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  * The following flag is set if the .gitmodules file is unmerged. We then
  19  * disable recursion for all submodules where .git/config doesn't have a
  20  * matching config entry because we can't guess what might be configured in
  21  * .gitmodules unless the user resolves the conflict. When a command line
  22  * option is given (which always overrides configuration) this flag will be
  23  * ignored.
  24  */
  25 static int gitmodules_is_unmerged;
  26
  27 static int add_submodule_odb(const char *path)
  28 {
  29         struct strbuf objects_directory = STRBUF_INIT;
  30         struct alternate_object_database *alt_odb;
  31         int ret = 0;
  32         const char *git_dir;
  33
  34         strbuf_addf(&objects_directory, "%s/.git", path);
  35         git_dir = read_gitfile_gently(objects_directory.buf);
  36         if (git_dir) {
  37                 strbuf_reset(&objects_directory);
  38                 strbuf_addstr(&objects_directory, git_dir);
  39         }
  40         strbuf_addstr(&objects_directory, "/objects/");
  41         if (!is_directory(objects_directory.buf)) {
  42                 ret = -1;
  43                 goto done;
  44         }
  45         /* avoid adding it twice */
  46         for (alt_odb = alt_odb_list; alt_odb; alt_odb = alt_odb->next)
  47                 if (alt_odb->name - alt_odb->base == objects_directory.len &&
  48                                 !strncmp(alt_odb->base, objects_directory.buf,
  49                                         objects_directory.len))
  50                         goto done;
  51
  52         alt_odb = xmalloc(objects_directory.len + 42 + sizeof(*alt_odb));
  53         alt_odb->next = alt_odb_list;
  54         strcpy(alt_odb->base, objects_directory.buf);
  55         alt_odb->name = alt_odb->base + objects_directory.len;
  56         alt_odb->name[2] = '/';
  57         alt_odb->name[40] = '\0';
  58         alt_odb->name[41] = '\0';
  59         alt_odb_list = alt_odb;
  60         prepare_alt_odb();
  61 done:
  62         strbuf_release(&objects_directory);
  63         return ret;
  64 }
  65
  66 void set_diffopt_flags_from_submodule_config(struct diff_options *diffopt,
  67                                              const char *path)
  68 {
  69         struct string_list_item *path_option, *ignore_option;
  70         path_option = unsorted_string_list_lookup(&config_name_for_path, path);
  71         if (path_option) {
  72                 ignore_option = unsorted_string_list_lookup(&config_ignore_for_name, path_option->util);
  73                 if (ignore_option)
  74                         handle_ignore_submodules_arg(diffopt, ignore_option->util);
  75                 else if (gitmodules_is_unmerged)
  76                         DIFF_OPT_SET(diffopt, IGNORE_SUBMODULES);
  77         }
  78 }
  79
  80 int submodule_config(const char *var, const char *value, void *cb)
  81 {
  82         if (!prefixcmp(var, "submodule."))
  83                 return parse_submodule_config_option(var, value);
  84         else if (!strcmp(var, "fetch.recursesubmodules")) {
  85                 config_fetch_recurse_submodules = parse_fetch_recurse_submodules_arg(var, value);
  86                 return 0;
  87         }
  88         return 0;
  89 }
  90
  91 void gitmodules_config(void)
  92 {
  93         const char *work_tree = get_git_work_tree();
  94         if (work_tree) {
  95                 struct strbuf gitmodules_path = STRBUF_INIT;
  96                 int pos;
  97                 strbuf_addstr(&gitmodules_path, work_tree);
  98                 strbuf_addstr(&gitmodules_path, "/.gitmodules");
  99                 if (read_cache() < 0)
 100                         die("index file corrupt");
 101                 pos = cache_name_pos(".gitmodules", 11);
 102                 if (pos < 0) { /* .gitmodules not found or isn't merged */
 103                         pos = -1 - pos;
 104                         if (active_nr > pos) {  /* there is a .gitmodules */
 105                                 const struct cache_entry *ce = active_cache[pos];
 106                                 if (ce_namelen(ce) == 11 &&
