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