builtin/merge.c

   1 /*
   2  * Builtin "git merge"
   3  *
   4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
   5  *
   6  * Based on git-merge.sh by Junio C Hamano.
   7  */
   8
   9 #include "cache.h"
  10 #include "parse-options.h"
  11 #include "builtin.h"
  12 #include "run-command.h"
  13 #include "diff.h"
  14 #include "refs.h"
  15 #include "commit.h"
  16 #include "diffcore.h"
  17 #include "revision.h"
  18 #include "unpack-trees.h"
  19 #include "cache-tree.h"
  20 #include "dir.h"
  21 #include "utf8.h"
  22 #include "log-tree.h"
  23 #include "color.h"
  24 #include "rerere.h"
  25 #include "help.h"
  26 #include "merge-recursive.h"
  27 #include "resolve-undo.h"
  28 #include "remote.h"
  29 #include "gpg-interface.h"
  30
  31 #define DEFAULT_TWOHEAD (1<<0)
  32 #define DEFAULT_OCTOPUS (1<<1)
  33 #define NO_FAST_FORWARD (1<<2)
  34 #define NO_TRIVIAL      (1<<3)
  35
  36 struct strategy {
  37         const char *name;
  38         unsigned attr;
  39 };
  40
  41 static const char * const builtin_merge_usage[] = {
  42         "git merge [options] [<commit>...]",
  43         "git merge [options] <msg> HEAD <commit>",
  44         "git merge --abort",
  45         NULL
  46 };
  47
  48 static int show_diffstat = 1, shortlog_len, squash;
  49 static int option_commit = 1, allow_fast_forward = 1;
  50 static int fast_forward_only, option_edit;
  51 static int allow_trivial = 1, have_message;
  52 static struct strbuf merge_msg;
  53 static struct commit_list *remoteheads;
  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 static const char *sign_commit;
  67
  68 static struct strategy all_strategy[] = {
  69         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  70         { "octopus",    DEFAULT_OCTOPUS },
  71         { "resolve",    0 },
  72         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  73         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  74 };
  75
  76 static const char *pull_twohead, *pull_octopus;
  77
  78 static int option_parse_message(const struct option *opt,
  79                                 const char *arg, int unset)
  80 {
  81         struct strbuf *buf = opt->value;
  82
  83         if (unset)
  84                 strbuf_setlen(buf, 0);
  85         else if (arg) {
  86                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  87                 have_message = 1;
  88         } else
  89                 return error(_("switch `m' requires a value"));
  90         return 0;
  91 }
  92
  93 static struct strategy *get_strategy(const char *name)
  94 {
  95         int i;
  96         struct strategy *ret;
  97         static struct cmdnames main_cmds, other_cmds;
  98         static int loaded;
  99
 100         if (!name)
 101                 return NULL;
 102
 103         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 104                 if (!strcmp(name, all_strategy[i].name))
 105                         return &all_strategy[i];
 106
 107         if (!loaded) {
 108                 struct cmdnames not_strategies;
 109                 loaded = 1;
 110
 111                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 112                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 113                 for (i = 0; i < main_cmds.cnt; i++) {
 114                         int j, found = 0;
 115                         struct cmdname *ent = main_cmds.names[i];
 116                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 117                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 118                                                 && !all_strategy[j].name[ent->len])
 119                                         found = 1;
 120                         if (!found)
 121                                 add_cmdname(&not_strategies, ent->name, ent->len);
 122                 }
 123                 exclude_cmds(&main_cmds, &not_strategies);
 124         }
 125         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 126                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 127                 fprintf(stderr, _("Available strategies are:"));
 128                 for (i = 0; i < main_cmds.cnt; i++)
 129                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 130                 fprintf(stderr, ".\n");
 131                 if (other_cmds.cnt) {
 132                         fprintf(stderr, _("Available custom strategies are:"));
 133                         for (i = 0; i < other_cmds.cnt; i++)
 134                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 135                         fprintf(stderr, ".\n");
 136                 }
 137                 exit(1);
 138         }
 139
 140         ret = xcalloc(1, sizeof(struct strategy));
 141         ret->name = xstrdup(name);
 142         ret->attr = NO_TRIVIAL;
 143         return ret;
 144 }
 145
 146 static void append_strategy(struct strategy *s)
 147 {
 148         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 149         use_strategies[use_strategies_nr++] = s;
 150 }
 151
 152 static int option_parse_strategy(const struct option *opt,
 153                                  const char *name, int unset)
 154 {
 155         if (unset)
 156                 return 0;
 157
 158         append_strategy(get_strategy(name));
 159         return 0;
 160 }
 161
 162 static int option_parse_x(const struct option *opt,
