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 struct string_list config_name_for_path;
  13 struct string_list config_fetch_recurse_submodules_for_name;
  14 struct string_list config_ignore_for_name;
  15 static int config_fetch_recurse_submodules = RECURSE_SUBMODULES_ON_DEMAND;
  16 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 int parse_fetch_recurse_submodules_arg(const char *opt, const char *arg)
 157 {
 158         switch (git_config_maybe_bool(opt, arg)) {
 159         case 1:
 160                 return RECURSE_SUBMODULES_ON;
 161         case 0:
 162                 return RECURSE_SUBMODULES_OFF;
 163         default:
 164                 if (!strcmp(arg, "on-demand"))
 165                         return RECURSE_SUBMODULES_ON_DEMAND;
 166                 die("bad %s argument: %s", opt, arg);
 167         }
 168 }
 169
 170 void show_submodule_summary(FILE *f, const char *path,
 171                 unsigned char one[20], unsigned char two[20],
 172                 unsigned dirty_submodule,
 173                 const char *del, const char *add, const char *reset)
 174 {
 175         struct rev_info rev;
 176         struct commit *commit, *left = left, *right = right;
 177         struct commit_list *merge_bases, *list;
 178         const char *message = NULL;
 179         struct strbuf sb = STRBUF_INIT;
 180         static const char *format = "  %m %s";
 181         int fast_forward = 0, fast_backward = 0;
 182
 183         if (is_null_sha1(two))
 184                 message = "(submodule deleted)";
 185         else if (add_submodule_odb(path))
 186                 message = "(not checked out)";
 187         else if (is_null_sha1(one))
 188                 message = "(new submodule)";
 189         else if (!(left = lookup_commit_reference(one)) ||
 190                  !(right = lookup_commit_reference(two)))
 191                 message = "(commits not present)";
 192
 193         if (!message) {
 194                 init_revisions(&rev, NULL);
 195                 setup_revisions(0, NULL, &rev, NULL);
 196                 rev.left_right = 1;
 197                 rev.first_parent_only = 1;
 198                 left->object.flags |= SYMMETRIC_LEFT;
 199                 add_pending_object(&rev, &left->object, path);
 200                 add_pending_object(&rev, &right->object, path);
 201                 merge_bases = get_merge_bases(left, right, 1);
 202                 if (merge_bases) {
 203                         if (merge_bases->item == left)
 204                                 fast_forward = 1;
 205                         else if (merge_bases->item == right)
 206                                 fast_backward = 1;
 207                 }
 208                 for (list = merge_bases; list; list = list->next) {
 209                         list->item->object.flags |= UNINTERESTING;
 210                         add_pending_object(&rev, &list->item->object,
 211                                 sha1_to_hex(list->item->object.sha1));
 212                 }
 213                 if (prepare_revision_walk(&rev))
 214                         message = "(revision walker failed)";
 215         }
 216
 217         if (dirty_submodule & DIRTY_SUBMODULE_UNTRACKED)
 218                 fprintf(f, "Submodule %s contains untracked content\n", path);
 219         if (dirty_submodule & DIRTY_SUBMODULE_MODIFIED)
 220                 fprintf(f, "Submodule %s contains modified content\n", path);
 221
 222         if (!hashcmp(one, two)) {
 223                 strbuf_release(&sb);
 224                 return;
 225         }
 226
 227         strbuf_addf(&sb, "Submodule %s %s..", path,
 228                         find_unique_abbrev(one, DEFAULT_ABBREV));
 229         if (!fast_backward && !fast_forward)
 230                 strbuf_addch(&sb, '.');
 231         strbuf_addf(&sb, "%s", find_unique_abbrev(two, DEFAULT_ABBREV));
 232         if (message)
 233                 strbuf_addf(&sb, " %s\n", message);
 234         else
 235                 strbuf_addf(&sb, "%s:\n", fast_backward ? " (rewind)" : "");
 236         fwrite(sb.buf, sb.len, 1, f);
 237
 238         if (!message) {
 239                 while ((commit = get_revision(&rev))) {
 240                         struct pretty_print_context ctx = {0};
 241                         ctx.date_mode = rev.date_mode;
 242                         strbuf_setlen(&sb, 0);
 243                         if (commit->object.flags & SYMMETRIC_LEFT) {
 244                                 if (del)
