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 #include "sha1-array.h"
  12 #include "argv-array.h"
  13
  14 static struct string_list config_name_for_path;
  15 static struct string_list config_fetch_recurse_submodules_for_name;
  16 static struct string_list config_ignore_for_name;
  17 static int config_fetch_recurse_submodules = RECURSE_SUBMODULES_ON_DEMAND;
  18 static struct string_list changed_submodule_paths;
  19 static int initialized_fetch_ref_tips;
  20 static struct sha1_array ref_tips_before_fetch;
  21 static struct sha1_array ref_tips_after_fetch;
  22
  23 /*
  24  * The following flag is set if the .gitmodules file is unmerged. We then
  25  * disable recursion for all submodules where .git/config doesn't have a
  26  * matching config entry because we can't guess what might be configured in
  27  * .gitmodules unless the user resolves the conflict. When a command line
  28  * option is given (which always overrides configuration) this flag will be
  29  * ignored.
  30  */
  31 static int gitmodules_is_unmerged;
  32
  33 static int add_submodule_odb(const char *path)
  34 {
  35         struct strbuf objects_directory = STRBUF_INIT;
  36         struct alternate_object_database *alt_odb;
  37         int ret = 0;
  38         const char *git_dir;
  39
  40         strbuf_addf(&objects_directory, "%s/.git", path);
  41         git_dir = read_gitfile_gently(objects_directory.buf);
  42         if (git_dir) {
  43                 strbuf_reset(&objects_directory);
  44                 strbuf_addstr(&objects_directory, git_dir);
  45         }
  46         strbuf_addstr(&objects_directory, "/objects/");
  47         if (!is_directory(objects_directory.buf)) {
  48                 ret = -1;
  49                 goto done;
  50         }
  51         /* avoid adding it twice */
  52         for (alt_odb = alt_odb_list; alt_odb; alt_odb = alt_odb->next)
  53                 if (alt_odb->name - alt_odb->base == objects_directory.len &&
  54                                 !strncmp(alt_odb->base, objects_directory.buf,
  55                                         objects_directory.len))
  56                         goto done;
  57
  58         alt_odb = xmalloc(objects_directory.len + 42 + sizeof(*alt_odb));
  59         alt_odb->next = alt_odb_list;
  60         strcpy(alt_odb->base, objects_directory.buf);
  61         alt_odb->name = alt_odb->base + objects_directory.len;
  62         alt_odb->name[2] = '/';
  63         alt_odb->name[40] = '\0';
  64         alt_odb->name[41] = '\0';
  65         alt_odb_list = alt_odb;
  66         prepare_alt_odb();
  67 done:
  68         strbuf_release(&objects_directory);
  69         return ret;
  70 }
  71
  72 void set_diffopt_flags_from_submodule_config(struct diff_options *diffopt,
  73                                              const char *path)
  74 {
  75         struct string_list_item *path_option, *ignore_option;
  76         path_option = unsorted_string_list_lookup(&config_name_for_path, path);
  77         if (path_option) {
  78                 ignore_option = unsorted_string_list_lookup(&config_ignore_for_name, path_option->util);
  79                 if (ignore_option)
  80                         handle_ignore_submodules_arg(diffopt, ignore_option->util);
  81                 else if (gitmodules_is_unmerged)
  82                         DIFF_OPT_SET(diffopt, IGNORE_SUBMODULES);
  83         }
  84 }
  85
  86 int submodule_config(const char *var, const char *value, void *cb)
  87 {
  88         if (!prefixcmp(var, "submodule."))
