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