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