INIT;
 341         char *lbase_dir, *rbase_dir;
 342         size_t ldir_len, rdir_len, wtdir_len;
 343         const char *workdir, *tmp;
 344         int ret = 0, i;
 345         FILE *fp;
 346         struct hashmap working_tree_dups = HASHMAP_INIT(working_tree_entry_cmp,
 347                                                         NULL);
 348         struct hashmap submodules = HASHMAP_INIT(pair_cmp, NULL);
 349         struct hashmap symlinks2 = HASHMAP_INIT(pair_cmp, NULL);
 350         struct hashmap_iter iter;
 351         struct pair_entry *entry;
 352         struct index_state wtindex;
 353         struct checkout lstate, rstate;
 354         int rc, flags = RUN_GIT_CMD, err = 0;
 355         const char *helper_argv[] = { "difftool--helper", NULL, NULL, NULL };
 356         struct hashmap wt_modified, tmp_modified;
 357         int indices_loaded = 0;
 358
 359         workdir = get_git_work_tree();
 360
 361         /* Setup temp directories */
 362         tmp = getenv("TMPDIR");
 363         xsnprintf(tmpdir, sizeof(tmpdir), "%s/git-difftool.XXXXXX", tmp ? tmp : "/tmp");
 364         if (!mkdtemp(tmpdir))
 365                 return error("could not create '%s'", tmpdir);
 366         strbuf_addf(&ldir, "%s/left/", tmpdir);
 367         strbuf_addf(&rdir, "%s/right/", tmpdir);
 368         strbuf_addstr(&wtdir, workdir);
 369         if (!wtdir.len || !is_dir_sep(wtdir.buf[wtdir.len - 1]))
 370                 strbuf_addch(&wtdir, '/');
 371         mkdir(ldir.buf, 0700);
 372         mkdir(rdir.buf, 0700);
 373
 374         memset(&wtindex, 0, sizeof(wtindex));
 375
 376         memset(&lstate, 0, sizeof(lstate));
 377         lstate.base_dir = lbase_dir = xstrdup(ldir.buf);
 378         lstate.base_dir_len = ldir.len;
 379         lstate.force = 1;
 380         memset(&rstate, 0, sizeof(rstate));
 381         rstate.base_dir = rbase_dir = xstrdup(rdir.buf);
 382         rstate.base_dir_len = rdir.len;
 383         rstate.force = 1;
 384
 385         ldir_len = ldir.len;
 386         rdir_len = rdir.len;
 387         wtdir_len = wtdir.len;
 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         if (start_command(child))
 396                 die("could not obtain raw diff");
 397         fp = xfdopen(child->out, "r");
 398
 399         /* Build index info for left and right sides of the diff */
 400         i = 0;
 401         while (!strbuf_getline_nul(&info, fp)) {
 402                 int lmode, rmode;
 403                 struct object_id loid, roid;
 404                 char status;
 405                 const char *src_path, *dst_path;
 406
 407                 if (starts_with(info.buf, "::"))
 408                         die(N_("combined diff formats ('-c' and '--cc') are "
 409                                "not supported in\n"
 410                                "directory diff mode ('-d' and '--dir-diff')."));
 411
 412                 if (parse_index_info(info.buf, &lmode, &rmode, &loid, &roid,
 413                                      &status))
 414                         break;
 415                 if (strbuf_getline_nul(&lpath, fp))
 416                         break;
 417                 src_path = lpath.buf;
 418
 419                 i++;
 420                 if (status != 'C' && status != 'R') {
 421                         dst_path = src_path;
 422                 } else {
 423                         if (strbuf_getline_nul(&rpath, fp))
 424                                 break;
 425                         dst_path = rpath.buf;
 426                 }
 427
 428                 if (S_ISGITLINK(lmode) || S_ISGITLINK(rmode)) {
 429                         strbuf_reset(&buf);
 430                         strbuf_addf(&buf, "Subproject commit %s",
 431                                     oid_to_hex(&loid));
 432                         add_left_or_right(&submodules, src_path, buf.buf, 0);
 433                         strbuf_reset(&buf);
 434                         strbuf_addf(&buf, "Subproject commit %s",
 435                                     oid_to_hex(&roid));
 436                         if (oideq(&loid, &roid))
 437                                 strbuf_addstr(&buf, "-dirty");
 438                         add_left_or_right(&submodules, dst_path, buf.buf, 1);
 439                         continue;
 440                 }
 441
 442                 if (S_ISLNK(lmode)) {
 443                         char *content = get_symlink(&loid, src_path);
 444                         add_left_or_right(&symlinks2, src_path, content, 0);
 445                         free(content);
 446                 }
 447
 448                 if (S_ISLNK(rmode)) {
 449                         char *content = get_symlink(&roid, dst_path);
 450                         add_left_or_right(&symlinks2, dst_path, content, 1);
 451                         free(content);
 452                 }
 453
 454                 if (lmode && status != 'C') {
 455                         if (checkout_path(lmode, &loid, src_path, &lstate)) {
 456                                 ret = error("could not write '%s'", src_path);
