Merge branch 'np/log-graph-octopus-fix'
[git] / builtin / difftool.c
1 /*
2  * "git difftool" builtin command
3  *
4  * This is a wrapper around the GIT_EXTERNAL_DIFF-compatible
5  * git-difftool--helper script.
6  *
7  * This script exports GIT_EXTERNAL_DIFF and GIT_PAGER for use by git.
8  * The GIT_DIFF* variables are exported for use by git-difftool--helper.
9  *
10  * Any arguments that are unknown to this script are forwarded to 'git diff'.
11  *
12  * Copyright (C) 2016 Johannes Schindelin
13  */
14 #include "cache.h"
15 #include "config.h"
16 #include "builtin.h"
17 #include "run-command.h"
18 #include "exec-cmd.h"
19 #include "parse-options.h"
20 #include "argv-array.h"
21 #include "strbuf.h"
22 #include "lockfile.h"
23 #include "object-store.h"
24 #include "dir.h"
25
26 static char *diff_gui_tool;
27 static int trust_exit_code;
28
29 static const char *const builtin_difftool_usage[] = {
30         N_("git difftool [<options>] [<commit> [<commit>]] [--] [<path>...]"),
31         NULL
32 };
33
34 static int difftool_config(const char *var, const char *value, void *cb)
35 {
36         if (!strcmp(var, "diff.guitool")) {
37                 diff_gui_tool = xstrdup(value);
38                 return 0;
39         }
40
41         if (!strcmp(var, "difftool.trustexitcode")) {
42                 trust_exit_code = git_config_bool(var, value);
43                 return 0;
44         }
45
46         return git_default_config(var, value, cb);
47 }
48
49 static int print_tool_help(void)
50 {
51         const char *argv[] = { "mergetool", "--tool-help=diff", NULL };
52         return run_command_v_opt(argv, RUN_GIT_CMD);
53 }
54
55 static int parse_index_info(char *p, int *mode1, int *mode2,
56                             struct object_id *oid1, struct object_id *oid2,
57                             char *status)
58 {
59         if (*p != ':')
60                 return error("expected ':', got '%c'", *p);
61         *mode1 = (int)strtol(p + 1, &p, 8);
62         if (*p != ' ')
63                 return error("expected ' ', got '%c'", *p);
64         *mode2 = (int)strtol(p + 1, &p, 8);
65         if (*p != ' ')
66                 return error("expected ' ', got '%c'", *p);
67         if (get_oid_hex(++p, oid1))
68                 return error("expected object ID, got '%s'", p + 1);
69         p += GIT_SHA1_HEXSZ;
70         if (*p != ' ')
71                 return error("expected ' ', got '%c'", *p);
72         if (get_oid_hex(++p, oid2))
73                 return error("expected object ID, got '%s'", p + 1);
74         p += GIT_SHA1_HEXSZ;
75         if (*p != ' ')
76                 return error("expected ' ', got '%c'", *p);
77         *status = *++p;
78         if (!*status)
79                 return error("missing status");
80         if (p[1] && !isdigit(p[1]))
81                 return error("unexpected trailer: '%s'", p + 1);
82         return 0;
83 }
84
85 /*
86  * Remove any trailing slash from $workdir
87  * before starting to avoid double slashes in symlink targets.
88  */
89 static void add_path(struct strbuf *buf, size_t base_len, const char *path)
90 {
91         strbuf_setlen(buf, base_len);
92         if (buf->len && buf->buf[buf->len - 1] != '/')
93                 strbuf_addch(buf, '/');
94         strbuf_addstr(buf, path);
95 }
96
97 /*
98  * Determine whether we can simply reuse the file in the worktree.
