Merge branch 'ss/doc-svn' into maint
[git] / submodule.c
1 #include "cache.h"
2 #include "submodule.h"
3 #include "dir.h"
4 #include "diff.h"
5 #include "commit.h"
6 #include "revision.h"
7 #include "run-command.h"
8 #include "diffcore.h"
9 #include "refs.h"
10 #include "string-list.h"
11
12 static struct string_list config_name_for_path;
13 static struct string_list config_fetch_recurse_submodules_for_name;
14 static struct string_list config_ignore_for_name;
15 static int config_fetch_recurse_submodules = RECURSE_SUBMODULES_ON_DEMAND;
16 static struct string_list changed_submodule_paths;
17
18 static int add_submodule_odb(const char *path)
19 {
20         struct strbuf objects_directory = STRBUF_INIT;
21         struct alternate_object_database *alt_odb;
22         int ret = 0;
23         const char *git_dir;
24
25         strbuf_addf(&objects_directory, "%s/.git", path);
26         git_dir = read_gitfile_gently(objects_directory.buf);
27         if (git_dir) {
28                 strbuf_reset(&objects_directory);
29                 strbuf_addstr(&objects_directory, git_dir);
30         }
31         strbuf_addstr(&objects_directory, "/objects/");
32         if (!is_directory(objects_directory.buf)) {
33                 ret = -1;
34                 goto done;
35         }
36         /* avoid adding it twice */
37         for (alt_odb = alt_odb_list; alt_odb; alt_odb = alt_odb->next)
38                 if (alt_odb->name - alt_odb->base == objects_directory.len &&
39                                 !strncmp(alt_odb->base, objects_directory.buf,
40                                         objects_directory.len))
41                         goto done;
42
43         alt_odb = xmalloc(objects_directory.len + 42 + sizeof(*alt_odb));
44         alt_odb->next = alt_odb_list;
45         strcpy(alt_odb->base, objects_directory.buf);
46         alt_odb->name = alt_odb->base + objects_directory.len;
47         alt_odb->name[2] = '/';
48         alt_odb->name[40] = '\0';
49         alt_odb->name[41] = '\0';
50         alt_odb_list = alt_odb;
51         prepare_alt_odb();
52 done:
53         strbuf_release(&objects_directory);
54         return ret;
55 }
56
57 void set_diffopt_flags_from_submodule_config(struct diff_options *diffopt,
58                                              const char *path)
59 {
60         struct string_list_item *path_option, *ignore_option;
61         path_option = unsorted_string_list_lookup(&config_name_for_path, path);
62         if (path_option) {
63                 ignore_option = unsorted_string_list_lookup(&config_ignore_for_name, path_option->util);
64                 if (ignore_option)
65                         handle_ignore_submodules_arg(diffopt, ignore_option->util);
66         }
67 }
68
69 int submodule_config(const char *var, const char *value, void *cb)
70 {
71         if (!prefixcmp(var, "submodule."))
