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_VARIABLE
  15 #include "builtin.h"
  16 #include "abspath.h"
  17 #include "config.h"
  18 #include "copy.h"
  19 #include "run-command.h"
  20 #include "environment.h"
  21 #include "exec-cmd.h"
  22 #include "gettext.h"
  23 #include "hex.h"
  24 #include "parse-options.h"
  25 #include "read-cache-ll.h"
  26 #include "sparse-index.h"
  27 #include "strvec.h"
  28 #include "strbuf.h"
  29 #include "lockfile.h"
  30 #include "object-file.h"
  31 #include "object-store-ll.h"
  32 #include "dir.h"
  33 #include "entry.h"
  34 #include "setup.h"
  35
  36 static int trust_exit_code;
  37
  38 static const char *const builtin_difftool_usage[] = {
  39         N_("git difftool [<options>] [<commit> [<commit>]] [--] [<path>...]"),
  40         NULL
  41 };
  42
  43 static int difftool_config(const char *var, const char *value,
  44                            const struct config_context *ctx, void *cb)
  45 {
  46         if (!strcmp(var, "difftool.trustexitcode")) {
  47                 trust_exit_code = git_config_bool(var, value);
  48                 return 0;
  49         }
  50
  51         return git_default_config(var, value, ctx, cb);
  52 }
  53
  54 static int print_tool_help(void)
  55 {
  56         struct child_process cmd = CHILD_PROCESS_INIT;
  57
  58         cmd.git_cmd = 1;
  59         strvec_pushl(&cmd.args, "mergetool", "--tool-help=diff", NULL);
  60         return run_command(&cmd);
  61 }
  62
  63 static int parse_index_info(char *p, int *mode1, int *mode2,
  64                             struct object_id *oid1, struct object_id *oid2,
  65                             char *status)
  66 {
  67         if (*p != ':')
  68                 return error("expected ':', got '%c'", *p);
  69         *mode1 = (int)strtol(p + 1, &p, 8);
  70         if (*p != ' ')
  71                 return error("expected ' ', got '%c'", *p);
  72         *mode2 = (int)strtol(p + 1, &p, 8);
  73         if (*p != ' ')
  74                 return error("expected ' ', got '%c'", *p);
  75         if (parse_oid_hex(++p, oid1, (const char **)&p))
  76                 return error("expected object ID, got '%s'", p);
  77         if (*p != ' ')
  78                 return error("expected ' ', got '%c'", *p);
  79         if (parse_oid_hex(++p, oid2, (const char **)&p))
  80                 return error("expected object ID, got '%s'", p);
  81         if (*p != ' ')
  82                 return error("expected ' ', got '%c'", *p);
  83         *status = *++p;
  84         if (!*status)
  85                 return error("missing status");
  86         if (p[1] && !isdigit(p[1]))
  87                 return error("unexpected trailer: '%s'", p + 1);
  88         return 0;
  89 }
  90
  91 /*
  92  * Remove any trailing slash from $workdir
  93  * before starting to avoid double slashes in symlink targets.
  94  */
  95 static void add_path(struct strbuf *buf, size_t base_len, const char *path)
  96 {
  97         strbuf_setlen(buf, base_len);
  98         if (buf->len && buf->buf[buf->len - 1] != '/')
  99                 strbuf_addch(buf, '/');
 100         strbuf_addstr(buf, path);
 101 }
 102
 103 /*
 104  * Determine whether we can simply reuse the file in the worktree.