99  */
100 static int use_wt_file(const char *workdir, const char *name,
101                        struct object_id *oid)
102 {
103         struct strbuf buf = STRBUF_INIT;
104         struct stat st;
105         int use = 0;
106
107         strbuf_addstr(&buf, workdir);
108         add_path(&buf, buf.len, name);
109
110         if (!lstat(buf.buf, &st) && !S_ISLNK(st.st_mode)) {
111                 struct object_id wt_oid;
112                 int fd = open(buf.buf, O_RDONLY);
113
114                 if (fd >= 0 &&
115                     !index_fd(&the_index, &wt_oid, fd, &st, OBJ_BLOB, name, 0)) {
116                         if (is_null_oid(oid)) {
117                                 oidcpy(oid, &wt_oid);
118                                 use = 1;
119                         } else if (oideq(oid, &wt_oid))
120                                 use = 1;
121                 }
122         }
123
124         strbuf_release(&buf);
125
126         return use;
127 }
128
129 struct working_tree_entry {
130         struct hashmap_entry entry;
131         char path[FLEX_ARRAY];
132 };
133
134 static int working_tree_entry_cmp(const void *unused_cmp_data,
135                                   const void *entry,
136                                   const void *entry_or_key,
137                                   const void *unused_keydata)
138 {
139         const struct working_tree_entry *a = entry;
140         const struct working_tree_entry *b = entry_or_key;
141         return strcmp(a->path, b->path);
142 }
143
144 /*
145  * The `left` and `right` entries hold paths for the symlinks hashmap,
146  * and a SHA-1 surrounded by brief text for submodules.
147  */
148 struct pair_entry {
149         struct hashmap_entry entry;
150         char left[PATH_MAX], right[PATH_MAX];
151         const char path[FLEX_ARRAY];
152 };
153
154 static int pair_cmp(const void *unused_cmp_data,
155                     const void *entry,
156                     const void *entry_or_key,
157                     const void *unused_keydata)
158 {
159         const struct pair_entry *a = entry;
160         const struct pair_entry *b = entry_or_key;
161
162         return strcmp(a->path, b->path);
163 }
164
165 static void add_left_or_right(struct hashmap *map, const char *path,
166                               const char *content, int is_right)
167 {
168         struct pair_entry *e, *existing;
169
170         FLEX_ALLOC_STR(e, path, path);
171         hashmap_entry_init(e, strhash(path));
172         existing = hashmap_get(map, e, NULL);
173         if (existing) {
174                 free(e);
175                 e = existing;
176         } else {
177                 e->left[0] = e->right[0] = '\0';
178                 hashmap_add(map, e);
179         }
180         strlcpy(is_right ? e->right : e->left, content, PATH_MAX);
181 }
182
183 struct path_entry {
184         struct hashmap_entry entry;
185         char path[FLEX_ARRAY];
186 };
187
188 static int path_entry_cmp(const void *unused_cmp_data,
189                           const void *entry,
190                           const void *entry_or_key,
191                           const void *key)
192 {
193         const struct path_entry *a = entry;
194         const struct path_entry *b = entry_or_key;
195
196         return strcmp(a->path, key ? key : b->path);
197 }
198
199 static void changed_files(struct hashmap *result, const char *index_path,
200                           const char *workdir)
201 {
202         struct child_process update_index = CHILD_PROCESS_INIT;
203         struct child_process diff_files = CHILD_PROCESS_INIT;
204         struct strbuf index_env = STRBUF_INIT, buf = STRBUF_INIT;
205         const char *git_dir = absolute_path(get_git_dir()), *env[] = {
206                 NULL, NULL
207         };
208         FILE *fp;
209
210         strbuf_addf(&index_env, "GIT_INDEX_FILE=%s", index_path);
211         env[0] = index_env.buf;
212
213         argv_array_pushl(&update_index.args,
214                          "--git-dir", git_dir, "--work-tree", workdir,
215                          "update-index", "--really-refresh", "-q",
216                          "--unmerged", NULL);
217         update_index.no_stdin = 1;
218         update_index.no_stdout = 1;
219         update_index.no_stderr = 1;
220         update_index.git_cmd = 1;
221         update_index.use_shell = 0;
222         update_index.clean_on_exit = 1;
223         update_index.dir = workdir;
224         update_index.env = env;
225         /* Ignore any errors of update-index */
226         run_command(&update_index);
227
228         argv_array_pushl(&diff_files.args,
229                          "--git-dir", git_dir, "--work-tree", workdir,
230                          "diff-files", "--name-only", "-z", NULL);
231         diff_files.no_stdin = 1;
232         diff_files.git_cmd = 1;
233         diff_files.use_shell = 0;