  89                 return parse_submodule_config_option(var, value);
  90         else if (!strcmp(var, "fetch.recursesubmodules")) {
  91                 config_fetch_recurse_submodules = parse_fetch_recurse_submodules_arg(var, value);
  92                 return 0;
  93         }
  94         return 0;
  95 }
  96
  97 void gitmodules_config(void)
  98 {
  99         const char *work_tree = get_git_work_tree();
 100         if (work_tree) {
 101                 struct strbuf gitmodules_path = STRBUF_INIT;
 102                 int pos;
 103                 strbuf_addstr(&gitmodules_path, work_tree);
 104                 strbuf_addstr(&gitmodules_path, "/.gitmodules");
 105                 if (read_cache() < 0)
 106                         die("index file corrupt");
 107                 pos = cache_name_pos(".gitmodules", 11);
 108                 if (pos < 0) { /* .gitmodules not found or isn't merged */
 109                         pos = -1 - pos;
 110                         if (active_nr > pos) {  /* there is a .gitmodules */
 111                                 const struct cache_entry *ce = active_cache[pos];
 112                                 if (ce_namelen(ce) == 11 &&
 113                                     !memcmp(ce->name, ".gitmodules", 11))
 114                                         gitmodules_is_unmerged = 1;
 115                         }
 116                 }
 117
 118                 if (!gitmodules_is_unmerged)
 119                         git_config_from_file(submodule_config, gitmodules_path.buf, NULL);
 120                 strbuf_release(&gitmodules_path);
 121         }
 122 }
 123
 124 int parse_submodule_config_option(const char *var, const char *value)
 125 {
 126         int len;
 127         struct string_list_item *config;
 128         struct strbuf submodname = STRBUF_INIT;
 129
 130         var += 10;              /* Skip "submodule." */
 131
 132         len = strlen(var);
 133         if ((len > 5) && !strcmp(var + len - 5, ".path")) {
 134                 strbuf_add(&submodname, var, len - 5);
 135                 config = unsorted_string_list_lookup(&config_name_for_path, value);
 136                 if (config)
 137                         free(config->util);
 138                 else
 139                         config = string_list_append(&config_name_for_path, xstrdup(value));
 140                 config->util = strbuf_detach(&submodname, NULL);
 141                 strbuf_release(&submodname);
 142         } else if ((len > 23) && !strcmp(var + len - 23, ".fetchrecursesubmodules")) {
 143                 strbuf_add(&submodname, var, len - 23);
 144                 config = unsorted_string_list_lookup(&config_fetch_recurse_submodules_for_name, submodname.buf);
 145                 if (!config)
 146                         config = string_list_append(&config_fetch_recurse_submodules_for_name,
 147                                                     strbuf_detach(&submodname, NULL));
 148                 config->util = (void *)(intptr_t)parse_fetch_recurse_submodules_arg(var, value);
 149                 strbuf_release(&submodname);
 150         } else if ((len > 7) && !strcmp(var + len - 7, ".ignore")) {
 151                 if (strcmp(value, "untracked") && strcmp(value, "dirty") &&
 152                     strcmp(value, "all") && strcmp(value, "none")) {
 153                         warning("Invalid parameter \"%s\" for config option \"submodule.%s.ignore\"", value, var);
 154                         return 0;
 155                 }
 156
 157                 strbuf_add(&submodname, var, len - 7);
 158                 config = unsorted_string_list_lookup(&config_ignore_for_name, submodname.buf);
 159                 if (config)
 160                         free(config->util);
 161                 else
 162                         config = string_list_append(&config_ignore_for_name,
 163                                                     strbuf_detach(&submodname, NULL));
 164                 strbuf_release(&submodname);
 165                 config->util = xstrdup(value);
 166                 return 0;