 163                           const char *arg, int unset)
 164 {
 165         if (unset)
 166                 return 0;
 167
 168         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 169         xopts[xopts_nr++] = xstrdup(arg);
 170         return 0;
 171 }
 172
 173 static int option_parse_n(const struct option *opt,
 174                           const char *arg, int unset)
 175 {
 176         show_diffstat = unset;
 177         return 0;
 178 }
 179
 180 static struct option builtin_merge_options[] = {
 181         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 182                 "do not show a diffstat at the end of the merge",
 183                 PARSE_OPT_NOARG, option_parse_n },
 184         OPT_BOOLEAN(0, "stat", &show_diffstat,
 185                 "show a diffstat at the end of the merge"),
 186         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 187         { OPTION_INTEGER, 0, "log", &shortlog_len, "n",
 188           "add (at most <n>) entries from shortlog to merge commit message",
 189           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 190         OPT_BOOLEAN(0, "squash", &squash,
 191                 "create a single commit instead of doing a merge"),
 192         OPT_BOOLEAN(0, "commit", &option_commit,
 193                 "perform a commit if the merge succeeds (default)"),
 194         OPT_BOOLEAN('e', "edit", &option_edit,
 195                 "edit message before committing"),
 196         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 197                 "allow fast-forward (default)"),
 198         OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
 199                 "abort if fast-forward is not possible"),
 200         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 201         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
 202                 "merge strategy to use", option_parse_strategy),
 203         OPT_CALLBACK('X', "strategy-option", &xopts, "option=value",
 204                 "option for selected merge strategy", option_parse_x),
 205         OPT_CALLBACK('m', "message", &merge_msg, "message",
 206                 "merge commit message (for a non-fast-forward merge)",
 207                 option_parse_message),
 208         OPT__VERBOSITY(&verbosity),
 209         OPT_BOOLEAN(0, "abort", &abort_current_merge,
 210                 "abort the current in-progress merge"),
 211         OPT_SET_INT(0, "progress", &show_progress, "force progress reporting", 1),
 212         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, "key id",
 213           "GPG sign commit", PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 214         OPT_END()
 215 };
 216
 217 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 218 static void drop_save(void)
 219 {
 220         unlink(git_path("MERGE_HEAD"));
 221         unlink(git_path("MERGE_MSG"));
 222         unlink(git_path("MERGE_MODE"));
 223 }
 224
 225 static int save_state(unsigned char *stash)
 226 {
 227         int len;
 228         struct child_process cp;
 229         struct strbuf buffer = STRBUF_INIT;
 230         const char *argv[] = {"stash", "create", NULL};
 231
 232         memset(&cp, 0, sizeof(cp));
 233         cp.argv = argv;
 234         cp.out = -1;
 235         cp.git_cmd = 1;
 236
 237         if (start_command(&cp))
 238                 die(_("could not run stash."));
 239         len = strbuf_read(&buffer, cp.out, 1024);
 240         close(cp.out);
 241
 242         if (finish_command(&cp) || len < 0)
 243                 die(_("stash failed"));
 244         else if (!len)          /* no changes */
 245                 return -1;
 246         strbuf_setlen(&buffer, buffer.len-1);
 247         if (get_sha1(buffer.buf, stash))
 248                 die(_("not a valid object: %s"), buffer.buf);
 249         return 0;
 250 }
 251
 252 static void read_empty(unsigned const char *sha1, int verbose)
 253 {
 254         int i = 0;
 255         const char *args[7];
 256
 257         args[i++] = "read-tree";
 258         if (verbose)
 259                 args[i++] = "-v";
 260         args[i++] = "-m";
 261         args[i++] = "-u";
 262         args[i++] = EMPTY_TREE_SHA1_HEX;
 263         args[i++] = sha1_to_hex(sha1);
 264         args[i] = NULL;
 265
 266         if (run_command_v_opt(args, RUN_GIT_CMD))
 267                 die(_("read-tree failed"));
 268 }
 269
 270 static void reset_hard(unsigned const char *sha1, int verbose)
 271 {
 272         int i = 0;
 273         const char *args[6];
 274
 275         args[i++] = "read-tree";
 276         if (verbose)
 277                 args[i++] = "-v";
 278         args[i++] = "--reset";
 279         args[i++] = "-u";
 280         args[i++] = sha1_to_hex(sha1);
 281         args[i] = NULL;
 282
 283         if (run_command_v_opt(args, RUN_GIT_CMD))
 284                 die(_("read-tree failed"));
 285 }
 286
 287 static void restore_state(const unsigned char *head,
 288                           const unsigned char *stash)
 289 {
 290         struct strbuf sb = STRBUF_INIT;
 291         const char *args[] = { "stash", "apply", NULL, NULL };
 292
 293         if (is_null_sha1(stash))
 294                 return;
 295
 296         reset_hard(head, 1);
 297
 298         args[2] = sha1_to_hex(stash);
 299
 300         /*
 301          * It is OK to ignore error here, for example when there was
 302          * nothing to restore.
