builtin/merge.c

   1 /*
   2  * Builtin "git merge"
   3  *
   4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
   5  *
   6  * Based on git-merge.sh by Junio C Hamano.
   7  */
   8
   9 #include "cache.h"
  10 #include "parse-options.h"
  11 #include "builtin.h"
  12 #include "run-command.h"
  13 #include "diff.h"
  14 #include "refs.h"
  15 #include "commit.h"
  16 #include "diffcore.h"
  17 #include "revision.h"
  18 #include "unpack-trees.h"
  19 #include "cache-tree.h"
  20 #include "dir.h"
  21 #include "utf8.h"
  22 #include "log-tree.h"
  23 #include "color.h"
  24 #include "rerere.h"
  25 #include "help.h"
  26 #include "merge-recursive.h"
  27 #include "resolve-undo.h"
  28 #include "remote.h"
  29
  30 #define DEFAULT_TWOHEAD (1<<0)
  31 #define DEFAULT_OCTOPUS (1<<1)
  32 #define NO_FAST_FORWARD (1<<2)
  33 #define NO_TRIVIAL      (1<<3)
  34
  35 struct strategy {
  36         const char *name;
  37         unsigned attr;
  38 };
  39
  40 static const char * const builtin_merge_usage[] = {
  41         "git merge [options] [<commit>...]",
  42         "git merge [options] <msg> HEAD <commit>",
  43         "git merge --abort",
  44         NULL
  45 };
  46
  47 static int show_diffstat = 1, shortlog_len, squash;
  48 static int option_commit = 1, allow_fast_forward = 1;
  49 static int fast_forward_only, option_edit;
  50 static int allow_trivial = 1, have_message;
  51 static struct strbuf merge_msg = STRBUF_INIT;
  52 static struct commit_list *remoteheads;
  53 static struct strategy **use_strategies;
  54 static size_t use_strategies_nr, use_strategies_alloc;
  55 static const char **xopts;
  56 static size_t xopts_nr, xopts_alloc;
  57 static const char *branch;
  58 static char *branch_mergeoptions;
  59 static int option_renormalize;
  60 static int verbosity;
  61 static int allow_rerere_auto;
  62 static int abort_current_merge;
  63 static int show_progress = -1;
  64 static int default_to_upstream;
  65
  66 static struct strategy all_strategy[] = {
  67         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  68         { "octopus",    DEFAULT_OCTOPUS },
  69         { "resolve",    0 },
  70         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  71         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  72 };
  73
  74 static const char *pull_twohead, *pull_octopus;
  75
  76 static int option_parse_message(const struct option *opt,
  77                                 const char *arg, int unset)
  78 {
  79         struct strbuf *buf = opt->value;
  80
  81         if (unset)
  82                 strbuf_setlen(buf, 0);
  83         else if (arg) {
  84                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  85                 have_message = 1;
  86         } else
  87                 return error(_("switch `m' requires a value"));
  88         return 0;
  89 }
  90
  91 static struct strategy *get_strategy(const char *name)
  92 {
  93         int i;
  94         struct strategy *ret;
  95         static struct cmdnames main_cmds, other_cmds;
  96         static int loaded;
  97
  98         if (!name)
  99                 return NULL;
 100
 101         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 102                 if (!strcmp(name, all_strategy[i].name))
 103                         return &all_strategy[i];
 104
 105         if (!loaded) {
 106                 struct cmdnames not_strategies;
 107                 loaded = 1;
 108
 109                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 110                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 111                 for (i = 0; i < main_cmds.cnt; i++) {
 112                         int j, found = 0;
 113                         struct cmdname *ent = main_cmds.names[i];
 114                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 115                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 116                                                 && !all_strategy[j].name[ent->len])
 117                                         found = 1;
 118                         if (!found)
 119                                 add_cmdname(&not_strategies, ent->name, ent->len);
 120                 }
 121                 exclude_cmds(&main_cmds, &not_strategies);
 122         }
 123         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 124                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 125                 fprintf(stderr, _("Available strategies are:"));
 126                 for (i = 0; i < main_cmds.cnt; i++)
 127                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 128                 fprintf(stderr, ".\n");
 129                 if (other_cmds.cnt) {
 130                         fprintf(stderr, _("Available custom strategies are:"));
 131                         for (i = 0; i < other_cmds.cnt; i++)
 132                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 133                         fprintf(stderr, ".\n");
 134                 }
 135                 exit(1);
 136         }
 137
 138         ret = xcalloc(1, sizeof(struct strategy));
 139         ret->name = xstrdup(name);
 140         ret->attr = NO_TRIVIAL;
 141         return ret;
 142 }
 143
 144 static void append_strategy(struct strategy *s)
 145 {
 146         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 147         use_strategies[use_strategies_nr++] = s;
 148 }
 149
 150 static int option_parse_strategy(const struct option *opt,
 151                                  const char *name, int unset)
 152 {
 153         if (unset)
 154                 return 0;
 155
 156         append_strategy(get_strategy(name));
 157         return 0;
 158 }
 159
 160 static int option_parse_x(const struct option *opt,
 161                           const char *arg, int unset)
 162 {
 163         if (unset)
 164                 return 0;
 165
 166         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 167         xopts[xopts_nr++] = xstrdup(arg);
 168         return 0;
 169 }
 170
 171 static int option_parse_n(const struct option *opt,
 172                           const char *arg, int unset)
 173 {
 174         show_diffstat = unset;
 175         return 0;
 176 }
 177
 178 static struct option builtin_merge_options[] = {
 179         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 180                 "do not show a diffstat at the end of the merge",
 181                 PARSE_OPT_NOARG, option_parse_n },
 182         OPT_BOOLEAN(0, "stat", &show_diffstat,
 183                 "show a diffstat at the end of the merge"),
 184         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 185         { OPTION_INTEGER, 0, "log", &shortlog_len, "n",
 186           "add (at most <n>) entries from shortlog to merge commit message",
 187           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 188         OPT_BOOLEAN(0, "squash", &squash,
 189                 "create a single commit instead of doing a merge"),
 190         OPT_BOOLEAN(0, "commit", &option_commit,
 191                 "perform a commit if the merge succeeds (default)"),
 192         OPT_BOOLEAN('e', "edit", &option_edit,
 193                 "edit message before committing"),