 105  */
 106 static int use_wt_file(const char *workdir, const char *name,
 107                        struct object_id *oid)
 108 {
 109         struct strbuf buf = STRBUF_INIT;
 110         struct stat st;
 111         int use = 0;
 112
 113         strbuf_addstr(&buf, workdir);
 114         add_path(&buf, buf.len, name);
 115
 116         if (!lstat(buf.buf, &st) && !S_ISLNK(st.st_mode)) {
 117                 struct object_id wt_oid;
 118                 int fd = open(buf.buf, O_RDONLY);
 119
 120                 if (fd >= 0 &&
 121                     !index_fd(&the_index, &wt_oid, fd, &st, OBJ_BLOB, name, 0)) {
 122                         if (is_null_oid(oid)) {
 123                                 oidcpy(oid, &wt_oid);
 124                                 use = 1;
 125                         } else if (oideq(oid, &wt_oid))
 126                                 use = 1;
 127                 }
 128         }
 129
 130         strbuf_release(&buf);
 131
 132         return use;
 133 }
 134
 135 struct working_tree_entry {
 136         struct hashmap_entry entry;
 137         char path[FLEX_ARRAY];
 138 };
 139
 140 static int working_tree_entry_cmp(const void *cmp_data UNUSED,
 141                                   const struct hashmap_entry *eptr,
 142                                   const struct hashmap_entry *entry_or_key,
 143                                   const void *keydata UNUSED)
 144 {
 145         const struct working_tree_entry *a, *b;
 146
 147         a = container_of(eptr, const struct working_tree_entry, entry);
 148         b = container_of(entry_or_key, const struct working_tree_entry, entry);
 149
 150         return strcmp(a->path, b->path);
 151 }
 152
 153 /*
 154  * The `left` and `right` entries hold paths for the symlinks hashmap,
 155  * and a SHA-1 surrounded by brief text for submodules.
 156  */
 157 struct pair_entry {
 158         struct hashmap_entry entry;
 159         char left[PATH_MAX], right[PATH_MAX];
 160         const char path[FLEX_ARRAY];
 161 };
 162
 163 static int pair_cmp(const void *cmp_data UNUSED,
 164                     const struct hashmap_entry *eptr,
 165                     const struct hashmap_entry *entry_or_key,
 166                     const void *keydata UNUSED)
 167 {
 168         const struct pair_entry *a, *b;
 169
 170         a = container_of(eptr, const struct pair_entry, entry);
 171         b = container_of(entry_or_key, const struct pair_entry, entry);
 172
 173         return strcmp(a->path, b->path);
 174 }
 175
 176 static void add_left_or_right(struct hashmap *map, const char *path,
 177                               const char *content, int is_right)
 178 {
 179         struct pair_entry *e, *existing;
 180
 181         FLEX_ALLOC_STR(e, path, path);
 182         hashmap_entry_init(&e->entry, strhash(path));
 183         existing = hashmap_get_entry(map, e, entry, NULL);
 184         if (existing) {
 185                 free(e);
 186                 e = existing;
 187         } else {
 188                 e->left[0] = e->right[0] = '\0';
 189                 hashmap_add(map, &e->entry);
 190         }
 191         strlcpy(is_right ? e->right : e->left, content, PATH_MAX);
 192 }
 193
 194 struct path_entry {
 195         struct hashmap_entry entry;
 196         char path[FLEX_ARRAY];
 197 };
 198
 199 static int path_entry_cmp(const void *cmp_data UNUSED,
 200                           const struct hashmap_entry *eptr,
 201                           const struct hashmap_entry *entry_or_key,
 202                           const void *key)
 203 {
 204         const struct path_entry *a, *b;
 205
 206         a = container_of(eptr, const struct path_entry, entry);
 207         b = container_of(entry_or_key, const struct path_entry, entry);
 208
 209         return strcmp(a->path, key ? key : b->path);
 210 }
 211
 212 static void changed_files(struct hashmap *result, const char *index_path,
 213                           const char *workdir)
 214 {
 215         struct child_process update_index = CHILD_PROCESS_INIT;
 216         struct child_process diff_files = CHILD_PROCESS_INIT;
 217         struct strbuf buf = STRBUF_INIT;
 218         const char *git_dir = absolute_path(get_git_dir());
 219         FILE *fp;
 220
 221         strvec_pushl(&update_index.args,
 222                      "--git-dir", git_dir, "--work-tree", workdir,
 223                      "update-index", "--really-refresh", "-q",
 224                      "--unmerged", NULL);
 225         update_index.no_stdin = 1;
 226         update_index.no_stdout = 1;
 227         update_index.no_stderr = 1;
 228         update_index.git_cmd = 1;
 229         update_index.use_shell = 0;
 230         update_index.clean_on_exit = 1;
 231         update_index.dir = workdir;
 232         strvec_pushf(&update_index.env, "GIT_INDEX_FILE=%s", index_path);
 233         /* Ignore any errors of update-index */
 234         run_command(&update_index);