 303          */
 304         run_command_v_opt(args, RUN_GIT_CMD);
 305
 306         strbuf_release(&sb);
 307         refresh_cache(REFRESH_QUIET);
 308 }
 309
 310 /* This is called when no merge was necessary. */
 311 static void finish_up_to_date(const char *msg)
 312 {
 313         if (verbosity >= 0)
 314                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 315         drop_save();
 316 }
 317
 318 static void squash_message(struct commit *commit)
 319 {
 320         struct rev_info rev;
 321         struct strbuf out = STRBUF_INIT;
 322         struct commit_list *j;
 323         int fd;
 324         struct pretty_print_context ctx = {0};
 325
 326         printf(_("Squash commit -- not updating HEAD\n"));
 327         fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
 328         if (fd < 0)
 329                 die_errno(_("Could not write to '%s'"), git_path("SQUASH_MSG"));
 330
 331         init_revisions(&rev, NULL);
 332         rev.ignore_merges = 1;
 333         rev.commit_format = CMIT_FMT_MEDIUM;
 334
 335         commit->object.flags |= UNINTERESTING;
 336         add_pending_object(&rev, &commit->object, NULL);
 337
 338         for (j = remoteheads; j; j = j->next)
 339                 add_pending_object(&rev, &j->item->object, NULL);
 340
 341         setup_revisions(0, NULL, &rev, NULL);
 342         if (prepare_revision_walk(&rev))
 343                 die(_("revision walk setup failed"));
 344
 345         ctx.abbrev = rev.abbrev;
 346         ctx.date_mode = rev.date_mode;
 347         ctx.fmt = rev.commit_format;
 348
 349         strbuf_addstr(&out, "Squashed commit of the following:\n");
 350         while ((commit = get_revision(&rev)) != NULL) {
 351                 strbuf_addch(&out, '\n');
 352                 strbuf_addf(&out, "commit %s\n",
 353                         sha1_to_hex(commit->object.sha1));
 354                 pretty_print_commit(&ctx, commit, &out);
 355         }
 356         if (write(fd, out.buf, out.len) < 0)
 357                 die_errno(_("Writing SQUASH_MSG"));
 358         if (close(fd))
 359                 die_errno(_("Finishing SQUASH_MSG"));
 360         strbuf_release(&out);
 361 }
 362
 363 static void finish(struct commit *head_commit,
 364                    const unsigned char *new_head, const char *msg)
 365 {
 366         struct strbuf reflog_message = STRBUF_INIT;
 367         const unsigned char *head = head_commit->object.sha1;
 368
 369         if (!msg)
 370                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 371         else {
 372                 if (verbosity >= 0)
 373                         printf("%s\n", msg);
 374                 strbuf_addf(&reflog_message, "%s: %s",
 375                         getenv("GIT_REFLOG_ACTION"), msg);
 376         }
 377         if (squash) {
 378                 squash_message(head_commit);
 379         } else {
 380                 if (verbosity >= 0 && !merge_msg.len)
 381                         printf(_("No merge message -- not updating HEAD\n"));
 382                 else {
 383                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 384                         update_ref(reflog_message.buf, "HEAD",
 385                                 new_head, head, 0,
 386                                 DIE_ON_ERR);
 387                         /*
 388                          * We ignore errors in 'gc --auto', since the
 389                          * user should see them.
 390                          */
 391                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 392                 }
 393         }
 394         if (new_head && show_diffstat) {
 395                 struct diff_options opts;
 396                 diff_setup(&opts);
 397                 opts.output_format |=
 398                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 399                 opts.detect_rename = DIFF_DETECT_RENAME;
 400                 if (diff_setup_done(&opts) < 0)
 401                         die(_("diff_setup_done failed"));
 402                 diff_tree_sha1(head, new_head, "", &opts);
 403                 diffcore_std(&opts);
 404                 diff_flush(&opts);
 405         }
 406
 407         /* Run a post-merge hook */
 408         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
 409
 410         strbuf_release(&reflog_message);
 411 }
 412
 413 /* Get the name for the merge commit's message. */
 414 static void merge_name(const char *remote, struct strbuf *msg)
 415 {
 416         struct commit *remote_head;
 417         unsigned char branch_head[20], buf_sha[20];
 418         struct strbuf buf = STRBUF_INIT;
 419         struct strbuf bname = STRBUF_INIT;
 420         const char *ptr;
 421         char *found_ref;
 422         int len, early;
 423
 424         strbuf_branchname(&bname, remote);
 425         remote = bname.buf;
 426
 427         memset(branch_head, 0, sizeof(branch_head));
 428         remote_head = get_merge_parent(remote);
 429         if (!remote_head)
 430                 die(_("'%s' does not point to a commit"), remote);
 431
 432         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 433                 if (!prefixcmp(found_ref, "refs/heads/")) {
 434                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 435                                     sha1_to_hex(branch_head), remote);
 436                         goto cleanup;
 437                 }
 438                 if (!prefixcmp(found_ref, "refs/tags/")) {
 439                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 440                                     sha1_to_hex(branch_head), remote);
 441                         goto cleanup;
 442                 }
 443                 if (!prefixcmp(found_ref, "refs/remotes/")) {
 444                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 445                                     sha1_to_hex(branch_head), remote);
 446                         goto cleanup;
 447                 }
 448         }
 449
 450         /* See if remote matches <name>^^^.. or <name>~<number> */
 451         for (len = 0, ptr = remote + strlen(remote);
 452              remote < ptr && ptr[-1] == '^';
 453              ptr--)
 454                 len++;
 455         if (len)
 456                 early = 1;
 457         else {
 458                 early = 0;
 459                 ptr = strrchr(remote, '~');
 460                 if (ptr) {
 461                         int seen_nonzero = 0;