 194         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 195                 "allow fast-forward (default)"),
 196         OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
 197                 "abort if fast-forward is not possible"),
 198         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 199         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
 200                 "merge strategy to use", option_parse_strategy),
 201         OPT_CALLBACK('X', "strategy-option", &xopts, "option=value",
 202                 "option for selected merge strategy", option_parse_x),
 203         OPT_CALLBACK('m', "message", &merge_msg, "message",
 204                 "merge commit message (for a non-fast-forward merge)",
 205                 option_parse_message),
 206         OPT__VERBOSITY(&verbosity),
 207         OPT_BOOLEAN(0, "abort", &abort_current_merge,
 208                 "abort the current in-progress merge"),
 209         OPT_SET_INT(0, "progress", &show_progress, "force progress reporting", 1),
 210         OPT_END()
 211 };
 212
 213 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 214 static void drop_save(void)
 215 {
 216         unlink(git_path("MERGE_HEAD"));
 217         unlink(git_path("MERGE_MSG"));
 218         unlink(git_path("MERGE_MODE"));
 219 }
 220
 221 static int save_state(unsigned char *stash)
 222 {
 223         int len;
 224         struct child_process cp;
 225         struct strbuf buffer = STRBUF_INIT;
 226         const char *argv[] = {"stash", "create", NULL};
 227
 228         memset(&cp, 0, sizeof(cp));
 229         cp.argv = argv;
 230         cp.out = -1;
 231         cp.git_cmd = 1;
 232
 233         if (start_command(&cp))
 234                 die(_("could not run stash."));
 235         len = strbuf_read(&buffer, cp.out, 1024);
 236         close(cp.out);
 237
 238         if (finish_command(&cp) || len < 0)
 239                 die(_("stash failed"));
 240         else if (!len)          /* no changes */
 241                 return -1;
 242         strbuf_setlen(&buffer, buffer.len-1);
 243         if (get_sha1(buffer.buf, stash))
 244                 die(_("not a valid object: %s"), buffer.buf);
 245         return 0;
 246 }
 247
 248 static void read_empty(unsigned const char *sha1, int verbose)
 249 {
 250         int i = 0;
 251         const char *args[7];
 252
 253         args[i++] = "read-tree";
 254         if (verbose)
 255                 args[i++] = "-v";
 256         args[i++] = "-m";
 257         args[i++] = "-u";
 258         args[i++] = EMPTY_TREE_SHA1_HEX;
 259         args[i++] = sha1_to_hex(sha1);
 260         args[i] = NULL;
 261
 262         if (run_command_v_opt(args, RUN_GIT_CMD))
 263                 die(_("read-tree failed"));
 264 }
 265
 266 static void reset_hard(unsigned const char *sha1, int verbose)
 267 {
 268         int i = 0;
 269         const char *args[6];
 270
 271         args[i++] = "read-tree";
 272         if (verbose)
 273                 args[i++] = "-v";
 274         args[i++] = "--reset";
 275         args[i++] = "-u";
 276         args[i++] = sha1_to_hex(sha1);
 277         args[i] = NULL;
 278
 279         if (run_command_v_opt(args, RUN_GIT_CMD))
 280                 die(_("read-tree failed"));
 281 }
 282
 283 static void restore_state(const unsigned char *head,
 284                           const unsigned char *stash)
 285 {
 286         struct strbuf sb = STRBUF_INIT;
 287         const char *args[] = { "stash", "apply", NULL, NULL };
 288
 289         if (is_null_sha1(stash))
 290                 return;
 291
 292         reset_hard(head, 1);
 293
 294         args[2] = sha1_to_hex(stash);
 295
 296         /*
 297          * It is OK to ignore error here, for example when there was
 298          * nothing to restore.
 299          */
 300         run_command_v_opt(args, RUN_GIT_CMD);
 301
 302         strbuf_release(&sb);
 303         refresh_cache(REFRESH_QUIET);
 304 }
 305
 306 /* This is called when no merge was necessary. */
 307 static void finish_up_to_date(const char *msg)
 308 {
 309         if (verbosity >= 0)
 310                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 311         drop_save();
 312 }
 313
 314 static void squash_message(struct commit *commit)
 315 {
 316         struct rev_info rev;
 317         struct strbuf out = STRBUF_INIT;
 318         struct commit_list *j;
 319         const char *filename;
 320         int fd;
 321         struct pretty_print_context ctx = {0};
 322
 323         printf(_("Squash commit -- not updating HEAD\n"));
 324         filename = git_path("SQUASH_MSG");
 325         fd = open(filename, O_WRONLY | O_CREAT, 0666);
 326         if (fd < 0)
 327                 die_errno(_("Could not write to '%s'"), filename);
 328
 329         init_revisions(&rev, NULL);
 330         rev.ignore_merges = 1;
 331         rev.commit_format = CMIT_FMT_MEDIUM;
 332
 333         commit->object.flags |= UNINTERESTING;
 334         add_pending_object(&rev, &commit->object, NULL);
 335
 336         for (j = remoteheads; j; j = j->next)
 337                 add_pending_object(&rev, &j->item->object, NULL);
 338
 339         setup_revisions(0, NULL, &rev, NULL);
 340         if (prepare_revision_walk(&rev))
 341                 die(_("revision walk setup failed"));
 342
 343         ctx.abbrev = rev.abbrev;
 344         ctx.date_mode = rev.date_mode;
 345         ctx.fmt = rev.commit_format;
 346
 347         strbuf_addstr(&out, "Squashed commit of the following:\n");
 348         while ((commit = get_revision(&rev)) != NULL) {
 349                 strbuf_addch(&out, '\n');
 350                 strbuf_addf(&out, "commit %s\n",
 351                         sha1_to_hex(commit->object.sha1));
 352                 pretty_print_commit(&ctx, commit, &out);
 353         }
 354         if (write(fd, out.buf, out.len) < 0)
 355                 die_errno(_("Writing SQUASH_MSG"));
 356         if (close(fd))
 357                 die_errno(_("Finishing SQUASH_MSG"));
 358         strbuf_release(&out);
 359 }
 360
 361 static void finish(struct commit *head_commit,
 362                    const unsigned char *new_head, const char *msg)
 363 {
 364         struct strbuf reflog_message = STRBUF_INIT;
 365         const unsigned char *head = head_commit->object.sha1;
 366
 367         if (!msg)
 368                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 369         else {
 370                 if (verbosity >= 0)
 371                         printf("%s\n", msg);
 372                 strbuf_addf(&reflog_message, "%s: %s",
 373                         getenv("GIT_REFLOG_ACTION"), msg);
 374         }
 375         if (squash) {
 376                 squash_message(head_commit);
 377         } else {
 378                 if (verbosity >= 0 && !merge_msg.len)
 379                         printf(_("No merge message -- not updating HEAD\n"));
 380                 else {
 381                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 382                         update_ref(reflog_message.buf, "HEAD",
 383                                 new_head, head, 0,
 384                                 DIE_ON_ERR);
 385                         /*
 386                          * We ignore errors in 'gc --auto', since the
 387                          * user should see them.