 167         }
 168         return 0;
 169 }
 170
 171 void handle_ignore_submodules_arg(struct diff_options *diffopt,
 172                                   const char *arg)
 173 {
 174         DIFF_OPT_CLR(diffopt, IGNORE_SUBMODULES);
 175         DIFF_OPT_CLR(diffopt, IGNORE_UNTRACKED_IN_SUBMODULES);
 176         DIFF_OPT_CLR(diffopt, IGNORE_DIRTY_SUBMODULES);
 177
 178         if (!strcmp(arg, "all"))
 179                 DIFF_OPT_SET(diffopt, IGNORE_SUBMODULES);
 180         else if (!strcmp(arg, "untracked"))
 181                 DIFF_OPT_SET(diffopt, IGNORE_UNTRACKED_IN_SUBMODULES);
 182         else if (!strcmp(arg, "dirty"))
 183                 DIFF_OPT_SET(diffopt, IGNORE_DIRTY_SUBMODULES);
 184         else if (strcmp(arg, "none"))
 185                 die("bad --ignore-submodules argument: %s", arg);
 186 }
 187
 188 static int prepare_submodule_summary(struct rev_info *rev, const char *path,
 189                 struct commit *left, struct commit *right,
 190                 int *fast_forward, int *fast_backward)
 191 {
 192         struct commit_list *merge_bases, *list;
 193
 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         return prepare_revision_walk(rev);
 214 }
 215
 216 static void print_submodule_summary(struct rev_info *rev, FILE *f,
 217                 const char *del, const char *add, const char *reset)
 218 {
 219         static const char format[] = "  %m %s";
 220         struct strbuf sb = STRBUF_INIT;
 221         struct commit *commit;
 222
 223         while ((commit = get_revision(rev))) {
 224                 struct pretty_print_context ctx = {0};
 225                 ctx.date_mode = rev->date_mode;
 226                 strbuf_setlen(&sb, 0);
 227                 if (commit->object.flags & SYMMETRIC_LEFT) {
 228                         if (del)
 229                                 strbuf_addstr(&sb, del);
 230                 }
 231                 else if (add)
 232                         strbuf_addstr(&sb, add);
 233                 format_commit_message(commit, format, &sb, &ctx);
 234                 if (reset)
 235                         strbuf_addstr(&sb, reset);
 236                 strbuf_addch(&sb, '\n');
 237                 fprintf(f, "%s", sb.buf);
 238         }
 239         strbuf_release(&sb);
 240 }
 241
 242 int parse_fetch_recurse_submodules_arg(const char *opt, const char *arg)
 243 {
 244         switch (git_config_maybe_bool(opt, arg)) {
 245         case 1:
 246                 return RECURSE_SUBMODULES_ON;
 247         case 0:
 248                 return RECURSE_SUBMODULES_OFF;
 249         default:
 250                 if (!strcmp(arg, "on-demand"))
 251                         return RECURSE_SUBMODULES_ON_DEMAND;
 252                 die("bad %s argument: %s", opt, arg);
 253         }
 254 }
 255
 256 void show_submodule_summary(FILE *f, const char *path,
 257                 unsigned char one[20], unsigned char two[20],
 258                 unsigned dirty_submodule,
 259                 const char *del, const char *add, const char *reset)
 260 {
 261         struct rev_info rev;
 262         struct commit *left = left, *right = right;
 263         const char *message = NULL;
 264         struct strbuf sb = STRBUF_INIT;
 265         int fast_forward = 0, fast_backward = 0;
 266
 267         if (is_null_sha1(two))
 268                 message = "(submodule deleted)";
 269         else if (add_submodule_odb(path))
 270                 message = "(not checked out)";
 271         else if (is_null_sha1(one))
 272                 message = "(new submodule)";
 273         else if (!(left = lookup_commit_reference(one)) ||
 274                  !(right = lookup_commit_reference(two)))
 275                 message = "(commits not present)";
 276
 277         if (!message &&
 278             prepare_submodule_summary(&rev, path, left, right,
 279                                         &fast_forward, &fast_backward))
 280                 message = "(revision walker failed)";
 281
 282         if (dirty_submodule & DIRTY_SUBMODULE_UNTRACKED)