 457                                 goto finish;
 458                         }
 459                 }
 460
 461                 if (rmode && !S_ISLNK(rmode)) {
 462                         struct working_tree_entry *entry;
 463
 464                         /* Avoid duplicate working_tree entries */
 465                         FLEX_ALLOC_STR(entry, path, dst_path);
 466                         hashmap_entry_init(&entry->entry, strhash(dst_path));
 467                         if (hashmap_get(&working_tree_dups, &entry->entry,
 468                                         NULL)) {
 469                                 free(entry);
 470                                 continue;
 471                         }
 472                         hashmap_add(&working_tree_dups, &entry->entry);
 473
 474                         if (!use_wt_file(workdir, dst_path, &roid)) {
 475                                 if (checkout_path(rmode, &roid, dst_path,
 476                                                   &rstate)) {
 477                                         ret = error("could not write '%s'",
 478                                                     dst_path);
 479                                         goto finish;
 480                                 }
 481                         } else if (!is_null_oid(&roid)) {
 482                                 /*
 483                                  * Changes in the working tree need special
 484                                  * treatment since they are not part of the
 485                                  * index.
 486                                  */
 487                                 struct cache_entry *ce2 =
 488                                         make_cache_entry(&wtindex, rmode, &roid,
 489                                                          dst_path, 0, 0);
 490
 491                                 add_index_entry(&wtindex, ce2,
 492                                                 ADD_CACHE_JUST_APPEND);
 493
 494                                 add_path(&rdir, rdir_len, dst_path);
 495                                 if (ensure_leading_directories(rdir.buf)) {
 496                                         ret = error("could not create "
 497                                                     "directory for '%s'",
 498                                                     dst_path);
 499                                         goto finish;
 500                                 }
 501                                 add_path(&wtdir, wtdir_len, dst_path);
 502                                 if (symlinks) {
 503                                         if (symlink(wtdir.buf, rdir.buf)) {
 504                                                 ret = error_errno("could not symlink '%s' to '%s'", wtdir.buf, rdir.buf);
 505                                                 goto finish;
 506                                         }
 507                                 } else {
 508                                         struct stat st;
 509                                         if (stat(wtdir.buf, &st))
 510                                                 st.st_mode = 0644;
 511                                         if (copy_file(rdir.buf, wtdir.buf,
 512                                                       st.st_mode)) {
 513                                                 ret = error("could not copy '%s' to '%s'", wtdir.buf, rdir.buf);
 514                                                 goto finish;
 515                                         }
 516                                 }
 517                         }
 518                 }
 519         }
 520
 521         fclose(fp);
 522         fp = NULL;
 523         if (finish_command(child)) {
 524                 ret = error("error occurred running diff --raw");
 525                 goto finish;
 526         }
 527
 528         if (!i)
 529                 goto finish;
 530
 531         /*
 532          * Changes to submodules require special treatment.This loop writes a
 533          * temporary file to both the left and right directories to show the
 534          * change in the recorded SHA1 for the submodule.
 535          */
 536         hashmap_for_each_entry(&submodules, &iter, entry,
 537                                 entry /* member name */) {
 538                 if (*entry->left) {
 539                         add_path(&ldir, ldir_len, entry->path);
 540                         ensure_leading_directories(ldir.buf);
 541                         write_file(ldir.buf, "%s", entry->left);
 542                 }
 543                 if (*entry->right) {
 544                         add_path(&rdir, rdir_len, entry->path);
 545                         ensure_leading_directories(rdir.buf);
 546                         write_file(rdir.buf, "%s", entry->right);
 547                 }
 548         }
 549
 550         /*
 551          * Symbolic links require special treatment.The standard "git diff"
 552          * shows only the link itself, not the contents of the link target.
 553          * This loop replicates that behavior.