 388                          */
 389                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 390                 }
 391         }
 392         if (new_head && show_diffstat) {
 393                 struct diff_options opts;
 394                 diff_setup(&opts);
 395                 opts.output_format |=
 396                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 397                 opts.detect_rename = DIFF_DETECT_RENAME;
 398                 if (diff_setup_done(&opts) < 0)
 399                         die(_("diff_setup_done failed"));
 400                 diff_tree_sha1(head, new_head, "", &opts);
 401                 diffcore_std(&opts);
 402                 diff_flush(&opts);
 403         }
 404
 405         /* Run a post-merge hook */
 406         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
 407
 408         strbuf_release(&reflog_message);
 409 }
 410
 411 static struct object *want_commit(const char *name)
 412 {
 413         struct object *obj;
 414         unsigned char sha1[20];
 415         if (get_sha1(name, sha1))
 416                 return NULL;
 417         obj = parse_object(sha1);
 418         return peel_to_type(name, 0, obj, OBJ_COMMIT);
 419 }
 420
 421 /* Get the name for the merge commit's message. */
 422 static void merge_name(const char *remote, struct strbuf *msg)
 423 {
 424         struct object *remote_head;
 425         unsigned char branch_head[20], buf_sha[20];
 426         struct strbuf buf = STRBUF_INIT;
 427         struct strbuf bname = STRBUF_INIT;
 428         const char *ptr;
 429         char *found_ref;
 430         int len, early;
 431
 432         strbuf_branchname(&bname, remote);
 433         remote = bname.buf;
 434
 435         memset(branch_head, 0, sizeof(branch_head));
 436         remote_head = want_commit(remote);
 437         if (!remote_head)
 438                 die(_("'%s' does not point to a commit"), remote);
 439
 440         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 441                 if (!prefixcmp(found_ref, "refs/heads/")) {
 442                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 443                                     sha1_to_hex(branch_head), remote);
 444                         goto cleanup;
 445                 }
 446                 if (!prefixcmp(found_ref, "refs/remotes/")) {
 447                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 448                                     sha1_to_hex(branch_head), remote);
 449                         goto cleanup;
 450                 }
 451         }
 452
 453         /* See if remote matches <name>^^^.. or <name>~<number> */
 454         for (len = 0, ptr = remote + strlen(remote);
 455              remote < ptr && ptr[-1] == '^';
 456              ptr--)
 457                 len++;
 458         if (len)
 459                 early = 1;
 460         else {
 461                 early = 0;
 462                 ptr = strrchr(remote, '~');
 463                 if (ptr) {
 464                         int seen_nonzero = 0;
 465
 466                         len++; /* count ~ */
 467                         while (*++ptr && isdigit(*ptr)) {
 468                                 seen_nonzero |= (*ptr != '0');
 469                                 len++;
 470                         }
 471                         if (*ptr)
 472                                 len = 0; /* not ...~<number> */
 473                         else if (seen_nonzero)
 474                                 early = 1;
 475                         else if (len == 1)
 476                                 early = 1; /* "name~" is "name~1"! */
 477                 }
 478         }
 479         if (len) {
 480                 struct strbuf truname = STRBUF_INIT;
 481                 strbuf_addstr(&truname, "refs/heads/");
 482                 strbuf_addstr(&truname, remote);
 483                 strbuf_setlen(&truname, truname.len - len);
 484                 if (resolve_ref(truname.buf, buf_sha, 1, NULL)) {
 485                         strbuf_addf(msg,
 486                                     "%s\t\tbranch '%s'%s of .\n",
 487                                     sha1_to_hex(remote_head->sha1),
 488                                     truname.buf + 11,
 489                                     (early ? " (early part)" : ""));
 490                         strbuf_release(&truname);
 491                         goto cleanup;
 492                 }
 493         }
 494
 495         if (!strcmp(remote, "FETCH_HEAD") &&
 496                         !access(git_path("FETCH_HEAD"), R_OK)) {
 497                 const char *filename;
 498                 FILE *fp;
 499                 struct strbuf line = STRBUF_INIT;
 500                 char *ptr;
 501
 502                 filename = git_path("FETCH_HEAD");
 503                 fp = fopen(filename, "r");
 504                 if (!fp)
 505                         die_errno(_("could not open '%s' for reading"),
 506                                   filename);
 507                 strbuf_getline(&line, fp, '\n');
 508                 fclose(fp);
 509                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 510                 if (ptr)
 511                         strbuf_remove(&line, ptr-line.buf+1, 13);
 512                 strbuf_addbuf(msg, &line);
 513                 strbuf_release(&line);
 514                 goto cleanup;
 515         }
 516         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 517                 sha1_to_hex(remote_head->sha1), remote);
 518 cleanup:
 519         strbuf_release(&buf);
 520         strbuf_release(&bname);
 521 }
 522
 523 static void parse_branch_merge_options(char *bmo)
 524 {
 525         const char **argv;
 526         int argc;
 527
 528         if (!bmo)
 529                 return;
 530         argc = split_cmdline(bmo, &argv);
 531         if (argc < 0)
 532                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 533                     split_cmdline_strerror(argc));
 534         argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 535         memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 536         argc++;
 537         argv[0] = "branch.*.mergeoptions";
 538         parse_options(argc, argv, NULL, builtin_merge_options,
 539                       builtin_merge_usage, 0);
 540         free(argv);
 541 }
 542
 543 static int git_merge_config(const char *k, const char *v, void *cb)
 544 {
 545         if (branch && !prefixcmp(k, "branch.") &&
 546                 !prefixcmp(k + 7, branch) &&
 547                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 548                 free(branch_mergeoptions);
 549                 branch_mergeoptions = xstrdup(v);
 550                 return 0;
 551         }
 552
 553         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 554                 show_diffstat = git_config_bool(k, v);
 555         else if (!strcmp(k, "pull.twohead"))
 556                 return git_config_string(&pull_twohead, k, v);
 557         else if (!strcmp(k, "pull.octopus"))
 558                 return git_config_string(&pull_octopus, k, v);
 559         else if (!strcmp(k, "merge.renormalize"))
 560                 option_renormalize = git_config_bool(k, v);
 561         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary")) {
 562                 int is_bool;
 563                 shortlog_len = git_config_bool_or_int(k, v, &is_bool);
 564                 if (!is_bool && shortlog_len < 0)