234         diff_files.clean_on_exit = 1;
235         diff_files.out = -1;
236         diff_files.dir = workdir;
237         diff_files.env = env;
238         if (start_command(&diff_files))
239                 die("could not obtain raw diff");
240         fp = xfdopen(diff_files.out, "r");
241         while (!strbuf_getline_nul(&buf, fp)) {
242                 struct path_entry *entry;
243                 FLEX_ALLOC_STR(entry, path, buf.buf);
244                 hashmap_entry_init(entry, strhash(buf.buf));
245                 hashmap_add(result, entry);
246         }
247         fclose(fp);
248         if (finish_command(&diff_files))
249                 die("diff-files did not exit properly");
250         strbuf_release(&index_env);
251         strbuf_release(&buf);
252 }
253
254 static NORETURN void exit_cleanup(const char *tmpdir, int exit_code)
255 {
256         struct strbuf buf = STRBUF_INIT;
257         strbuf_addstr(&buf, tmpdir);
258         remove_dir_recursively(&buf, 0);
259         if (exit_code)
260                 warning(_("failed: %d"), exit_code);
261         exit(exit_code);
262 }
263
264 static int ensure_leading_directories(char *path)
265 {
266         switch (safe_create_leading_directories(path)) {
267                 case SCLD_OK:
268                 case SCLD_EXISTS:
269                         return 0;
270                 default:
271                         return error(_("could not create leading directories "
272                                        "of '%s'"), path);
273         }
274 }
275
276 /*
277  * Unconditional writing of a plain regular file is what
278  * "git difftool --dir-diff" wants to do for symlinks.  We are preparing two
279  * temporary directories to be fed to a Git-unaware tool that knows how to
280  * show a diff of two directories (e.g. "diff -r A B").
281  *
282  * Because the tool is Git-unaware, if a symbolic link appears in either of
283  * these temporary directories, it will try to dereference and show the
284  * difference of the target of the symbolic link, which is not what we want,
285  * as the goal of the dir-diff mode is to produce an output that is logically
286  * equivalent to what "git diff" produces.
287  *
288  * Most importantly, we want to get textual comparison of the result of the
289  * readlink(2).  get_symlink() provides that---it returns the contents of
290  * the symlink that gets written to a regular file to force the external tool
291  * to compare the readlink(2) result as text, even on a filesystem that is
292  * capable of doing a symbolic link.
293  */
294 static char *get_symlink(const struct object_id *oid, const char *path)
295 {
296         char *data;
297         if (is_null_oid(oid)) {
298                 /* The symlink is unknown to Git so read from the filesystem */
299                 struct strbuf link = STRBUF_INIT;
300                 if (has_symlinks) {
301                         if (strbuf_readlink(&link, path, strlen(path)))
302                                 die(_("could not read symlink %s"), path);
303                 } else if (strbuf_read_file(&link, path, 128))
304                         die(_("could not read symlink file %s"), path);
305
306                 data = strbuf_detach(&link, NULL);
307         } else {
308                 enum object_type type;
309                 unsigned long size;
310                 data = read_object_file(oid, &type, &size);
311                 if (!data)
312                         die(_("could not read object %s for symlink %s"),
313                                 oid_to_hex(oid), path);
314         }
315
316         return data;
317 }
318
319 static int checkout_path(unsigned mode, struct object_id *oid,
320                          const char *path, const struct checkout *state)
321 {
322         struct cache_entry *ce;
323         int ret;
324
325         ce = make_transient_cache_entry(mode, oid, path, 0);
326         ret = checkout_entry(ce, state, NULL);
327
328         discard_cache_entry(ce);
329         return ret;
330 }
331
332 static int run_dir_diff(const char *extcmd, int symlinks, const char *prefix,
333                         int argc, const char **argv)
334 {
335         char tmpdir[PATH_MAX];
336         struct strbuf info = STRBUF_INIT, lpath = STRBUF_INIT;
337         struct strbuf rpath = STRBUF_INIT, buf = STRBUF_INIT;
338         struct strbuf ldir = STRBUF_INIT, rdir = STRBUF_INIT;
339         struct strbuf wtdir = STRBUF_INIT;
340         char *lbase_dir, *rbase_dir;
341         size_t ldir_len, rdir_len, wtdir_len;
342         const char *workdir, *tmp;
343         int ret = 0, i;
344         FILE *fp;
345         struct hashmap working_tree_dups, submodules, symlinks2;
346         struct hashmap_iter iter;
347         struct pair_entry *entry;
348         struct index_state wtindex;
349         struct checkout lstate, rstate;
350         int rc, flags = RUN_GIT_CMD, err = 0;