 107                                     !memcmp(ce->name, ".gitmodules", 11))
 108                                         gitmodules_is_unmerged = 1;
 109                         }
 110                 }
 111
 112                 if (!gitmodules_is_unmerged)
 113                         git_config_from_file(submodule_config, gitmodules_path.buf, NULL);
 114                 strbuf_release(&gitmodules_path);
 115         }
 116 }
 117
 118 int parse_submodule_config_option(const char *var, const char *value)
 119 {
 120         int len;
 121         struct string_list_item *config;
 122         struct strbuf submodname = STRBUF_INIT;
 123
 124         var += 10;              /* Skip "submodule." */
 125
 126         len = strlen(var);
 127         if ((len > 5) && !strcmp(var + len - 5, ".path")) {
 128                 strbuf_add(&submodname, var, len - 5);
 129                 config = unsorted_string_list_lookup(&config_name_for_path, value);
 130                 if (config)
 131                         free(config->util);
 132                 else
 133                         config = string_list_append(&config_name_for_path, xstrdup(value));
 134                 config->util = strbuf_detach(&submodname, NULL);
 135                 strbuf_release(&submodname);
 136         } else if ((len > 23) && !strcmp(var + len - 23, ".fetchrecursesubmodules")) {
 137                 strbuf_add(&submodname, var, len - 23);
 138                 config = unsorted_string_list_lookup(&config_fetch_recurse_submodules_for_name, submodname.buf);
 139                 if (!config)
 140                         config = string_list_append(&config_fetch_recurse_submodules_for_name,
 141                                                     strbuf_detach(&submodname, NULL));
 142                 config->util = (void *)(intptr_t)parse_fetch_recurse_submodules_arg(var, value);
 143                 strbuf_release(&submodname);
 144         } else if ((len > 7) && !strcmp(var + len - 7, ".ignore")) {
 145                 if (strcmp(value, "untracked") && strcmp(value, "dirty") &&
 146                     strcmp(value, "all") && strcmp(value, "none")) {
 147                         warning("Invalid parameter \"%s\" for config option \"submodule.%s.ignore\"", value, var);
 148                         return 0;
 149                 }
 150
 151                 strbuf_add(&submodname, var, len - 7);
 152                 config = unsorted_string_list_lookup(&config_ignore_for_name, submodname.buf);
 153                 if (config)
 154                         free(config->util);
 155                 else
 156                         config = string_list_append(&config_ignore_for_name,
 157                                                     strbuf_detach(&submodname, NULL));
 158                 strbuf_release(&submodname);
 159                 config->util = xstrdup(value);
 160                 return 0;
 161         }
 162         return 0;
 163 }
 164
 165 void handle_ignore_submodules_arg(struct diff_options *diffopt,
 166                                   const char *arg)
 167 {
 168         DIFF_OPT_CLR(diffopt, IGNORE_SUBMODULES);
 169         DIFF_OPT_CLR(diffopt, IGNORE_UNTRACKED_IN_SUBMODULES);
 170         DIFF_OPT_CLR(diffopt, IGNORE_DIRTY_SUBMODULES);
 171
 172         if (!strcmp(arg, "all"))
 173                 DIFF_OPT_SET(diffopt, IGNORE_SUBMODULES);
 174         else if (!strcmp(arg, "untracked"))
 175                 DIFF_OPT_SET(diffopt, IGNORE_UNTRACKED_IN_SUBMODULES);
 176         else if (!strcmp(arg, "dirty"))
 177                 DIFF_OPT_SET(diffopt, IGNORE_DIRTY_SUBMODULES);
 178         else if (strcmp(arg, "none"))
 179                 die("bad --ignore-submodules argument: %s", arg);
 180 }
 181
 182 static int prepare_submodule_summary(struct rev_info *rev, const char *path,
 183                 struct commit *left, struct commit *right,
 184                 int *fast_forward, int *fast_backward)
 185 {
 186         struct commit_list *merge_bases, *list;
 187
 188         init_revisions(rev, NULL);
 189         setup_revisions(0, NULL, rev, NULL);
 190         rev->left_right = 1;
 191         rev->first_parent_only = 1;
 192         left->object.flags |= SYMMETRIC_LEFT;
 193         add_pending_object(rev, &left->object, path);