72                 return parse_submodule_config_option(var, value);
73         else if (!strcmp(var, "fetch.recursesubmodules")) {
74                 config_fetch_recurse_submodules = parse_fetch_recurse_submodules_arg(var, value);
75                 return 0;
76         }
77         return 0;
78 }
79
80 void gitmodules_config(void)
81 {
82         const char *work_tree = get_git_work_tree();
83         if (work_tree) {
84                 struct strbuf gitmodules_path = STRBUF_INIT;
85                 strbuf_addstr(&gitmodules_path, work_tree);
86                 strbuf_addstr(&gitmodules_path, "/.gitmodules");
87                 git_config_from_file(submodule_config, gitmodules_path.buf, NULL);
88                 strbuf_release(&gitmodules_path);
89         }
90 }
91
92 int parse_submodule_config_option(const char *var, const char *value)
93 {
94         int len;
95         struct string_list_item *config;
96         struct strbuf submodname = STRBUF_INIT;
97
98         var += 10;              /* Skip "submodule." */
99
100         len = strlen(var);
101         if ((len > 5) && !strcmp(var + len - 5, ".path")) {
102                 strbuf_add(&submodname, var, len - 5);
103                 config = unsorted_string_list_lookup(&config_name_for_path, value);
104                 if (config)
105                         free(config->util);
106                 else
107                         config = string_list_append(&config_name_for_path, xstrdup(value));
108                 config->util = strbuf_detach(&submodname, NULL);
109                 strbuf_release(&submodname);
110         } else if ((len > 23) && !strcmp(var + len - 23, ".fetchrecursesubmodules")) {
111                 strbuf_add(&submodname, var, len - 23);
112                 config = unsorted_string_list_lookup(&config_fetch_recurse_submodules_for_name, submodname.buf);
113                 if (!config)
114                         config = string_list_append(&config_fetch_recurse_submodules_for_name,
115                                                     strbuf_detach(&submodname, NULL));
116                 config->util = (void *)(intptr_t)parse_fetch_recurse_submodules_arg(var, value);
117                 strbuf_release(&submodname);
118         } else if ((len > 7) && !strcmp(var + len - 7, ".ignore")) {
119                 if (strcmp(value, "untracked") && strcmp(value, "dirty") &&
120                     strcmp(value, "all") && strcmp(value, "none")) {
121                         warning("Invalid parameter \"%s\" for config option \"submodule.%s.ignore\"", value, var);
122                         return 0;
123                 }
124
125                 strbuf_add(&submodname, var, len - 7);
126                 config = unsorted_string_list_lookup(&config_ignore_for_name, submodname.buf);
127                 if (config)
128                         free(config->util);
129                 else
130                         config = string_list_append(&config_ignore_for_name,
131                                                     strbuf_detach(&submodname, NULL));
132                 strbuf_release(&submodname);
133                 config->util = xstrdup(value);
134                 return 0;
135         }
136         return 0;
137 }
138
139 void handle_ignore_submodules_arg(struct diff_options *diffopt,
140                                   const char *arg)
141 {
142         DIFF_OPT_CLR(diffopt, IGNORE_SUBMODULES);
143         DIFF_OPT_CLR(diffopt, IGNORE_UNTRACKED_IN_SUBMODULES);
144         DIFF_OPT_CLR(diffopt, IGNORE_DIRTY_SUBMODULES);
145
146         if (!strcmp(arg, "all"))
147                 DIFF_OPT_SET(diffopt, IGNORE_SUBMODULES);
148         else if (!strcmp(arg, "untracked"))
149                 DIFF_OPT_SET(diffopt, IGNORE_UNTRACKED_IN_SUBMODULES);
150         else if (!strcmp(arg, "dirty"))
151                 DIFF_OPT_SET(diffopt, IGNORE_DIRTY_SUBMODULES);
152         else if (strcmp(arg, "none"))
153                 die("bad --ignore-submodules argument: %s", arg);
154 }
155
156 static int prepare_submodule_summary(struct rev_info *rev, const char *path,
157                 struct commit *left, struct commit *right,
158                 int *fast_forward, int *fast_backward)
159 {
160         struct commit_list *merge_bases, *list;
