Merge branch 'pw/rebase-x-sanity-check'
[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 #define USE_THE_INDEX_COMPATIBILITY_MACROS
15 #include "cache.h"
16 #include "config.h"
17 #include "builtin.h"
18 #include "run-command.h"
19 #include "exec-cmd.h"
20 #include "parse-options.h"
21 #include "argv-array.h"
22 #include "strbuf.h"
23 #include "lockfile.h"
24 #include "object-store.h"
25 #include "dir.h"
26
27 static char *diff_gui_tool;
28 static int trust_exit_code;
29
30 static const char *const builtin_difftool_usage[] = {
31         N_("git difftool [<options>] [<commit> [<commit>]] [--] [<path>...]"),
32         NULL
33 };
34
35 static int difftool_config(const char *var, const char *value, void *cb)
36 {
37         if (!strcmp(var, "diff.guitool")) {
38                 diff_gui_tool = xstrdup(value);
39                 return 0;
40         }
41
42         if (!strcmp(var, "difftool.trustexitcode")) {
43                 trust_exit_code = git_config_bool(var, value);
44                 return 0;
45         }
46
47         return git_default_config(var, value, cb);
48 }
49
50 static int print_tool_help(void)
51 {
52         const char *argv[] = { "mergetool", "--tool-help=diff", NULL };
53         return run_command_v_opt(argv, RUN_GIT_CMD);
54 }
55
56 static int parse_index_info(char *p, int *mode1, int *mode2,
57                             struct object_id *oid1, struct object_id *oid2,
58                             char *status)
59 {
60         if (*p != ':')
61                 return error("expected ':', got '%c'", *p);
62         *mode1 = (int)strtol(p + 1, &p, 8);
63         if (*p != ' ')
64                 return error("expected ' ', got '%c'", *p);
65         *mode2 = (int)strtol(p + 1, &p, 8);
66         if (*p != ' ')
67                 return error("expected ' ', got '%c'", *p);
68         if (get_oid_hex(++p, oid1))
69                 return error("expected object ID, got '%s'", p + 1);
70         p += GIT_SHA1_HEXSZ;
71         if (*p != ' ')
72                 return error("expected ' ', got '%c'", *p);
73         if (get_oid_hex(++p, oid2))
74                 return error("expected object ID, got '%s'", p + 1);
75         p += GIT_SHA1_HEXSZ;
76         if (*p != ' ')
77                 return error("expected ' ', got '%c'", *p);
78         *status = *++p;
79         if (!*status)
80                 return error("missing status");
81         if (p[1] && !isdigit(p[1]))
82                 return error("unexpected trailer: '%s'", p + 1);
83         return 0;
84 }
85
86 /*
87  * Remove any trailing slash from $workdir
88  * before starting to avoid double slashes in symlink targets.
89  */
90 static void add_path(struct strbuf *buf, size_t base_len, const char *path)
91 {
92         strbuf_setlen(buf, base_len);
93         if (buf->len && buf->buf[buf->len - 1] != '/')
94                 strbuf_addch(buf, '/');
95         strbuf_addstr(buf, path);
96 }
97
98 /*
99  * Determine whether we can simply reuse the file in the worktree.
100  */
101 static int use_wt_file(const char *workdir, const char *name,
102                        struct object_id *oid)
103 {
104         struct strbuf buf = STRBUF_INIT;
105         struct stat st;
106         int use = 0;
107
108         strbuf_addstr(&buf, workdir);
109         add_path(&buf, buf.len, name);
110
111         if (!lstat(buf.buf, &st) && !S_ISLNK(st.st_mode)) {
112                 struct object_id wt_oid;
113                 int fd = open(buf.buf, O_RDONLY);
114
115                 if (fd >= 0 &&
116                     !index_fd(&the_index, &wt_oid, fd, &st, OBJ_BLOB, name, 0)) {
117                         if (is_null_oid(oid)) {
118                                 oidcpy(oid, &wt_oid);
119                                 use = 1;
120                         } else if (oideq(oid, &wt_oid))
121                                 use = 1;
122                 }
123         }
124
125         strbuf_release(&buf);
126
127         return use;
128 }
129
130 struct working_tree_entry {
131         struct hashmap_entry entry;
132         char path[FLEX_ARRAY];
133 };
134
135 static int working_tree_entry_cmp(const void *unused_cmp_data,
136                                   const void *entry,
137                                   const void *entry_or_key,
138                                   const void *unused_keydata)
139 {
140         const struct working_tree_entry *a = entry;
141         const struct working_tree_entry *b = entry_or_key;
142         return strcmp(a->path, b->path);
143 }
144
145 /*
146  * The `left` and `right` entries hold paths for the symlinks hashmap,
147  * and a SHA-1 surrounded by brief text for submodules.