 194         add_pending_object(rev, &right->object, path);
 195         merge_bases = get_merge_bases(left, right, 1);
 196         if (merge_bases) {
 197                 if (merge_bases->item == left)
 198                         *fast_forward = 1;
 199                 else if (merge_bases->item == right)
 200                         *fast_backward = 1;
 201         }
 202         for (list = merge_bases; list; list = list->next) {
 203                 list->item->object.flags |= UNINTERESTING;
 204                 add_pending_object(rev, &list->item->object,
 205                         sha1_to_hex(list->item->object.sha1));
 206         }
 207         return prepare_revision_walk(rev);
 208 }
 209
 210 static void print_submodule_summary(struct rev_info *rev, FILE *f,
 211                 const char *del, const char *add, const char *reset)
 212 {
 213         static const char format[] = "  %m %s";
 214         struct strbuf sb = STRBUF_INIT;
 215         struct commit *commit;
 216
 217         while ((commit = get_revision(rev))) {
 218                 struct pretty_print_context ctx = {0};
 219                 ctx.date_mode = rev->date_mode;
 220                 strbuf_setlen(&sb, 0);
 221                 if (commit->object.flags & SYMMETRIC_LEFT) {
 222                         if (del)
 223                                 strbuf_addstr(&sb, del);
 224                 }
 225                 else if (add)
 226                         strbuf_addstr(&sb, add);
 227                 format_commit_message(commit, format, &sb, &ctx);
 228                 if (reset)
 229                         strbuf_addstr(&sb, reset);
 230                 strbuf_addch(&sb, '\n');
 231                 fprintf(f, "%s", sb.buf);
 232         }
 233         strbuf_release(&sb);
 234 }
 235
 236 int parse_fetch_recurse_submodules_arg(const char *opt, const char *arg)
 237 {
 238         switch (git_config_maybe_bool(opt, arg)) {
 239         case 1:
 240                 return RECURSE_SUBMODULES_ON;
 241         case 0:
 242                 return RECURSE_SUBMODULES_OFF;
 243         default:
 244                 if (!strcmp(arg, "on-demand"))
 245                         return RECURSE_SUBMODULES_ON_DEMAND;
 246                 die("bad %s argument: %s", opt, arg);
 247         }
 248 }
 249
 250 void show_submodule_summary(FILE *f, const char *path,
 251                 unsigned char one[20], unsigned char two[20],
 252                 unsigned dirty_submodule,
 253                 const char *del, const char *add, const char *reset)
 254 {
 255         struct rev_info rev;
 256         struct commit *left = left, *right = right;
 257         const char *message = NULL;
 258         struct strbuf sb = STRBUF_INIT;
 259         int fast_forward = 0, fast_backward = 0;
 260
 261         if (is_null_sha1(two))
 262                 message = "(submodule deleted)";
 263         else if (add_submodule_odb(path))
 264                 message = "(not checked out)";
 265         else if (is_null_sha1(one))
 266                 message = "(new submodule)";
 267         else if (!(left = lookup_commit_reference(one)) ||
 268                  !(right = lookup_commit_reference(two)))
 269                 message = "(commits not present)";
 270
 271         if (!message &&
 272             prepare_submodule_summary(&rev, path, left, right,
 273                                         &fast_forward, &fast_backward))
 274                 message = "(revision walker failed)";
 275
 276         if (dirty_submodule & DIRTY_SUBMODULE_UNTRACKED)
 277                 fprintf(f, "Submodule %s contains untracked content\n", path);
 278         if (dirty_submodule & DIRTY_SUBMODULE_MODIFIED)
 279                 fprintf(f, "Submodule %s contains modified content\n", path);
 280
 281         if (!hashcmp(one, two)) {
 282                 strbuf_release(&sb);
 283                 return;
 284         }
 285
 286         strbuf_addf(&sb, "Submodule %s %s..", path,
 287                         find_unique_abbrev(one, DEFAULT_ABBREV));
 288         if (!fast_backward && !fast_forward)
 289                 strbuf_addch(&sb, '.');
 290         strbuf_addf(&sb, "%s", find_unique_abbrev(two, DEFAULT_ABBREV));
