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 #include "fmt-merge-msg.h"
  30
  31 #define DEFAULT_TWOHEAD (1<<0)
  32 #define DEFAULT_OCTOPUS (1<<1)
  33 #define NO_FAST_FORWARD (1<<2)
  34 #define NO_TRIVIAL      (1<<3)
  35
  36 struct strategy {
  37         const char *name;
  38         unsigned attr;
  39 };
  40
  41 static const char * const builtin_merge_usage[] = {
  42         "git merge [options] [<commit>...]",
  43         "git merge [options] <msg> HEAD <commit>",
  44         "git merge --abort",
  45         NULL
  46 };
  47
  48 static int show_diffstat = 1, shortlog_len = -1, squash;
  49 static int option_commit = 1, allow_fast_forward = 1;
  50 static int fast_forward_only, option_edit;
  51 static int allow_trivial = 1, have_message;
  52 static int overwrite_ignore = 1;
  53 static struct strbuf merge_msg = STRBUF_INIT;
  54 static struct commit_list *remoteheads;
  55 static struct strategy **use_strategies;
  56 static size_t use_strategies_nr, use_strategies_alloc;
  57 static const char **xopts;
  58 static size_t xopts_nr, xopts_alloc;
  59 static const char *branch;
  60 static char *branch_mergeoptions;
  61 static int option_renormalize;
  62 static int verbosity;
  63 static int allow_rerere_auto;
  64 static int abort_current_merge;
  65 static int show_progress = -1;
  66 static int default_to_upstream;
  67
  68 static struct strategy all_strategy[] = {
  69         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  70         { "octopus",    DEFAULT_OCTOPUS },
  71         { "resolve",    0 },
  72         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  73         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  74 };
  75
  76 static const char *pull_twohead, *pull_octopus;
  77
  78 static int option_parse_message(const struct option *opt,
  79                                 const char *arg, int unset)
  80 {
  81         struct strbuf *buf = opt->value;
  82
  83         if (unset)
  84                 strbuf_setlen(buf, 0);
  85         else if (arg) {
  86                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  87                 have_message = 1;
  88         } else
  89                 return error(_("switch `m' requires a value"));
  90         return 0;
  91 }
  92
  93 static struct strategy *get_strategy(const char *name)
  94 {
  95         int i;
  96         struct strategy *ret;
  97         static struct cmdnames main_cmds, other_cmds;
  98         static int loaded;
  99
 100         if (!name)
 101                 return NULL;
 102
 103         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 104                 if (!strcmp(name, all_strategy[i].name))
 105                         return &all_strategy[i];
 106
 107         if (!loaded) {
 108                 struct cmdnames not_strategies;
 109                 loaded = 1;
 110
 111                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 112                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 113                 for (i = 0; i < main_cmds.cnt; i++) {
 114                         int j, found = 0;
 115                         struct cmdname *ent = main_cmds.names[i];
 116                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 117                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 118                                                 && !all_strategy[j].name[ent->len])
 119                                         found = 1;
 120                         if (!found)
 121                                 add_cmdname(&not_strategies, ent->name, ent->len);
 122                 }
 123                 exclude_cmds(&main_cmds, &not_strategies);
 124         }
 125         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 126                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 127                 fprintf(stderr, _("Available strategies are:"));
 128                 for (i = 0; i < main_cmds.cnt; i++)
 129                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 130                 fprintf(stderr, ".\n");
 131                 if (other_cmds.cnt) {
 132                         fprintf(stderr, _("Available custom strategies are:"));
 133                         for (i = 0; i < other_cmds.cnt; i++)
 134                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 135                         fprintf(stderr, ".\n");
 136                 }
 137                 exit(1);
 138         }
 139
 140         ret = xcalloc(1, sizeof(struct strategy));
 141         ret->name = xstrdup(name);
 142         ret->attr = NO_TRIVIAL;
 143         return ret;
 144 }
 145
 146 static void append_strategy(struct strategy *s)
 147 {
 148         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 149         use_strategies[use_strategies_nr++] = s;
 150 }
 151
 152 static int option_parse_strategy(const struct option *opt,
 153                                  const char *name, int unset)
 154 {
 155         if (unset)
 156                 return 0;
 157
 158         append_strategy(get_strategy(name));
 159         return 0;
 160 }
 161
 162 static int option_parse_x(const struct option *opt,
 163                           const char *arg, int unset)
 164 {
 165         if (unset)
 166                 return 0;
 167
 168         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 169         xopts[xopts_nr++] = xstrdup(arg);
 170         return 0;
 171 }
 172
 173 static int option_parse_n(const struct option *opt,
 174                           const char *arg, int unset)
 175 {
 176         show_diffstat = unset;
 177         return 0;
 178 }
 179
 180 static struct option builtin_merge_options[] = {
 181         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 182                 "do not show a diffstat at the end of the merge",
 183                 PARSE_OPT_NOARG, option_parse_n },
 184         OPT_BOOLEAN(0, "stat", &show_diffstat,
 185                 "show a diffstat at the end of the merge"),
 186         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 187         { OPTION_INTEGER, 0, "log", &shortlog_len, "n",
 188           "add (at most <n>) entries from shortlog to merge commit message",
 189           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 190         OPT_BOOLEAN(0, "squash", &squash,
 191                 "create a single commit instead of doing a merge"),
 192         OPT_BOOLEAN(0, "commit", &option_commit,
 193                 "perform a commit if the merge succeeds (default)"),
 194         OPT_BOOLEAN('e', "edit", &option_edit,
 195                 "edit message before committing"),
 196         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 197                 "allow fast-forward (default)"),
 198         OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
 199                 "abort if fast-forward is not possible"),
 200         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 201         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