 462
 463                         len++; /* count ~ */
 464                         while (*++ptr && isdigit(*ptr)) {
 465                                 seen_nonzero |= (*ptr != '0');
 466                                 len++;
 467                         }
 468                         if (*ptr)
 469                                 len = 0; /* not ...~<number> */
 470                         else if (seen_nonzero)
 471                                 early = 1;
 472                         else if (len == 1)
 473                                 early = 1; /* "name~" is "name~1"! */
 474                 }
 475         }
 476         if (len) {
 477                 struct strbuf truname = STRBUF_INIT;
 478                 strbuf_addstr(&truname, "refs/heads/");
 479                 strbuf_addstr(&truname, remote);
 480                 strbuf_setlen(&truname, truname.len - len);
 481                 if (resolve_ref(truname.buf, buf_sha, 1, NULL)) {
 482                         strbuf_addf(msg,
 483                                     "%s\t\tbranch '%s'%s of .\n",
 484                                     sha1_to_hex(remote_head->object.sha1),
 485                                     truname.buf + 11,
 486                                     (early ? " (early part)" : ""));
 487                         strbuf_release(&truname);
 488                         goto cleanup;
 489                 }
 490         }
 491
 492         if (!strcmp(remote, "FETCH_HEAD") &&
 493                         !access(git_path("FETCH_HEAD"), R_OK)) {
 494                 FILE *fp;
 495                 struct strbuf line = STRBUF_INIT;
 496                 char *ptr;
 497
 498                 fp = fopen(git_path("FETCH_HEAD"), "r");
 499                 if (!fp)
 500                         die_errno(_("could not open '%s' for reading"),
 501                                   git_path("FETCH_HEAD"));
 502                 strbuf_getline(&line, fp, '\n');
 503                 fclose(fp);
 504                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 505                 if (ptr)
 506                         strbuf_remove(&line, ptr-line.buf+1, 13);
 507                 strbuf_addbuf(msg, &line);
 508                 strbuf_release(&line);
 509                 goto cleanup;
 510         }
 511         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 512                 sha1_to_hex(remote_head->object.sha1), remote);
 513 cleanup:
 514         strbuf_release(&buf);
 515         strbuf_release(&bname);
 516 }
 517
 518 static void parse_branch_merge_options(char *bmo)
 519 {
 520         const char **argv;
 521         int argc;
 522
 523         if (!bmo)
 524                 return;
 525         argc = split_cmdline(bmo, &argv);
 526         if (argc < 0)
 527                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 528                     split_cmdline_strerror(argc));
 529         argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 530         memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 531         argc++;
 532         argv[0] = "branch.*.mergeoptions";
 533         parse_options(argc, argv, NULL, builtin_merge_options,
 534                       builtin_merge_usage, 0);
 535         free(argv);
 536 }
 537
 538 static int git_merge_config(const char *k, const char *v, void *cb)
 539 {
 540         int status;
 541
 542         if (branch && !prefixcmp(k, "branch.") &&
 543                 !prefixcmp(k + 7, branch) &&
 544                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 545                 free(branch_mergeoptions);
 546                 branch_mergeoptions = xstrdup(v);
 547                 return 0;
 548         }
 549
 550         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 551                 show_diffstat = git_config_bool(k, v);
 552         else if (!strcmp(k, "pull.twohead"))
 553                 return git_config_string(&pull_twohead, k, v);
 554         else if (!strcmp(k, "pull.octopus"))
 555                 return git_config_string(&pull_octopus, k, v);
 556         else if (!strcmp(k, "merge.renormalize"))
 557                 option_renormalize = git_config_bool(k, v);
 558         else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary")) {
 559                 int is_bool;
 560                 shortlog_len = git_config_bool_or_int(k, v, &is_bool);
 561                 if (!is_bool && shortlog_len < 0)
 562                         return error(_("%s: negative length %s"), k, v);
 563                 if (is_bool && shortlog_len)
 564                         shortlog_len = DEFAULT_MERGE_LOG_LEN;
 565                 return 0;
 566         } else if (!strcmp(k, "merge.ff")) {
 567                 int boolval = git_config_maybe_bool(k, v);
 568                 if (0 <= boolval) {
 569                         allow_fast_forward = boolval;
 570                 } else if (v && !strcmp(v, "only")) {
 571                         allow_fast_forward = 1;
 572                         fast_forward_only = 1;
 573                 } /* do not barf on values from future versions of git */
 574                 return 0;
 575         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 576                 default_to_upstream = git_config_bool(k, v);
 577                 return 0;
 578         }
 579
 580         status = git_gpg_config(k, v, NULL);
 581         if (status)
 582                 return status;
 583         return git_diff_ui_config(k, v, cb);
 584 }
 585
 586 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 587                              unsigned char *one)
 588 {
 589         int i, nr_trees = 0;
 590         struct tree *trees[MAX_UNPACK_TREES];
 591         struct tree_desc t[MAX_UNPACK_TREES];
 592         struct unpack_trees_options opts;
 593
 594         memset(&opts, 0, sizeof(opts));
 595         opts.head_idx = 2;
 596         opts.src_index = &the_index;
 597         opts.dst_index = &the_index;
 598         opts.update = 1;
 599         opts.verbose_update = 1;
 600         opts.trivial_merges_only = 1;
 601         opts.merge = 1;
 602         trees[nr_trees] = parse_tree_indirect(common);
 603         if (!trees[nr_trees++])
 604                 return -1;
 605         trees[nr_trees] = parse_tree_indirect(head);
 606         if (!trees[nr_trees++])
 607                 return -1;
 608         trees[nr_trees] = parse_tree_indirect(one);
 609         if (!trees[nr_trees++])