 291         if (message)
 292                 strbuf_addf(&sb, " %s\n", message);
 293         else
 294                 strbuf_addf(&sb, "%s:\n", fast_backward ? " (rewind)" : "");
 295         fwrite(sb.buf, sb.len, 1, f);
 296
 297         if (!message) {
 298                 print_submodule_summary(&rev, f, del, add, reset);
 299                 clear_commit_marks(left, ~0);
 300                 clear_commit_marks(right, ~0);
 301         }
 302
 303         strbuf_release(&sb);
 304 }
 305
 306 void set_config_fetch_recurse_submodules(int value)
 307 {
 308         config_fetch_recurse_submodules = value;
 309 }
 310
 311 static int is_submodule_commit_present(const char *path, unsigned char sha1[20])
 312 {
 313         int is_present = 0;
 314         if (!add_submodule_odb(path) && lookup_commit_reference(sha1)) {
 315                 /* Even if the submodule is checked out and the commit is
 316                  * present, make sure it is reachable from a ref. */
 317                 struct child_process cp;
 318                 const char *argv[] = {"rev-list", "-n", "1", NULL, "--not", "--all", NULL};
 319                 struct strbuf buf = STRBUF_INIT;
 320
 321                 argv[3] = sha1_to_hex(sha1);
 322                 memset(&cp, 0, sizeof(cp));
 323                 cp.argv = argv;
 324                 cp.env = local_repo_env;
 325                 cp.git_cmd = 1;
 326                 cp.no_stdin = 1;
 327                 cp.out = -1;
 328                 cp.dir = path;
 329                 if (!run_command(&cp) && !strbuf_read(&buf, cp.out, 1024))
 330                         is_present = 1;
 331
 332                 close(cp.out);
 333                 strbuf_release(&buf);
 334         }
 335         return is_present;
 336 }
 337
 338 static void submodule_collect_changed_cb(struct diff_queue_struct *q,
 339                                          struct diff_options *options,
 340                                          void *data)
 341 {
 342         int i;
 343         for (i = 0; i < q->nr; i++) {
 344                 struct diff_filepair *p = q->queue[i];
 345                 if (!S_ISGITLINK(p->two->mode))
 346                         continue;
 347
 348                 if (S_ISGITLINK(p->one->mode)) {
 349                         /* NEEDSWORK: We should honor the name configured in
 350                          * the .gitmodules file of the commit we are examining
 351                          * here to be able to correctly follow submodules
 352                          * being moved around. */
 353                         struct string_list_item *path;
 354                         path = unsorted_string_list_lookup(&changed_submodule_paths, p->two->path);
 355                         if (!path && !is_submodule_commit_present(p->two->path, p->two->sha1))
 356                                 string_list_append(&changed_submodule_paths, xstrdup(p->two->path));
 357                 } else {
 358                         /* Submodule is new or was moved here */
 359                         /* NEEDSWORK: When the .git directories of submodules
 360                          * live inside the superprojects .git directory some
 361                          * day we should fetch new submodules directly into
 362                          * that location too when config or options request
 363                          * that so they can be checked out from there. */
 364                         continue;
 365                 }
 366         }
 367 }
 368
 369 void check_for_new_submodule_commits(unsigned char new_sha1[20])
 370 {
 371         struct rev_info rev;
 372         struct commit *commit;
 373         const char *argv[] = {NULL, NULL, "--not", "--all", NULL};
 374         int argc = ARRAY_SIZE(argv) - 1;
 375
 376         init_revisions(&rev, NULL);
 377         argv[1] = xstrdup(sha1_to_hex(new_sha1));
 378         setup_revisions(argc, argv, &rev, NULL);
 379         if (prepare_revision_walk(&rev))
 380                 die("revision walk setup failed");
 381
 382         /*
 383          * Collect all submodules (whether checked out or not) for which new
 384          * commits have been recorded upstream in "changed_submodule_paths".