148  */
149 struct pair_entry {
150         struct hashmap_entry entry;
151         char left[PATH_MAX], right[PATH_MAX];
152         const char path[FLEX_ARRAY];
153 };
154
155 static int pair_cmp(const void *unused_cmp_data,
156                     const void *entry,
157                     const void *entry_or_key,
158                     const void *unused_keydata)
159 {
160         const struct pair_entry *a = entry;
161         const struct pair_entry *b = entry_or_key;
162
163         return strcmp(a->path, b->path);
164 }
165
166 static void add_left_or_right(struct hashmap *map, const char *path,
167                               const char *content, int is_right)
168 {
169         struct pair_entry *e, *existing;
170
171         FLEX_ALLOC_STR(e, path, path);
172         hashmap_entry_init(e, strhash(path));
173         existing = hashmap_get(map, e, NULL);
174         if (existing) {
175                 free(e);
176                 e = existing;
177         } else {
178                 e->left[0] = e->right[0] = '\0';
179                 hashmap_add(map, e);
180         }
181         strlcpy(is_right ? e->right : e->left, content, PATH_MAX);
182 }
183
184 struct path_entry {
185         struct hashmap_entry entry;
186         char path[FLEX_ARRAY];
187 };
188
189 static int path_entry_cmp(const void *unused_cmp_data,
190                           const void *entry,
191                           const void *entry_or_key,
192                           const void *key)
193 {
194         const struct path_entry *a = entry;
195         const struct path_entry *b = entry_or_key;
196
197         return strcmp(a->path, key ? key : b->path);
198 }
199
200 static void changed_files(struct hashmap *result, const char *index_path,
201                           const char *workdir)
202 {
203         struct child_process update_index = CHILD_PROCESS_INIT;
204         struct child_process diff_files = CHILD_PROCESS_INIT;
205         struct strbuf index_env = STRBUF_INIT, buf = STRBUF_INIT;
206         const char *git_dir = absolute_path(get_git_dir()), *env[] = {
207                 NULL, NULL
208         };
209         FILE *fp;
210
211         strbuf_addf(&index_env, "GIT_INDEX_FILE=%s", index_path);
212         env[0] = index_env.buf;
213
214         argv_array_pushl(&update_index.args,
215                          "--git-dir", git_dir, "--work-tree", workdir,
216                          "update-index", "--really-refresh", "-q",
217                          "--unmerged", NULL);
218         update_index.no_stdin = 1;
219         update_index.no_stdout = 1;
220         update_index.no_stderr = 1;
221         update_index.git_cmd = 1;
222         update_index.use_shell = 0;
223         update_index.clean_on_exit = 1;
224         update_index.dir = workdir;
225         update_index.env = env;
226         /* Ignore any errors of update-index */
227         run_command(&update_index);
228
229         argv_array_pushl(&diff_files.args,
230                          "--git-dir", git_dir, "--work-tree", workdir,
231                          "diff-files", "--name-only", "-z", NULL);
232         diff_files.no_stdin = 1;
233         diff_files.git_cmd = 1;
234         diff_files.use_shell = 0;
235         diff_files.clean_on_exit = 1;
236         diff_files.out = -1;
237         diff_files.dir = workdir;
238         diff_files.env = env;
239         if (start_command(&diff_files))
240                 die("could not obtain raw diff");
241         fp = xfdopen(diff_files.out, "r");
242         while (!strbuf_getline_nul(&buf, fp)) {
243                 struct path_entry *entry;
244                 FLEX_ALLOC_STR(entry, path, buf.buf);
245                 hashmap_entry_init(entry, strhash(buf.buf));
246                 hashmap_add(result, entry);
247         }
248         fclose(fp);
249         if (finish_command(&diff_files))
250                 die("diff-files did not exit properly");
251         strbuf_release(&index_env);
252         strbuf_release(&buf);
253 }
254
255 static NORETURN void exit_cleanup(const char *tmpdir, int exit_code)
256 {
257         struct strbuf buf = STRBUF_INIT;
258         strbuf_addstr(&buf, tmpdir);
259         remove_dir_recursively(&buf, 0);
260         if (exit_code)
261                 warning(_("failed: %d"), exit_code);
262         exit(exit_code);
263 }
264
265 static int ensure_leading_directories(char *path)
266 {
267         switch (safe_create_leading_directories(path)) {
268                 case SCLD_OK:
269                 case SCLD_EXISTS:
270                         return 0;
271                 default:
272                         return error(_("could not create leading directories "
273                                        "of '%s'"), path);
274         }
275 }
276
277 /*
278  * Unconditional writing of a plain regular file is what
279  * "git difftool --dir-diff" wants to do for symlinks.  We are preparing two
280  * temporary directories to be fed to a Git-unaware tool that knows how to
281  * show a diff of two directories (e.g. "diff -r A B").