 565                         return error(_("%s: negative length %s"), k, v);
 566                 if (is_bool && shortlog_len)
 567                         shortlog_len = DEFAULT_MERGE_LOG_LEN;
 568                 return 0;
 569         } else if (!strcmp(k, "merge.ff")) {
 570                 int boolval = git_config_maybe_bool(k, v);
 571                 if (0 <= boolval) {
 572                         allow_fast_forward = boolval;
 573                 } else if (v && !strcmp(v, "only")) {
 574                         allow_fast_forward = 1;
 575                         fast_forward_only = 1;
 576                 } /* do not barf on values from future versions of git */
 577                 return 0;
 578         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 579                 default_to_upstream = git_config_bool(k, v);
 580                 return 0;
 581         }
 582         return git_diff_ui_config(k, v, cb);
 583 }
 584
 585 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 586                              unsigned char *one)
 587 {
 588         int i, nr_trees = 0;
 589         struct tree *trees[MAX_UNPACK_TREES];
 590         struct tree_desc t[MAX_UNPACK_TREES];
 591         struct unpack_trees_options opts;
 592
 593         memset(&opts, 0, sizeof(opts));
 594         opts.head_idx = 2;
 595         opts.src_index = &the_index;
 596         opts.dst_index = &the_index;
 597         opts.update = 1;
 598         opts.verbose_update = 1;
 599         opts.trivial_merges_only = 1;
 600         opts.merge = 1;
 601         trees[nr_trees] = parse_tree_indirect(common);
 602         if (!trees[nr_trees++])
 603                 return -1;
 604         trees[nr_trees] = parse_tree_indirect(head);
 605         if (!trees[nr_trees++])
 606                 return -1;
 607         trees[nr_trees] = parse_tree_indirect(one);
 608         if (!trees[nr_trees++])
 609                 return -1;
 610         opts.fn = threeway_merge;
 611         cache_tree_free(&active_cache_tree);
 612         for (i = 0; i < nr_trees; i++) {
 613                 parse_tree(trees[i]);
 614                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 615         }
 616         if (unpack_trees(nr_trees, t, &opts))
 617                 return -1;
 618         return 0;
 619 }
 620
 621 static void write_tree_trivial(unsigned char *sha1)
 622 {
 623         if (write_cache_as_tree(sha1, 0, NULL))
 624                 die(_("git write-tree failed to write a tree"));
 625 }
 626
 627 static const char *merge_argument(struct commit *commit)
 628 {
 629         if (commit)
 630                 return sha1_to_hex(commit->object.sha1);
 631         else
 632                 return EMPTY_TREE_SHA1_HEX;
 633 }
 634
 635 int try_merge_command(const char *strategy, size_t xopts_nr,
 636                       const char **xopts, struct commit_list *common,
 637                       const char *head_arg, struct commit_list *remotes)
 638 {
 639         const char **args;
 640         int i = 0, x = 0, ret;
 641         struct commit_list *j;
 642         struct strbuf buf = STRBUF_INIT;
 643
 644         args = xmalloc((4 + xopts_nr + commit_list_count(common) +
 645                         commit_list_count(remotes)) * sizeof(char *));
 646         strbuf_addf(&buf, "merge-%s", strategy);
 647         args[i++] = buf.buf;
 648         for (x = 0; x < xopts_nr; x++) {
 649                 char *s = xmalloc(strlen(xopts[x])+2+1);
 650                 strcpy(s, "--");
 651                 strcpy(s+2, xopts[x]);
 652                 args[i++] = s;
 653         }
 654         for (j = common; j; j = j->next)
 655                 args[i++] = xstrdup(merge_argument(j->item));
 656         args[i++] = "--";
 657         args[i++] = head_arg;
 658         for (j = remotes; j; j = j->next)
 659                 args[i++] = xstrdup(merge_argument(j->item));
 660         args[i] = NULL;
 661         ret = run_command_v_opt(args, RUN_GIT_CMD);
 662         strbuf_release(&buf);
 663         i = 1;
 664         for (x = 0; x < xopts_nr; x++)
 665                 free((void *)args[i++]);
 666         for (j = common; j; j = j->next)
 667                 free((void *)args[i++]);
 668         i += 2;
 669         for (j = remotes; j; j = j->next)
 670                 free((void *)args[i++]);
 671         free(args);
 672         discard_cache();
 673         if (read_cache() < 0)
 674                 die(_("failed to read the cache"));
 675         resolve_undo_clear();
 676
 677         return ret;
 678 }
 679
 680 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 681                               struct commit *head, const char *head_arg)
 682 {
 683         int index_fd;
 684         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 685
 686         index_fd = hold_locked_index(lock, 1);
 687         refresh_cache(REFRESH_QUIET);
 688         if (active_cache_changed &&
 689                         (write_cache(index_fd, active_cache, active_nr) ||
 690                          commit_locked_index(lock)))
 691                 return error(_("Unable to write index."));
 692         rollback_lock_file(lock);
 693
 694         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 695                 int clean, x;
 696                 struct commit *result;
 697                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 698                 int index_fd;
 699                 struct commit_list *reversed = NULL;
 700                 struct merge_options o;
 701                 struct commit_list *j;
 702
 703                 if (remoteheads->next) {
 704                         error(_("Not handling anything other than two heads merge."));
 705                         return 2;
 706                 }
 707
 708                 init_merge_options(&o);
 709                 if (!strcmp(strategy, "subtree"))
 710                         o.subtree_shift = "";
 711
 712                 o.renormalize = option_renormalize;
 713                 o.show_rename_progress =
 714                         show_progress == -1 ? isatty(2) : show_progress;
 715
 716                 for (x = 0; x < xopts_nr; x++)
 717                         if (parse_merge_opt(&o, xopts[x]))
 718                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 719
 720                 o.branch1 = head_arg;
 721                 o.branch2 = remoteheads->item->util;
 722
 723                 for (j = common; j; j = j->next)
 724                         commit_list_insert(j->item, &reversed);
 725
 726                 index_fd = hold_locked_index(lock, 1);
 727                 clean = merge_recursive(&o, head,
 728                                 remoteheads->item, reversed, &result);
 729                 if (active_cache_changed &&
 730                                 (write_cache(index_fd, active_cache, active_nr) ||
 731                                  commit_locked_index(lock)))
 732                         die (_("unable to write %s"), get_index_file());
 733                 rollback_lock_file(lock);
 734                 return clean ? 0 : 1;
 735         } else {
 736                 return try_merge_command(strategy, xopts_nr, xopts,
 737                                                 common, head_arg, remoteheads);
 738         }
 739 }
 740
 741 static void count_diff_files(struct diff_queue_struct *q,
 742                              struct diff_options *opt, void *data)
 743 {
 744         int *count = data;