161
162         init_revisions(rev, NULL);
163         setup_revisions(0, NULL, rev, NULL);
164         rev->left_right = 1;
165         rev->first_parent_only = 1;
166         left->object.flags |= SYMMETRIC_LEFT;
167         add_pending_object(rev, &left->object, path);
168         add_pending_object(rev, &right->object, path);
169         merge_bases = get_merge_bases(left, right, 1);
170         if (merge_bases) {
171                 if (merge_bases->item == left)
172                         *fast_forward = 1;
173                 else if (merge_bases->item == right)
174                         *fast_backward = 1;
175         }
176         for (list = merge_bases; list; list = list->next) {
177                 list->item->object.flags |= UNINTERESTING;
178                 add_pending_object(rev, &list->item->object,
179                         sha1_to_hex(list->item->object.sha1));
180         }
181         return prepare_revision_walk(rev);
182 }
183
184 static void print_submodule_summary(struct rev_info *rev, FILE *f,
185                 const char *del, const char *add, const char *reset)
186 {
187         static const char format[] = "  %m %s";
188         struct strbuf sb = STRBUF_INIT;
189         struct commit *commit;
190
191         while ((commit = get_revision(rev))) {
192                 struct pretty_print_context ctx = {0};
193                 ctx.date_mode = rev->date_mode;
194                 strbuf_setlen(&sb, 0);
195                 if (commit->object.flags & SYMMETRIC_LEFT) {
196                         if (del)
197                                 strbuf_addstr(&sb, del);
198                 }
199                 else if (add)
200                         strbuf_addstr(&sb, add);
201                 format_commit_message(commit, format, &sb, &ctx);
202                 if (reset)
203                         strbuf_addstr(&sb, reset);
204                 strbuf_addch(&sb, '\n');
205                 fprintf(f, "%s", sb.buf);
206         }
207         strbuf_release(&sb);
208 }
209
210 int parse_fetch_recurse_submodules_arg(const char *opt, const char *arg)
211 {
212         switch (git_config_maybe_bool(opt, arg)) {
213         case 1:
214                 return RECURSE_SUBMODULES_ON;
215         case 0:
216                 return RECURSE_SUBMODULES_OFF;
217         default:
218                 if (!strcmp(arg, "on-demand"))
219                         return RECURSE_SUBMODULES_ON_DEMAND;
220                 die("bad %s argument: %s", opt, arg);
221         }
222 }
223
224 void show_submodule_summary(FILE *f, const char *path,
225                 unsigned char one[20], unsigned char two[20],
226                 unsigned dirty_submodule,
227                 const char *del, const char *add, const char *reset)
228 {
229         struct rev_info rev;
230         struct commit *left = left, *right = right;
231         const char *message = NULL;
232         struct strbuf sb = STRBUF_INIT;
233         int fast_forward = 0, fast_backward = 0;
234
235         if (is_null_sha1(two))
236                 message = "(submodule deleted)";
237         else if (add_submodule_odb(path))
238                 message = "(not checked out)";
239         else if (is_null_sha1(one))
240                 message = "(new submodule)";
241         else if (!(left = lookup_commit_reference(one)) ||
242                  !(right = lookup_commit_reference(two)))
243                 message = "(commits not present)";
244
245         if (!message &&
246             prepare_submodule_summary(&rev, path, left, right,
247                                         &fast_forward, &fast_backward))
248                 message = "(revision walker failed)";
249
250         if (dirty_submodule & DIRTY_SUBMODULE_UNTRACKED)
251                 fprintf(f, "Submodule %s contains untracked content\n", path);
252         if (dirty_submodule & DIRTY_SUBMODULE_MODIFIED)
253                 fprintf(f, "Submodule %s contains modified content\n", path);
254
255         if (!hashcmp(one, two)) {
256                 strbuf_release(&sb);
257                 return;
258         }
259
260         strbuf_addf(&sb, "Submodule %s %s..", path,
261                         find_unique_abbrev(one, DEFAULT_ABBREV));
262         if (!fast_backward && !fast_forward)