 202                 "merge strategy to use", option_parse_strategy),
 203         OPT_CALLBACK('X', "strategy-option", &xopts, "option=value",
 204                 "option for selected merge strategy", option_parse_x),
 205         OPT_CALLBACK('m', "message", &merge_msg, "message",
 206                 "merge commit message (for a non-fast-forward merge)",
 207                 option_parse_message),
 208         OPT__VERBOSITY(&verbosity),
 209         OPT_BOOLEAN(0, "abort", &abort_current_merge,
 210                 "abort the current in-progress merge"),
 211         OPT_SET_INT(0, "progress", &show_progress, "force progress reporting", 1),
 212         OPT_BOOLEAN(0, "overwrite-ignore", &overwrite_ignore, "update ignored files (default)"),
 213         OPT_END()
 214 };
 215
 216 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 217 static void drop_save(void)
 218 {
 219         unlink(git_path("MERGE_HEAD"));
 220         unlink(git_path("MERGE_MSG"));
 221         unlink(git_path("MERGE_MODE"));
 222 }
 223
 224 static int save_state(unsigned char *stash)
 225 {
 226         int len;
 227         struct child_process cp;
 228         struct strbuf buffer = STRBUF_INIT;
 229         const char *argv[] = {"stash", "create", NULL};
 230
 231         memset(&cp, 0, sizeof(cp));
 232         cp.argv = argv;
 233         cp.out = -1;
 234         cp.git_cmd = 1;
 235
 236         if (start_command(&cp))
 237                 die(_("could not run stash."));
 238         len = strbuf_read(&buffer, cp.out, 1024);
 239         close(cp.out);
 240
 241         if (finish_command(&cp) || len < 0)
 242                 die(_("stash failed"));
 243         else if (!len)          /* no changes */
 244                 return -1;
 245         strbuf_setlen(&buffer, buffer.len-1);
 246         if (get_sha1(buffer.buf, stash))
 247                 die(_("not a valid object: %s"), buffer.buf);
 248         return 0;
 249 }
 250
 251 static void read_empty(unsigned const char *sha1, int verbose)
 252 {
 253         int i = 0;
 254         const char *args[7];
 255
 256         args[i++] = "read-tree";
 257         if (verbose)
 258                 args[i++] = "-v";
 259         args[i++] = "-m";
 260         args[i++] = "-u";
 261         args[i++] = EMPTY_TREE_SHA1_HEX;
 262         args[i++] = sha1_to_hex(sha1);
 263         args[i] = NULL;
 264
 265         if (run_command_v_opt(args, RUN_GIT_CMD))
 266                 die(_("read-tree failed"));
 267 }
 268
 269 static void reset_hard(unsigned const char *sha1, int verbose)
 270 {
 271         int i = 0;
 272         const char *args[6];
 273
 274         args[i++] = "read-tree";
 275         if (verbose)
 276                 args[i++] = "-v";
 277         args[i++] = "--reset";
 278         args[i++] = "-u";
 279         args[i++] = sha1_to_hex(sha1);
 280         args[i] = NULL;
 281
 282         if (run_command_v_opt(args, RUN_GIT_CMD))
 283                 die(_("read-tree failed"));
 284 }
 285
 286 static void restore_state(const unsigned char *head,
 287                           const unsigned char *stash)
 288 {
 289         struct strbuf sb = STRBUF_INIT;
 290         const char *args[] = { "stash", "apply", NULL, NULL };
 291
 292         if (is_null_sha1(stash))
 293                 return;
 294
 295         reset_hard(head, 1);
 296
 297         args[2] = sha1_to_hex(stash);
 298
 299         /*
 300          * It is OK to ignore error here, for example when there was
 301          * nothing to restore.
 302          */
 303         run_command_v_opt(args, RUN_GIT_CMD);
 304
 305         strbuf_release(&sb);
 306         refresh_cache(REFRESH_QUIET);
 307 }
 308
 309 /* This is called when no merge was necessary. */
 310 static void finish_up_to_date(const char *msg)
 311 {
 312         if (verbosity >= 0)
 313                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 314         drop_save();
 315 }
 316
 317 static void squash_message(struct commit *commit)
 318 {
 319         struct rev_info rev;
 320         struct strbuf out = STRBUF_INIT;
 321         struct commit_list *j;
 322         const char *filename;
 323         int fd;
 324         struct pretty_print_context ctx = {0};
 325
 326         printf(_("Squash commit -- not updating HEAD\n"));
 327         filename = git_path("SQUASH_MSG");
 328         fd = open(filename, O_WRONLY | O_CREAT, 0666);
 329         if (fd < 0)
 330                 die_errno(_("Could not write to '%s'"), filename);
 331
 332         init_revisions(&rev, NULL);
 333         rev.ignore_merges = 1;
 334         rev.commit_format = CMIT_FMT_MEDIUM;
 335
 336         commit->object.flags |= UNINTERESTING;
 337         add_pending_object(&rev, &commit->object, NULL);
 338
 339         for (j = remoteheads; j; j = j->next)
 340                 add_pending_object(&rev, &j->item->object, NULL);
 341
 342         setup_revisions(0, NULL, &rev, NULL);
 343         if (prepare_revision_walk(&rev))
 344                 die(_("revision walk setup failed"));
 345
 346         ctx.abbrev = rev.abbrev;
 347         ctx.date_mode = rev.date_mode;
 348         ctx.fmt = rev.commit_format;
 349
 350         strbuf_addstr(&out, "Squashed commit of the following:\n");
 351         while ((commit = get_revision(&rev)) != NULL) {
 352                 strbuf_addch(&out, '\n');
 353                 strbuf_addf(&out, "commit %s\n",
 354                         sha1_to_hex(commit->object.sha1));
 355                 pretty_print_commit(&ctx, commit, &out);
 356         }
 357         if (write(fd, out.buf, out.len) < 0)
 358                 die_errno(_("Writing SQUASH_MSG"));
 359         if (close(fd))
 360                 die_errno(_("Finishing SQUASH_MSG"));
 361         strbuf_release(&out);
 362 }
 363
 364 static void finish(struct commit *head_commit,
 365                    const unsigned char *new_head, const char *msg)
 366 {
 367         struct strbuf reflog_message = STRBUF_INIT;
 368         const unsigned char *head = head_commit->object.sha1;
 369
 370         if (!msg)
 371                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 372         else {
 373                 if (verbosity >= 0)
 374                         printf("%s\n", msg);
 375                 strbuf_addf(&reflog_message, "%s: %s",
 376                         getenv("GIT_REFLOG_ACTION"), msg);
 377         }
 378         if (squash) {
 379                 squash_message(head_commit);
 380         } else {
 381                 if (verbosity >= 0 && !merge_msg.len)
 382                         printf(_("No merge message -- not updating HEAD\n"));
 383                 else {
 384                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 385                         update_ref(reflog_message.buf, "HEAD",
 386                                 new_head, head, 0,
 387                                 DIE_ON_ERR);
 388                         /*
 389                          * We ignore errors in 'gc --auto', since the
 390                          * user should see them.