 745
 746         (*count) += q->nr;
 747 }
 748
 749 static int count_unmerged_entries(void)
 750 {
 751         int i, ret = 0;
 752
 753         for (i = 0; i < active_nr; i++)
 754                 if (ce_stage(active_cache[i]))
 755                         ret++;
 756
 757         return ret;
 758 }
 759
 760 int checkout_fast_forward(const unsigned char *head, const unsigned char *remote)
 761 {
 762         struct tree *trees[MAX_UNPACK_TREES];
 763         struct unpack_trees_options opts;
 764         struct tree_desc t[MAX_UNPACK_TREES];
 765         int i, fd, nr_trees = 0;
 766         struct dir_struct dir;
 767         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 768
 769         refresh_cache(REFRESH_QUIET);
 770
 771         fd = hold_locked_index(lock_file, 1);
 772
 773         memset(&trees, 0, sizeof(trees));
 774         memset(&opts, 0, sizeof(opts));
 775         memset(&t, 0, sizeof(t));
 776         memset(&dir, 0, sizeof(dir));
 777         dir.flags |= DIR_SHOW_IGNORED;
 778         setup_standard_excludes(&dir);
 779         opts.dir = &dir;
 780
 781         opts.head_idx = 1;
 782         opts.src_index = &the_index;
 783         opts.dst_index = &the_index;
 784         opts.update = 1;
 785         opts.verbose_update = 1;
 786         opts.merge = 1;
 787         opts.fn = twoway_merge;
 788         setup_unpack_trees_porcelain(&opts, "merge");
 789
 790         trees[nr_trees] = parse_tree_indirect(head);
 791         if (!trees[nr_trees++])
 792                 return -1;
 793         trees[nr_trees] = parse_tree_indirect(remote);
 794         if (!trees[nr_trees++])
 795                 return -1;
 796         for (i = 0; i < nr_trees; i++) {
 797                 parse_tree(trees[i]);
 798                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 799         }
 800         if (unpack_trees(nr_trees, t, &opts))
 801                 return -1;
 802         if (write_cache(fd, active_cache, active_nr) ||
 803                 commit_locked_index(lock_file))
 804                 die(_("unable to write new index file"));
 805         return 0;
 806 }
 807
 808 static void split_merge_strategies(const char *string, struct strategy **list,
 809                                    int *nr, int *alloc)
 810 {
 811         char *p, *q, *buf;
 812
 813         if (!string)
 814                 return;
 815
 816         buf = xstrdup(string);
 817         q = buf;
 818         for (;;) {
 819                 p = strchr(q, ' ');
 820                 if (!p) {
 821                         ALLOC_GROW(*list, *nr + 1, *alloc);
 822                         (*list)[(*nr)++].name = xstrdup(q);
 823                         free(buf);
 824                         return;
 825                 } else {
 826                         *p = '\0';
 827                         ALLOC_GROW(*list, *nr + 1, *alloc);
 828                         (*list)[(*nr)++].name = xstrdup(q);
 829                         q = ++p;
 830                 }
 831         }
 832 }
 833
 834 static void add_strategies(const char *string, unsigned attr)
 835 {
 836         struct strategy *list = NULL;
 837         int list_alloc = 0, list_nr = 0, i;
 838
 839         memset(&list, 0, sizeof(list));
 840         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 841         if (list) {
 842                 for (i = 0; i < list_nr; i++)
 843                         append_strategy(get_strategy(list[i].name));
 844                 return;
 845         }
 846         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 847                 if (all_strategy[i].attr & attr)
 848                         append_strategy(&all_strategy[i]);
 849
 850 }
 851
 852 static void write_merge_msg(struct strbuf *msg)
 853 {
 854         const char *filename = git_path("MERGE_MSG");
 855         int fd = open(filename, O_WRONLY | O_CREAT, 0666);
 856         if (fd < 0)
 857                 die_errno(_("Could not open '%s' for writing"),
 858                           filename);
 859         if (write_in_full(fd, msg->buf, msg->len) != msg->len)
 860                 die_errno(_("Could not write to '%s'"), filename);
 861         close(fd);
 862 }
 863
 864 static void read_merge_msg(struct strbuf *msg)
 865 {
 866         const char *filename = git_path("MERGE_MSG");
 867         strbuf_reset(msg);
 868         if (strbuf_read_file(msg, filename, 0) < 0)
 869                 die_errno(_("Could not read from '%s'"), filename);
 870 }
 871
 872 static void write_merge_state(void);
 873 static void abort_commit(const char *err_msg)
 874 {
 875         if (err_msg)
 876                 error("%s", err_msg);
 877         fprintf(stderr,
 878                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 879         write_merge_state();
 880         exit(1);
 881 }
 882
 883 static void prepare_to_commit(void)
 884 {
 885         struct strbuf msg = STRBUF_INIT;
 886         strbuf_addbuf(&msg, &merge_msg);
 887         strbuf_addch(&msg, '\n');
 888         write_merge_msg(&msg);
 889         run_hook(get_index_file(), "prepare-commit-msg",
 890                  git_path("MERGE_MSG"), "merge", NULL, NULL);
 891         if (option_edit) {
 892                 if (launch_editor(git_path("MERGE_MSG"), NULL, NULL))
 893                         abort_commit(NULL);
 894         }
 895         read_merge_msg(&msg);
 896         stripspace(&msg, option_edit);
 897         if (!msg.len)
 898                 abort_commit(_("Empty commit message."));
 899         strbuf_release(&merge_msg);
 900         strbuf_addbuf(&merge_msg, &msg);
 901         strbuf_release(&msg);
 902 }
 903
 904 static int merge_trivial(struct commit *head)
 905 {
 906         unsigned char result_tree[20], result_commit[20];
 907         struct commit_list *parent = xmalloc(sizeof(*parent));
 908
 909         write_tree_trivial(result_tree);
 910         printf(_("Wonderful.\n"));
 911         parent->item = head;
 912         parent->next = xmalloc(sizeof(*parent->next));
 913         parent->next->item = remoteheads->item;
 914         parent->next->next = NULL;
 915         prepare_to_commit();
 916         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 917         finish(head, result_commit, "In-index merge");
 918         drop_save();
 919         return 0;
 920 }
 921
 922 static int finish_automerge(struct commit *head,
 923                             struct commit_list *common,
 924                             unsigned char *result_tree,
 925                             const char *wt_strategy)
 926 {
 927         struct commit_list *parents = NULL, *j;
 928         struct strbuf buf = STRBUF_INIT;
 929         unsigned char result_commit[20];
 930
 931         free_commit_list(common);
 932         if (allow_fast_forward) {
 933                 parents = remoteheads;
 934                 commit_list_insert(head, &parents);
 935                 parents = reduce_heads(parents);
 936         } else {
 937                 struct commit_list **pptr = &parents;
 938
 939                 pptr = &commit_list_insert(head,
 940                                 pptr)->next;
 941                 for (j = remoteheads; j; j = j->next)
 942                         pptr = &commit_list_insert(j->item, pptr)->next;
 943         }
 944         strbuf_addch(&merge_msg, '\n');
 945         prepare_to_commit();
 946         free_commit_list(remoteheads);
