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