 391                          */
 392                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 393                 }
 394         }
 395         if (new_head && show_diffstat) {
 396                 struct diff_options opts;
 397                 diff_setup(&opts);
 398                 opts.output_format |=
 399                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 400                 opts.detect_rename = DIFF_DETECT_RENAME;
 401                 if (diff_setup_done(&opts) < 0)
 402                         die(_("diff_setup_done failed"));
 403                 diff_tree_sha1(head, new_head, "", &opts);
 404                 diffcore_std(&opts);
 405                 diff_flush(&opts);
 406         }
 407
 408         /* Run a post-merge hook */
 409         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
 410
 411         strbuf_release(&reflog_message);
 412 }
 413
 414 /* Get the name for the merge commit's message. */
 415 static void merge_name(const char *remote, struct strbuf *msg)
 416 {
 417         struct commit *remote_head;
 418         unsigned char branch_head[20];
 419         struct strbuf buf = STRBUF_INIT;
 420         struct strbuf bname = STRBUF_INIT;
 421         const char *ptr;
 422         char *found_ref;
 423         int len, early;
 424
 425         strbuf_branchname(&bname, remote);
 426         remote = bname.buf;
 427
 428         memset(branch_head, 0, sizeof(branch_head));
 429         remote_head = get_merge_parent(remote);
 430         if (!remote_head)
 431                 die(_("'%s' does not point to a commit"), remote);
 432
 433         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 434                 if (!prefixcmp(found_ref, "refs/heads/")) {
 435                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 436                                     sha1_to_hex(branch_head), remote);
 437                         goto cleanup;
 438                 }
 439                 if (!prefixcmp(found_ref, "refs/tags/")) {
 440                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 441                                     sha1_to_hex(branch_head), remote);
 442                         goto cleanup;
 443                 }
 444                 if (!prefixcmp(found_ref, "refs/remotes/")) {
 445                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 446                                     sha1_to_hex(branch_head), remote);
 447                         goto cleanup;
 448                 }
 449         }
 450
 451         /* See if remote matches <name>^^^.. or <name>~<number> */
 452         for (len = 0, ptr = remote + strlen(remote);
 453              remote < ptr && ptr[-1] == '^';
 454              ptr--)
 455                 len++;
 456         if (len)
 457                 early = 1;
 458         else {
 459                 early = 0;
 460                 ptr = strrchr(remote, '~');
 461                 if (ptr) {
 462                         int seen_nonzero = 0;
 463
 464                         len++; /* count ~ */
 465                         while (*++ptr && isdigit(*ptr)) {
 466                                 seen_nonzero |= (*ptr != '0');
 467                                 len++;
 468                         }
 469                         if (*ptr)
 470                                 len = 0; /* not ...~<number> */
 471                         else if (seen_nonzero)
 472                                 early = 1;
 473                         else if (len == 1)
 474                                 early = 1; /* "name~" is "name~1"! */
 475                 }
 476         }
 477         if (len) {
 478                 struct strbuf truname = STRBUF_INIT;
 479                 strbuf_addstr(&truname, "refs/heads/");
 480                 strbuf_addstr(&truname, remote);
 481                 strbuf_setlen(&truname, truname.len - len);
 482                 if (ref_exists(truname.buf)) {
 483                         strbuf_addf(msg,
 484                                     "%s\t\tbranch '%s'%s of .\n",
 485                                     sha1_to_hex(remote_head->object.sha1),
 486                                     truname.buf + 11,
 487                                     (early ? " (early part)" : ""));
 488                         strbuf_release(&truname);
 489                         goto cleanup;
 490                 }
 491         }
 492
 493         if (!strcmp(remote, "FETCH_HEAD") &&
 494                         !access(git_path("FETCH_HEAD"), R_OK)) {
 495                 const char *filename;
 496                 FILE *fp;
 497                 struct strbuf line = STRBUF_INIT;
 498                 char *ptr;
 499
 500                 filename = git_path("FETCH_HEAD");
 501                 fp = fopen(filename, "r");
 502                 if (!fp)
 503                         die_errno(_("could not open '%s' for reading"),
 504                                   filename);
 505                 strbuf_getline(&line, fp, '\n');
 506                 fclose(fp);
 507                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 508                 if (ptr)
 509                         strbuf_remove(&line, ptr-line.buf+1, 13);
 510                 strbuf_addbuf(msg, &line);
 511                 strbuf_release(&line);
 512                 goto cleanup;
 513         }
 514         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 515                 sha1_to_hex(remote_head->object.sha1), remote);
 516 cleanup:
 517         strbuf_release(&buf);
 518         strbuf_release(&bname);
 519 }
 520
 521 static void parse_branch_merge_options(char *bmo)
 522 {
 523         const char **argv;
 524         int argc;
 525
 526         if (!bmo)
 527                 return;
 528         argc = split_cmdline(bmo, &argv);
 529         if (argc < 0)
 530                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 531                     split_cmdline_strerror(argc));
 532         argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 533         memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 534         argc++;
 535         argv[0] = "branch.*.mergeoptions";
 536         parse_options(argc, argv, NULL, builtin_merge_options,
 537                       builtin_merge_usage, 0);
 538         free(argv);
 539 }
 540
 541 static int git_merge_config(const char *k, const char *v, void *cb)
 542 {
 543         int status;
 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.ff")) {
 562                 int boolval = git_config_maybe_bool(k, v);
 563                 if (0 <= boolval) {
 564                         allow_fast_forward = boolval;
 565                 } else if (v && !strcmp(v, "only")) {
 566                         allow_fast_forward = 1;
 567                         fast_forward_only = 1;
 568                 } /* do not barf on values from future versions of git */
 569                 return 0;
 570         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 571                 default_to_upstream = git_config_bool(k, v);
 572                 return 0;
 573         }
 574         status = fmt_merge_msg_config(k, v, cb);
 575         if (status)
 576                 return status;
 577         return git_diff_ui_config(k, v, cb);
 578 }
 579
 580 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 581                              unsigned char *one)
 582 {
 583         int i, nr_trees = 0;
 584         struct tree *trees[MAX_UNPACK_TREES];
 585         struct tree_desc t[MAX_UNPACK_TREES];
 586         struct unpack_trees_options opts;
 587
 588         memset(&opts, 0, sizeof(opts));
 589         opts.head_idx = 2;
 590         opts.src_index = &the_index;
 591         opts.dst_index = &the_index;
 592         opts.update = 1;
 593         opts.verbose_update = 1;
 594         opts.trivial_merges_only = 1;
 595         opts.merge = 1;
 596         trees[nr_trees] = parse_tree_indirect(common);
 597         if (!trees[nr_trees++])
 598                 return -1;
 599         trees[nr_trees] = parse_tree_indirect(head);