 947         commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 948         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 949         finish(head, result_commit, buf.buf);
 950         strbuf_release(&buf);
 951         drop_save();
 952         return 0;
 953 }
 954
 955 static int suggest_conflicts(int renormalizing)
 956 {
 957         const char *filename;
 958         FILE *fp;
 959         int pos;
 960
 961         filename = git_path("MERGE_MSG");
 962         fp = fopen(filename, "a");
 963         if (!fp)
 964                 die_errno(_("Could not open '%s' for writing"), filename);
 965         fprintf(fp, "\nConflicts:\n");
 966         for (pos = 0; pos < active_nr; pos++) {
 967                 struct cache_entry *ce = active_cache[pos];
 968
 969                 if (ce_stage(ce)) {
 970                         fprintf(fp, "\t%s\n", ce->name);
 971                         while (pos + 1 < active_nr &&
 972                                         !strcmp(ce->name,
 973                                                 active_cache[pos + 1]->name))
 974                                 pos++;
 975                 }
 976         }
 977         fclose(fp);
 978         rerere(allow_rerere_auto);
 979         printf(_("Automatic merge failed; "
 980                         "fix conflicts and then commit the result.\n"));
 981         return 1;
 982 }
 983
 984 static struct commit *is_old_style_invocation(int argc, const char **argv,
 985                                               const unsigned char *head)
 986 {
 987         struct commit *second_token = NULL;
 988         if (argc > 2) {
 989                 unsigned char second_sha1[20];
 990
 991                 if (get_sha1(argv[1], second_sha1))
 992                         return NULL;
 993                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 994                 if (!second_token)
 995                         die(_("'%s' is not a commit"), argv[1]);
 996                 if (hashcmp(second_token->object.sha1, head))
 997                         return NULL;
 998         }
 999         return second_token;
1000 }
1001
1002 static int evaluate_result(void)
1003 {
1004         int cnt = 0;
1005         struct rev_info rev;
1006
1007         /* Check how many files differ. */
1008         init_revisions(&rev, "");
1009         setup_revisions(0, NULL, &rev, NULL);
1010         rev.diffopt.output_format |=
1011                 DIFF_FORMAT_CALLBACK;
1012         rev.diffopt.format_callback = count_diff_files;
1013         rev.diffopt.format_callback_data = &cnt;
1014         run_diff_files(&rev, 0);
1015
1016         /*
1017          * Check how many unmerged entries are
1018          * there.
1019          */
1020         cnt += count_unmerged_entries();
1021
1022         return cnt;
1023 }
1024
1025 /*
1026  * Pretend as if the user told us to merge with the tracking
1027  * branch we have for the upstream of the current branch
1028  */
1029 static int setup_with_upstream(const char ***argv)
1030 {
1031         struct branch *branch = branch_get(NULL);
1032         int i;
1033         const char **args;
1034
1035         if (!branch)
1036                 die(_("No current branch."));
1037         if (!branch->remote)
1038                 die(_("No remote for the current branch."));
1039         if (!branch->merge_nr)
1040                 die(_("No default upstream defined for the current branch."));
1041
1042         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
1043         for (i = 0; i < branch->merge_nr; i++) {
1044                 if (!branch->merge[i]->dst)
1045                         die(_("No remote tracking branch for %s from %s"),
1046                             branch->merge[i]->src, branch->remote_name);
1047                 args[i] = branch->merge[i]->dst;
1048         }
1049         args[i] = NULL;
1050         *argv = args;
1051         return i;
1052 }
1053
1054 static void write_merge_state(void)
1055 {
1056         const char *filename;
1057         int fd;
1058         struct commit_list *j;
1059         struct strbuf buf = STRBUF_INIT;
1060
1061         for (j = remoteheads; j; j = j->next)
1062                 strbuf_addf(&buf, "%s\n",
1063                         sha1_to_hex(j->item->object.sha1));
1064         filename = git_path("MERGE_HEAD");
1065         fd = open(filename, O_WRONLY | O_CREAT, 0666);
1066         if (fd < 0)
1067                 die_errno(_("Could not open '%s' for writing"), filename);
1068         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1069                 die_errno(_("Could not write to '%s'"), filename);
1070         close(fd);
1071         strbuf_addch(&merge_msg, '\n');
1072         write_merge_msg(&merge_msg);
1073
1074         filename = git_path("MERGE_MODE");
1075         fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
1076         if (fd < 0)
1077                 die_errno(_("Could not open '%s' for writing"), filename);
1078         strbuf_reset(&buf);
1079         if (!allow_fast_forward)
1080                 strbuf_addf(&buf, "no-ff");
1081         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1082                 die_errno(_("Could not write to '%s'"), filename);
1083         close(fd);
1084 }
1085
1086 int cmd_merge(int argc, const char **argv, const char *prefix)
1087 {
1088         unsigned char result_tree[20];
1089         unsigned char stash[20];
1090         unsigned char head_sha1[20];
1091         struct commit *head_commit;
1092         struct strbuf buf = STRBUF_INIT;
1093         const char *head_arg;
1094         int flag, i;
1095         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1096         struct commit_list *common = NULL;
1097         const char *best_strategy = NULL, *wt_strategy = NULL;
1098         struct commit_list **remotes = &remoteheads;
1099
1100         if (argc == 2 && !strcmp(argv[1], "-h"))
1101                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1102
1103         /*
1104          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1105          * current branch.
1106          */
1107         branch = resolve_ref("HEAD", head_sha1, 0, &flag);
1108         if (branch && !prefixcmp(branch, "refs/heads/"))
1109                 branch += 11;
1110         if (!branch || is_null_sha1(head_sha1))
1111                 head_commit = NULL;
1112         else
1113                 head_commit = lookup_commit_or_die(head_sha1, "HEAD");
1114
1115         git_config(git_merge_config, NULL);
1116
1117         if (branch_mergeoptions)
1118                 parse_branch_merge_options(branch_mergeoptions);
1119         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1120                         builtin_merge_usage, 0);
1121
1122         if (verbosity < 0 && show_progress == -1)
1123                 show_progress = 0;
1124
1125         if (abort_current_merge) {
1126                 int nargc = 2;
1127                 const char *nargv[] = {"reset", "--merge", NULL};
1128
1129                 if (!file_exists(git_path("MERGE_HEAD")))
1130                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1131
1132                 /* Invoke 'git reset --merge' */
1133                 return cmd_reset(nargc, nargv, prefix);
1134         }
1135
1136         if (read_cache_unmerged())
1137                 die_resolve_conflict("merge");
1138
1139         if (file_exists(git_path("MERGE_HEAD"))) {
1140                 /*
1141                  * There is no unmerged entry, don't advise 'git
1142                  * add/rm <file>', just 'git commit'.