 245                                         strbuf_addstr(&sb, del);
 246                         }
 247                         else if (add)
 248                                 strbuf_addstr(&sb, add);
 249                         format_commit_message(commit, format, &sb, &ctx);
 250                         if (reset)
 251                                 strbuf_addstr(&sb, reset);
 252                         strbuf_addch(&sb, '\n');
 253                         fprintf(f, "%s", sb.buf);
 254                 }
 255                 clear_commit_marks(left, ~0);
 256                 clear_commit_marks(right, ~0);
 257         }
 258         strbuf_release(&sb);
 259 }
 260
 261 void set_config_fetch_recurse_submodules(int value)
 262 {
 263         config_fetch_recurse_submodules = value;
 264 }
 265
 266 static void submodule_collect_changed_cb(struct diff_queue_struct *q,
 267                                          struct diff_options *options,
 268                                          void *data)
 269 {
 270         int i;
 271         for (i = 0; i < q->nr; i++) {
 272                 struct diff_filepair *p = q->queue[i];
 273                 if (!S_ISGITLINK(p->two->mode))
 274                         continue;
 275
 276                 if (S_ISGITLINK(p->one->mode)) {
 277                         /* NEEDSWORK: We should honor the name configured in
 278                          * the .gitmodules file of the commit we are examining
 279                          * here to be able to correctly follow submodules
 280                          * being moved around. */
 281                         struct string_list_item *path;
 282                         path = unsorted_string_list_lookup(&changed_submodule_paths, p->two->path);
 283                         if (!path)
 284                                 string_list_append(&changed_submodule_paths, xstrdup(p->two->path));
 285                 } else {
 286                         /* Submodule is new or was moved here */
 287                         /* NEEDSWORK: When the .git directories of submodules
 288                          * live inside the superprojects .git directory some
 289                          * day we should fetch new submodules directly into
 290                          * that location too when config or options request
 291                          * that so they can be checked out from there. */
 292                         continue;
 293                 }
 294         }
 295 }
 296
 297 void check_for_new_submodule_commits(unsigned char new_sha1[20])
 298 {
 299         struct rev_info rev;
 300         struct commit *commit;
 301         const char *argv[] = {NULL, NULL, "--not", "--all", NULL};
 302         int argc = ARRAY_SIZE(argv) - 1;
 303
 304         init_revisions(&rev, NULL);
 305         argv[1] = xstrdup(sha1_to_hex(new_sha1));
 306         setup_revisions(argc, argv, &rev, NULL);
 307         if (prepare_revision_walk(&rev))
 308                 die("revision walk setup failed");
 309
 310         /*
 311          * Collect all submodules (whether checked out or not) for which new
 312          * commits have been recorded upstream in "changed_submodule_paths".
 313          */
 314         while ((commit = get_revision(&rev))) {
 315                 struct commit_list *parent = commit->parents;
 316                 while (parent) {
 317                         struct diff_options diff_opts;
 318                         diff_setup(&diff_opts);
 319                         diff_opts.output_format |= DIFF_FORMAT_CALLBACK;
 320                         diff_opts.format_callback = submodule_collect_changed_cb;
 321                         if (diff_setup_done(&diff_opts) < 0)
 322                                 die("diff_setup_done failed");
 323                         diff_tree_sha1(parent->item->object.sha1, commit->object.sha1, "", &diff_opts);
 324                         diffcore_std(&diff_opts);
 325                         diff_flush(&diff_opts);
 326                         parent = parent->next;
 327                 }
 328         }
 329         free((char *)argv[1]);
 330 }
 331
 332 int fetch_populated_submodules(int num_options, const char **options,
 333                                const char *prefix, int command_line_option,
 334                                int quiet)
 335 {
 336         int i, result = 0, argc = 0, default_argc;
 337         struct child_process cp;
 338         const char **argv;