 600         if (!trees[nr_trees++])
 601                 return -1;
 602         trees[nr_trees] = parse_tree_indirect(one);
 603         if (!trees[nr_trees++])
 604                 return -1;
 605         opts.fn = threeway_merge;
 606         cache_tree_free(&active_cache_tree);
 607         for (i = 0; i < nr_trees; i++) {
 608                 parse_tree(trees[i]);
 609                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 610         }
 611         if (unpack_trees(nr_trees, t, &opts))
 612                 return -1;
 613         return 0;
 614 }
 615
 616 static void write_tree_trivial(unsigned char *sha1)
 617 {
 618         if (write_cache_as_tree(sha1, 0, NULL))
 619                 die(_("git write-tree failed to write a tree"));
 620 }
 621
 622 static const char *merge_argument(struct commit *commit)
 623 {
 624         if (commit)
 625                 return sha1_to_hex(commit->object.sha1);
 626         else
 627                 return EMPTY_TREE_SHA1_HEX;
 628 }
 629
 630 int try_merge_command(const char *strategy, size_t xopts_nr,
 631                       const char **xopts, struct commit_list *common,
 632                       const char *head_arg, struct commit_list *remotes)
 633 {
 634         const char **args;
 635         int i = 0, x = 0, ret;
 636         struct commit_list *j;
 637         struct strbuf buf = STRBUF_INIT;
 638
 639         args = xmalloc((4 + xopts_nr + commit_list_count(common) +
 640                         commit_list_count(remotes)) * sizeof(char *));
 641         strbuf_addf(&buf, "merge-%s", strategy);
 642         args[i++] = buf.buf;
 643         for (x = 0; x < xopts_nr; x++) {
 644                 char *s = xmalloc(strlen(xopts[x])+2+1);
 645                 strcpy(s, "--");
 646                 strcpy(s+2, xopts[x]);
 647                 args[i++] = s;
 648         }
 649         for (j = common; j; j = j->next)
 650                 args[i++] = xstrdup(merge_argument(j->item));
 651         args[i++] = "--";
 652         args[i++] = head_arg;
 653         for (j = remotes; j; j = j->next)
 654                 args[i++] = xstrdup(merge_argument(j->item));
 655         args[i] = NULL;
 656         ret = run_command_v_opt(args, RUN_GIT_CMD);
 657         strbuf_release(&buf);
 658         i = 1;
 659         for (x = 0; x < xopts_nr; x++)
 660                 free((void *)args[i++]);
 661         for (j = common; j; j = j->next)
 662                 free((void *)args[i++]);
 663         i += 2;
 664         for (j = remotes; j; j = j->next)
 665                 free((void *)args[i++]);
 666         free(args);
 667         discard_cache();
 668         if (read_cache() < 0)
 669                 die(_("failed to read the cache"));
 670         resolve_undo_clear();
 671
 672         return ret;
 673 }
 674
 675 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 676                               struct commit *head, const char *head_arg)
 677 {
 678         int index_fd;
 679         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 680
 681         index_fd = hold_locked_index(lock, 1);
 682         refresh_cache(REFRESH_QUIET);
 683         if (active_cache_changed &&
 684                         (write_cache(index_fd, active_cache, active_nr) ||
 685                          commit_locked_index(lock)))
 686                 return error(_("Unable to write index."));
 687         rollback_lock_file(lock);
 688
 689         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 690                 int clean, x;
 691                 struct commit *result;
 692                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 693                 int index_fd;
 694                 struct commit_list *reversed = NULL;
 695                 struct merge_options o;
 696                 struct commit_list *j;
 697
 698                 if (remoteheads->next) {
 699                         error(_("Not handling anything other than two heads merge."));
 700                         return 2;
 701                 }
 702
 703                 init_merge_options(&o);
 704                 if (!strcmp(strategy, "subtree"))
 705                         o.subtree_shift = "";
 706
 707                 o.renormalize = option_renormalize;
 708                 o.show_rename_progress =
 709                         show_progress == -1 ? isatty(2) : show_progress;
 710
 711                 for (x = 0; x < xopts_nr; x++)
 712                         if (parse_merge_opt(&o, xopts[x]))
 713                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 714
 715                 o.branch1 = head_arg;
 716                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 717
 718                 for (j = common; j; j = j->next)
 719                         commit_list_insert(j->item, &reversed);
 720
 721                 index_fd = hold_locked_index(lock, 1);
 722                 clean = merge_recursive(&o, head,
 723                                 remoteheads->item, reversed, &result);
 724                 if (active_cache_changed &&
 725                                 (write_cache(index_fd, active_cache, active_nr) ||
 726                                  commit_locked_index(lock)))
 727                         die (_("unable to write %s"), get_index_file());
 728                 rollback_lock_file(lock);
 729                 return clean ? 0 : 1;
 730         } else {
 731                 return try_merge_command(strategy, xopts_nr, xopts,
 732                                                 common, head_arg, remoteheads);
 733         }
 734 }
 735
 736 static void count_diff_files(struct diff_queue_struct *q,
 737                              struct diff_options *opt, void *data)
 738 {
 739         int *count = data;
 740
 741         (*count) += q->nr;
 742 }
 743
 744 static int count_unmerged_entries(void)
 745 {
 746         int i, ret = 0;
 747
 748         for (i = 0; i < active_nr; i++)
 749                 if (ce_stage(active_cache[i]))
 750                         ret++;
 751
 752         return ret;
 753 }
 754
 755 int checkout_fast_forward(const unsigned char *head, const unsigned char *remote)
 756 {
 757         struct tree *trees[MAX_UNPACK_TREES];
 758         struct unpack_trees_options opts;
 759         struct tree_desc t[MAX_UNPACK_TREES];
 760         int i, fd, nr_trees = 0;
 761         struct dir_struct dir;
 762         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 763
 764         refresh_cache(REFRESH_QUIET);
 765
 766         fd = hold_locked_index(lock_file, 1);
 767
 768         memset(&trees, 0, sizeof(trees));
 769         memset(&opts, 0, sizeof(opts));
 770         memset(&t, 0, sizeof(t));
 771         if (overwrite_ignore) {
 772                 memset(&dir, 0, sizeof(dir));
 773                 dir.flags |= DIR_SHOW_IGNORED;
 774                 setup_standard_excludes(&dir);
 775                 opts.dir = &dir;
 776         }
 777
 778         opts.head_idx = 1;
 779         opts.src_index = &the_index;
 780         opts.dst_index = &the_index;
 781         opts.update = 1;
 782         opts.verbose_update = 1;
 783         opts.merge = 1;
 784         opts.fn = twoway_merge;
 785         setup_unpack_trees_porcelain(&opts, "merge");
 786
 787         trees[nr_trees] = parse_tree_indirect(head);
 788         if (!trees[nr_trees++])
 789                 return -1;
 790         trees[nr_trees] = parse_tree_indirect(remote);
 791         if (!trees[nr_trees++])
 792                 return -1;
 793         for (i = 0; i < nr_trees; i++) {
 794                 parse_tree(trees[i]);
 795                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 796         }
 797         if (unpack_trees(nr_trees, t, &opts))
 798                 return -1;
 799         if (write_cache(fd, active_cache, active_nr) ||
 800                 commit_locked_index(lock_file))
 801                 die(_("unable to write new index file"));
 802         return 0;
 803 }
 804
 805 static void split_merge_strategies(const char *string, struct strategy **list,