1143                  */
1144                 if (advice_resolve_conflict)
1145                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1146                                   "Please, commit your changes before you can merge."));
1147                 else
1148                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1149         }
1150         if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1151                 if (advice_resolve_conflict)
1152                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1153                             "Please, commit your changes before you can merge."));
1154                 else
1155                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1156         }
1157         resolve_undo_clear();
1158
1159         if (verbosity < 0)
1160                 show_diffstat = 0;
1161
1162         if (squash) {
1163                 if (!allow_fast_forward)
1164                         die(_("You cannot combine --squash with --no-ff."));
1165                 option_commit = 0;
1166         }
1167
1168         if (!allow_fast_forward && fast_forward_only)
1169                 die(_("You cannot combine --no-ff with --ff-only."));
1170
1171         if (!abort_current_merge) {
1172                 if (!argc && default_to_upstream)
1173                         argc = setup_with_upstream(&argv);
1174                 else if (argc == 1 && !strcmp(argv[0], "-"))
1175                         argv[0] = "@{-1}";
1176         }
1177         if (!argc)
1178                 usage_with_options(builtin_merge_usage,
1179                         builtin_merge_options);
1180
1181         /*
1182          * This could be traditional "merge <msg> HEAD <commit>..."  and
1183          * the way we can tell it is to see if the second token is HEAD,
1184          * but some people might have misused the interface and used a
1185          * committish that is the same as HEAD there instead.
1186          * Traditional format never would have "-m" so it is an
1187          * additional safety measure to check for it.
1188          */
1189
1190         if (!have_message && head_commit &&
1191             is_old_style_invocation(argc, argv, head_commit->object.sha1)) {
1192                 strbuf_addstr(&merge_msg, argv[0]);
1193                 head_arg = argv[1];
1194                 argv += 2;
1195                 argc -= 2;
1196         } else if (!head_commit) {
1197                 struct object *remote_head;
1198                 /*
1199                  * If the merged head is a valid one there is no reason
1200                  * to forbid "git merge" into a branch yet to be born.
1201                  * We do the same for "git pull".
1202                  */
1203                 if (argc != 1)
1204                         die(_("Can merge only exactly one commit into "
1205                                 "empty head"));
1206                 if (squash)
1207                         die(_("Squash commit into empty head not supported yet"));
1208                 if (!allow_fast_forward)
1209                         die(_("Non-fast-forward commit does not make sense into "
1210                             "an empty head"));
1211                 remote_head = want_commit(argv[0]);
1212                 if (!remote_head)
1213                         die(_("%s - not something we can merge"), argv[0]);
1214                 read_empty(remote_head->sha1, 0);
1215                 update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
1216                                 DIE_ON_ERR);
1217                 return 0;
1218         } else {
1219                 struct strbuf merge_names = STRBUF_INIT;
1220
1221                 /* We are invoked directly as the first-class UI. */
1222                 head_arg = "HEAD";
1223
1224                 /*
1225                  * All the rest are the commits being merged;
1226                  * prepare the standard merge summary message to
1227                  * be appended to the given message.  If remote
1228                  * is invalid we will die later in the common
1229                  * codepath so we discard the error in this
1230                  * loop.
1231                  */
1232                 for (i = 0; i < argc; i++)
1233                         merge_name(argv[i], &merge_names);
1234
1235                 if (!have_message || shortlog_len) {
1236                         fmt_merge_msg(&merge_names, &merge_msg, !have_message,
1237                                       shortlog_len);
1238                         if (merge_msg.len)
1239                                 strbuf_setlen(&merge_msg, merge_msg.len - 1);
1240                 }
1241         }
1242
1243         if (!head_commit || !argc)
1244                 usage_with_options(builtin_merge_usage,
1245                         builtin_merge_options);
1246
1247         strbuf_addstr(&buf, "merge");
1248         for (i = 0; i < argc; i++)
1249                 strbuf_addf(&buf, " %s", argv[i]);
1250         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1251         strbuf_reset(&buf);
1252
1253         for (i = 0; i < argc; i++) {
1254                 struct object *o;
1255                 struct commit *commit;
1256
1257                 o = want_commit(argv[i]);
1258                 if (!o)
1259                         die(_("%s - not something we can merge"), argv[i]);
1260                 commit = lookup_commit(o->sha1);
1261                 commit->util = (void *)argv[i];
1262                 remotes = &commit_list_insert(commit, remotes)->next;
1263
1264                 strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
1265                 setenv(buf.buf, argv[i], 1);
1266                 strbuf_reset(&buf);
1267         }
1268
1269         if (!use_strategies) {
1270                 if (!remoteheads->next)
1271                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1272                 else
1273                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1274         }
1275
1276         for (i = 0; i < use_strategies_nr; i++) {
1277                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1278                         allow_fast_forward = 0;
1279                 if (use_strategies[i]->attr & NO_TRIVIAL)
1280                         allow_trivial = 0;
1281         }
1282
1283         if (!remoteheads->next)
1284                 common = get_merge_bases(head_commit, remoteheads->item, 1);
1285         else {
1286                 struct commit_list *list = remoteheads;
1287                 commit_list_insert(head_commit, &list);
1288                 common = get_octopus_merge_bases(list);
1289                 free(list);
1290         }
1291
1292         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
1293                    NULL, 0, DIE_ON_ERR);
1294
1295         if (!common)
1296                 ; /* No common ancestors found. We need a real merge. */
1297         else if (!remoteheads->next && !common->next &&
1298                         common->item == remoteheads->item) {
1299                 /*
1300                  * If head can reach all the merge then we are up to date.
1301                  * but first the most common case of merging one remote.