 283                 fprintf(f, "Submodule %s contains untracked content\n", path);
 284         if (dirty_submodule & DIRTY_SUBMODULE_MODIFIED)
 285                 fprintf(f, "Submodule %s contains modified content\n", path);
 286
 287         if (!hashcmp(one, two)) {
 288                 strbuf_release(&sb);
 289                 return;
 290         }
 291
 292         strbuf_addf(&sb, "Submodule %s %s..", path,
 293                         find_unique_abbrev(one, DEFAULT_ABBREV));
 294         if (!fast_backward && !fast_forward)
 295                 strbuf_addch(&sb, '.');
 296         strbuf_addf(&sb, "%s", find_unique_abbrev(two, DEFAULT_ABBREV));
 297         if (message)
 298                 strbuf_addf(&sb, " %s\n", message);
 299         else
 300                 strbuf_addf(&sb, "%s:\n", fast_backward ? " (rewind)" : "");
 301         fwrite(sb.buf, sb.len, 1, f);
 302
 303         if (!message) {
 304                 print_submodule_summary(&rev, f, del, add, reset);
 305                 clear_commit_marks(left, ~0);
 306                 clear_commit_marks(right, ~0);
 307         }
 308
 309         strbuf_release(&sb);
 310 }
 311
 312 void set_config_fetch_recurse_submodules(int value)
 313 {
 314         config_fetch_recurse_submodules = value;
 315 }
 316
 317 static int is_submodule_commit_present(const char *path, unsigned char sha1[20])
 318 {
 319         int is_present = 0;
 320         if (!add_submodule_odb(path) && lookup_commit_reference(sha1)) {
 321                 /* Even if the submodule is checked out and the commit is
 322                  * present, make sure it is reachable from a ref. */
 323                 struct child_process cp;
 324                 const char *argv[] = {"rev-list", "-n", "1", NULL, "--not", "--all", NULL};
 325                 struct strbuf buf = STRBUF_INIT;
 326
 327                 argv[3] = sha1_to_hex(sha1);
 328                 memset(&cp, 0, sizeof(cp));
 329                 cp.argv = argv;
 330                 cp.env = local_repo_env;
 331                 cp.git_cmd = 1;
 332                 cp.no_stdin = 1;
 333                 cp.out = -1;
 334                 cp.dir = path;
 335                 if (!run_command(&cp) && !strbuf_read(&buf, cp.out, 1024))
 336                         is_present = 1;
 337
 338                 close(cp.out);
 339                 strbuf_release(&buf);
 340         }
 341         return is_present;
 342 }
 343
 344 static void submodule_collect_changed_cb(struct diff_queue_struct *q,
 345                                          struct diff_options *options,
 346                                          void *data)
 347 {
 348         int i;
 349         for (i = 0; i < q->nr; i++) {
 350                 struct diff_filepair *p = q->queue[i];
 351                 if (!S_ISGITLINK(p->two->mode))
 352                         continue;
 353
 354                 if (S_ISGITLINK(p->one->mode)) {
 355                         /* NEEDSWORK: We should honor the name configured in
 356                          * the .gitmodules file of the commit we are examining
 357                          * here to be able to correctly follow submodules
 358                          * being moved around. */
 359                         struct string_list_item *path;
 360                         path = unsorted_string_list_lookup(&changed_submodule_paths, p->two->path);
 361                         if (!path && !is_submodule_commit_present(p->two->path, p->two->sha1))
 362                                 string_list_append(&changed_submodule_paths, xstrdup(p->two->path));
 363                 } else {
 364                         /* Submodule is new or was moved here */
 365                         /* NEEDSWORK: When the .git directories of submodules
 366                          * live inside the superprojects .git directory some
 367                          * day we should fetch new submodules directly into
 368                          * that location too when config or options request
 369                          * that so they can be checked out from there. */
 370                         continue;