263                 strbuf_addch(&sb, '.');
264         strbuf_addf(&sb, "%s", find_unique_abbrev(two, DEFAULT_ABBREV));
265         if (message)
266                 strbuf_addf(&sb, " %s\n", message);
267         else
268                 strbuf_addf(&sb, "%s:\n", fast_backward ? " (rewind)" : "");
269         fwrite(sb.buf, sb.len, 1, f);
270
271         if (!message) {
272                 print_submodule_summary(&rev, f, del, add, reset);
273                 clear_commit_marks(left, ~0);
274                 clear_commit_marks(right, ~0);
275         }
276
277         strbuf_release(&sb);
278 }
279
280 void set_config_fetch_recurse_submodules(int value)
281 {
282         config_fetch_recurse_submodules = value;
283 }
284
285 static int is_submodule_commit_present(const char *path, unsigned char sha1[20])
286 {
287         int is_present = 0;
288         if (!add_submodule_odb(path) && lookup_commit_reference(sha1)) {
289                 /* Even if the submodule is checked out and the commit is
290                  * present, make sure it is reachable from a ref. */
291                 struct child_process cp;
292                 const char *argv[] = {"rev-list", "-n", "1", NULL, "--not", "--all", NULL};
293                 struct strbuf buf = STRBUF_INIT;
294
295                 argv[3] = sha1_to_hex(sha1);
296                 memset(&cp, 0, sizeof(cp));
297                 cp.argv = argv;
298                 cp.env = local_repo_env;
299                 cp.git_cmd = 1;
300                 cp.no_stdin = 1;
301                 cp.out = -1;
302                 cp.dir = path;
303                 if (!run_command(&cp) && !strbuf_read(&buf, cp.out, 1024))
304                         is_present = 1;
305
306                 close(cp.out);
307                 strbuf_release(&buf);
308         }
309         return is_present;
310 }
311
312 static void submodule_collect_changed_cb(struct diff_queue_struct *q,
313                                          struct diff_options *options,
314                                          void *data)
315 {
316         int i;
317         for (i = 0; i < q->nr; i++) {
318                 struct diff_filepair *p = q->queue[i];
319                 if (!S_ISGITLINK(p->two->mode))
320                         continue;
321
322                 if (S_ISGITLINK(p->one->mode)) {
323                         /* NEEDSWORK: We should honor the name configured in
324                          * the .gitmodules file of the commit we are examining
325                          * here to be able to correctly follow submodules
326                          * being moved around. */
327                         struct string_list_item *path;
328                         path = unsorted_string_list_lookup(&changed_submodule_paths, p->two->path);
329                         if (!path && !is_submodule_commit_present(p->two->path, p->two->sha1))
330                                 string_list_append(&changed_submodule_paths, xstrdup(p->two->path));
331                 } else {
332                         /* Submodule is new or was moved here */
333                         /* NEEDSWORK: When the .git directories of submodules
334                          * live inside the superprojects .git directory some
335                          * day we should fetch new submodules directly into
336                          * that location too when config or options request
337                          * that so they can be checked out from there. */
338                         continue;
339                 }
340         }
341 }
342
343 void check_for_new_submodule_commits(unsigned char new_sha1[20])
344 {
345         struct rev_info rev;
346         struct commit *commit;
347         const char *argv[] = {NULL, NULL, "--not", "--all", NULL};
348         int argc = ARRAY_SIZE(argv) - 1;
349
350         init_revisions(&rev, NULL);
351         argv[1] = xstrdup(sha1_to_hex(new_sha1));
352         setup_revisions(argc, argv, &rev, NULL);
353         if (prepare_revision_walk(&rev))
354                 die("revision walk setup failed");
355
356         /*
357          * Collect all submodules (whether checked out or not) for which new
358          * commits have been recorded upstream in "changed_submodule_paths".