 806                                    int *nr, int *alloc)
 807 {
 808         char *p, *q, *buf;
 809
 810         if (!string)
 811                 return;
 812
 813         buf = xstrdup(string);
 814         q = buf;
 815         for (;;) {
 816                 p = strchr(q, ' ');
 817                 if (!p) {
 818                         ALLOC_GROW(*list, *nr + 1, *alloc);
 819                         (*list)[(*nr)++].name = xstrdup(q);
 820                         free(buf);
 821                         return;
 822                 } else {
 823                         *p = '\0';
 824                         ALLOC_GROW(*list, *nr + 1, *alloc);
 825                         (*list)[(*nr)++].name = xstrdup(q);
 826                         q = ++p;
 827                 }
 828         }
 829 }
 830
 831 static void add_strategies(const char *string, unsigned attr)
 832 {
 833         struct strategy *list = NULL;
 834         int list_alloc = 0, list_nr = 0, i;
 835
 836         memset(&list, 0, sizeof(list));
 837         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 838         if (list) {
 839                 for (i = 0; i < list_nr; i++)
 840                         append_strategy(get_strategy(list[i].name));
 841                 return;
 842         }
 843         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 844                 if (all_strategy[i].attr & attr)
 845                         append_strategy(&all_strategy[i]);
 846
 847 }
 848
 849 static void write_merge_msg(struct strbuf *msg)
 850 {
 851         const char *filename = git_path("MERGE_MSG");
 852         int fd = open(filename, O_WRONLY | O_CREAT, 0666);
 853         if (fd < 0)
 854                 die_errno(_("Could not open '%s' for writing"),
 855                           filename);
 856         if (write_in_full(fd, msg->buf, msg->len) != msg->len)
 857                 die_errno(_("Could not write to '%s'"), filename);
 858         close(fd);
 859 }
 860
 861 static void read_merge_msg(struct strbuf *msg)
 862 {
 863         const char *filename = git_path("MERGE_MSG");
 864         strbuf_reset(msg);
 865         if (strbuf_read_file(msg, filename, 0) < 0)
 866                 die_errno(_("Could not read from '%s'"), filename);
 867 }
 868
 869 static void write_merge_state(void);
 870 static void abort_commit(const char *err_msg)
 871 {
 872         if (err_msg)
 873                 error("%s", err_msg);
 874         fprintf(stderr,
 875                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 876         write_merge_state();
 877         exit(1);
 878 }
 879
 880 static void prepare_to_commit(void)
 881 {
 882         struct strbuf msg = STRBUF_INIT;
 883         strbuf_addbuf(&msg, &merge_msg);
 884         strbuf_addch(&msg, '\n');
 885         write_merge_msg(&msg);
 886         run_hook(get_index_file(), "prepare-commit-msg",
 887                  git_path("MERGE_MSG"), "merge", NULL, NULL);
 888         if (option_edit) {
 889                 if (launch_editor(git_path("MERGE_MSG"), NULL, NULL))
 890                         abort_commit(NULL);
 891         }
 892         read_merge_msg(&msg);
 893         stripspace(&msg, option_edit);
 894         if (!msg.len)
 895                 abort_commit(_("Empty commit message."));
 896         strbuf_release(&merge_msg);
 897         strbuf_addbuf(&merge_msg, &msg);
 898         strbuf_release(&msg);
 899 }
 900
 901 static int merge_trivial(struct commit *head)
 902 {
 903         unsigned char result_tree[20], result_commit[20];
 904         struct commit_list *parent = xmalloc(sizeof(*parent));
 905
 906         write_tree_trivial(result_tree);
 907         printf(_("Wonderful.\n"));
 908         parent->item = head;
 909         parent->next = xmalloc(sizeof(*parent->next));
 910         parent->next->item = remoteheads->item;
 911         parent->next->next = NULL;
 912         prepare_to_commit();
 913         if (commit_tree(&merge_msg, result_tree, parent, result_commit, NULL))
 914                 die(_("failed to write commit object"));
 915         finish(head, result_commit, "In-index merge");
 916         drop_save();
 917         return 0;
 918 }
 919
 920 static int finish_automerge(struct commit *head,
 921                             struct commit_list *common,
 922                             unsigned char *result_tree,
 923                             const char *wt_strategy)
 924 {
 925         struct commit_list *parents = NULL, *j;
 926         struct strbuf buf = STRBUF_INIT;
 927         unsigned char result_commit[20];
 928
 929         free_commit_list(common);
 930         if (allow_fast_forward) {
 931                 parents = remoteheads;
 932                 commit_list_insert(head, &parents);
 933                 parents = reduce_heads(parents);
 934         } else {
 935                 struct commit_list **pptr = &parents;
 936
 937                 pptr = &commit_list_insert(head,
 938                                 pptr)->next;
 939                 for (j = remoteheads; j; j = j->next)
 940                         pptr = &commit_list_insert(j->item, pptr)->next;
 941         }
 942         strbuf_addch(&merge_msg, '\n');
 943         prepare_to_commit();
 944         free_commit_list(remoteheads);
 945         if (commit_tree(&merge_msg, result_tree, parents, result_commit, NULL))
 946                 die(_("failed to write commit object"));
 947         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 948         finish(head, result_commit, buf.buf);
 949         strbuf_release(&buf);
 950         drop_save();
 951         return 0;
 952 }
 953
 954 static int suggest_conflicts(int renormalizing)
 955 {
 956         const char *filename;
 957         FILE *fp;
 958         int pos;
 959
 960         filename = git_path("MERGE_MSG");
 961         fp = fopen(filename, "a");
 962         if (!fp)
 963                 die_errno(_("Could not open '%s' for writing"), filename);
 964         fprintf(fp, "\nConflicts:\n");
 965         for (pos = 0; pos < active_nr; pos++) {
 966                 struct cache_entry *ce = active_cache[pos];
 967
 968                 if (ce_stage(ce)) {
 969                         fprintf(fp, "\t%s\n", ce->name);
 970                         while (pos + 1 < active_nr &&
 971                                         !strcmp(ce->name,
 972                                                 active_cache[pos + 1]->name))
 973                                 pos++;
 974                 }
 975         }
 976         fclose(fp);
 977         rerere(allow_rerere_auto);
 978         printf(_("Automatic merge failed; "
 979                         "fix conflicts and then commit the result.\n"));
 980         return 1;
 981 }
 982
 983 static struct commit *is_old_style_invocation(int argc, const char **argv,
 984                                               const unsigned char *head)
 985 {
 986         struct commit *second_token = NULL;
 987         if (argc > 2) {
 988                 unsigned char second_sha1[20];
 989
 990                 if (get_sha1(argv[1], second_sha1))
 991                         return NULL;
 992                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 993                 if (!second_token)
 994                         die(_("'%s' is not a commit"), argv[1]);
 995                 if (hashcmp(second_token->object.sha1, head))
 996                         return NULL;
 997         }
 998         return second_token;
 999 }
1000
1001 static int evaluate_result(void)
1002 {
1003         int cnt = 0;
1004         struct rev_info rev;
1005
1006         /* Check how many files differ. */
1007         init_revisions(&rev, "");
1008         setup_revisions(0, NULL, &rev, NULL);
1009         rev.diffopt.output_format |=
1010                 DIFF_FORMAT_CALLBACK;
1011         rev.diffopt.format_callback = count_diff_files;
1012         rev.diffopt.format_callback_data = &cnt;
1013         run_diff_files(&rev, 0);
1014
1015         /*
1016          * Check how many unmerged entries are
1017          * there.