 371                 }
 372         }
 373 }
 374
 375 static int add_sha1_to_array(const char *ref, const unsigned char *sha1,
 376                              int flags, void *data)
 377 {
 378         sha1_array_append(data, sha1);
 379         return 0;
 380 }
 381
 382 void check_for_new_submodule_commits(unsigned char new_sha1[20])
 383 {
 384         if (!initialized_fetch_ref_tips) {
 385                 for_each_ref(add_sha1_to_array, &ref_tips_before_fetch);
 386                 initialized_fetch_ref_tips = 1;
 387         }
 388
 389         sha1_array_append(&ref_tips_after_fetch, new_sha1);
 390 }
 391
 392 static void add_sha1_to_argv(const unsigned char sha1[20], void *data)
 393 {
 394         argv_array_push(data, sha1_to_hex(sha1));
 395 }
 396
 397 static void calculate_changed_submodule_paths(void)
 398 {
 399         struct rev_info rev;
 400         struct commit *commit;
 401         struct argv_array argv = ARGV_ARRAY_INIT;
 402
 403         init_revisions(&rev, NULL);
 404         argv_array_push(&argv, "--"); /* argv[0] program name */
 405         sha1_array_for_each_unique(&ref_tips_after_fetch,
 406                                    add_sha1_to_argv, &argv);
 407         argv_array_push(&argv, "--not");
 408         sha1_array_for_each_unique(&ref_tips_before_fetch,
 409                                    add_sha1_to_argv, &argv);
 410         setup_revisions(argv.argc, argv.argv, &rev, NULL);
 411         if (prepare_revision_walk(&rev))
 412                 die("revision walk setup failed");
 413
 414         /*
 415          * Collect all submodules (whether checked out or not) for which new
 416          * commits have been recorded upstream in "changed_submodule_paths".
 417          */
 418         while ((commit = get_revision(&rev))) {
 419                 struct commit_list *parent = commit->parents;
 420                 while (parent) {
 421                         struct diff_options diff_opts;
 422                         diff_setup(&diff_opts);
 423                         diff_opts.output_format |= DIFF_FORMAT_CALLBACK;
 424                         diff_opts.format_callback = submodule_collect_changed_cb;
 425                         if (diff_setup_done(&diff_opts) < 0)
 426                                 die("diff_setup_done failed");
 427                         diff_tree_sha1(parent->item->object.sha1, commit->object.sha1, "", &diff_opts);
 428                         diffcore_std(&diff_opts);
 429                         diff_flush(&diff_opts);
 430                         parent = parent->next;
 431                 }
 432         }
 433
 434         argv_array_clear(&argv);
 435         sha1_array_clear(&ref_tips_before_fetch);
 436         sha1_array_clear(&ref_tips_after_fetch);
 437         initialized_fetch_ref_tips = 0;
 438 }
 439
 440 int fetch_populated_submodules(int num_options, const char **options,
 441                                const char *prefix, int command_line_option,
 442                                int quiet)
 443 {
 444         int i, result = 0, argc = 0, default_argc;
 445         struct child_process cp;
 446         const char **argv;
 447         struct string_list_item *name_for_path;
 448         const char *work_tree = get_git_work_tree();
 449         if (!work_tree)
 450                 goto out;
 451
 452         if (!the_index.initialized)
 453                 if (read_cache() < 0)
 454                         die("index file corrupt");
 455
 456         /* 6: "fetch" (options) --recurse-submodules-default default "--submodule-prefix" prefix NULL */
 457         argv = xcalloc(num_options + 6, sizeof(const char *));
 458         argv[argc++] = "fetch";
 459         for (i = 0; i < num_options; i++)
 460                 argv[argc++] = options[i];
 461         argv[argc++] = "--recurse-submodules-default";
 462         default_argc = argc++;
 463         argv[argc++] = "--submodule-prefix";
 464
 465         memset(&cp, 0, sizeof(cp));
 466         cp.argv = argv;
 467         cp.env = local_repo_env;
 468         cp.git_cmd = 1;