 610                 return -1;
 611         opts.fn = threeway_merge;
 612         cache_tree_free(&active_cache_tree);
 613         for (i = 0; i < nr_trees; i++) {
 614                 parse_tree(trees[i]);
 615                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 616         }
 617         if (unpack_trees(nr_trees, t, &opts))
 618                 return -1;
 619         return 0;
 620 }
 621
 622 static void write_tree_trivial(unsigned char *sha1)
 623 {
 624         if (write_cache_as_tree(sha1, 0, NULL))
 625                 die(_("git write-tree failed to write a tree"));
 626 }
 627
 628 static const char *merge_argument(struct commit *commit)
 629 {
 630         if (commit)
 631                 return sha1_to_hex(commit->object.sha1);
 632         else
 633                 return EMPTY_TREE_SHA1_HEX;
 634 }
 635
 636 int try_merge_command(const char *strategy, size_t xopts_nr,
 637                       const char **xopts, struct commit_list *common,
 638                       const char *head_arg, struct commit_list *remotes)
 639 {
 640         const char **args;
 641         int i = 0, x = 0, ret;
 642         struct commit_list *j;
 643         struct strbuf buf = STRBUF_INIT;
 644
 645         args = xmalloc((4 + xopts_nr + commit_list_count(common) +
 646                         commit_list_count(remotes)) * sizeof(char *));
 647         strbuf_addf(&buf, "merge-%s", strategy);
 648         args[i++] = buf.buf;
 649         for (x = 0; x < xopts_nr; x++) {
 650                 char *s = xmalloc(strlen(xopts[x])+2+1);
 651                 strcpy(s, "--");
 652                 strcpy(s+2, xopts[x]);
 653                 args[i++] = s;
 654         }
 655         for (j = common; j; j = j->next)
 656                 args[i++] = xstrdup(merge_argument(j->item));
 657         args[i++] = "--";
 658         args[i++] = head_arg;
 659         for (j = remotes; j; j = j->next)
 660                 args[i++] = xstrdup(merge_argument(j->item));
 661         args[i] = NULL;
 662         ret = run_command_v_opt(args, RUN_GIT_CMD);
 663         strbuf_release(&buf);
 664         i = 1;
 665         for (x = 0; x < xopts_nr; x++)
 666                 free((void *)args[i++]);
 667         for (j = common; j; j = j->next)
 668                 free((void *)args[i++]);
 669         i += 2;
 670         for (j = remotes; j; j = j->next)
 671                 free((void *)args[i++]);
 672         free(args);
 673         discard_cache();
 674         if (read_cache() < 0)
 675                 die(_("failed to read the cache"));
 676         resolve_undo_clear();
 677
 678         return ret;
 679 }
 680
 681 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 682                               struct commit *head, const char *head_arg)
 683 {
 684         int index_fd;
 685         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 686
 687         index_fd = hold_locked_index(lock, 1);
 688         refresh_cache(REFRESH_QUIET);
 689         if (active_cache_changed &&
 690                         (write_cache(index_fd, active_cache, active_nr) ||
 691                          commit_locked_index(lock)))
 692                 return error(_("Unable to write index."));
 693         rollback_lock_file(lock);
 694
 695         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 696                 int clean, x;
 697                 struct commit *result;
 698                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 699                 int index_fd;
 700                 struct commit_list *reversed = NULL;
 701                 struct merge_options o;
 702                 struct commit_list *j;
 703
 704                 if (remoteheads->next) {
 705                         error(_("Not handling anything other than two heads merge."));
 706                         return 2;
 707                 }
 708
 709                 init_merge_options(&o);
 710                 if (!strcmp(strategy, "subtree"))
 711                         o.subtree_shift = "";
 712
 713                 o.renormalize = option_renormalize;
 714                 o.show_rename_progress =
 715                         show_progress == -1 ? isatty(2) : show_progress;
 716
 717                 for (x = 0; x < xopts_nr; x++)
 718                         if (parse_merge_opt(&o, xopts[x]))
 719                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 720
 721                 o.branch1 = head_arg;
 722                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 723
 724                 for (j = common; j; j = j->next)
 725                         commit_list_insert(j->item, &reversed);
 726
 727                 index_fd = hold_locked_index(lock, 1);
 728                 clean = merge_recursive(&o, head,
 729                                 remoteheads->item, reversed, &result);
 730                 if (active_cache_changed &&
 731                                 (write_cache(index_fd, active_cache, active_nr) ||
 732                                  commit_locked_index(lock)))
 733                         die (_("unable to write %s"), get_index_file());
 734                 rollback_lock_file(lock);
 735                 return clean ? 0 : 1;
 736         } else {
 737                 return try_merge_command(strategy, xopts_nr, xopts,
 738                                                 common, head_arg, remoteheads);
 739         }
 740 }
 741
 742 static void count_diff_files(struct diff_queue_struct *q,
 743                              struct diff_options *opt, void *data)
 744 {
 745         int *count = data;
 746
 747         (*count) += q->nr;
 748 }
 749
 750 static int count_unmerged_entries(void)
 751 {
 752         int i, ret = 0;
 753
 754         for (i = 0; i < active_nr; i++)
 755                 if (ce_stage(active_cache[i]))
 756                         ret++;
 757
 758         return ret;
 759 }
 760
 761 int checkout_fast_forward(const unsigned char *head, const unsigned char *remote)
 762 {
 763         struct tree *trees[MAX_UNPACK_TREES];
 764         struct unpack_trees_options opts;
 765         struct tree_desc t[MAX_UNPACK_TREES];
 766         int i, fd, nr_trees = 0;
 767         struct dir_struct dir;
 768         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 769
 770         refresh_cache(REFRESH_QUIET);
 771
 772         fd = hold_locked_index(lock_file, 1);
 773
 774         memset(&trees, 0, sizeof(trees));
 775         memset(&opts, 0, sizeof(opts));