1018          */
1019         cnt += count_unmerged_entries();
1020
1021         return cnt;
1022 }
1023
1024 /*
1025  * Pretend as if the user told us to merge with the tracking
1026  * branch we have for the upstream of the current branch
1027  */
1028 static int setup_with_upstream(const char ***argv)
1029 {
1030         struct branch *branch = branch_get(NULL);
1031         int i;
1032         const char **args;
1033
1034         if (!branch)
1035                 die(_("No current branch."));
1036         if (!branch->remote)
1037                 die(_("No remote for the current branch."));
1038         if (!branch->merge_nr)
1039                 die(_("No default upstream defined for the current branch."));
1040
1041         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
1042         for (i = 0; i < branch->merge_nr; i++) {
1043                 if (!branch->merge[i]->dst)
1044                         die(_("No remote tracking branch for %s from %s"),
1045                             branch->merge[i]->src, branch->remote_name);
1046                 args[i] = branch->merge[i]->dst;
1047         }
1048         args[i] = NULL;
1049         *argv = args;
1050         return i;
1051 }
1052
1053 static void write_merge_state(void)
1054 {
1055         const char *filename;
1056         int fd;
1057         struct commit_list *j;
1058         struct strbuf buf = STRBUF_INIT;
1059
1060         for (j = remoteheads; j; j = j->next) {
1061                 unsigned const char *sha1;
1062                 struct commit *c = j->item;
1063                 if (c->util && merge_remote_util(c)->obj) {
1064                         sha1 = merge_remote_util(c)->obj->sha1;
1065                 } else {
1066                         sha1 = c->object.sha1;
1067                 }
1068                 strbuf_addf(&buf, "%s\n", sha1_to_hex(sha1));
1069         }
1070         filename = git_path("MERGE_HEAD");
1071         fd = open(filename, O_WRONLY | O_CREAT, 0666);
1072         if (fd < 0)
1073                 die_errno(_("Could not open '%s' for writing"), filename);
1074         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1075                 die_errno(_("Could not write to '%s'"), filename);
1076         close(fd);
1077         strbuf_addch(&merge_msg, '\n');
1078         write_merge_msg(&merge_msg);
1079
1080         filename = git_path("MERGE_MODE");
1081         fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
1082         if (fd < 0)
1083                 die_errno(_("Could not open '%s' for writing"), filename);
1084         strbuf_reset(&buf);
1085         if (!allow_fast_forward)
1086                 strbuf_addf(&buf, "no-ff");
1087         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1088                 die_errno(_("Could not write to '%s'"), filename);
1089         close(fd);
1090 }
1091
1092 int cmd_merge(int argc, const char **argv, const char *prefix)
1093 {
1094         unsigned char result_tree[20];
1095         unsigned char stash[20];
1096         unsigned char head_sha1[20];
1097         struct commit *head_commit;
1098         struct strbuf buf = STRBUF_INIT;
1099         const char *head_arg;
1100         int flag, i, ret = 0;
1101         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1102         struct commit_list *common = NULL;
1103         const char *best_strategy = NULL, *wt_strategy = NULL;
1104         struct commit_list **remotes = &remoteheads;
1105         void *branch_to_free;
1106
1107         if (argc == 2 && !strcmp(argv[1], "-h"))
1108                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1109
1110         /*
1111          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1112          * current branch.
1113          */
1114         branch = branch_to_free = resolve_refdup("HEAD", head_sha1, 0, &flag);
1115         if (branch && !prefixcmp(branch, "refs/heads/"))
1116                 branch += 11;
1117         if (!branch || is_null_sha1(head_sha1))
1118                 head_commit = NULL;
1119         else
1120                 head_commit = lookup_commit_or_die(head_sha1, "HEAD");
1121
1122         git_config(git_merge_config, NULL);
1123
1124         if (branch_mergeoptions)
1125                 parse_branch_merge_options(branch_mergeoptions);
1126         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1127                         builtin_merge_usage, 0);
1128         if (shortlog_len < 0)
1129                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1130
1131         if (verbosity < 0 && show_progress == -1)
1132                 show_progress = 0;
1133
1134         if (abort_current_merge) {
1135                 int nargc = 2;
1136                 const char *nargv[] = {"reset", "--merge", NULL};
1137
1138                 if (!file_exists(git_path("MERGE_HEAD")))
1139                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1140
1141                 /* Invoke 'git reset --merge' */
1142                 ret = cmd_reset(nargc, nargv, prefix);
1143                 goto done;
1144         }
1145
1146         if (read_cache_unmerged())
1147                 die_resolve_conflict("merge");
1148
1149         if (file_exists(git_path("MERGE_HEAD"))) {
1150                 /*
1151                  * There is no unmerged entry, don't advise 'git
1152                  * add/rm <file>', just 'git commit'.