359          */
360         while ((commit = get_revision(&rev))) {
361                 struct commit_list *parent = commit->parents;
362                 while (parent) {
363                         struct diff_options diff_opts;
364                         diff_setup(&diff_opts);
365                         diff_opts.output_format |= DIFF_FORMAT_CALLBACK;
366                         diff_opts.format_callback = submodule_collect_changed_cb;
367                         if (diff_setup_done(&diff_opts) < 0)
368                                 die("diff_setup_done failed");
369                         diff_tree_sha1(parent->item->object.sha1, commit->object.sha1, "", &diff_opts);
370                         diffcore_std(&diff_opts);
371                         diff_flush(&diff_opts);
372                         parent = parent->next;
373                 }
374         }
375         free((char *)argv[1]);
376 }
377
378 int fetch_populated_submodules(int num_options, const char **options,
379                                const char *prefix, int command_line_option,
380                                int quiet)
381 {
382         int i, result = 0, argc = 0, default_argc;
383         struct child_process cp;
384         const char **argv;
385         struct string_list_item *name_for_path;
386         const char *work_tree = get_git_work_tree();
387         if (!work_tree)
388                 goto out;
389
390         if (!the_index.initialized)
391                 if (read_cache() < 0)
392                         die("index file corrupt");
393
394         /* 6: "fetch" (options) --recurse-submodules-default default "--submodule-prefix" prefix NULL */
395         argv = xcalloc(num_options + 6, sizeof(const char *));
396         argv[argc++] = "fetch";
397         for (i = 0; i < num_options; i++)
398                 argv[argc++] = options[i];
399         argv[argc++] = "--recurse-submodules-default";
400         default_argc = argc++;
401         argv[argc++] = "--submodule-prefix";
402
403         memset(&cp, 0, sizeof(cp));
404         cp.argv = argv;
405         cp.env = local_repo_env;
406         cp.git_cmd = 1;
407         cp.no_stdin = 1;
408
409         for (i = 0; i < active_nr; i++) {
410                 struct strbuf submodule_path = STRBUF_INIT;
411                 struct strbuf submodule_git_dir = STRBUF_INIT;
412                 struct strbuf submodule_prefix = STRBUF_INIT;
413                 struct cache_entry *ce = active_cache[i];
414                 const char *git_dir, *name, *default_argv;
415
416                 if (!S_ISGITLINK(ce->ce_mode))
417                         continue;
418
419                 name = ce->name;
420                 name_for_path = unsorted_string_list_lookup(&config_name_for_path, ce->name);
421                 if (name_for_path)
422                         name = name_for_path->util;
423
424                 default_argv = "yes";
425                 if (command_line_option == RECURSE_SUBMODULES_DEFAULT) {
426                         struct string_list_item *fetch_recurse_submodules_option;
427                         fetch_recurse_submodules_option = unsorted_string_list_lookup(&config_fetch_recurse_submodules_for_name, name);
428                         if (fetch_recurse_submodules_option) {
429                                 if ((intptr_t)fetch_recurse_submodules_option->util == RECURSE_SUBMODULES_OFF)
430                                         continue;
431                                 if ((intptr_t)fetch_recurse_submodules_option->util == RECURSE_SUBMODULES_ON_DEMAND) {
432                                         if (!unsorted_string_list_lookup(&changed_submodule_paths, ce->name))
433                                                 continue;
434                                         default_argv = "on-demand";
435                                 }
436                         } else {
437                                 if (config_fetch_recurse_submodules == RECURSE_SUBMODULES_OFF)
438                                         continue;
439                                 if (config_fetch_recurse_submodules == RECURSE_SUBMODULES_ON_DEMAND) {
440                                         if (!unsorted_string_list_lookup(&changed_submodule_paths, ce->name))
441                                                 continue;
442                                         default_argv = "on-demand";
443                                 }
444                         }
445                 } else if (command_line_option == RECURSE_SUBMODULES_ON_DEMAND) {
446                         if (!unsorted_string_list_lookup(&changed_submodule_paths, ce->name))
447                                 continue;
448                         default_argv = "on-demand";
449                 }
450
451                 strbuf_addf(&submodule_path, "%s/%s", work_tree, ce->name);
452                 strbuf_addf(&submodule_git_dir, "%s/.git", submodule_path.buf);
453                 strbuf_addf(&submodule_prefix, "%s%s/", prefix, ce->name);