 339         struct string_list_item *name_for_path;
 340         const char *work_tree = get_git_work_tree();
 341         if (!work_tree)
 342                 goto out;
 343
 344         if (!the_index.initialized)
 345                 if (read_cache() < 0)
 346                         die("index file corrupt");
 347
 348         /* 6: "fetch" (options) --recurse-submodules-default default "--submodule-prefix" prefix NULL */
 349         argv = xcalloc(num_options + 6, sizeof(const char *));
 350         argv[argc++] = "fetch";
 351         for (i = 0; i < num_options; i++)
 352                 argv[argc++] = options[i];
 353         argv[argc++] = "--recurse-submodules-default";
 354         default_argc = argc++;
 355         argv[argc++] = "--submodule-prefix";
 356
 357         memset(&cp, 0, sizeof(cp));
 358         cp.argv = argv;
 359         cp.env = local_repo_env;
 360         cp.git_cmd = 1;
 361         cp.no_stdin = 1;
 362
 363         for (i = 0; i < active_nr; i++) {
 364                 struct strbuf submodule_path = STRBUF_INIT;
 365                 struct strbuf submodule_git_dir = STRBUF_INIT;
 366                 struct strbuf submodule_prefix = STRBUF_INIT;
 367                 struct cache_entry *ce = active_cache[i];
 368                 const char *git_dir, *name, *default_argv;
 369
 370                 if (!S_ISGITLINK(ce->ce_mode))
 371                         continue;
 372
 373                 name = ce->name;
 374                 name_for_path = unsorted_string_list_lookup(&config_name_for_path, ce->name);
 375                 if (name_for_path)
 376                         name = name_for_path->util;
 377
 378                 default_argv = "yes";
 379                 if (command_line_option == RECURSE_SUBMODULES_DEFAULT) {
 380                         struct string_list_item *fetch_recurse_submodules_option;
 381                         fetch_recurse_submodules_option = unsorted_string_list_lookup(&config_fetch_recurse_submodules_for_name, name);
 382                         if (fetch_recurse_submodules_option) {
 383                                 if ((intptr_t)fetch_recurse_submodules_option->util == RECURSE_SUBMODULES_OFF)
 384                                         continue;
 385                                 if ((intptr_t)fetch_recurse_submodules_option->util == RECURSE_SUBMODULES_ON_DEMAND) {
 386                                         if (!unsorted_string_list_lookup(&changed_submodule_paths, ce->name))
 387                                                 continue;
 388                                         default_argv = "on-demand";
 389                                 }
 390                         } else {
 391                                 if (config_fetch_recurse_submodules == RECURSE_SUBMODULES_OFF)
 392                                         continue;
 393                                 if (config_fetch_recurse_submodules == RECURSE_SUBMODULES_ON_DEMAND) {
 394                                         if (!unsorted_string_list_lookup(&changed_submodule_paths, ce->name))
 395                                                 continue;
 396                                         default_argv = "on-demand";
 397                                 }
 398                         }
 399                 } else if (command_line_option == RECURSE_SUBMODULES_ON_DEMAND) {
 400                         if (!unsorted_string_list_lookup(&changed_submodule_paths, ce->name))
 401                                 continue;
 402                         default_argv = "on-demand";
 403                 }
 404
 405                 strbuf_addf(&submodule_path, "%s/%s", work_tree, ce->name);
 406                 strbuf_addf(&submodule_git_dir, "%s/.git", submodule_path.buf);
 407                 strbuf_addf(&submodule_prefix, "%s%s/", prefix, ce->name);
 408                 git_dir = read_gitfile_gently(submodule_git_dir.buf);
 409                 if (!git_dir)
 410                         git_dir = submodule_git_dir.buf;
 411                 if (is_directory(git_dir)) {
 412                         if (!quiet)
 413                                 printf("Fetching submodule %s%s\n", prefix, ce->name);
 414                         cp.dir = submodule_path.buf;
 415                         argv[default_argc] = default_argv;
 416                         argv[argc] = submodule_prefix.buf;
 417                         if (run_command(&cp))
 418                                 result = 1;
 419                 }