1153                  */
1154                 if (advice_resolve_conflict)
1155                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1156                                   "Please, commit your changes before you can merge."));
1157                 else
1158                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1159         }
1160         if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1161                 if (advice_resolve_conflict)
1162                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1163                             "Please, commit your changes before you can merge."));
1164                 else
1165                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1166         }
1167         resolve_undo_clear();
1168
1169         if (verbosity < 0)
1170                 show_diffstat = 0;
1171
1172         if (squash) {
1173                 if (!allow_fast_forward)
1174                         die(_("You cannot combine --squash with --no-ff."));
1175                 option_commit = 0;
1176         }
1177
1178         if (!allow_fast_forward && fast_forward_only)
1179                 die(_("You cannot combine --no-ff with --ff-only."));
1180
1181         if (!abort_current_merge) {
1182                 if (!argc) {
1183                         if (default_to_upstream)
1184                                 argc = setup_with_upstream(&argv);
1185                         else
1186                                 die(_("No commit specified and merge.defaultToUpstream not set."));
1187                 } else if (argc == 1 && !strcmp(argv[0], "-"))
1188                         argv[0] = "@{-1}";
1189         }
1190         if (!argc)
1191                 usage_with_options(builtin_merge_usage,
1192                         builtin_merge_options);
1193
1194         /*
1195          * This could be traditional "merge <msg> HEAD <commit>..."  and
1196          * the way we can tell it is to see if the second token is HEAD,
1197          * but some people might have misused the interface and used a
1198          * committish that is the same as HEAD there instead.
1199          * Traditional format never would have "-m" so it is an
1200          * additional safety measure to check for it.
1201          */
1202
1203         if (!have_message && head_commit &&
1204             is_old_style_invocation(argc, argv, head_commit->object.sha1)) {
1205                 strbuf_addstr(&merge_msg, argv[0]);
1206                 head_arg = argv[1];
1207                 argv += 2;
1208                 argc -= 2;
1209         } else if (!head_commit) {
1210                 struct commit *remote_head;
1211                 /*
1212                  * If the merged head is a valid one there is no reason
1213                  * to forbid "git merge" into a branch yet to be born.
1214                  * We do the same for "git pull".
1215                  */
1216                 if (argc != 1)
1217                         die(_("Can merge only exactly one commit into "
1218                                 "empty head"));
1219                 if (squash)
1220                         die(_("Squash commit into empty head not supported yet"));
1221                 if (!allow_fast_forward)
1222                         die(_("Non-fast-forward commit does not make sense into "
1223                             "an empty head"));
1224                 remote_head = get_merge_parent(argv[0]);
1225                 if (!remote_head)
1226                         die(_("%s - not something we can merge"), argv[0]);
1227                 read_empty(remote_head->object.sha1, 0);
1228                 update_ref("initial pull", "HEAD", remote_head->object.sha1,
1229                            NULL, 0, DIE_ON_ERR);
1230                 goto done;
1231         } else {
1232                 struct strbuf merge_names = STRBUF_INIT;
1233
1234                 /* We are invoked directly as the first-class UI. */
1235                 head_arg = "HEAD";
1236
1237                 /*
1238                  * All the rest are the commits being merged; prepare
1239                  * the standard merge summary message to be appended
1240                  * to the given message.
1241                  */
1242                 for (i = 0; i < argc; i++)
1243                         merge_name(argv[i], &merge_names);
1244
1245                 if (!have_message || shortlog_len) {
1246                         struct fmt_merge_msg_opts opts;
1247                         memset(&opts, 0, sizeof(opts));
1248                         opts.add_title = !have_message;
1249                         opts.shortlog_len = shortlog_len;
1250
1251                         fmt_merge_msg(&merge_names, &merge_msg, &opts);
1252                         if (merge_msg.len)
1253                                 strbuf_setlen(&merge_msg, merge_msg.len - 1);
1254                 }
1255         }
1256
1257         if (!head_commit || !argc)
1258                 usage_with_options(builtin_merge_usage,
1259                         builtin_merge_options);
1260
1261         strbuf_addstr(&buf, "merge");
1262         for (i = 0; i < argc; i++)
1263                 strbuf_addf(&buf, " %s", argv[i]);
1264         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1265         strbuf_reset(&buf);
1266
1267         for (i = 0; i < argc; i++) {
1268                 struct commit *commit = get_merge_parent(argv[i]);
1269                 if (!commit)
1270                         die(_("%s - not something we can merge"), argv[i]);
1271                 remotes = &commit_list_insert(commit, remotes)->next;
1272                 strbuf_addf(&buf, "GITHEAD_%s",
1273                             sha1_to_hex(commit->object.sha1));
1274                 setenv(buf.buf, argv[i], 1);
1275                 strbuf_reset(&buf);
1276                 if (merge_remote_util(commit) &&
1277                     merge_remote_util(commit)->obj &&
1278                     merge_remote_util(commit)->obj->type == OBJ_TAG) {
1279                         option_edit = 1;
1280                         allow_fast_forward = 0;
1281                 }
1282         }
1283
1284         if (!use_strategies) {
1285                 if (!remoteheads->next)
1286                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1287                 else
1288                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1289         }
1290
1291         for (i = 0; i < use_strategies_nr; i++) {
1292                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1293                         allow_fast_forward = 0;
1294                 if (use_strategies[i]->attr & NO_TRIVIAL)
1295                         allow_trivial = 0;
1296         }
1297
1298         if (!remoteheads->next)
1299                 common = get_merge_bases(head_commit, remoteheads->item, 1);
1300         else {
1301                 struct commit_list *list = remoteheads;
1302                 commit_list_insert(head_commit, &list);
1303                 common = get_octopus_merge_bases(list);
1304                 free(list);
1305         }
1306
1307         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
1308                    NULL, 0, DIE_ON_ERR);
1309
1310         if (!common)
1311                 ; /* No common ancestors found. We need a real merge. */
1312         else if (!remoteheads->next && !common->next &&
1313                         common->item == remoteheads->item) {
1314                 /*
1315                  * If head can reach all the merge then we are up to date.
1316                  * but first the most common case of merging one remote.
1317                  */
1318                 finish_up_to_date("Already up-to-date.");
1319                 goto done;
1320         } else if (allow_fast_forward && !remoteheads->next &&
1321                         !common->next &&
1322                         !hashcmp(common->item->object.sha1, head_commit->object.sha1)) {
1323                 /* Again the most common case of merging one remote. */
1324                 struct strbuf msg = STRBUF_INIT;
1325                 struct commit *commit;
1326                 char hex[41];
1327
1328                 strcpy(hex, find_unique_abbrev(head_commit->object.sha1, DEFAULT_ABBREV));
1329
1330                 if (verbosity >= 0)
1331                         printf(_("Updating %s..%s\n"),
1332                                 hex,
1333                                 find_unique_abbrev(remoteheads->item->object.sha1,
1334                                 DEFAULT_ABBREV));
1335                 strbuf_addstr(&msg, "Fast-forward");
1336                 if (have_message)
1337                         strbuf_addstr(&msg,
1338                                 " (no commit created; -m option ignored)");
1339                 commit = remoteheads->item;
1340                 if (!commit) {
1341                         ret = 1;
1342                         goto done;
1343                 }
1344
1345                 if (checkout_fast_forward(head_commit->object.sha1,
1346                                           commit->object.sha1)) {
1347                         ret = 1;
1348                         goto done;
1349                 }
1350
1351                 finish(head_commit, commit->object.sha1, msg.buf);
1352                 drop_save();
1353                 goto done;
1354         } else if (!remoteheads->next && common->next)
1355                 ;
1356                 /*
1357                  * We are not doing octopus and not fast-forward.  Need
1358                  * a real merge.