1302                  */
1303                 finish_up_to_date("Already up-to-date.");
1304                 return 0;
1305         } else if (allow_fast_forward && !remoteheads->next &&
1306                         !common->next &&
1307                         !hashcmp(common->item->object.sha1, head_commit->object.sha1)) {
1308                 /* Again the most common case of merging one remote. */
1309                 struct strbuf msg = STRBUF_INIT;
1310                 struct object *o;
1311                 char hex[41];
1312
1313                 strcpy(hex, find_unique_abbrev(head_commit->object.sha1, DEFAULT_ABBREV));
1314
1315                 if (verbosity >= 0)
1316                         printf(_("Updating %s..%s\n"),
1317                                 hex,
1318                                 find_unique_abbrev(remoteheads->item->object.sha1,
1319                                 DEFAULT_ABBREV));
1320                 strbuf_addstr(&msg, "Fast-forward");
1321                 if (have_message)
1322                         strbuf_addstr(&msg,
1323                                 " (no commit created; -m option ignored)");
1324                 o = want_commit(sha1_to_hex(remoteheads->item->object.sha1));
1325                 if (!o)
1326                         return 1;
1327
1328                 if (checkout_fast_forward(head_commit->object.sha1, remoteheads->item->object.sha1))
1329                         return 1;
1330
1331                 finish(head_commit, o->sha1, msg.buf);
1332                 drop_save();
1333                 return 0;
1334         } else if (!remoteheads->next && common->next)
1335                 ;
1336                 /*
1337                  * We are not doing octopus and not fast-forward.  Need
1338                  * a real merge.
1339                  */
1340         else if (!remoteheads->next && !common->next && option_commit) {
1341                 /*
1342                  * We are not doing octopus, not fast-forward, and have
1343                  * only one common.
1344                  */
1345                 refresh_cache(REFRESH_QUIET);
1346                 if (allow_trivial && !fast_forward_only) {
1347                         /* See if it is really trivial. */
1348                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1349                         printf(_("Trying really trivial in-index merge...\n"));
1350                         if (!read_tree_trivial(common->item->object.sha1,
1351                                         head_commit->object.sha1, remoteheads->item->object.sha1))
1352                                 return merge_trivial(head_commit);
1353                         printf(_("Nope.\n"));
1354                 }
1355         } else {
1356                 /*
1357                  * An octopus.  If we can reach all the remote we are up
1358                  * to date.
1359                  */
1360                 int up_to_date = 1;
1361                 struct commit_list *j;
1362
1363                 for (j = remoteheads; j; j = j->next) {
1364                         struct commit_list *common_one;
1365
1366                         /*
1367                          * Here we *have* to calculate the individual
1368                          * merge_bases again, otherwise "git merge HEAD^
1369                          * HEAD^^" would be missed.
1370                          */
1371                         common_one = get_merge_bases(head_commit, j->item, 1);
1372                         if (hashcmp(common_one->item->object.sha1,
1373                                 j->item->object.sha1)) {
1374                                 up_to_date = 0;
1375                                 break;
1376                         }
1377                 }
1378                 if (up_to_date) {
1379                         finish_up_to_date("Already up-to-date. Yeeah!");
1380                         return 0;
1381                 }
1382         }
1383
1384         if (fast_forward_only)
1385                 die(_("Not possible to fast-forward, aborting."));
1386
1387         /* We are going to make a new commit. */
1388         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1389
1390         /*
1391          * At this point, we need a real merge.  No matter what strategy
1392          * we use, it would operate on the index, possibly affecting the
1393          * working tree, and when resolved cleanly, have the desired
1394          * tree in the index -- this means that the index must be in
1395          * sync with the head commit.  The strategies are responsible
1396          * to ensure this.
1397          */
1398         if (use_strategies_nr == 1 ||
1399             /*
1400              * Stash away the local changes so that we can try more than one.
1401              */
1402             save_state(stash))
1403                 hashcpy(stash, null_sha1);
1404
1405         for (i = 0; i < use_strategies_nr; i++) {
1406                 int ret;
1407                 if (i) {
1408                         printf(_("Rewinding the tree to pristine...\n"));
1409                         restore_state(head_commit->object.sha1, stash);
1410                 }
1411                 if (use_strategies_nr != 1)
1412                         printf(_("Trying merge strategy %s...\n"),
1413                                 use_strategies[i]->name);
1414                 /*
1415                  * Remember which strategy left the state in the working
1416                  * tree.
1417                  */
1418                 wt_strategy = use_strategies[i]->name;
1419
1420                 ret = try_merge_strategy(use_strategies[i]->name,
1421                                          common, head_commit, head_arg);
1422                 if (!option_commit && !ret) {
1423                         merge_was_ok = 1;
1424                         /*
1425                          * This is necessary here just to avoid writing
1426                          * the tree, but later we will *not* exit with
1427                          * status code 1 because merge_was_ok is set.
1428                          */
1429                         ret = 1;
1430                 }
1431
1432                 if (ret) {
1433                         /*
1434                          * The backend exits with 1 when conflicts are
1435                          * left to be resolved, with 2 when it does not
1436                          * handle the given merge at all.
1437                          */
1438                         if (ret == 1) {
1439                                 int cnt = evaluate_result();
1440
1441                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1442                                         best_strategy = use_strategies[i]->name;
1443                                         best_cnt = cnt;
1444                                 }
1445                         }
1446                         if (merge_was_ok)
1447                                 break;
1448                         else
1449                                 continue;
1450                 }
1451
1452                 /* Automerge succeeded. */
1453                 write_tree_trivial(result_tree);
1454                 automerge_was_ok = 1;
1455                 break;
1456         }
1457
1458         /*
1459          * If we have a resulting tree, that means the strategy module
1460          * auto resolved the merge cleanly.
1461          */
1462         if (automerge_was_ok)
1463                 return finish_automerge(head_commit, common, result_tree,
1464                                         wt_strategy);
1465
1466         /*
1467          * Pick the result from the best strategy and have the user fix
1468          * it up.
1469          */
1470         if (!best_strategy) {
1471                 restore_state(head_commit->object.sha1, stash);
1472                 if (use_strategies_nr > 1)
1473                         fprintf(stderr,
1474                                 _("No merge strategy handled the merge.\n"));
1475                 else
1476                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1477                                 use_strategies[0]->name);
1478                 return 2;
1479         } else if (best_strategy == wt_strategy)
1480                 ; /* We already have its result in the working tree. */
1481         else {
1482                 printf(_("Rewinding the tree to pristine...\n"));
1483                 restore_state(head_commit->object.sha1, stash);
1484                 printf(_("Using the %s to prepare resolving by hand.\n"),
1485                         best_strategy);
1486                 try_merge_strategy(best_strategy, common, head_commit, head_arg);
1487         }
1488
1489         if (squash)
1490                 finish(head_commit, NULL, NULL);
1491         else
1492                 write_merge_state();
1493
1494         if (merge_was_ok) {
1495                 fprintf(stderr, _("Automatic merge went well; "
1496                         "stopped before committing as requested\n"));
1497                 return 0;
1498         } else
1499                 return suggest_conflicts(option_renormalize);
1500 }