 469         cp.no_stdin = 1;
 470
 471         calculate_changed_submodule_paths();
 472
 473         for (i = 0; i < active_nr; i++) {
 474                 struct strbuf submodule_path = STRBUF_INIT;
 475                 struct strbuf submodule_git_dir = STRBUF_INIT;
 476                 struct strbuf submodule_prefix = STRBUF_INIT;
 477                 struct cache_entry *ce = active_cache[i];
 478                 const char *git_dir, *name, *default_argv;
 479
 480                 if (!S_ISGITLINK(ce->ce_mode))
 481                         continue;
 482
 483                 name = ce->name;
 484                 name_for_path = unsorted_string_list_lookup(&config_name_for_path, ce->name);
 485                 if (name_for_path)
 486                         name = name_for_path->util;
 487
 488                 default_argv = "yes";
 489                 if (command_line_option == RECURSE_SUBMODULES_DEFAULT) {
 490                         struct string_list_item *fetch_recurse_submodules_option;
 491                         fetch_recurse_submodules_option = unsorted_string_list_lookup(&config_fetch_recurse_submodules_for_name, name);
 492                         if (fetch_recurse_submodules_option) {
 493                                 if ((intptr_t)fetch_recurse_submodules_option->util == RECURSE_SUBMODULES_OFF)
 494                                         continue;
 495                                 if ((intptr_t)fetch_recurse_submodules_option->util == RECURSE_SUBMODULES_ON_DEMAND) {
 496                                         if (!unsorted_string_list_lookup(&changed_submodule_paths, ce->name))
 497                                                 continue;
 498                                         default_argv = "on-demand";
 499                                 }
 500                         } else {
 501                                 if ((config_fetch_recurse_submodules == RECURSE_SUBMODULES_OFF) ||
 502                                     gitmodules_is_unmerged)
 503                                         continue;
 504                                 if (config_fetch_recurse_submodules == RECURSE_SUBMODULES_ON_DEMAND) {
 505                                         if (!unsorted_string_list_lookup(&changed_submodule_paths, ce->name))
 506                                                 continue;
 507                                         default_argv = "on-demand";
 508                                 }
 509                         }
 510                 } else if (command_line_option == RECURSE_SUBMODULES_ON_DEMAND) {
 511                         if (!unsorted_string_list_lookup(&changed_submodule_paths, ce->name))
 512                                 continue;
 513                         default_argv = "on-demand";
 514                 }
 515
 516                 strbuf_addf(&submodule_path, "%s/%s", work_tree, ce->name);
 517                 strbuf_addf(&submodule_git_dir, "%s/.git", submodule_path.buf);
 518                 strbuf_addf(&submodule_prefix, "%s%s/", prefix, ce->name);
 519                 git_dir = read_gitfile_gently(submodule_git_dir.buf);
 520                 if (!git_dir)
 521                         git_dir = submodule_git_dir.buf;
 522                 if (is_directory(git_dir)) {
 523                         if (!quiet)
 524                                 printf("Fetching submodule %s%s\n", prefix, ce->name);
 525                         cp.dir = submodule_path.buf;
 526                         argv[default_argc] = default_argv;
 527                         argv[argc] = submodule_prefix.buf;
 528                         if (run_command(&cp))
 529                                 result = 1;
 530                 }
 531                 strbuf_release(&submodule_path);
 532                 strbuf_release(&submodule_git_dir);
 533                 strbuf_release(&submodule_prefix);
 534         }
 535         free(argv);
 536 out:
 537         string_list_clear(&changed_submodule_paths, 1);
 538         return result;
 539 }
 540
 541 unsigned is_submodule_modified(const char *path, int ignore_untracked)
 542 {