 235
 236         strvec_pushl(&diff_files.args,
 237                      "--git-dir", git_dir, "--work-tree", workdir,
 238                      "diff-files", "--name-only", "-z", NULL);
 239         diff_files.no_stdin = 1;
 240         diff_files.git_cmd = 1;
 241         diff_files.use_shell = 0;
 242         diff_files.clean_on_exit = 1;
 243         diff_files.out = -1;
 244         diff_files.dir = workdir;
 245         strvec_pushf(&diff_files.env, "GIT_INDEX_FILE=%s", index_path);
 246         if (start_command(&diff_files))
 247                 die("could not obtain raw diff");
 248         fp = xfdopen(diff_files.out, "r");
 249         while (!strbuf_getline_nul(&buf, fp)) {
 250                 struct path_entry *entry;
 251                 FLEX_ALLOC_STR(entry, path, buf.buf);
 252                 hashmap_entry_init(&entry->entry, strhash(buf.buf));
 253                 hashmap_add(result, &entry->entry);
 254         }
 255         fclose(fp);
 256         if (finish_command(&diff_files))
 257                 die("diff-files did not exit properly");
 258         strbuf_release(&buf);
 259 }
 260
 261 static int ensure_leading_directories(char *path)
 262 {
 263         switch (safe_create_leading_directories(path)) {
 264                 case SCLD_OK:
 265                 case SCLD_EXISTS:
 266                         return 0;
 267                 default:
 268                         return error(_("could not create leading directories "
 269                                        "of '%s'"), path);
 270         }
 271 }
 272
 273 /*
 274  * Unconditional writing of a plain regular file is what
 275  * "git difftool --dir-diff" wants to do for symlinks.  We are preparing two
 276  * temporary directories to be fed to a Git-unaware tool that knows how to
 277  * show a diff of two directories (e.g. "diff -r A B").
 278  *
 279  * Because the tool is Git-unaware, if a symbolic link appears in either of
 280  * these temporary directories, it will try to dereference and show the
 281  * difference of the target of the symbolic link, which is not what we want,
 282  * as the goal of the dir-diff mode is to produce an output that is logically
 283  * equivalent to what "git diff" produces.
 284  *
 285  * Most importantly, we want to get textual comparison of the result of the
 286  * readlink(2).  get_symlink() provides that---it returns the contents of
 287  * the symlink that gets written to a regular file to force the external tool
 288  * to compare the readlink(2) result as text, even on a filesystem that is
 289  * capable of doing a symbolic link.
 290  */
 291 static char *get_symlink(const struct object_id *oid, const char *path)
 292 {
 293         char *data;
 294         if (is_null_oid(oid)) {
 295                 /* The symlink is unknown to Git so read from the filesystem */
 296                 struct strbuf link = STRBUF_INIT;
 297                 if (has_symlinks) {
 298                         if (strbuf_readlink(&link, path, strlen(path)))
 299                                 die(_("could not read symlink %s"), path);
 300                 } else if (strbuf_read_file(&link, path, 128))
 301                         die(_("could not read symlink file %s"), path);
 302
 303                 data = strbuf_detach(&link, NULL);
 304         } else {
 305                 enum object_type type;
 306                 unsigned long size;
 307                 data = repo_read_object_file(the_repository, oid, &type,
 308                                              &size);
 309                 if (!data)
 310                         die(_("could not read object %s for symlink %s"),
 311                                 oid_to_hex(oid), path);
 312         }
 313
 314         return data;
 315 }
 316
 317 static int checkout_path(unsigned mode, struct object_id *oid,
 318                          const char *path, const struct checkout *state)
 319 {
 320         struct cache_entry *ce;
 321         int ret;
 322
 323         ce = make_transient_cache_entry(mode, oid, path, 0, NULL);
 324         ret = checkout_entry(ce, state, NULL, NULL);
 325
 326         discard_cache_entry(ce);
 327         return ret;
 328 }
 329
 330 static void write_file_in_directory(struct strbuf *dir, size_t dir_len,
 331                         const char *path, const char *content)
 332 {
 333         add_path(dir, dir_len, path);
 334         ensure_leading_directories(dir->buf);
 335         unlink(dir->buf);
 336         write_file(dir->buf, "%s", content);
 337 }
 338
 339 /* Write the file contents for the left and right sides of the difftool
 340  * dir-diff representation for submodules and symlinks. Symlinks and submodules
 341  * are written as regular text files so that external diff tools can diff them
 342  * as text files, resulting in behavior that is analogous to to what "git diff"
 343  * displays for symlink and submodule diffs.