 554          */
 555         hashmap_for_each_entry(&symlinks2, &iter, entry,
 556                                 entry /* member name */) {
 557                 if (*entry->left) {
 558                         add_path(&ldir, ldir_len, entry->path);
 559                         ensure_leading_directories(ldir.buf);
 560                         unlink(ldir.buf);
 561                         write_file(ldir.buf, "%s", entry->left);
 562                 }
 563                 if (*entry->right) {
 564                         add_path(&rdir, rdir_len, entry->path);
 565                         ensure_leading_directories(rdir.buf);
 566                         unlink(rdir.buf);
 567                         write_file(rdir.buf, "%s", entry->right);
 568                 }
 569         }
 570
 571         strbuf_release(&buf);
 572
 573         strbuf_setlen(&ldir, ldir_len);
 574         helper_argv[1] = ldir.buf;
 575         strbuf_setlen(&rdir, rdir_len);
 576         helper_argv[2] = rdir.buf;
 577
 578         if (extcmd) {
 579                 helper_argv[0] = extcmd;
 580                 flags = 0;
 581         } else
 582                 setenv("GIT_DIFFTOOL_DIRDIFF", "true", 1);
 583         rc = run_command_v_opt(helper_argv, flags);
 584
 585         /* TODO: audit for interaction with sparse-index. */
 586         ensure_full_index(&wtindex);
 587
 588         /*
 589          * If the diff includes working copy files and those
 590          * files were modified during the diff, then the changes
 591          * should be copied back to the working tree.
 592          * Do not copy back files when symlinks are used and the
 593          * external tool did not replace the original link with a file.
 594          *
 595          * These hashes are loaded lazily since they aren't needed
 596          * in the common case of --symlinks and the difftool updating
 597          * files through the symlink.
 598          */
 599         hashmap_init(&wt_modified, path_entry_cmp, NULL, wtindex.cache_nr);
 600         hashmap_init(&tmp_modified, path_entry_cmp, NULL, wtindex.cache_nr);
 601
 602         for (i = 0; i < wtindex.cache_nr; i++) {
 603                 struct hashmap_entry dummy;
 604                 const char *name = wtindex.cache[i]->name;
 605                 struct stat st;
 606
 607                 add_path(&rdir, rdir_len, name);
 608                 if (lstat(rdir.buf, &st))
 609                         continue;
 610
 611                 if ((symlinks && S_ISLNK(st.st_mode)) || !S_ISREG(st.st_mode))
 612                         continue;
 613
 614                 if (!indices_loaded) {
 615                         struct lock_file lock = LOCK_INIT;
 616                         strbuf_reset(&buf);
 617                         strbuf_addf(&buf, "%s/wtindex", tmpdir);
 618                         if (hold_lock_file_for_update(&lock, buf.buf, 0) < 0 ||
 619                             write_locked_index(&wtindex, &lock, COMMIT_LOCK)) {
 620                                 ret = error("could not write %s", buf.buf);
 621                                 goto finish;
 622                         }
 623                         changed_files(&wt_modified, buf.buf, workdir);
 624                         strbuf_setlen(&rdir, rdir_len);
 625                         changed_files(&tmp_modified, buf.buf, rdir.buf);
 626                         add_path(&rdir, rdir_len, name);
 627                         indices_loaded = 1;
 628                 }
 629
 630                 hashmap_entry_init(&dummy, strhash(name));
 631                 if (hashmap_get(&tmp_modified, &dummy, name)) {
 632                         add_path(&wtdir, wtdir_len, name);
 633                         if (hashmap_get(&wt_modified, &dummy, name)) {
 634                                 warning(_("both files modified: '%s' and '%s'."),
 635                                         wtdir.buf, rdir.buf);
 636                                 warning(_("working tree file has been left."));
 637                                 warning("%s", "");
 638                                 err = 1;
 639                         } else if (unlink(wtdir.buf) ||
 640                                    copy_file(wtdir.buf, rdir.buf, st.st_mode))
 641                                 warning_errno(_("could not copy '%s' to '%s'"),
 642                                               rdir.buf, wtdir.buf);
 643                 }
 644         }
 645
 646         if (err) {
 647                 warning(_("temporary files exist in '%s'."), tmpdir);
 648                 warning(_("you may want to cleanup or recover these."));
 649                 exit(1);
 650         } else
 651                 exit_cleanup(tmpdir, rc);
 652
 653 finish:
 654         if (fp)
 655                 fclose(fp);
 656
 657         free(lbase_dir);