 385          */
 386         while ((commit = get_revision(&rev))) {
 387                 struct commit_list *parent = commit->parents;
 388                 while (parent) {
 389                         struct diff_options diff_opts;
 390                         diff_setup(&diff_opts);
 391                         diff_opts.output_format |= DIFF_FORMAT_CALLBACK;
 392                         diff_opts.format_callback = submodule_collect_changed_cb;
 393                         if (diff_setup_done(&diff_opts) < 0)
 394                                 die("diff_setup_done failed");
 395                         diff_tree_sha1(parent->item->object.sha1, commit->object.sha1, "", &diff_opts);
 396                         diffcore_std(&diff_opts);
 397                         diff_flush(&diff_opts);
 398                         parent = parent->next;
 399                 }
 400         }
 401         free((char *)argv[1]);
 402 }
 403
 404 int fetch_populated_submodules(int num_options, const char **options,
 405                                const char *prefix, int command_line_option,
 406                                int quiet)
 407 {
 408         int i, result = 0, argc = 0, default_argc;
 409         struct child_process cp;
 410         const char **argv;
 411         struct string_list_item *name_for_path;
 412         const char *work_tree = get_git_work_tree();
 413         if (!work_tree)
 414                 goto out;
 415
 416         if (!the_index.initialized)
 417                 if (read_cache() < 0)
 418                         die("index file corrupt");
 419
 420         /* 6: "fetch" (options) --recurse-submodules-default default "--submodule-prefix" prefix NULL */
 421         argv = xcalloc(num_options + 6, sizeof(const char *));
 422         argv[argc++] = "fetch";
 423         for (i = 0; i < num_options; i++)
 424                 argv[argc++] = options[i];
 425         argv[argc++] = "--recurse-submodules-default";
 426         default_argc = argc++;
 427         argv[argc++] = "--submodule-prefix";
 428
 429         memset(&cp, 0, sizeof(cp));
 430         cp.argv = argv;
 431         cp.env = local_repo_env;
 432         cp.git_cmd = 1;
 433         cp.no_stdin = 1;
 434
 435         for (i = 0; i < active_nr; i++) {
 436                 struct strbuf submodule_path = STRBUF_INIT;
 437                 struct strbuf submodule_git_dir = STRBUF_INIT;
 438                 struct strbuf submodule_prefix = STRBUF_INIT;
 439                 struct cache_entry *ce = active_cache[i];
 440                 const char *git_dir, *name, *default_argv;
 441
 442                 if (!S_ISGITLINK(ce->ce_mode))
 443                         continue;
 444
 445                 name = ce->name;
 446                 name_for_path = unsorted_string_list_lookup(&config_name_for_path, ce->name);
 447                 if (name_for_path)
 448                         name = name_for_path->util;
 449
 450                 default_argv = "yes";
 451                 if (command_line_option == RECURSE_SUBMODULES_DEFAULT) {
 452                         struct string_list_item *fetch_recurse_submodules_option;
 453                         fetch_recurse_submodules_option = unsorted_string_list_lookup(&config_fetch_recurse_submodules_for_name, name);
 454                         if (fetch_recurse_submodules_option) {
 455                                 if ((intptr_t)fetch_recurse_submodules_option->util == RECURSE_SUBMODULES_OFF)
 456                                         continue;
 457                                 if ((intptr_t)fetch_recurse_submodules_option->util == RECURSE_SUBMODULES_ON_DEMAND) {
 458                                         if (!unsorted_string_list_lookup(&changed_submodule_paths, ce->name))
 459                                                 continue;
 460                                         default_argv = "on-demand";
 461                                 }
 462                         } else {
 463                                 if ((config_fetch_recurse_submodules == RECURSE_SUBMODULES_OFF) ||
 464                                     gitmodules_is_unmerged)
 465                                         continue;
 466                                 if (config_fetch_recurse_submodules == RECURSE_SUBMODULES_ON_DEMAND) {
 467                                         if (!unsorted_string_list_lookup(&changed_submodule_paths, ce->name))
 468                                                 continue;
 469                                         default_argv = "on-demand";
 470                                 }
 471                         }
 472                 } else if (command_line_option == RECURSE_SUBMODULES_ON_DEMAND) {
 473                         if (!unsorted_string_list_lookup(&changed_submodule_paths, ce->name))
 474                                 continue;
 475                         default_argv = "on-demand";
 476                 }
 477
 478                 strbuf_addf(&submodule_path, "%s/%s", work_tree, ce->name);
 479                 strbuf_addf(&submodule_git_dir, "%s/.git", submodule_path.buf);
 480                 strbuf_addf(&submodule_prefix, "%s%s/", prefix, ce->name);