1359                  */
1360         else if (!remoteheads->next && !common->next && option_commit) {
1361                 /*
1362                  * We are not doing octopus, not fast-forward, and have
1363                  * only one common.
1364                  */
1365                 refresh_cache(REFRESH_QUIET);
1366                 if (allow_trivial && !fast_forward_only) {
1367                         /* See if it is really trivial. */
1368                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1369                         printf(_("Trying really trivial in-index merge...\n"));
1370                         if (!read_tree_trivial(common->item->object.sha1,
1371                                                head_commit->object.sha1,
1372                                                remoteheads->item->object.sha1)) {
1373                                 ret = merge_trivial(head_commit);
1374                                 goto done;
1375                         }
1376                         printf(_("Nope.\n"));
1377                 }
1378         } else {
1379                 /*
1380                  * An octopus.  If we can reach all the remote we are up
1381                  * to date.
1382                  */
1383                 int up_to_date = 1;
1384                 struct commit_list *j;
1385
1386                 for (j = remoteheads; j; j = j->next) {
1387                         struct commit_list *common_one;
1388
1389                         /*
1390                          * Here we *have* to calculate the individual
1391                          * merge_bases again, otherwise "git merge HEAD^
1392                          * HEAD^^" would be missed.
1393                          */
1394                         common_one = get_merge_bases(head_commit, j->item, 1);
1395                         if (hashcmp(common_one->item->object.sha1,
1396                                 j->item->object.sha1)) {
1397                                 up_to_date = 0;
1398                                 break;
1399                         }
1400                 }
1401                 if (up_to_date) {
1402                         finish_up_to_date("Already up-to-date. Yeeah!");
1403                         goto done;
1404                 }
1405         }
1406
1407         if (fast_forward_only)
1408                 die(_("Not possible to fast-forward, aborting."));
1409
1410         /* We are going to make a new commit. */
1411         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1412
1413         /*
1414          * At this point, we need a real merge.  No matter what strategy
1415          * we use, it would operate on the index, possibly affecting the
1416          * working tree, and when resolved cleanly, have the desired
1417          * tree in the index -- this means that the index must be in
1418          * sync with the head commit.  The strategies are responsible
1419          * to ensure this.
1420          */
1421         if (use_strategies_nr == 1 ||
1422             /*
1423              * Stash away the local changes so that we can try more than one.
1424              */
1425             save_state(stash))
1426                 hashcpy(stash, null_sha1);
1427
1428         for (i = 0; i < use_strategies_nr; i++) {
1429                 int ret;
1430                 if (i) {
1431                         printf(_("Rewinding the tree to pristine...\n"));
1432                         restore_state(head_commit->object.sha1, stash);
1433                 }
1434                 if (use_strategies_nr != 1)
1435                         printf(_("Trying merge strategy %s...\n"),
1436                                 use_strategies[i]->name);
1437                 /*
1438                  * Remember which strategy left the state in the working
1439                  * tree.
1440                  */
1441                 wt_strategy = use_strategies[i]->name;
1442
1443                 ret = try_merge_strategy(use_strategies[i]->name,
1444                                          common, head_commit, head_arg);
1445                 if (!option_commit && !ret) {
1446                         merge_was_ok = 1;
1447                         /*
1448                          * This is necessary here just to avoid writing
1449                          * the tree, but later we will *not* exit with
1450                          * status code 1 because merge_was_ok is set.
1451                          */
1452                         ret = 1;
1453                 }
1454
1455                 if (ret) {
1456                         /*
1457                          * The backend exits with 1 when conflicts are
1458                          * left to be resolved, with 2 when it does not
1459                          * handle the given merge at all.
1460                          */
1461                         if (ret == 1) {
1462                                 int cnt = evaluate_result();
1463
1464                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1465                                         best_strategy = use_strategies[i]->name;
1466                                         best_cnt = cnt;
1467                                 }
1468                         }
1469                         if (merge_was_ok)
1470                                 break;
1471                         else
1472                                 continue;
1473                 }
1474
1475                 /* Automerge succeeded. */
1476                 write_tree_trivial(result_tree);
1477                 automerge_was_ok = 1;
1478                 break;
1479         }
1480
1481         /*
1482          * If we have a resulting tree, that means the strategy module
1483          * auto resolved the merge cleanly.
1484          */
1485         if (automerge_was_ok) {
1486                 ret = finish_automerge(head_commit, common, result_tree,
1487                                        wt_strategy);
1488                 goto done;
1489         }
1490
1491         /*
1492          * Pick the result from the best strategy and have the user fix
1493          * it up.
1494          */
1495         if (!best_strategy) {
1496                 restore_state(head_commit->object.sha1, stash);
1497                 if (use_strategies_nr > 1)
1498                         fprintf(stderr,
1499                                 _("No merge strategy handled the merge.\n"));
1500                 else
1501                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1502                                 use_strategies[0]->name);
1503                 ret = 2;
1504                 goto done;
1505         } else if (best_strategy == wt_strategy)
1506                 ; /* We already have its result in the working tree. */
1507         else {
1508                 printf(_("Rewinding the tree to pristine...\n"));
1509                 restore_state(head_commit->object.sha1, stash);
1510                 printf(_("Using the %s to prepare resolving by hand.\n"),
1511                         best_strategy);
1512                 try_merge_strategy(best_strategy, common, head_commit, head_arg);
1513         }
1514
1515         if (squash)
1516                 finish(head_commit, NULL, NULL);
1517         else
1518                 write_merge_state();
1519
1520         if (merge_was_ok)
1521                 fprintf(stderr, _("Automatic merge went well; "
1522                         "stopped before committing as requested\n"));
1523         else
1524                 ret = suggest_conflicts(option_renormalize);
1525
1526 done:
1527         free(branch_to_free);
1528         return ret;
1529 }