282  *
283  * Because the tool is Git-unaware, if a symbolic link appears in either of
284  * these temporary directories, it will try to dereference and show the
285  * difference of the target of the symbolic link, which is not what we want,
286  * as the goal of the dir-diff mode is to produce an output that is logically
287  * equivalent to what "git diff" produces.
288  *
289  * Most importantly, we want to get textual comparison of the result of the
290  * readlink(2).  get_symlink() provides that---it returns the contents of
291  * the symlink that gets written to a regular file to force the external tool
292  * to compare the readlink(2) result as text, even on a filesystem that is
293  * capable of doing a symbolic link.
294  */
295 static char *get_symlink(const struct object_id *oid, const char *path)
296 {
297         char *data;
298         if (is_null_oid(oid)) {
299                 /* The symlink is unknown to Git so read from the filesystem */
300                 struct strbuf link = STRBUF_INIT;
301                 if (has_symlinks) {
302                         if (strbuf_readlink(&link, path, strlen(path)))
303                                 die(_("could not read symlink %s"), path);
304                 } else if (strbuf_read_file(&link, path, 128))
305                         die(_("could not read symlink file %s"), path);
306
307                 data = strbuf_detach(&link, NULL);
308         } else {
309                 enum object_type type;
310                 unsigned long size;
311                 data = read_object_file(oid, &type, &size);
312                 if (!data)
313                         die(_("could not read object %s for symlink %s"),
314                                 oid_to_hex(oid), path);
315         }
316
317         return data;
318 }
319
320 static int checkout_path(unsigned mode, struct object_id *oid,
321                          const char *path, const struct checkout *state)
322 {
323         struct cache_entry *ce;
324         int ret;
325
326         ce = make_transient_cache_entry(mode, oid, path, 0);
327         ret = checkout_entry(ce, state, NULL, NULL);
328
329         discard_cache_entry(ce);
330         return ret;
331 }
332
333 static int run_dir_diff(const char *extcmd, int symlinks, const char *prefix,
334                         int argc, const char **argv)
335 {
336         char tmpdir[PATH_MAX];
337         struct strbuf info = STRBUF_INIT, lpath = STRBUF_INIT;
338         struct strbuf rpath = STRBUF_INIT, buf = STRBUF_INIT;
339         struct strbuf ldir = STRBUF_INIT, rdir = STRBUF_INIT;
340         struct strbuf wtdir = STRBUF_INIT;
341         char *lbase_dir, *rbase_dir;
342         size_t ldir_len, rdir_len, wtdir_len;
343         const char *workdir, *tmp;
344         int ret = 0, i;
345         FILE *fp;
346         struct hashmap working_tree_dups, submodules, symlinks2;
347         struct hashmap_iter iter;
348         struct pair_entry *entry;
349         struct index_state wtindex;
350         struct checkout lstate, rstate;
351         int rc, flags = RUN_GIT_CMD, err = 0;
352         struct child_process child = CHILD_PROCESS_INIT;
353         const char *helper_argv[] = { "difftool--helper", NULL, NULL, NULL };
354         struct hashmap wt_modified, tmp_modified;
355         int indices_loaded = 0;
356
357         workdir = get_git_work_tree();
358
359         /* Setup temp directories */
360         tmp = getenv("TMPDIR");
361         xsnprintf(tmpdir, sizeof(tmpdir), "%s/git-difftool.XXXXXX", tmp ? tmp : "/tmp");
362         if (!mkdtemp(tmpdir))
363                 return error("could not create '%s'", tmpdir);
364         strbuf_addf(&ldir, "%s/left/", tmpdir);
365         strbuf_addf(&rdir, "%s/right/", tmpdir);
366         strbuf_addstr(&wtdir, workdir);
367         if (!wtdir.len || !is_dir_sep(wtdir.buf[wtdir.len - 1]))
368                 strbuf_addch(&wtdir, '/');
369         mkdir(ldir.buf, 0700);
370         mkdir(rdir.buf, 0700);
371
372         memset(&wtindex, 0, sizeof(wtindex));
373
374         memset(&lstate, 0, sizeof(lstate));
375         lstate.base_dir = lbase_dir = xstrdup(ldir.buf);
376         lstate.base_dir_len = ldir.len;
377         lstate.force = 1;
378         memset(&rstate, 0, sizeof(rstate));
379         rstate.base_dir = rbase_dir = xstrdup(rdir.buf);