351         struct child_process child = CHILD_PROCESS_INIT;
352         const char *helper_argv[] = { "difftool--helper", NULL, NULL, NULL };
353         struct hashmap wt_modified, tmp_modified;
354         int indices_loaded = 0;
355
356         workdir = get_git_work_tree();
357
358         /* Setup temp directories */
359         tmp = getenv("TMPDIR");
360         xsnprintf(tmpdir, sizeof(tmpdir), "%s/git-difftool.XXXXXX", tmp ? tmp : "/tmp");
361         if (!mkdtemp(tmpdir))
362                 return error("could not create '%s'", tmpdir);
363         strbuf_addf(&ldir, "%s/left/", tmpdir);
364         strbuf_addf(&rdir, "%s/right/", tmpdir);
365         strbuf_addstr(&wtdir, workdir);
366         if (!wtdir.len || !is_dir_sep(wtdir.buf[wtdir.len - 1]))
367                 strbuf_addch(&wtdir, '/');
368         mkdir(ldir.buf, 0700);
369         mkdir(rdir.buf, 0700);
370
371         memset(&wtindex, 0, sizeof(wtindex));
372
373         memset(&lstate, 0, sizeof(lstate));
374         lstate.base_dir = lbase_dir = xstrdup(ldir.buf);
375         lstate.base_dir_len = ldir.len;
376         lstate.force = 1;
377         memset(&rstate, 0, sizeof(rstate));
378         rstate.base_dir = rbase_dir = xstrdup(rdir.buf);
379         rstate.base_dir_len = rdir.len;
380         rstate.force = 1;
381
382         ldir_len = ldir.len;
383         rdir_len = rdir.len;
384         wtdir_len = wtdir.len;
385
386         hashmap_init(&working_tree_dups, working_tree_entry_cmp, NULL, 0);
387         hashmap_init(&submodules, pair_cmp, NULL, 0);
388         hashmap_init(&symlinks2, pair_cmp, NULL, 0);
389
390         child.no_stdin = 1;
391         child.git_cmd = 1;
392         child.use_shell = 0;
393         child.clean_on_exit = 1;
394         child.dir = prefix;
395         child.out = -1;
396         argv_array_pushl(&child.args, "diff", "--raw", "--no-abbrev", "-z",
397                          NULL);
398         for (i = 0; i < argc; i++)
399                 argv_array_push(&child.args, argv[i]);
400         if (start_command(&child))
401                 die("could not obtain raw diff");
402         fp = xfdopen(child.out, "r");
403
404         /* Build index info for left and right sides of the diff */
405         i = 0;
406         while (!strbuf_getline_nul(&info, fp)) {
407                 int lmode, rmode;
408                 struct object_id loid, roid;
409                 char status;
410                 const char *src_path, *dst_path;
411
412                 if (starts_with(info.buf, "::"))
413                         die(N_("combined diff formats('-c' and '--cc') are "
414                                "not supported in\n"
415                                "directory diff mode('-d' and '--dir-diff')."));
416
417                 if (parse_index_info(info.buf, &lmode, &rmode, &loid, &roid,
418                                      &status))
419                         break;
420                 if (strbuf_getline_nul(&lpath, fp))
421                         break;
422                 src_path = lpath.buf;
423
424                 i++;
425                 if (status != 'C' && status != 'R') {
426                         dst_path = src_path;
427                 } else {
428                         if (strbuf_getline_nul(&rpath, fp))
429                                 break;
430                         dst_path = rpath.buf;
431                 }
432
433                 if (S_ISGITLINK(lmode) || S_ISGITLINK(rmode)) {
434                         strbuf_reset(&buf);
435                         strbuf_addf(&buf, "Subproject commit %s",
436                                     oid_to_hex(&loid));
437                         add_left_or_right(&submodules, src_path, buf.buf, 0);
438                         strbuf_reset(&buf);
439                         strbuf_addf(&buf, "Subproject commit %s",
440                                     oid_to_hex(&roid));
441                         if (oideq(&loid, &roid))
442                                 strbuf_addstr(&buf, "-dirty");
443                         add_left_or_right(&submodules, dst_path, buf.buf, 1);
444                         continue;
445                 }
446
447                 if (S_ISLNK(lmode)) {
448                         char *content = get_symlink(&loid, src_path);
449                         add_left_or_right(&symlinks2, src_path, content, 0);
450                         free(content);
451                 }
452
453                 if (S_ISLNK(rmode)) {
454                         char *content = get_symlink(&roid, dst_path);
455                         add_left_or_right(&symlinks2, dst_path, content, 1);
456                         free(content);
457                 }
458
459                 if (lmode && status != 'C') {
460                         if (checkout_path(lmode, &loid, src_path, &lstate)) {
461                                 ret = error("could not write '%s'", src_path);