 344  */
 345 static void write_standin_files(struct pair_entry *entry,
 346                         struct strbuf *ldir, size_t ldir_len,
 347                         struct strbuf *rdir, size_t rdir_len)
 348 {
 349         if (*entry->left)
 350                 write_file_in_directory(ldir, ldir_len, entry->path, entry->left);
 351         if (*entry->right)
 352                 write_file_in_directory(rdir, rdir_len, entry->path, entry->right);
 353 }
 354
 355 static int run_dir_diff(const char *extcmd, int symlinks, const char *prefix,
 356                         struct child_process *child)
 357 {
 358         struct strbuf info = STRBUF_INIT, lpath = STRBUF_INIT;
 359         struct strbuf rpath = STRBUF_INIT, buf = STRBUF_INIT;
 360         struct strbuf ldir = STRBUF_INIT, rdir = STRBUF_INIT;
 361         struct strbuf wtdir = STRBUF_INIT;
 362         struct strbuf tmpdir = STRBUF_INIT;
 363         char *lbase_dir = NULL, *rbase_dir = NULL;
 364         size_t ldir_len, rdir_len, wtdir_len;
 365         const char *workdir, *tmp;
 366         int ret = 0, i;
 367         FILE *fp = NULL;
 368         struct hashmap working_tree_dups = HASHMAP_INIT(working_tree_entry_cmp,
 369                                                         NULL);
 370         struct hashmap submodules = HASHMAP_INIT(pair_cmp, NULL);
 371         struct hashmap symlinks2 = HASHMAP_INIT(pair_cmp, NULL);
 372         struct hashmap_iter iter;
 373         struct pair_entry *entry;
 374         struct index_state wtindex = INDEX_STATE_INIT(the_repository);
 375         struct checkout lstate, rstate;
 376         int err = 0;
 377         struct child_process cmd = CHILD_PROCESS_INIT;
 378         struct hashmap wt_modified, tmp_modified;
 379         int indices_loaded = 0;
 380
 381         workdir = get_git_work_tree();
 382
 383         /* Setup temp directories */
 384         tmp = getenv("TMPDIR");
 385         strbuf_add_absolute_path(&tmpdir, tmp ? tmp : "/tmp");
 386         strbuf_trim_trailing_dir_sep(&tmpdir);
 387         strbuf_addstr(&tmpdir, "/git-difftool.XXXXXX");
 388         if (!mkdtemp(tmpdir.buf)) {
 389                 ret = error("could not create '%s'", tmpdir.buf);
 390                 goto finish;
 391         }
 392         strbuf_addf(&ldir, "%s/left/", tmpdir.buf);
 393         strbuf_addf(&rdir, "%s/right/", tmpdir.buf);
 394         strbuf_addstr(&wtdir, workdir);
 395         if (!wtdir.len || !is_dir_sep(wtdir.buf[wtdir.len - 1]))
 396                 strbuf_addch(&wtdir, '/');
 397         mkdir(ldir.buf, 0700);
 398         mkdir(rdir.buf, 0700);
 399
 400         memset(&lstate, 0, sizeof(lstate));
 401         lstate.base_dir = lbase_dir = xstrdup(ldir.buf);
 402         lstate.base_dir_len = ldir.len;
 403         lstate.force = 1;
 404         memset(&rstate, 0, sizeof(rstate));
 405         rstate.base_dir = rbase_dir = xstrdup(rdir.buf);
 406         rstate.base_dir_len = rdir.len;
 407         rstate.force = 1;
 408
 409         ldir_len = ldir.len;
 410         rdir_len = rdir.len;
 411         wtdir_len = wtdir.len;
 412
 413         child->no_stdin = 1;
 414         child->git_cmd = 1;
 415         child->use_shell = 0;
 416         child->clean_on_exit = 1;
 417         child->dir = prefix;
 418         child->out = -1;
 419         if (start_command(child))
 420                 die("could not obtain raw diff");
 421         fp = xfdopen(child->out, "r");
 422
 423         /* Build index info for left and right sides of the diff */
 424         i = 0;
 425         while (!strbuf_getline_nul(&info, fp)) {
 426                 int lmode, rmode;
 427                 struct object_id loid, roid;
 428                 char status;
 429                 const char *src_path, *dst_path;
 430
 431                 if (starts_with(info.buf, "::"))
 432                         die(N_("combined diff formats ('-c' and '--cc') are "