454                 git_dir = read_gitfile_gently(submodule_git_dir.buf);
455                 if (!git_dir)
456                         git_dir = submodule_git_dir.buf;
457                 if (is_directory(git_dir)) {
458                         if (!quiet)
459                                 printf("Fetching submodule %s%s\n", prefix, ce->name);
460                         cp.dir = submodule_path.buf;
461                         argv[default_argc] = default_argv;
462                         argv[argc] = submodule_prefix.buf;
463                         if (run_command(&cp))
464                                 result = 1;
465                 }
466                 strbuf_release(&submodule_path);
467                 strbuf_release(&submodule_git_dir);
468                 strbuf_release(&submodule_prefix);
469         }
470         free(argv);
471 out:
472         string_list_clear(&changed_submodule_paths, 1);
473         return result;
474 }
475
476 unsigned is_submodule_modified(const char *path, int ignore_untracked)
477 {
478         ssize_t len;
479         struct child_process cp;
480         const char *argv[] = {
481                 "status",
482                 "--porcelain",
483                 NULL,
484                 NULL,
485         };
486         struct strbuf buf = STRBUF_INIT;
487         unsigned dirty_submodule = 0;
488         const char *line, *next_line;
489         const char *git_dir;
490
491         strbuf_addf(&buf, "%s/.git", path);
492         git_dir = read_gitfile_gently(buf.buf);
493         if (!git_dir)
494                 git_dir = buf.buf;
495         if (!is_directory(git_dir)) {
496                 strbuf_release(&buf);
497                 /* The submodule is not checked out, so it is not modified */
498                 return 0;
499
500         }
501         strbuf_reset(&buf);
502
503         if (ignore_untracked)
504                 argv[2] = "-uno";
505
506         memset(&cp, 0, sizeof(cp));
507         cp.argv = argv;
508         cp.env = local_repo_env;
509         cp.git_cmd = 1;
510         cp.no_stdin = 1;
511         cp.out = -1;
512         cp.dir = path;
513         if (start_command(&cp))
514                 die("Could not run git status --porcelain");
515
516         len = strbuf_read(&buf, cp.out, 1024);
517         line = buf.buf;
518         while (len > 2) {
519                 if ((line[0] == '?') && (line[1] == '?')) {
520                         dirty_submodule |= DIRTY_SUBMODULE_UNTRACKED;
521                         if (dirty_submodule & DIRTY_SUBMODULE_MODIFIED)
522                                 break;
523                 } else {
524                         dirty_submodule |= DIRTY_SUBMODULE_MODIFIED;
525                         if (ignore_untracked ||
526                             (dirty_submodule & DIRTY_SUBMODULE_UNTRACKED))
527                                 break;
528                 }
529                 next_line = strchr(line, '\n');
530                 if (!next_line)
531                         break;
532                 next_line++;
533                 len -= (next_line - line);
534                 line = next_line;
535         }
536         close(cp.out);
537
538         if (finish_command(&cp))
539                 die("git status --porcelain failed");
540
541         strbuf_release(&buf);
542         return dirty_submodule;
543 }
544
545 static int find_first_merges(struct object_array *result, const char *path,
546                 struct commit *a, struct commit *b)
547 {
548         int i, j;
549         struct object_array merges;
550         struct commit *commit;
551         int contains_another;
552
553         char merged_revision[42];
554         const char *rev_args[] = { "rev-list", "--merges", "--ancestry-path",
555                                    "--all", merged_revision, NULL };
556         struct rev_info revs;
557         struct setup_revision_opt rev_opts;
558
559         memset(&merges, 0, sizeof(merges));
560         memset(result, 0, sizeof(struct object_array));
561         memset(&rev_opts, 0, sizeof(rev_opts));
562
563         /* get all revisions that merge commit a */
564         snprintf(merged_revision, sizeof(merged_revision), "^%s",
565                         sha1_to_hex(a->object.sha1));
566         init_revisions(&revs, NULL);
567         rev_opts.submodule = path;
568         setup_revisions(sizeof(rev_args)/sizeof(char *)-1, rev_args, &revs, &rev_opts);
569
570         /* save all revisions from the above list that contain b */
571         if (prepare_revision_walk(&revs))
572                 die("revision walk setup failed");
573         while ((commit = get_revision(&revs)) != NULL) {
574                 struct object *o = &(commit->object);
575                 if (in_merge_bases(b, &commit, 1))
576                         add_object_array(o, NULL, &merges);
577         }
578
579         /* Now we've got all merges that contain a and b. Prune all
580          * merges that contain another found merge and save them in
581          * result.