 543         ssize_t len;
 544         struct child_process cp;
 545         const char *argv[] = {
 546                 "status",
 547                 "--porcelain",
 548                 NULL,
 549                 NULL,
 550         };
 551         struct strbuf buf = STRBUF_INIT;
 552         unsigned dirty_submodule = 0;
 553         const char *line, *next_line;
 554         const char *git_dir;
 555
 556         strbuf_addf(&buf, "%s/.git", path);
 557         git_dir = read_gitfile_gently(buf.buf);
 558         if (!git_dir)
 559                 git_dir = buf.buf;
 560         if (!is_directory(git_dir)) {
 561                 strbuf_release(&buf);
 562                 /* The submodule is not checked out, so it is not modified */
 563                 return 0;
 564
 565         }
 566         strbuf_reset(&buf);
 567
 568         if (ignore_untracked)
 569                 argv[2] = "-uno";
 570
 571         memset(&cp, 0, sizeof(cp));
 572         cp.argv = argv;
 573         cp.env = local_repo_env;
 574         cp.git_cmd = 1;
 575         cp.no_stdin = 1;
 576         cp.out = -1;
 577         cp.dir = path;
 578         if (start_command(&cp))
 579                 die("Could not run git status --porcelain");
 580
 581         len = strbuf_read(&buf, cp.out, 1024);
 582         line = buf.buf;
 583         while (len > 2) {
 584                 if ((line[0] == '?') && (line[1] == '?')) {
 585                         dirty_submodule |= DIRTY_SUBMODULE_UNTRACKED;
 586                         if (dirty_submodule & DIRTY_SUBMODULE_MODIFIED)
 587                                 break;
 588                 } else {
 589                         dirty_submodule |= DIRTY_SUBMODULE_MODIFIED;
 590                         if (ignore_untracked ||
 591                             (dirty_submodule & DIRTY_SUBMODULE_UNTRACKED))
 592                                 break;
 593                 }
 594                 next_line = strchr(line, '\n');
 595                 if (!next_line)
 596                         break;
 597                 next_line++;
 598                 len -= (next_line - line);
 599                 line = next_line;
 600         }
 601         close(cp.out);
 602
 603         if (finish_command(&cp))
 604                 die("git status --porcelain failed");
 605
 606         strbuf_release(&buf);
 607         return dirty_submodule;
 608 }
 609
 610 static int find_first_merges(struct object_array *result, const char *path,
 611                 struct commit *a, struct commit *b)
 612 {
 613         int i, j;
 614         struct object_array merges;
 615         struct commit *commit;
 616         int contains_another;
 617
 618         char merged_revision[42];
 619         const char *rev_args[] = { "rev-list", "--merges", "--ancestry-path",
 620                                    "--all", merged_revision, NULL };
 621         struct rev_info revs;
 622         struct setup_revision_opt rev_opts;
 623
 624         memset(&merges, 0, sizeof(merges));
 625         memset(result, 0, sizeof(struct object_array));
 626         memset(&rev_opts, 0, sizeof(rev_opts));
 627
 628         /* get all revisions that merge commit a */
 629         snprintf(merged_revision, sizeof(merged_revision), "^%s",
 630                         sha1_to_hex(a->object.sha1));
 631         init_revisions(&revs, NULL);
 632         rev_opts.submodule = path;
 633         setup_revisions(sizeof(rev_args)/sizeof(char *)-1, rev_args, &revs, &rev_opts);
 634
 635         /* save all revisions from the above list that contain b */
 636         if (prepare_revision_walk(&revs))
 637                 die("revision walk setup failed");
 638         while ((commit = get_revision(&revs)) != NULL) {
 639                 struct object *o = &(commit->object);
 640                 if (in_merge_bases(b, &commit, 1))
 641                         add_object_array(o, NULL, &merges);
 642         }
 643
 644         /* Now we've got all merges that contain a and b. Prune all
 645          * merges that contain another found merge and save them in
 646          * result.