 433                                "not supported in\n"
 434                                "directory diff mode ('-d' and '--dir-diff')."));
 435
 436                 if (parse_index_info(info.buf, &lmode, &rmode, &loid, &roid,
 437                                      &status))
 438                         break;
 439                 if (strbuf_getline_nul(&lpath, fp))
 440                         break;
 441                 src_path = lpath.buf;
 442
 443                 i++;
 444                 if (status != 'C' && status != 'R') {
 445                         dst_path = src_path;
 446                 } else {
 447                         if (strbuf_getline_nul(&rpath, fp))
 448                                 break;
 449                         dst_path = rpath.buf;
 450                 }
 451
 452                 if (S_ISGITLINK(lmode) || S_ISGITLINK(rmode)) {
 453                         strbuf_reset(&buf);
 454                         strbuf_addf(&buf, "Subproject commit %s",
 455                                     oid_to_hex(&loid));
 456                         add_left_or_right(&submodules, src_path, buf.buf, 0);
 457                         strbuf_reset(&buf);
 458                         strbuf_addf(&buf, "Subproject commit %s",
 459                                     oid_to_hex(&roid));
 460                         if (oideq(&loid, &roid))
 461                                 strbuf_addstr(&buf, "-dirty");
 462                         add_left_or_right(&submodules, dst_path, buf.buf, 1);
 463                         continue;
 464                 }
 465
 466                 if (S_ISLNK(lmode)) {
 467                         char *content = get_symlink(&loid, src_path);
 468                         add_left_or_right(&symlinks2, src_path, content, 0);
 469                         free(content);
 470                 }
 471
 472                 if (S_ISLNK(rmode)) {
 473                         char *content = get_symlink(&roid, dst_path);
 474                         add_left_or_right(&symlinks2, dst_path, content, 1);
 475                         free(content);
 476                 }
 477
 478                 if (lmode && status != 'C') {
 479                         if (checkout_path(lmode, &loid, src_path, &lstate)) {
 480                                 ret = error("could not write '%s'", src_path);
 481                                 goto finish;
 482                         }
 483                 }
 484
 485                 if (rmode && !S_ISLNK(rmode)) {
 486                         struct working_tree_entry *entry;
 487
 488                         /* Avoid duplicate working_tree entries */
 489                         FLEX_ALLOC_STR(entry, path, dst_path);
 490                         hashmap_entry_init(&entry->entry, strhash(dst_path));
 491                         if (hashmap_get(&working_tree_dups, &entry->entry,
 492                                         NULL)) {
 493                                 free(entry);
 494                                 continue;
 495                         }
 496                         hashmap_add(&working_tree_dups, &entry->entry);
 497
 498                         if (!use_wt_file(workdir, dst_path, &roid)) {
 499                                 if (checkout_path(rmode, &roid, dst_path,
 500                                                   &rstate)) {
 501                                         ret = error("could not write '%s'",
 502                                                     dst_path);
 503                                         goto finish;
 504                                 }
 505                         } else if (!is_null_oid(&roid)) {
 506                                 /*
 507                                  * Changes in the working tree need special
 508                                  * treatment since they are not part of the
 509                                  * index.