 776         memset(&t, 0, sizeof(t));
 777         memset(&dir, 0, sizeof(dir));
 778         dir.flags |= DIR_SHOW_IGNORED;
 779         dir.exclude_per_dir = ".gitignore";
 780         opts.dir = &dir;
 781
 782         opts.head_idx = 1;
 783         opts.src_index = &the_index;
 784         opts.dst_index = &the_index;
 785         opts.update = 1;
 786         opts.verbose_update = 1;
 787         opts.merge = 1;
 788         opts.fn = twoway_merge;
 789         setup_unpack_trees_porcelain(&opts, "merge");
 790
 791         trees[nr_trees] = parse_tree_indirect(head);
 792         if (!trees[nr_trees++])
 793                 return -1;
 794         trees[nr_trees] = parse_tree_indirect(remote);
 795         if (!trees[nr_trees++])
 796                 return -1;
 797         for (i = 0; i < nr_trees; i++) {
 798                 parse_tree(trees[i]);
 799                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 800         }
 801         if (unpack_trees(nr_trees, t, &opts))
 802                 return -1;
 803         if (write_cache(fd, active_cache, active_nr) ||
 804                 commit_locked_index(lock_file))
 805                 die(_("unable to write new index file"));
 806         return 0;
 807 }
 808
 809 static void split_merge_strategies(const char *string, struct strategy **list,
 810                                    int *nr, int *alloc)
 811 {
 812         char *p, *q, *buf;
 813
 814         if (!string)
 815                 return;
 816
 817         buf = xstrdup(string);
 818         q = buf;
 819         for (;;) {
 820                 p = strchr(q, ' ');
 821                 if (!p) {
 822                         ALLOC_GROW(*list, *nr + 1, *alloc);
 823                         (*list)[(*nr)++].name = xstrdup(q);
 824                         free(buf);
 825                         return;
 826                 } else {
 827                         *p = '\0';
 828                         ALLOC_GROW(*list, *nr + 1, *alloc);
 829                         (*list)[(*nr)++].name = xstrdup(q);
 830                         q = ++p;
 831                 }
 832         }
 833 }
 834
 835 static void add_strategies(const char *string, unsigned attr)
 836 {
 837         struct strategy *list = NULL;
 838         int list_alloc = 0, list_nr = 0, i;
 839
 840         memset(&list, 0, sizeof(list));
 841         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 842         if (list) {
 843                 for (i = 0; i < list_nr; i++)
 844                         append_strategy(get_strategy(list[i].name));
 845                 return;
 846         }
 847         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 848                 if (all_strategy[i].attr & attr)
 849                         append_strategy(&all_strategy[i]);
 850
 851 }
 852
 853 static void write_merge_msg(struct strbuf *msg)
 854 {
 855         int fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
 856         if (fd < 0)
 857                 die_errno(_("Could not open '%s' for writing"),
 858                           git_path("MERGE_MSG"));
 859         if (write_in_full(fd, msg->buf, msg->len) != msg->len)
 860                 die_errno(_("Could not write to '%s'"), git_path("MERGE_MSG"));
 861         close(fd);
 862 }
 863
 864 static void read_merge_msg(struct strbuf *msg)
 865 {
 866         strbuf_reset(msg);
 867         if (strbuf_read_file(msg, git_path("MERGE_MSG"), 0) < 0)
 868                 die_errno(_("Could not read from '%s'"), git_path("MERGE_MSG"));
 869 }
 870
 871 static void write_merge_state(void);
 872 static void abort_commit(const char *err_msg)
 873 {
 874         if (err_msg)
 875                 error("%s", err_msg);
 876         fprintf(stderr,
 877                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 878         write_merge_state();
 879         exit(1);
 880 }
 881
 882 static void prepare_to_commit(void)
 883 {
 884         struct strbuf msg = STRBUF_INIT;
 885         strbuf_addbuf(&msg, &merge_msg);
 886         strbuf_addch(&msg, '\n');
 887         write_merge_msg(&msg);
 888         run_hook(get_index_file(), "prepare-commit-msg",
 889                  git_path("MERGE_MSG"), "merge", NULL, NULL);
 890         if (option_edit) {
 891                 if (launch_editor(git_path("MERGE_MSG"), NULL, NULL))
 892                         abort_commit(NULL);
 893         }
 894         read_merge_msg(&msg);
 895         stripspace(&msg, option_edit);
 896         if (!msg.len)
 897                 abort_commit(_("Empty commit message."));
 898         strbuf_release(&merge_msg);
 899         strbuf_addbuf(&merge_msg, &msg);
 900         strbuf_release(&msg);
 901 }
 902
 903 static int merge_trivial(struct commit *head)
 904 {
 905         unsigned char result_tree[20], result_commit[20];
 906         struct commit_list *parent = xmalloc(sizeof(*parent));
 907
 908         write_tree_trivial(result_tree);
 909         printf(_("Wonderful.\n"));
 910         parent->item = head;
 911         parent->next = xmalloc(sizeof(*parent->next));
 912         parent->next->item = remoteheads->item;
 913         parent->next->next = NULL;
 914         prepare_to_commit();
 915         commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL,
 916                     sign_commit);
 917         finish(head, result_commit, "In-index merge");
 918         drop_save();
 919         return 0;
 920 }
 921
 922 static int finish_automerge(struct commit *head,
 923                             struct commit_list *common,
 924                             unsigned char *result_tree,
 925                             const char *wt_strategy)
 926 {
 927         struct commit_list *parents = NULL, *j;
 928         struct strbuf buf = STRBUF_INIT;
 929         unsigned char result_commit[20];
 930
 931         free_commit_list(common);
 932         if (allow_fast_forward) {
 933                 parents = remoteheads;
 934                 commit_list_insert(head, &parents);
 935                 parents = reduce_heads(parents);
 936         } else {
 937                 struct commit_list **pptr = &parents;
 938
 939                 pptr = &commit_list_insert(head,
 940                                 pptr)->next;
 941                 for (j = remoteheads; j; j = j->next)
 942                         pptr = &commit_list_insert(j->item, pptr)->next;
 943         }
 944         strbuf_addch(&merge_msg, '\n');
 945         prepare_to_commit();