462                                 goto finish;
463                         }
464                 }
465
466                 if (rmode && !S_ISLNK(rmode)) {
467                         struct working_tree_entry *entry;
468
469                         /* Avoid duplicate working_tree entries */
470                         FLEX_ALLOC_STR(entry, path, dst_path);
471                         hashmap_entry_init(entry, strhash(dst_path));
472                         if (hashmap_get(&working_tree_dups, entry, NULL)) {
473                                 free(entry);
474                                 continue;
475                         }
476                         hashmap_add(&working_tree_dups, entry);
477
478                         if (!use_wt_file(workdir, dst_path, &roid)) {
479                                 if (checkout_path(rmode, &roid, dst_path,
480                                                   &rstate)) {
481                                         ret = error("could not write '%s'",
482                                                     dst_path);
483                                         goto finish;
484                                 }
485                         } else if (!is_null_oid(&roid)) {
486                                 /*
487                                  * Changes in the working tree need special
488                                  * treatment since they are not part of the
489                                  * index.
490                                  */
491                                 struct cache_entry *ce2 =
492                                         make_cache_entry(&wtindex, rmode, &roid,
493                                                          dst_path, 0, 0);
494
495                                 add_index_entry(&wtindex, ce2,
496                                                 ADD_CACHE_JUST_APPEND);
497
498                                 add_path(&rdir, rdir_len, dst_path);
499                                 if (ensure_leading_directories(rdir.buf)) {
500                                         ret = error("could not create "
501                                                     "directory for '%s'",
502                                                     dst_path);
503                                         goto finish;
504                                 }
505                                 add_path(&wtdir, wtdir_len, dst_path);
506                                 if (symlinks) {
507                                         if (symlink(wtdir.buf, rdir.buf)) {
508                                                 ret = error_errno("could not symlink '%s' to '%s'", wtdir.buf, rdir.buf);
509                                                 goto finish;
510                                         }
511                                 } else {
512                                         struct stat st;
513                                         if (stat(wtdir.buf, &st))
514                                                 st.st_mode = 0644;
515                                         if (copy_file(rdir.buf, wtdir.buf,
516                                                       st.st_mode)) {
517                                                 ret = error("could not copy '%s' to '%s'", wtdir.buf, rdir.buf);
518                                                 goto finish;
519                                         }
520                                 }
521                         }
522                 }
523         }
524
525         fclose(fp);
526         fp = NULL;
527         if (finish_command(&child)) {
528                 ret = error("error occurred running diff --raw");
529                 goto finish;
530         }
531
532         if (!i)
533                 goto finish;
534
535         /*
536          * Changes to submodules require special treatment.This loop writes a
537          * temporary file to both the left and right directories to show the
538          * change in the recorded SHA1 for the submodule.
539          */
540         hashmap_iter_init(&submodules, &iter);
541         while ((entry = hashmap_iter_next(&iter))) {
542                 if (*entry->left) {
543                         add_path(&ldir, ldir_len, entry->path);
544                         ensure_leading_directories(ldir.buf);
545                         write_file(ldir.buf, "%s", entry->left);
546                 }
547                 if (*entry->right) {
548                         add_path(&rdir, rdir_len, entry->path);
549                         ensure_leading_directories(rdir.buf);
550                         write_file(rdir.buf, "%s", entry->right);
551                 }
552         }
553
554         /*
555          * Symbolic links require special treatment.The standard "git diff"
556          * shows only the link itself, not the contents of the link target.
557          * This loop replicates that behavior.