 658         free(rbase_dir);
 659         strbuf_release(&ldir);
 660         strbuf_release(&rdir);
 661         strbuf_release(&wtdir);
 662         strbuf_release(&buf);
 663
 664         return ret;
 665 }
 666
 667 static int run_file_diff(int prompt, const char *prefix,
 668                          struct child_process *child)
 669 {
 670         const char *env[] = {
 671                 "GIT_PAGER=", "GIT_EXTERNAL_DIFF=git-difftool--helper", NULL,
 672                 NULL
 673         };
 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         child->git_cmd = 1;
 681         child->dir = prefix;
 682         strvec_pushv(&child->env_array, env);
 683
 684         return run_command(child);
 685 }
 686
 687 int cmd_difftool(int argc, const char **argv, const char *prefix)
 688 {
 689         int use_gui_tool = 0, dir_diff = 0, prompt = -1, symlinks = 0,
 690             tool_help = 0, no_index = 0;
 691         static char *difftool_cmd = NULL, *extcmd = NULL;
 692         struct option builtin_difftool_options[] = {
 693                 OPT_BOOL('g', "gui", &use_gui_tool,
 694                          N_("use `diff.guitool` instead of `diff.tool`")),
 695                 OPT_BOOL('d', "dir-diff", &dir_diff,
 696                          N_("perform a full-directory diff")),
 697                 OPT_SET_INT_F('y', "no-prompt", &prompt,
 698                         N_("do not prompt before launching a diff tool"),
 699                         0, PARSE_OPT_NONEG),
 700                 OPT_SET_INT_F(0, "prompt", &prompt, NULL,
 701                         1, PARSE_OPT_NONEG | PARSE_OPT_HIDDEN),
 702                 OPT_BOOL(0, "symlinks", &symlinks,
 703                          N_("use symlinks in dir-diff mode")),
 704                 OPT_STRING('t', "tool", &difftool_cmd, N_("tool"),
 705                            N_("use the specified diff tool")),
 706                 OPT_BOOL(0, "tool-help", &tool_help,
 707                          N_("print a list of diff tools that may be used with "
 708                             "`--tool`")),
 709                 OPT_BOOL(0, "trust-exit-code", &trust_exit_code,
 710                          N_("make 'git-difftool' exit when an invoked diff "
 711                             "tool returns a non-zero exit code")),
 712                 OPT_STRING('x', "extcmd", &extcmd, N_("command"),
 713                            N_("specify a custom command for viewing diffs")),
 714                 OPT_BOOL(0, "no-index", &no_index, N_("passed to `diff`")),
 715                 OPT_END()
 716         };
 717         struct child_process child = CHILD_PROCESS_INIT;
 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         if (!no_index && !startup_info->have_repository)
 730                 die(_("difftool requires worktree or --no-index"));
 731
 732         if (!no_index){
 733                 setup_work_tree();
 734                 setenv(GIT_DIR_ENVIRONMENT, absolute_path(get_git_dir()), 1);
 735                 setenv(GIT_WORK_TREE_ENVIRONMENT, absolute_path(get_git_work_tree()), 1);
 736         } else if (dir_diff)
 737                 die(_("--dir-diff is incompatible with --no-index"));
 738
 739         if (use_gui_tool + !!difftool_cmd + !!extcmd > 1)
 740                 die(_("--gui, --tool and --extcmd are mutually exclusive"));
 741
 742         if (use_gui_tool)
 743                 setenv("GIT_MERGETOOL_GUI", "true", 1);
 744         else if (difftool_cmd) {
 745                 if (*difftool_cmd)
 746                         setenv("GIT_DIFF_TOOL", difftool_cmd, 1);
 747                 else
 748                         die(_("no <tool> given for --tool=<tool>"));
 749         }
 750
 751         if (extcmd) {
 752                 if (*extcmd)
 753                         setenv("GIT_DIFFTOOL_EXTCMD", extcmd, 1);
 754                 else
 755                         die(_("no <cmd> given for --extcmd=<cmd>"));
 756         }
 757
 758         setenv("GIT_DIFFTOOL_TRUST_EXIT_CODE",
 759                trust_exit_code ? "true" : "false", 1);
 760
 761         /*
 762          * In directory diff mode, 'git-difftool--helper' is called once
 763          * to compare the a / b directories. In file diff mode, 'git diff'
 764          * will invoke a separate instance of 'git-difftool--helper' for
 765          * each file that changed.
 766          */
 767         strvec_push(&child.args, "diff");
 768         if (no_index)
 769                 strvec_push(&child.args, "--no-index");
 770         if (dir_diff)
 771                 strvec_pushl(&child.args, "--raw", "--no-abbrev", "-z", NULL);
 772         strvec_pushv(&child.args, argv);
 773
 774         if (dir_diff)
 775                 return run_dir_diff(extcmd, symlinks, prefix, &child);
 776         return run_file_diff(prompt, prefix, &child);
 777 }