 481                 git_dir = read_gitfile_gently(submodule_git_dir.buf);
 482                 if (!git_dir)
 483                         git_dir = submodule_git_dir.buf;
 484                 if (is_directory(git_dir)) {
 485                         if (!quiet)
 486                                 printf("Fetching submodule %s%s\n", prefix, ce->name);
 487                         cp.dir = submodule_path.buf;
 488                         argv[default_argc] = default_argv;
 489                         argv[argc] = submodule_prefix.buf;
 490                         if (run_command(&cp))
 491                                 result = 1;
 492                 }
 493                 strbuf_release(&submodule_path);
 494                 strbuf_release(&submodule_git_dir);
 495                 strbuf_release(&submodule_prefix);
 496         }
 497         free(argv);
 498 out:
 499         string_list_clear(&changed_submodule_paths, 1);
 500         return result;
 501 }
 502
 503 unsigned is_submodule_modified(const char *path, int ignore_untracked)
 504 {
 505         ssize_t len;
 506         struct child_process cp;
 507         const char *argv[] = {
 508                 "status",
 509                 "--porcelain",
 510                 NULL,
 511                 NULL,
 512         };
 513         struct strbuf buf = STRBUF_INIT;
 514         unsigned dirty_submodule = 0;
 515         const char *line, *next_line;
 516         const char *git_dir;
 517
 518         strbuf_addf(&buf, "%s/.git", path);
 519         git_dir = read_gitfile_gently(buf.buf);
 520         if (!git_dir)
 521                 git_dir = buf.buf;
 522         if (!is_directory(git_dir)) {
 523                 strbuf_release(&buf);
 524                 /* The submodule is not checked out, so it is not modified */
 525                 return 0;
 526
 527         }
 528         strbuf_reset(&buf);
 529
 530         if (ignore_untracked)
 531                 argv[2] = "-uno";
 532
 533         memset(&cp, 0, sizeof(cp));
 534         cp.argv = argv;
 535         cp.env = local_repo_env;
 536         cp.git_cmd = 1;
 537         cp.no_stdin = 1;
 538         cp.out = -1;
 539         cp.dir = path;
 540         if (start_command(&cp))
 541                 die("Could not run git status --porcelain");
 542
 543         len = strbuf_read(&buf, cp.out, 1024);
 544         line = buf.buf;
 545         while (len > 2) {
 546                 if ((line[0] == '?') && (line[1] == '?')) {
 547                         dirty_submodule |= DIRTY_SUBMODULE_UNTRACKED;
 548                         if (dirty_submodule & DIRTY_SUBMODULE_MODIFIED)
 549                                 break;
 550                 } else {
 551                         dirty_submodule |= DIRTY_SUBMODULE_MODIFIED;
 552                         if (ignore_untracked ||
 553                             (dirty_submodule & DIRTY_SUBMODULE_UNTRACKED))
 554                                 break;
 555                 }
 556                 next_line = strchr(line, '\n');
 557                 if (!next_line)
 558                         break;
 559                 next_line++;
 560                 len -= (next_line - line);
 561                 line = next_line;
 562         }
 563         close(cp.out);
 564
 565         if (finish_command(&cp))
 566                 die("git status --porcelain failed");
 567
 568         strbuf_release(&buf);
 569         return dirty_submodule;
 570 }
 571
 572 static int find_first_merges(struct object_array *result, const char *path,
 573                 struct commit *a, struct commit *b)
 574 {
 575         int i, j;
 576         struct object_array merges;
 577         struct commit *commit;
 578         int contains_another;
 579
 580         char merged_revision[42];
 581         const char *rev_args[] = { "rev-list", "--merges", "--ancestry-path",
 582                                    "--all", merged_revision, NULL };
 583         struct rev_info revs;
 584         struct setup_revision_opt rev_opts;
 585
 586         memset(&merges, 0, sizeof(merges));
 587         memset(result, 0, sizeof(struct object_array));
 588         memset(&rev_opts, 0, sizeof(rev_opts));
 589
 590         /* get all revisions that merge commit a */
 591         snprintf(merged_revision, sizeof(merged_revision), "^%s",
 592                         sha1_to_hex(a->object.sha1));
 593         init_revisions(&revs, NULL);
 594         rev_opts.submodule = path;
 595         setup_revisions(sizeof(rev_args)/sizeof(char *)-1, rev_args, &revs, &rev_opts);
 596
 597         /* save all revisions from the above list that contain b */
 598         if (prepare_revision_walk(&revs))
 599                 die("revision walk setup failed");
 600         while ((commit = get_revision(&revs)) != NULL) {
 601                 struct object *o = &(commit->object);
 602                 if (in_merge_bases(b, &commit, 1))
 603                         add_object_array(o, NULL, &merges);
 604         }
 605
 606         /* Now we've got all merges that contain a and b. Prune all
 607          * merges that contain another found merge and save them in
 608          * result.