558          */
559         hashmap_iter_init(&symlinks2, &iter);
560         while ((entry = hashmap_iter_next(&iter))) {
561                 if (*entry->left) {
562                         add_path(&ldir, ldir_len, entry->path);
563                         ensure_leading_directories(ldir.buf);
564                         write_file(ldir.buf, "%s", entry->left);
565                 }
566                 if (*entry->right) {
567                         add_path(&rdir, rdir_len, entry->path);
568                         ensure_leading_directories(rdir.buf);
569                         write_file(rdir.buf, "%s", entry->right);
570                 }
571         }
572
573         strbuf_release(&buf);
574
575         strbuf_setlen(&ldir, ldir_len);
576         helper_argv[1] = ldir.buf;
577         strbuf_setlen(&rdir, rdir_len);
578         helper_argv[2] = rdir.buf;
579
580         if (extcmd) {
581                 helper_argv[0] = extcmd;
582                 flags = 0;
583         } else
584                 setenv("GIT_DIFFTOOL_DIRDIFF", "true", 1);
585         rc = run_command_v_opt(helper_argv, flags);
586
587         /*
588          * If the diff includes working copy files and those
589          * files were modified during the diff, then the changes
590          * should be copied back to the working tree.
591          * Do not copy back files when symlinks are used and the
592          * external tool did not replace the original link with a file.
593          *
594          * These hashes are loaded lazily since they aren't needed
595          * in the common case of --symlinks and the difftool updating
596          * files through the symlink.
597          */
598         hashmap_init(&wt_modified, path_entry_cmp, NULL, wtindex.cache_nr);
599         hashmap_init(&tmp_modified, path_entry_cmp, NULL, wtindex.cache_nr);
600
601         for (i = 0; i < wtindex.cache_nr; i++) {
602                 struct hashmap_entry dummy;
603                 const char *name = wtindex.cache[i]->name;
604                 struct stat st;
605
606                 add_path(&rdir, rdir_len, name);
607                 if (lstat(rdir.buf, &st))
608                         continue;
609
610                 if ((symlinks && S_ISLNK(st.st_mode)) || !S_ISREG(st.st_mode))
611                         continue;
612
613                 if (!indices_loaded) {
614                         struct lock_file lock = LOCK_INIT;
615                         strbuf_reset(&buf);
616                         strbuf_addf(&buf, "%s/wtindex", tmpdir);
617                         if (hold_lock_file_for_update(&lock, buf.buf, 0) < 0 ||
618                             write_locked_index(&wtindex, &lock, COMMIT_LOCK)) {
619                                 ret = error("could not write %s", buf.buf);
620                                 goto finish;
621                         }
622                         changed_files(&wt_modified, buf.buf, workdir);
623                         strbuf_setlen(&rdir, rdir_len);
624                         changed_files(&tmp_modified, buf.buf, rdir.buf);
625                         add_path(&rdir, rdir_len, name);
626                         indices_loaded = 1;
627                 }
628
629                 hashmap_entry_init(&dummy, strhash(name));
630                 if (hashmap_get(&tmp_modified, &dummy, name)) {
631                         add_path(&wtdir, wtdir_len, name);
632                         if (hashmap_get(&wt_modified, &dummy, name)) {
633                                 warning(_("both files modified: '%s' and '%s'."),
634                                         wtdir.buf, rdir.buf);
635                                 warning(_("working tree file has been left."));
636                                 warning("%s", "");
637                                 err = 1;
638                         } else if (unlink(wtdir.buf) ||
639                                    copy_file(wtdir.buf, rdir.buf, st.st_mode))
640                                 warning_errno(_("could not copy '%s' to '%s'"),
641                                               rdir.buf, wtdir.buf);
642                 }
643         }
644
645         if (err) {
646                 warning(_("temporary files exist in '%s'."), tmpdir);
647                 warning(_("you may want to cleanup or recover these."));
648                 exit(1);
649         } else
650                 exit_cleanup(tmpdir, rc);
651
652 finish:
653         if (fp)
654                 fclose(fp);
655
656         free(lbase_dir);
657         free(rbase_dir);