 510                                  */
 511                                 struct cache_entry *ce2 =
 512                                         make_cache_entry(&wtindex, rmode, &roid,
 513                                                          dst_path, 0, 0);
 514
 515                                 add_index_entry(&wtindex, ce2,
 516                                                 ADD_CACHE_JUST_APPEND);
 517
 518                                 add_path(&rdir, rdir_len, dst_path);
 519                                 if (ensure_leading_directories(rdir.buf)) {
 520                                         ret = error("could not create "
 521                                                     "directory for '%s'",
 522                                                     dst_path);
 523                                         goto finish;
 524                                 }
 525                                 add_path(&wtdir, wtdir_len, dst_path);
 526                                 if (symlinks) {
 527                                         if (symlink(wtdir.buf, rdir.buf)) {
 528                                                 ret = error_errno("could not symlink '%s' to '%s'", wtdir.buf, rdir.buf);
 529                                                 goto finish;
 530                                         }
 531                                 } else {
 532                                         struct stat st;
 533                                         if (stat(wtdir.buf, &st))
 534                                                 st.st_mode = 0644;
 535                                         if (copy_file(rdir.buf, wtdir.buf,
 536                                                       st.st_mode)) {
 537                                                 ret = error("could not copy '%s' to '%s'", wtdir.buf, rdir.buf);
 538                                                 goto finish;
 539                                         }
 540                                 }
 541                         }
 542                 }
 543         }
 544
 545         fclose(fp);
 546         fp = NULL;
 547         if (finish_command(child)) {
 548                 ret = error("error occurred running diff --raw");
 549                 goto finish;
 550         }
 551
 552         if (!i)
 553                 goto finish;
 554
 555         /*
 556          * Changes to submodules require special treatment.This loop writes a
 557          * temporary file to both the left and right directories to show the
 558          * change in the recorded SHA1 for the submodule.
 559          */
 560         hashmap_for_each_entry(&submodules, &iter, entry,
 561                                 entry /* member name */) {
 562                 write_standin_files(entry, &ldir, ldir_len, &rdir, rdir_len);
 563         }
 564
 565         /*
 566          * Symbolic links require special treatment. The standard "git diff"
 567          * shows only the link itself, not the contents of the link target.
 568          * This loop replicates that behavior.
 569          */
 570         hashmap_for_each_entry(&symlinks2, &iter, entry,
 571                                 entry /* member name */) {
 572
 573                 write_standin_files(entry, &ldir, ldir_len, &rdir, rdir_len);
 574         }
 575
 576         strbuf_setlen(&ldir, ldir_len);
 577         strbuf_setlen(&rdir, rdir_len);
 578
 579         if (extcmd) {
 580                 strvec_push(&cmd.args, extcmd);
 581         } else {
 582                 strvec_push(&cmd.args, "difftool--helper");
 583                 cmd.git_cmd = 1;
 584                 setenv("GIT_DIFFTOOL_DIRDIFF", "true", 1);
 585         }
 586         strvec_pushl(&cmd.args, ldir.buf, rdir.buf, NULL);
 587         ret = run_command(&cmd);
 588
 589         /* TODO: audit for interaction with sparse-index. */
 590         ensure_full_index(&wtindex);
 591
 592         /*
 593          * If the diff includes working copy files and those
 594          * files were modified during the diff, then the changes
 595          * should be copied back to the working tree.
 596          * Do not copy back files when symlinks are used and the
 597          * external tool did not replace the original link with a file.
 598          *
 599          * These hashes are loaded lazily since they aren't needed
 600          * in the common case of --symlinks and the difftool updating
 601          * files through the symlink.