582          */
583         for (i = 0; i < merges.nr; i++) {
584                 struct commit *m1 = (struct commit *) merges.objects[i].item;
585
586                 contains_another = 0;
587                 for (j = 0; j < merges.nr; j++) {
588                         struct commit *m2 = (struct commit *) merges.objects[j].item;
589                         if (i != j && in_merge_bases(m2, &m1, 1)) {
590                                 contains_another = 1;
591                                 break;
592                         }
593                 }
594
595                 if (!contains_another)
596                         add_object_array(merges.objects[i].item,
597                                          merges.objects[i].name, result);
598         }
599
600         free(merges.objects);
601         return result->nr;
602 }
603
604 static void print_commit(struct commit *commit)
605 {
606         struct strbuf sb = STRBUF_INIT;
607         struct pretty_print_context ctx = {0};
608         ctx.date_mode = DATE_NORMAL;
609         format_commit_message(commit, " %h: %m %s", &sb, &ctx);
610         fprintf(stderr, "%s\n", sb.buf);
611         strbuf_release(&sb);
612 }
613
614 #define MERGE_WARNING(path, msg) \
615         warning("Failed to merge submodule %s (%s)", path, msg);
616
617 int merge_submodule(unsigned char result[20], const char *path,
618                     const unsigned char base[20], const unsigned char a[20],
619                     const unsigned char b[20])
620 {
621         struct commit *commit_base, *commit_a, *commit_b;
622         int parent_count;
623         struct object_array merges;
624
625         int i;
626
627         /* store a in result in case we fail */
628         hashcpy(result, a);
629
630         /* we can not handle deletion conflicts */
631         if (is_null_sha1(base))
632                 return 0;
633         if (is_null_sha1(a))
634                 return 0;
635         if (is_null_sha1(b))
636                 return 0;
637
638         if (add_submodule_odb(path)) {
639                 MERGE_WARNING(path, "not checked out");
640                 return 0;
641         }
642
643         if (!(commit_base = lookup_commit_reference(base)) ||
644             !(commit_a = lookup_commit_reference(a)) ||
645             !(commit_b = lookup_commit_reference(b))) {
646                 MERGE_WARNING(path, "commits not present");
647                 return 0;
648         }
649
650         /* check whether both changes are forward */
651         if (!in_merge_bases(commit_base, &commit_a, 1) ||
652             !in_merge_bases(commit_base, &commit_b, 1)) {
653                 MERGE_WARNING(path, "commits don't follow merge-base");
654                 return 0;
655         }
656
657         /* Case #1: a is contained in b or vice versa */
658         if (in_merge_bases(commit_a, &commit_b, 1)) {
659                 hashcpy(result, b);
660                 return 1;
661         }
662         if (in_merge_bases(commit_b, &commit_a, 1)) {
663                 hashcpy(result, a);
664                 return 1;
665         }
666
667         /*
668          * Case #2: There are one or more merges that contain a and b in
669          * the submodule. If there is only one, then present it as a
670          * suggestion to the user, but leave it marked unmerged so the
671          * user needs to confirm the resolution.
672          */
673
674         /* find commit which merges them */
675         parent_count = find_first_merges(&merges, path, commit_a, commit_b);
676         switch (parent_count) {
677         case 0:
678                 MERGE_WARNING(path, "merge following commits not found");
679                 break;
680
681         case 1:
682                 MERGE_WARNING(path, "not fast-forward");
683                 fprintf(stderr, "Found a possible merge resolution "
684                                 "for the submodule:\n");
685                 print_commit((struct commit *) merges.objects[0].item);
686                 fprintf(stderr,
687                         "If this is correct simply add it to the index "
688                         "for example\n"
689                         "by using:\n\n"
690                         "  git update-index --cacheinfo 160000 %s \"%s\"\n\n"
691                         "which will accept this suggestion.\n",
692                         sha1_to_hex(merges.objects[0].item->sha1), path);
693                 break;
694
695         default:
696                 MERGE_WARNING(path, "multiple merges found");
697                 for (i = 0; i < merges.nr; i++)
698                         print_commit((struct commit *) merges.objects[i].item);
699         }
700
701         free(merges.objects);
702         return 0;
703 }