380         rstate.base_dir_len = rdir.len;
381         rstate.force = 1;
382
383         ldir_len = ldir.len;
384         rdir_len = rdir.len;
385         wtdir_len = wtdir.len;
386
387         hashmap_init(&working_tree_dups, working_tree_entry_cmp, NULL, 0);
388         hashmap_init(&submodules, pair_cmp, NULL, 0);
389         hashmap_init(&symlinks2, pair_cmp, NULL, 0);
390
391         child.no_stdin = 1;
392         child.git_cmd = 1;
393         child.use_shell = 0;
394         child.clean_on_exit = 1;
395         child.dir = prefix;
396         child.out = -1;
397         argv_array_pushl(&child.args, "diff", "--raw", "--no-abbrev", "-z",
398                          NULL);
399         for (i = 0; i < argc; i++)
400                 argv_array_push(&child.args, argv[i]);
401         if (start_command(&child))
402                 die("could not obtain raw diff");
403         fp = xfdopen(child.out, "r");
404
405         /* Build index info for left and right sides of the diff */
406         i = 0;
407         while (!strbuf_getline_nul(&info, fp)) {
408                 int lmode, rmode;
409                 struct object_id loid, roid;
410                 char status;
411                 const char *src_path, *dst_path;
412
413                 if (starts_with(info.buf, "::"))
414                         die(N_("combined diff formats('-c' and '--cc') are "
415                                "not supported in\n"
416                                "directory diff mode('-d' and '--dir-diff')."));
417
418                 if (parse_index_info(info.buf, &lmode, &rmode, &loid, &roid,
419                                      &status))
420                         break;
421                 if (strbuf_getline_nul(&lpath, fp))
422                         break;
423                 src_path = lpath.buf;
424
425                 i++;
426                 if (status != 'C' && status != 'R') {
427                         dst_path = src_path;
428                 } else {
429                         if (strbuf_getline_nul(&rpath, fp))
430                                 break;
431                         dst_path = rpath.buf;
432                 }
433
434                 if (S_ISGITLINK(lmode) || S_ISGITLINK(rmode)) {
435                         strbuf_reset(&buf);
436                         strbuf_addf(&buf, "Subproject commit %s",
437                                     oid_to_hex(&loid));
438                         add_left_or_right(&submodules, src_path, buf.buf, 0);
439                         strbuf_reset(&buf);
440                         strbuf_addf(&buf, "Subproject commit %s",
441                                     oid_to_hex(&roid));
442                         if (oideq(&loid, &roid))
443                                 strbuf_addstr(&buf, "-dirty");
444                         add_left_or_right(&submodules, dst_path, buf.buf, 1);
445                         continue;
446                 }
447
448                 if (S_ISLNK(lmode)) {
449                         char *content = get_symlink(&loid, src_path);
450                         add_left_or_right(&symlinks2, src_path, content, 0);
451                         free(content);
452                 }
453
454                 if (S_ISLNK(rmode)) {
455                         char *content = get_symlink(&roid, dst_path);
456                         add_left_or_right(&symlinks2, dst_path, content, 1);
457                         free(content);
458                 }
459
460                 if (lmode && status != 'C') {
461                         if (checkout_path(lmode, &loid, src_path, &lstate)) {
462                                 ret = error("could not write '%s'", src_path);
463                                 goto finish;
464                         }
465                 }
466
467                 if (rmode && !S_ISLNK(rmode)) {
468                         struct working_tree_entry *entry;
469
470                         /* Avoid duplicate working_tree entries */
471                         FLEX_ALLOC_STR(entry, path, dst_path);
472                         hashmap_entry_init(entry, strhash(dst_path));
473                         if (hashmap_get(&working_tree_dups, entry, NULL)) {
474                                 free(entry);
475                                 continue;