 609          */
 610         for (i = 0; i < merges.nr; i++) {
 611                 struct commit *m1 = (struct commit *) merges.objects[i].item;
 612
 613                 contains_another = 0;
 614                 for (j = 0; j < merges.nr; j++) {
 615                         struct commit *m2 = (struct commit *) merges.objects[j].item;
 616                         if (i != j && in_merge_bases(m2, &m1, 1)) {
 617                                 contains_another = 1;
 618                                 break;
 619                         }
 620                 }
 621
 622                 if (!contains_another)
 623                         add_object_array(merges.objects[i].item,
 624                                          merges.objects[i].name, result);
 625         }
 626
 627         free(merges.objects);
 628         return result->nr;
 629 }
 630
 631 static void print_commit(struct commit *commit)
 632 {
 633         struct strbuf sb = STRBUF_INIT;
 634         struct pretty_print_context ctx = {0};
 635         ctx.date_mode = DATE_NORMAL;
 636         format_commit_message(commit, " %h: %m %s", &sb, &ctx);
 637         fprintf(stderr, "%s\n", sb.buf);
 638         strbuf_release(&sb);
 639 }
 640
 641 #define MERGE_WARNING(path, msg) \
 642         warning("Failed to merge submodule %s (%s)", path, msg);
 643
 644 int merge_submodule(unsigned char result[20], const char *path,
 645                     const unsigned char base[20], const unsigned char a[20],
 646                     const unsigned char b[20])
 647 {
 648         struct commit *commit_base, *commit_a, *commit_b;
 649         int parent_count;
 650         struct object_array merges;
 651
 652         int i;
 653
 654         /* store a in result in case we fail */
 655         hashcpy(result, a);
 656
 657         /* we can not handle deletion conflicts */
 658         if (is_null_sha1(base))
 659                 return 0;
 660         if (is_null_sha1(a))
 661                 return 0;
 662         if (is_null_sha1(b))
 663                 return 0;
 664
 665         if (add_submodule_odb(path)) {
 666                 MERGE_WARNING(path, "not checked out");
 667                 return 0;
 668         }
 669
 670         if (!(commit_base = lookup_commit_reference(base)) ||
 671             !(commit_a = lookup_commit_reference(a)) ||
 672             !(commit_b = lookup_commit_reference(b))) {
 673                 MERGE_WARNING(path, "commits not present");
 674                 return 0;
 675         }
 676
 677         /* check whether both changes are forward */
 678         if (!in_merge_bases(commit_base, &commit_a, 1) ||
 679             !in_merge_bases(commit_base, &commit_b, 1)) {
 680                 MERGE_WARNING(path, "commits don't follow merge-base");
 681                 return 0;
 682         }
 683
 684         /* Case #1: a is contained in b or vice versa */
 685         if (in_merge_bases(commit_a, &commit_b, 1)) {
 686                 hashcpy(result, b);
 687                 return 1;
 688         }
 689         if (in_merge_bases(commit_b, &commit_a, 1)) {
 690                 hashcpy(result, a);
 691                 return 1;
 692         }
 693
 694         /*
 695          * Case #2: There are one or more merges that contain a and b in
 696          * the submodule. If there is only one, then present it as a
 697          * suggestion to the user, but leave it marked unmerged so the
 698          * user needs to confirm the resolution.
 699          */
 700
 701         /* find commit which merges them */
 702         parent_count = find_first_merges(&merges, path, commit_a, commit_b);
 703         switch (parent_count) {
 704         case 0:
 705                 MERGE_WARNING(path, "merge following commits not found");
 706                 break;
 707
 708         case 1:
 709                 MERGE_WARNING(path, "not fast-forward");
 710                 fprintf(stderr, "Found a possible merge resolution "
 711                                 "for the submodule:\n");
 712                 print_commit((struct commit *) merges.objects[0].item);
 713                 fprintf(stderr,
 714                         "If this is correct simply add it to the index "
 715                         "for example\n"
 716                         "by using:\n\n"
 717                         "  git update-index --cacheinfo 160000 %s \"%s\"\n\n"
 718                         "which will accept this suggestion.\n",
 719                         sha1_to_hex(merges.objects[0].item->sha1), path);
 720                 break;
 721
 722         default:
 723                 MERGE_WARNING(path, "multiple merges found");
 724                 for (i = 0; i < merges.nr; i++)
 725                         print_commit((struct commit *) merges.objects[i].item);
 726         }
 727
 728         free(merges.objects);
 729         return 0;
 730 }