 946         free_commit_list(remoteheads);
 947         commit_tree(merge_msg.buf, result_tree, parents, result_commit,
 948                     NULL, sign_commit);
 949         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 950         finish(head, result_commit, buf.buf);
 951         strbuf_release(&buf);
 952         drop_save();
 953         return 0;
 954 }
 955
 956 static int suggest_conflicts(int renormalizing)
 957 {
 958         FILE *fp;
 959         int pos;
 960
 961         fp = fopen(git_path("MERGE_MSG"), "a");
 962         if (!fp)
 963                 die_errno(_("Could not open '%s' for writing"),
 964                           git_path("MERGE_MSG"));
 965         fprintf(fp, "\nConflicts:\n");
 966         for (pos = 0; pos < active_nr; pos++) {
 967                 struct cache_entry *ce = active_cache[pos];
 968
 969                 if (ce_stage(ce)) {
 970                         fprintf(fp, "\t%s\n", ce->name);
 971                         while (pos + 1 < active_nr &&
 972                                         !strcmp(ce->name,
 973                                                 active_cache[pos + 1]->name))
 974                                 pos++;
 975                 }
 976         }
 977         fclose(fp);
 978         rerere(allow_rerere_auto);
 979         printf(_("Automatic merge failed; "
 980                         "fix conflicts and then commit the result.\n"));
 981         return 1;
 982 }
 983
 984 static struct commit *is_old_style_invocation(int argc, const char **argv,
 985                                               const unsigned char *head)
 986 {
 987         struct commit *second_token = NULL;
 988         if (argc > 2) {
 989                 unsigned char second_sha1[20];
 990
 991                 if (get_sha1(argv[1], second_sha1))
 992                         return NULL;
 993                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 994                 if (!second_token)
 995                         die(_("'%s' is not a commit"), argv[1]);
 996                 if (hashcmp(second_token->object.sha1, head))
 997                         return NULL;
 998         }
 999         return second_token;
1000 }
1001
1002 static int evaluate_result(void)
1003 {
1004         int cnt = 0;
1005         struct rev_info rev;
1006
1007         /* Check how many files differ. */
1008         init_revisions(&rev, "");
1009         setup_revisions(0, NULL, &rev, NULL);
1010         rev.diffopt.output_format |=
1011                 DIFF_FORMAT_CALLBACK;
1012         rev.diffopt.format_callback = count_diff_files;
1013         rev.diffopt.format_callback_data = &cnt;
1014         run_diff_files(&rev, 0);
1015
1016         /*
1017          * Check how many unmerged entries are
1018          * there.
1019          */
1020         cnt += count_unmerged_entries();
1021
1022         return cnt;
1023 }
1024
1025 /*
1026  * Pretend as if the user told us to merge with the tracking
1027  * branch we have for the upstream of the current branch
1028  */
1029 static int setup_with_upstream(const char ***argv)
1030 {
1031         struct branch *branch = branch_get(NULL);
1032         int i;
1033         const char **args;
1034
1035         if (!branch)
1036                 die(_("No current branch."));
1037         if (!branch->remote)
1038                 die(_("No remote for the current branch."));
1039         if (!branch->merge_nr)
1040                 die(_("No default upstream defined for the current branch."));
1041
1042         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
1043         for (i = 0; i < branch->merge_nr; i++) {
1044                 if (!branch->merge[i]->dst)
1045                         die(_("No remote tracking branch for %s from %s"),
1046                             branch->merge[i]->src, branch->remote_name);
1047                 args[i] = branch->merge[i]->dst;
1048         }
1049         args[i] = NULL;
1050         *argv = args;
1051         return i;
1052 }
1053
1054 static void write_merge_state(void)
1055 {
1056         int fd;
1057         struct commit_list *j;
1058         struct strbuf buf = STRBUF_INIT;
1059
1060         for (j = remoteheads; j; j = j->next) {
1061                 unsigned const char *sha1;
1062                 struct commit *c = j->item;
1063                 if (c->util && merge_remote_util(c)->obj) {
1064                         sha1 = merge_remote_util(c)->obj->sha1;
1065                 } else {
1066                         sha1 = c->object.sha1;
1067                 }
1068                 strbuf_addf(&buf, "%s\n", sha1_to_hex(sha1));
1069         }
1070         fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1071         if (fd < 0)
1072                 die_errno(_("Could not open '%s' for writing"),
1073                           git_path("MERGE_HEAD"));
1074         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1075                 die_errno(_("Could not write to '%s'"), git_path("MERGE_HEAD"));
1076         close(fd);
1077         strbuf_addch(&merge_msg, '\n');
1078         write_merge_msg(&merge_msg);
1079         fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1080         if (fd < 0)
1081                 die_errno(_("Could not open '%s' for writing"),
1082                           git_path("MERGE_MODE"));
1083         strbuf_reset(&buf);
1084         if (!allow_fast_forward)
1085                 strbuf_addf(&buf, "no-ff");
1086         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1087                 die_errno(_("Could not write to '%s'"), git_path("MERGE_MODE"));
1088         close(fd);
1089 }
1090
1091 int cmd_merge(int argc, const char **argv, const char *prefix)
1092 {
1093         unsigned char result_tree[20];
1094         unsigned char stash[20];
1095         unsigned char head_sha1[20];
1096         struct commit *head_commit;
1097         struct strbuf buf = STRBUF_INIT;
1098         const char *head_arg;
1099         int flag, i;
1100         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1101         struct commit_list *common = NULL;
1102         const char *best_strategy = NULL, *wt_strategy = NULL;
1103         struct commit_list **remotes = &remoteheads;
1104
1105         if (argc == 2 && !strcmp(argv[1], "-h"))
1106                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1107
1108         /*
1109          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1110          * current branch.