 420                 strbuf_release(&submodule_path);
 421                 strbuf_release(&submodule_git_dir);
 422                 strbuf_release(&submodule_prefix);
 423         }
 424         free(argv);
 425 out:
 426         string_list_clear(&changed_submodule_paths, 1);
 427         return result;
 428 }
 429
 430 unsigned is_submodule_modified(const char *path, int ignore_untracked)
 431 {
 432         ssize_t len;
 433         struct child_process cp;
 434         const char *argv[] = {
 435                 "status",
 436                 "--porcelain",
 437                 NULL,
 438                 NULL,
 439         };
 440         struct strbuf buf = STRBUF_INIT;
 441         unsigned dirty_submodule = 0;
 442         const char *line, *next_line;
 443         const char *git_dir;
 444
 445         strbuf_addf(&buf, "%s/.git", path);
 446         git_dir = read_gitfile_gently(buf.buf);
 447         if (!git_dir)
 448                 git_dir = buf.buf;
 449         if (!is_directory(git_dir)) {
 450                 strbuf_release(&buf);
 451                 /* The submodule is not checked out, so it is not modified */
 452                 return 0;
 453
 454         }
 455         strbuf_reset(&buf);
 456
 457         if (ignore_untracked)
 458                 argv[2] = "-uno";
 459
 460         memset(&cp, 0, sizeof(cp));
 461         cp.argv = argv;
 462         cp.env = local_repo_env;
 463         cp.git_cmd = 1;
 464         cp.no_stdin = 1;
 465         cp.out = -1;
 466         cp.dir = path;
 467         if (start_command(&cp))
 468                 die("Could not run git status --porcelain");
 469
 470         len = strbuf_read(&buf, cp.out, 1024);
 471         line = buf.buf;
 472         while (len > 2) {
 473                 if ((line[0] == '?') && (line[1] == '?')) {
 474                         dirty_submodule |= DIRTY_SUBMODULE_UNTRACKED;
 475                         if (dirty_submodule & DIRTY_SUBMODULE_MODIFIED)
 476                                 break;
 477                 } else {
 478                         dirty_submodule |= DIRTY_SUBMODULE_MODIFIED;
 479                         if (ignore_untracked ||
 480                             (dirty_submodule & DIRTY_SUBMODULE_UNTRACKED))
 481                                 break;
 482                 }
 483                 next_line = strchr(line, '\n');
 484                 if (!next_line)
 485                         break;
 486                 next_line++;
 487                 len -= (next_line - line);
 488                 line = next_line;
 489         }
 490         close(cp.out);
 491
 492         if (finish_command(&cp))
 493                 die("git status --porcelain failed");
 494
 495         strbuf_release(&buf);
 496         return dirty_submodule;
 497 }
 498
 499 static int find_first_merges(struct object_array *result, const char *path,
 500                 struct commit *a, struct commit *b)
 501 {
 502         int i, j;
 503         struct object_array merges;
 504         struct commit *commit;
 505         int contains_another;
 506
 507         char merged_revision[42];
 508         const char *rev_args[] = { "rev-list", "--merges", "--ancestry-path",
 509                                    "--all", merged_revision, NULL };
 510         struct rev_info revs;
 511         struct setup_revision_opt rev_opts;
 512
 513         memset(&merges, 0, sizeof(merges));
 514         memset(result, 0, sizeof(struct object_array));
 515         memset(&rev_opts, 0, sizeof(rev_opts));
 516
 517         /* get all revisions that merge commit a */
 518         snprintf(merged_revision, sizeof(merged_revision), "^%s",
 519                         sha1_to_hex(a->object.sha1));
 520         init_revisions(&revs, NULL);
 521         rev_opts.submodule = path;
 522         setup_revisions(sizeof(rev_args)/sizeof(char *)-1, rev_args, &revs, &rev_opts);
 523
 524         /* save all revisions from the above list that contain b */
 525         if (prepare_revision_walk(&revs))
 526                 die("revision walk setup failed");
 527         while ((commit = get_revision(&revs)) != NULL) {
 528                 struct object *o = &(commit->object);
 529                 if (in_merge_bases(b, &commit, 1))
 530                         add_object_array(o, NULL, &merges);
 531         }
 532
 533         /* Now we've got all merges that contain a and b. Prune all
 534          * merges that contain another found merge and save them in
 535          * result.