 647          */
 648         for (i = 0; i < merges.nr; i++) {
 649                 struct commit *m1 = (struct commit *) merges.objects[i].item;
 650
 651                 contains_another = 0;
 652                 for (j = 0; j < merges.nr; j++) {
 653                         struct commit *m2 = (struct commit *) merges.objects[j].item;
 654                         if (i != j && in_merge_bases(m2, &m1, 1)) {
 655                                 contains_another = 1;
 656                                 break;
 657                         }
 658                 }
 659
 660                 if (!contains_another)
 661                         add_object_array(merges.objects[i].item,
 662                                          merges.objects[i].name, result);
 663         }
 664
 665         free(merges.objects);
 666         return result->nr;
 667 }
 668
 669 static void print_commit(struct commit *commit)
 670 {
 671         struct strbuf sb = STRBUF_INIT;
 672         struct pretty_print_context ctx = {0};
 673         ctx.date_mode = DATE_NORMAL;
 674         format_commit_message(commit, " %h: %m %s", &sb, &ctx);
 675         fprintf(stderr, "%s\n", sb.buf);
 676         strbuf_release(&sb);
 677 }
 678
 679 #define MERGE_WARNING(path, msg) \
 680         warning("Failed to merge submodule %s (%s)", path, msg);
 681
 682 int merge_submodule(unsigned char result[20], const char *path,
 683                     const unsigned char base[20], const unsigned char a[20],
 684                     const unsigned char b[20])
 685 {
 686         struct commit *commit_base, *commit_a, *commit_b;
 687         int parent_count;
 688         struct object_array merges;
 689
 690         int i;
 691
 692         /* store a in result in case we fail */
 693         hashcpy(result, a);
 694
 695         /* we can not handle deletion conflicts */
 696         if (is_null_sha1(base))
 697                 return 0;
 698         if (is_null_sha1(a))
 699                 return 0;
 700         if (is_null_sha1(b))
 701                 return 0;
 702
 703         if (add_submodule_odb(path)) {
 704                 MERGE_WARNING(path, "not checked out");
 705                 return 0;
 706         }
 707
 708         if (!(commit_base = lookup_commit_reference(base)) ||
 709             !(commit_a = lookup_commit_reference(a)) ||
 710             !(commit_b = lookup_commit_reference(b))) {
 711                 MERGE_WARNING(path, "commits not present");
 712                 return 0;
 713         }
 714
 715         /* check whether both changes are forward */
 716         if (!in_merge_bases(commit_base, &commit_a, 1) ||
 717             !in_merge_bases(commit_base, &commit_b, 1)) {
 718                 MERGE_WARNING(path, "commits don't follow merge-base");
 719                 return 0;
 720         }
 721
 722         /* Case #1: a is contained in b or vice versa */
 723         if (in_merge_bases(commit_a, &commit_b, 1)) {
 724                 hashcpy(result, b);
 725                 return 1;
 726         }
 727         if (in_merge_bases(commit_b, &commit_a, 1)) {
 728                 hashcpy(result, a);
 729                 return 1;
 730         }
 731
 732         /*
 733          * Case #2: There are one or more merges that contain a and b in
 734          * the submodule. If there is only one, then present it as a
 735          * suggestion to the user, but leave it marked unmerged so the
 736          * user needs to confirm the resolution.
 737          */
 738
 739         /* find commit which merges them */
 740         parent_count = find_first_merges(&merges, path, commit_a, commit_b);
 741         switch (parent_count) {
 742         case 0:
 743                 MERGE_WARNING(path, "merge following commits not found");
 744                 break;
 745
 746         case 1:
 747                 MERGE_WARNING(path, "not fast-forward");
 748                 fprintf(stderr, "Found a possible merge resolution "
 749                                 "for the submodule:\n");
 750                 print_commit((struct commit *) merges.objects[0].item);
 751                 fprintf(stderr,
 752                         "If this is correct simply add it to the index "
 753                         "for example\n"
 754                         "by using:\n\n"
 755                         "  git update-index --cacheinfo 160000 %s \"%s\"\n\n"
 756                         "which will accept this suggestion.\n",
 757                         sha1_to_hex(merges.objects[0].item->sha1), path);
 758                 break;
 759
 760         default:
 761                 MERGE_WARNING(path, "multiple merges found");
 762                 for (i = 0; i < merges.nr; i++)
 763                         print_commit((struct commit *) merges.objects[i].item);
 764         }
 765
 766         free(merges.objects);
 767         return 0;
 768 }