658         strbuf_release(&ldir);
659         strbuf_release(&rdir);
660         strbuf_release(&wtdir);
661         strbuf_release(&buf);
662
663         return ret;
664 }
665
666 static int run_file_diff(int prompt, const char *prefix,
667                          int argc, const char **argv)
668 {
669         struct argv_array args = ARGV_ARRAY_INIT;
670         const char *env[] = {
671                 "GIT_PAGER=", "GIT_EXTERNAL_DIFF=git-difftool--helper", NULL,
672                 NULL
673         };
674         int ret = 0, i;
675
676         if (prompt > 0)
677                 env[2] = "GIT_DIFFTOOL_PROMPT=true";
678         else if (!prompt)
679                 env[2] = "GIT_DIFFTOOL_NO_PROMPT=true";
680
681
682         argv_array_push(&args, "diff");
683         for (i = 0; i < argc; i++)
684                 argv_array_push(&args, argv[i]);
685         ret = run_command_v_opt_cd_env(args.argv, RUN_GIT_CMD, prefix, env);
686         exit(ret);
687 }
688
689 int cmd_difftool(int argc, const char **argv, const char *prefix)
690 {
691         int use_gui_tool = 0, dir_diff = 0, prompt = -1, symlinks = 0,
692             tool_help = 0;
693         static char *difftool_cmd = NULL, *extcmd = NULL;
694         struct option builtin_difftool_options[] = {
695                 OPT_BOOL('g', "gui", &use_gui_tool,
696                          N_("use `diff.guitool` instead of `diff.tool`")),
697                 OPT_BOOL('d', "dir-diff", &dir_diff,
698                          N_("perform a full-directory diff")),
699                 OPT_SET_INT_F('y', "no-prompt", &prompt,
700                         N_("do not prompt before launching a diff tool"),
701                         0, PARSE_OPT_NONEG),
702                 OPT_SET_INT_F(0, "prompt", &prompt, NULL,
703                         1, PARSE_OPT_NONEG | PARSE_OPT_HIDDEN),
704                 OPT_BOOL(0, "symlinks", &symlinks,
705                          N_("use symlinks in dir-diff mode")),
706                 OPT_STRING('t', "tool", &difftool_cmd, N_("tool"),
707                            N_("use the specified diff tool")),
708                 OPT_BOOL(0, "tool-help", &tool_help,
709                          N_("print a list of diff tools that may be used with "
710                             "`--tool`")),
711                 OPT_BOOL(0, "trust-exit-code", &trust_exit_code,
712                          N_("make 'git-difftool' exit when an invoked diff "
713                             "tool returns a non - zero exit code")),
714                 OPT_STRING('x', "extcmd", &extcmd, N_("command"),
715                            N_("specify a custom command for viewing diffs")),
716                 OPT_END()
717         };
718
719         git_config(difftool_config, NULL);
720         symlinks = has_symlinks;
721
722         argc = parse_options(argc, argv, prefix, builtin_difftool_options,
723                              builtin_difftool_usage, PARSE_OPT_KEEP_UNKNOWN |
724                              PARSE_OPT_KEEP_DASHDASH);
725
726         if (tool_help)
727                 return print_tool_help();
728
729         /* NEEDSWORK: once we no longer spawn anything, remove this */
730         setenv(GIT_DIR_ENVIRONMENT, absolute_path(get_git_dir()), 1);
731         setenv(GIT_WORK_TREE_ENVIRONMENT, absolute_path(get_git_work_tree()), 1);
732
733         if (use_gui_tool && diff_gui_tool && *diff_gui_tool)
734                 setenv("GIT_DIFF_TOOL", diff_gui_tool, 1);
735         else if (difftool_cmd) {
736                 if (*difftool_cmd)
737                         setenv("GIT_DIFF_TOOL", difftool_cmd, 1);
738                 else
739                         die(_("no <tool> given for --tool=<tool>"));
740         }
741
742         if (extcmd) {
743                 if (*extcmd)
744                         setenv("GIT_DIFFTOOL_EXTCMD", extcmd, 1);
745                 else
746                         die(_("no <cmd> given for --extcmd=<cmd>"));
747         }
748
749         setenv("GIT_DIFFTOOL_TRUST_EXIT_CODE",
750                trust_exit_code ? "true" : "false", 1);
751
752         /*
753          * In directory diff mode, 'git-difftool--helper' is called once
754          * to compare the a / b directories. In file diff mode, 'git diff'
755          * will invoke a separate instance of 'git-difftool--helper' for
756          * each file that changed.
757          */
758         if (dir_diff)
759                 return run_dir_diff(extcmd, symlinks, prefix, argc, argv);
760         return run_file_diff(prompt, prefix, argc, argv);
761 }