 536          */
 537         for (i = 0; i < merges.nr; i++) {
 538                 struct commit *m1 = (struct commit *) merges.objects[i].item;
 539
 540                 contains_another = 0;
 541                 for (j = 0; j < merges.nr; j++) {
 542                         struct commit *m2 = (struct commit *) merges.objects[j].item;
 543                         if (i != j && in_merge_bases(m2, &m1, 1)) {
 544                                 contains_another = 1;
 545                                 break;
 546                         }
 547                 }
 548
 549                 if (!contains_another)
 550                         add_object_array(merges.objects[i].item,
 551                                          merges.objects[i].name, result);
 552         }
 553
 554         free(merges.objects);
 555         return result->nr;
 556 }
 557
 558 static void print_commit(struct commit *commit)
 559 {
 560         struct strbuf sb = STRBUF_INIT;
 561         struct pretty_print_context ctx = {0};
 562         ctx.date_mode = DATE_NORMAL;
 563         format_commit_message(commit, " %h: %m %s", &sb, &ctx);
 564         fprintf(stderr, "%s\n", sb.buf);
 565         strbuf_release(&sb);
 566 }
 567
 568 #define MERGE_WARNING(path, msg) \
 569         warning("Failed to merge submodule %s (%s)", path, msg);
 570
 571 int merge_submodule(unsigned char result[20], const char *path,
 572                     const unsigned char base[20], const unsigned char a[20],
 573                     const unsigned char b[20])
 574 {
 575         struct commit *commit_base, *commit_a, *commit_b;
 576         int parent_count;
 577         struct object_array merges;
 578
 579         int i;
 580
 581         /* store a in result in case we fail */
 582         hashcpy(result, a);
 583
 584         /* we can not handle deletion conflicts */
 585         if (is_null_sha1(base))
 586                 return 0;
 587         if (is_null_sha1(a))
 588                 return 0;
 589         if (is_null_sha1(b))
 590                 return 0;
 591
 592         if (add_submodule_odb(path)) {
 593                 MERGE_WARNING(path, "not checked out");
 594                 return 0;
 595         }
 596
 597         if (!(commit_base = lookup_commit_reference(base)) ||
 598             !(commit_a = lookup_commit_reference(a)) ||
 599             !(commit_b = lookup_commit_reference(b))) {
 600                 MERGE_WARNING(path, "commits not present");
 601                 return 0;
 602         }
 603
 604         /* check whether both changes are forward */
 605         if (!in_merge_bases(commit_base, &commit_a, 1) ||
 606             !in_merge_bases(commit_base, &commit_b, 1)) {
 607                 MERGE_WARNING(path, "commits don't follow merge-base");
 608                 return 0;
 609         }
 610
 611         /* Case #1: a is contained in b or vice versa */
 612         if (in_merge_bases(commit_a, &commit_b, 1)) {
 613                 hashcpy(result, b);
 614                 return 1;
 615         }
 616         if (in_merge_bases(commit_b, &commit_a, 1)) {
 617                 hashcpy(result, a);
 618                 return 1;
 619         }
 620
 621         /*
 622          * Case #2: There are one or more merges that contain a and b in
 623          * the submodule. If there is only one, then present it as a
 624          * suggestion to the user, but leave it marked unmerged so the
 625          * user needs to confirm the resolution.
 626          */
 627
 628         /* find commit which merges them */
 629         parent_count = find_first_merges(&merges, path, commit_a, commit_b);
 630         switch (parent_count) {
 631         case 0:
 632                 MERGE_WARNING(path, "merge following commits not found");
 633                 break;
 634
 635         case 1:
 636                 MERGE_WARNING(path, "not fast-forward");
 637                 fprintf(stderr, "Found a possible merge resolution "
 638                                 "for the submodule:\n");
 639                 print_commit((struct commit *) merges.objects[0].item);
 640                 fprintf(stderr,
 641                         "If this is correct simply add it to the index "
 642                         "for example\n"
 643                         "by using:\n\n"
 644                         "  git update-index --cacheinfo 160000 %s \"%s\"\n\n"
 645                         "which will accept this suggestion.\n",
 646                         sha1_to_hex(merges.objects[0].item->sha1), path);
 647                 break;
 648
 649         default:
 650                 MERGE_WARNING(path, "multiple merges found");
 651                 for (i = 0; i < merges.nr; i++)
 652                         print_commit((struct commit *) merges.objects[i].item);
 653         }
 654
 655         free(merges.objects);
 656         return 0;
 657 }