 602          */
 603         hashmap_init(&wt_modified, path_entry_cmp, NULL, wtindex.cache_nr);
 604         hashmap_init(&tmp_modified, path_entry_cmp, NULL, wtindex.cache_nr);
 605
 606         for (i = 0; i < wtindex.cache_nr; i++) {
 607                 struct hashmap_entry dummy;
 608                 const char *name = wtindex.cache[i]->name;
 609                 struct stat st;
 610
 611                 add_path(&rdir, rdir_len, name);
 612                 if (lstat(rdir.buf, &st))
 613                         continue;
 614
 615                 if ((symlinks && S_ISLNK(st.st_mode)) || !S_ISREG(st.st_mode))
 616                         continue;
 617
 618                 if (!indices_loaded) {
 619                         struct lock_file lock = LOCK_INIT;
 620                         strbuf_reset(&buf);
 621                         strbuf_addf(&buf, "%s/wtindex", tmpdir.buf);
 622                         if (hold_lock_file_for_update(&lock, buf.buf, 0) < 0 ||
 623                             write_locked_index(&wtindex, &lock, COMMIT_LOCK)) {
 624                                 ret = error("could not write %s", buf.buf);
 625                                 goto finish;
 626                         }
 627                         changed_files(&wt_modified, buf.buf, workdir);
 628                         strbuf_setlen(&rdir, rdir_len);
 629                         changed_files(&tmp_modified, buf.buf, rdir.buf);
 630                         add_path(&rdir, rdir_len, name);
 631                         indices_loaded = 1;
 632                 }
 633
 634                 hashmap_entry_init(&dummy, strhash(name));
 635                 if (hashmap_get(&tmp_modified, &dummy, name)) {
 636                         add_path(&wtdir, wtdir_len, name);
 637                         if (hashmap_get(&wt_modified, &dummy, name)) {
 638                                 warning(_("both files modified: '%s' and '%s'."),
 639                                         wtdir.buf, rdir.buf);
 640                                 warning(_("working tree file has been left."));
 641                                 warning("%s", "");
 642                                 err = 1;
 643                         } else if (unlink(wtdir.buf) ||
 644                                    copy_file(wtdir.buf, rdir.buf, st.st_mode))
 645                                 warning_errno(_("could not copy '%s' to '%s'"),
 646                                               rdir.buf, wtdir.buf);
 647                 }
 648         }
 649
 650         if (err) {
 651                 warning(_("temporary files exist in '%s'."), tmpdir.buf);
 652                 warning(_("you may want to cleanup or recover these."));
 653                 ret = 1;
 654         } else {
 655                 remove_dir_recursively(&tmpdir, 0);
 656                 if (ret)
 657                         warning(_("failed: %d"), ret);
 658         }
 659
 660 finish:
 661         if (fp)
 662                 fclose(fp);
 663
 664         free(lbase_dir);
 665         free(rbase_dir);
 666         strbuf_release(&ldir);
 667         strbuf_release(&rdir);
 668         strbuf_release(&wtdir);
 669         strbuf_release(&buf);
 670         strbuf_release(&tmpdir);
 671
 672         return (ret < 0) ? 1 : ret;
 673 }
 674
 675 static int run_file_diff(int prompt, const char *prefix,
 676                          struct child_process *child)
 677 {
 678         const char *env[] = {
 679                 "GIT_PAGER=", "GIT_EXTERNAL_DIFF=git-difftool--helper", NULL,
 680                 NULL
 681         };
 682
 683         if (prompt > 0)
 684                 env[2] = "GIT_DIFFTOOL_PROMPT=true";
 685         else if (!prompt)
 686                 env[2] = "GIT_DIFFTOOL_NO_PROMPT=true";
 687
 688         child->git_cmd = 1;
 689         child->dir = prefix;
 690         strvec_pushv(&child->env, env);
 691
 692         return run_command(child);
 693 }
 694
 695 int cmd_difftool(int argc, const char **argv, const char *prefix)
 696 {
 697         int use_gui_tool = -1, dir_diff = 0, prompt = -1, symlinks = 0,
 698             tool_help = 0, no_index = 0;
 699         static char *difftool_cmd = NULL, *extcmd = NULL;
 700         struct option builtin_difftool_options[] = {
 701                 OPT_BOOL('g', "gui", &use_gui_tool,
 702                          N_("use `diff.guitool` instead of `diff.tool`")),