476                         }
477                         hashmap_add(&working_tree_dups, entry);
478
479                         if (!use_wt_file(workdir, dst_path, &roid)) {
480                                 if (checkout_path(rmode, &roid, dst_path,
481                                                   &rstate)) {
482                                         ret = error("could not write '%s'",
483                                                     dst_path);
484                                         goto finish;
485                                 }
486                         } else if (!is_null_oid(&roid)) {
487                                 /*
488                                  * Changes in the working tree need special
489                                  * treatment since they are not part of the
490                                  * index.
491                                  */
492                                 struct cache_entry *ce2 =
493                                         make_cache_entry(&wtindex, rmode, &roid,
494                                                          dst_path, 0, 0);
495
496                                 add_index_entry(&wtindex, ce2,
497                                                 ADD_CACHE_JUST_APPEND);
498
499                                 add_path(&rdir, rdir_len, dst_path);
500                                 if (ensure_leading_directories(rdir.buf)) {
501                                         ret = error("could not create "
502                                                     "directory for '%s'",
503                                                     dst_path);
504                                         goto finish;
505                                 }
506                                 add_path(&wtdir, wtdir_len, dst_path);
507                                 if (symlinks) {
508                                         if (symlink(wtdir.buf, rdir.buf)) {
509                                                 ret = error_errno("could not symlink '%s' to '%s'", wtdir.buf, rdir.buf);
510                                                 goto finish;
511                                         }
512                                 } else {
513                                         struct stat st;
514                                         if (stat(wtdir.buf, &st))
515                                                 st.st_mode = 0644;
516                                         if (copy_file(rdir.buf, wtdir.buf,
517                                                       st.st_mode)) {
518                                                 ret = error("could not copy '%s' to '%s'", wtdir.buf, rdir.buf);
519                                                 goto finish;
520                                         }
521                                 }
522                         }
523                 }
524         }
525
526         fclose(fp);
527         fp = NULL;
528         if (finish_command(&child)) {
529                 ret = error("error occurred running diff --raw");
530                 goto finish;
531         }
532
533         if (!i)
534                 goto finish;
535
536         /*
537          * Changes to submodules require special treatment.This loop writes a
538          * temporary file to both the left and right directories to show the
539          * change in the recorded SHA1 for the submodule.
540          */
541         hashmap_iter_init(&submodules, &iter);
542         while ((entry = hashmap_iter_next(&iter))) {
543                 if (*entry->left) {
544                         add_path(&ldir, ldir_len, entry->path);
545                         ensure_leading_directories(ldir.buf);
546                         write_file(ldir.buf, "%s", entry->left);
547                 }
548                 if (*entry->right) {
549                         add_path(&rdir, rdir_len, entry->path);
550                         ensure_leading_directories(rdir.buf);
551                         write_file(rdir.buf, "%s", entry->right);
552                 }
553         }
554
555         /*
556          * Symbolic links require special treatment.The standard "git diff"
557          * shows only the link itself, not the contents of the link target.
558          * This loop replicates that behavior.
559          */
560         hashmap_iter_init(&symlinks2, &iter);
561         while ((entry = hashmap_iter_next(&iter))) {
562                 if (*entry->left) {
563                         add_path(&ldir, ldir_len, entry->path);
564                         ensure_leading_directories(ldir.buf);
565                         write_file(ldir.buf, "%s", entry->left);
566                 }
567                 if (*entry->right) {
568                         add_path(&rdir, rdir_len, entry->path);
569                         ensure_leading_directories(rdir.buf);
570                         write_file(rdir.buf, "%s", entry->right);
571                 }
572         }
573
574         strbuf_release(&buf);
575
576         strbuf_setlen(&ldir, ldir_len);
577         helper_argv[1] = ldir.buf;
578         strbuf_setlen(&rdir, rdir_len);
579         helper_argv[2] = rdir.buf;
580
581         if (extcmd) {
582                 helper_argv[0] = extcmd;
583                 flags = 0;
584         } else
585                 setenv("GIT_DIFFTOOL_DIRDIFF", "true", 1);
586         rc = run_command_v_opt(helper_argv, flags);
587
588         /*
589          * If the diff includes working copy files and those
590          * files were modified during the diff, then the changes
591          * should be copied back to the working tree.
592          * Do not copy back files when symlinks are used and the
593          * external tool did not replace the original link with a file.
594          *
595          * These hashes are loaded lazily since they aren't needed
596          * in the common case of --symlinks and the difftool updating
597          * files through the symlink.
598          */
599         hashmap_init(&wt_modified, path_entry_cmp, NULL, wtindex.cache_nr);
600         hashmap_init(&tmp_modified, path_entry_cmp, NULL, wtindex.cache_nr);
601
602         for (i = 0; i < wtindex.cache_nr; i++) {
603                 struct hashmap_entry dummy;
604                 const char *name = wtindex.cache[i]->name;
605                 struct stat st;
606
607                 add_path(&rdir, rdir_len, name);
608                 if (lstat(rdir.buf, &st))
609                         continue;
610
611                 if ((symlinks && S_ISLNK(st.st_mode)) || !S_ISREG(st.st_mode))
612                         continue;
613
614                 if (!indices_loaded) {
615                         struct lock_file lock = LOCK_INIT;
616                         strbuf_reset(&buf);
617                         strbuf_addf(&buf, "%s/wtindex", tmpdir);
618                         if (hold_lock_file_for_update(&lock, buf.buf, 0) < 0 ||
619                             write_locked_index(&wtindex, &lock, COMMIT_LOCK)) {
620                                 ret = error("could not write %s", buf.buf);
621                                 goto finish;
622                         }
623                         changed_files(&wt_modified, buf.buf, workdir);
624                         strbuf_setlen(&rdir, rdir_len);
625                         changed_files(&tmp_modified, buf.buf, rdir.buf);
626                         add_path(&rdir, rdir_len, name);
627                         indices_loaded = 1;
628                 }
629
630                 hashmap_entry_init(&dummy, strhash(name));
631                 if (hashmap_get(&tmp_modified, &dummy, name)) {
632                         add_path(&wtdir, wtdir_len, name);
633                         if (hashmap_get(&wt_modified, &dummy, name)) {
634                                 warning(_("both files modified: '%s' and '%s'."),
635                                         wtdir.buf, rdir.buf);
636                                 warning(_("working tree file has been left."));
637                                 warning("%s", "");
638                                 err = 1;
639                         } else if (unlink(wtdir.buf) ||
640                                    copy_file(wtdir.buf, rdir.buf, st.st_mode))
641                                 warning_errno(_("could not copy '%s' to '%s'"),
642                                               rdir.buf, wtdir.buf);
643                 }
644         }
645
646         if (err) {
647                 warning(_("temporary files exist in '%s'."), tmpdir);
648                 warning(_("you may want to cleanup or recover these."));
649                 exit(1);
650         } else
651                 exit_cleanup(tmpdir, rc);
652
653 finish:
654         if (fp)
655                 fclose(fp);
656
657         free(lbase_dir);
658         free(rbase_dir);