 703                 OPT_BOOL('d', "dir-diff", &dir_diff,
 704                          N_("perform a full-directory diff")),
 705                 OPT_SET_INT_F('y', "no-prompt", &prompt,
 706                         N_("do not prompt before launching a diff tool"),
 707                         0, PARSE_OPT_NONEG),
 708                 OPT_SET_INT_F(0, "prompt", &prompt, NULL,
 709                         1, PARSE_OPT_NONEG | PARSE_OPT_HIDDEN),
 710                 OPT_BOOL(0, "symlinks", &symlinks,
 711                          N_("use symlinks in dir-diff mode")),
 712                 OPT_STRING('t', "tool", &difftool_cmd, N_("tool"),
 713                            N_("use the specified diff tool")),
 714                 OPT_BOOL(0, "tool-help", &tool_help,
 715                          N_("print a list of diff tools that may be used with "
 716                             "`--tool`")),
 717                 OPT_BOOL(0, "trust-exit-code", &trust_exit_code,
 718                          N_("make 'git-difftool' exit when an invoked diff "
 719                             "tool returns a non-zero exit code")),
 720                 OPT_STRING('x', "extcmd", &extcmd, N_("command"),
 721                            N_("specify a custom command for viewing diffs")),
 722                 OPT_BOOL(0, "no-index", &no_index, N_("passed to `diff`")),
 723                 OPT_END()
 724         };
 725         struct child_process child = CHILD_PROCESS_INIT;
 726
 727         git_config(difftool_config, NULL);
 728         symlinks = has_symlinks;
 729
 730         argc = parse_options(argc, argv, prefix, builtin_difftool_options,
 731                              builtin_difftool_usage, PARSE_OPT_KEEP_UNKNOWN_OPT |
 732                              PARSE_OPT_KEEP_DASHDASH);
 733
 734         if (tool_help)
 735                 return print_tool_help();
 736
 737         if (!no_index && !startup_info->have_repository)
 738                 die(_("difftool requires worktree or --no-index"));
 739
 740         if (!no_index){
 741                 setup_work_tree();
 742                 setenv(GIT_DIR_ENVIRONMENT, absolute_path(get_git_dir()), 1);
 743                 setenv(GIT_WORK_TREE_ENVIRONMENT, absolute_path(get_git_work_tree()), 1);
 744         } else if (dir_diff)
 745                 die(_("options '%s' and '%s' cannot be used together"), "--dir-diff", "--no-index");
 746
 747         die_for_incompatible_opt3(use_gui_tool == 1, "--gui",
 748                                   !!difftool_cmd, "--tool",
 749                                   !!extcmd, "--extcmd");
 750
 751         /*
 752          * Explicitly specified GUI option is forwarded to git-mergetool--lib.sh;
 753          * empty or unset means "use the difftool.guiDefault config or default to
 754          * false".
 755          */
 756         if (use_gui_tool == 1)
 757                 setenv("GIT_MERGETOOL_GUI", "true", 1);
 758         else if (use_gui_tool == 0)
 759                 setenv("GIT_MERGETOOL_GUI", "false", 1);
 760
 761         if (difftool_cmd) {
 762                 if (*difftool_cmd)
 763                         setenv("GIT_DIFF_TOOL", difftool_cmd, 1);
 764                 else
 765                         die(_("no <tool> given for --tool=<tool>"));
 766         }
 767
 768         if (extcmd) {
 769                 if (*extcmd)
 770                         setenv("GIT_DIFFTOOL_EXTCMD", extcmd, 1);
 771                 else
 772                         die(_("no <cmd> given for --extcmd=<cmd>"));
 773         }
 774
 775         setenv("GIT_DIFFTOOL_TRUST_EXIT_CODE",
 776                trust_exit_code ? "true" : "false", 1);
 777
 778         /*
 779          * In directory diff mode, 'git-difftool--helper' is called once
 780          * to compare the a / b directories. In file diff mode, 'git diff'
 781          * will invoke a separate instance of 'git-difftool--helper' for
 782          * each file that changed.
 783          */
 784         strvec_push(&child.args, "diff");
 785         if (no_index)
 786                 strvec_push(&child.args, "--no-index");
 787         if (dir_diff)
 788                 strvec_pushl(&child.args, "--raw", "--no-abbrev", "-z", NULL);
 789         strvec_pushv(&child.args, argv);
 790
 791         if (dir_diff)
 792                 return run_dir_diff(extcmd, symlinks, prefix, &child);
 793         return run_file_diff(prompt, prefix, &child);
 794 }