659         strbuf_release(&ldir);
660         strbuf_release(&rdir);
661         strbuf_release(&wtdir);
662         strbuf_release(&buf);
663
664         return ret;
665 }
666
667 static int run_file_diff(int prompt, const char *prefix,
668                          int argc, const char **argv)
669 {
670         struct argv_array args = ARGV_ARRAY_INIT;
671         const char *env[] = {
672                 "GIT_PAGER=", "GIT_EXTERNAL_DIFF=git-difftool--helper", NULL,
673                 NULL
674         };
675         int ret = 0, i;
676
677         if (prompt > 0)
678                 env[2] = "GIT_DIFFTOOL_PROMPT=true";
679         else if (!prompt)
680                 env[2] = "GIT_DIFFTOOL_NO_PROMPT=true";
681
682
683         argv_array_push(&args, "diff");
684         for (i = 0; i < argc; i++)
685                 argv_array_push(&args, argv[i]);
686         ret = run_command_v_opt_cd_env(args.argv, RUN_GIT_CMD, prefix, env);
687         exit(ret);
688 }
689
690 int cmd_difftool(int argc, const char **argv, const char *prefix)
691 {
692         int use_gui_tool = 0, dir_diff = 0, prompt = -1, symlinks = 0,
693             tool_help = 0;
694         static char *difftool_cmd = NULL, *extcmd = NULL;
695         struct option builtin_difftool_options[] = {
696                 OPT_BOOL('g', "gui", &use_gui_tool,
697                          N_("use `diff.guitool` instead of `diff.tool`")),
698                 OPT_BOOL('d', "dir-diff", &dir_diff,
699                          N_("perform a full-directory diff")),
700                 OPT_SET_INT_F('y', "no-prompt", &prompt,
701                         N_("do not prompt before launching a diff tool"),
702                         0, PARSE_OPT_NONEG),
703                 OPT_SET_INT_F(0, "prompt", &prompt, NULL,
704                         1, PARSE_OPT_NONEG | PARSE_OPT_HIDDEN),
705                 OPT_BOOL(0, "symlinks", &symlinks,
706                          N_("use symlinks in dir-diff mode")),
707                 OPT_STRING('t', "tool", &difftool_cmd, N_("tool"),
708                            N_("use the specified diff tool")),
709                 OPT_BOOL(0, "tool-help", &tool_help,
710                          N_("print a list of diff tools that may be used with "
711                             "`--tool`")),
712                 OPT_BOOL(0, "trust-exit-code", &trust_exit_code,
713                          N_("make 'git-difftool' exit when an invoked diff "
714                             "tool returns a non - zero exit code")),
715                 OPT_STRING('x', "extcmd", &extcmd, N_("command"),
716                            N_("specify a custom command for viewing diffs")),
717                 OPT_END()
718         };
719
720         git_config(difftool_config, NULL);
721         symlinks = has_symlinks;
722
723         argc = parse_options(argc, argv, prefix, builtin_difftool_options,
724                              builtin_difftool_usage, PARSE_OPT_KEEP_UNKNOWN |
725                              PARSE_OPT_KEEP_DASHDASH);
726
727         if (tool_help)
728                 return print_tool_help();
729
730         /* NEEDSWORK: once we no longer spawn anything, remove this */
731         setenv(GIT_DIR_ENVIRONMENT, absolute_path(get_git_dir()), 1);
732         setenv(GIT_WORK_TREE_ENVIRONMENT, absolute_path(get_git_work_tree()), 1);
733
734         if (use_gui_tool && diff_gui_tool && *diff_gui_tool)
735                 setenv("GIT_DIFF_TOOL", diff_gui_tool, 1);
736         else if (difftool_cmd) {
737                 if (*difftool_cmd)
738                         setenv("GIT_DIFF_TOOL", difftool_cmd, 1);
739                 else
740                         die(_("no <tool> given for --tool=<tool>"));
741         }
742
743         if (extcmd) {
744                 if (*extcmd)
745                         setenv("GIT_DIFFTOOL_EXTCMD", extcmd, 1);
746                 else
747                         die(_("no <cmd> given for --extcmd=<cmd>"));
748         }
749
750         setenv("GIT_DIFFTOOL_TRUST_EXIT_CODE",
751                trust_exit_code ? "true" : "false", 1);
752
753         /*
754          * In directory diff mode, 'git-difftool--helper' is called once
755          * to compare the a / b directories. In file diff mode, 'git diff'
756          * will invoke a separate instance of 'git-difftool--helper' for
757          * each file that changed.
758          */
759         if (dir_diff)
760                 return run_dir_diff(extcmd, symlinks, prefix, argc, argv);
761         return run_file_diff(prompt, prefix, argc, argv);
762 }