1111          */
1112         branch = resolve_ref("HEAD", head_sha1, 0, &flag);
1113         if (branch && !prefixcmp(branch, "refs/heads/"))
1114                 branch += 11;
1115         if (!branch || is_null_sha1(head_sha1))
1116                 head_commit = NULL;
1117         else
1118                 head_commit = lookup_commit_or_die(head_sha1, "HEAD");
1119
1120         git_config(git_merge_config, NULL);
1121
1122         if (branch_mergeoptions)
1123                 parse_branch_merge_options(branch_mergeoptions);
1124         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1125                         builtin_merge_usage, 0);
1126
1127         if (verbosity < 0 && show_progress == -1)
1128                 show_progress = 0;
1129
1130         if (abort_current_merge) {
1131                 int nargc = 2;
1132                 const char *nargv[] = {"reset", "--merge", NULL};
1133
1134                 if (!file_exists(git_path("MERGE_HEAD")))
1135                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1136
1137                 /* Invoke 'git reset --merge' */
1138                 return cmd_reset(nargc, nargv, prefix);
1139         }
1140
1141         if (read_cache_unmerged())
1142                 die_resolve_conflict("merge");
1143
1144         if (file_exists(git_path("MERGE_HEAD"))) {
1145                 /*
1146                  * There is no unmerged entry, don't advise 'git
1147                  * add/rm <file>', just 'git commit'.
1148                  */
1149                 if (advice_resolve_conflict)
1150                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1151                                   "Please, commit your changes before you can merge."));
1152                 else
1153                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1154         }
1155         if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1156                 if (advice_resolve_conflict)
1157                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1158                             "Please, commit your changes before you can merge."));
1159                 else
1160                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1161         }
1162         resolve_undo_clear();
1163
1164         if (verbosity < 0)
1165                 show_diffstat = 0;
1166
1167         if (squash) {
1168                 if (!allow_fast_forward)
1169                         die(_("You cannot combine --squash with --no-ff."));
1170                 option_commit = 0;
1171         }
1172
1173         if (!allow_fast_forward && fast_forward_only)
1174                 die(_("You cannot combine --no-ff with --ff-only."));
1175
1176         if (!abort_current_merge) {
1177                 if (!argc && default_to_upstream)
1178                         argc = setup_with_upstream(&argv);
1179                 else if (argc == 1 && !strcmp(argv[0], "-"))
1180                         argv[0] = "@{-1}";
1181         }
1182         if (!argc)
1183                 usage_with_options(builtin_merge_usage,
1184                         builtin_merge_options);
1185
1186         /*
1187          * This could be traditional "merge <msg> HEAD <commit>..."  and
1188          * the way we can tell it is to see if the second token is HEAD,
1189          * but some people might have misused the interface and used a
1190          * committish that is the same as HEAD there instead.
1191          * Traditional format never would have "-m" so it is an
1192          * additional safety measure to check for it.
1193          */
1194
1195         if (!have_message && head_commit &&
1196             is_old_style_invocation(argc, argv, head_commit->object.sha1)) {
1197                 strbuf_addstr(&merge_msg, argv[0]);
1198                 head_arg = argv[1];
1199                 argv += 2;
1200                 argc -= 2;
1201         } else if (!head_commit) {
1202                 struct commit *remote_head;
1203                 /*
1204                  * If the merged head is a valid one there is no reason
1205                  * to forbid "git merge" into a branch yet to be born.
1206                  * We do the same for "git pull".
1207                  */
1208                 if (argc != 1)
1209                         die(_("Can merge only exactly one commit into "
1210                                 "empty head"));
1211                 if (squash)
1212                         die(_("Squash commit into empty head not supported yet"));
1213                 if (!allow_fast_forward)
1214                         die(_("Non-fast-forward commit does not make sense into "
1215                             "an empty head"));
1216                 remote_head = get_merge_parent(argv[0]);
1217                 if (!remote_head)
1218                         die(_("%s - not something we can merge"), argv[0]);
1219                 read_empty(remote_head->object.sha1, 0);
1220                 update_ref("initial pull", "HEAD", remote_head->object.sha1,
1221                            NULL, 0, DIE_ON_ERR);
1222                 return 0;
1223         } else {
1224                 struct strbuf merge_names = STRBUF_INIT;
1225
1226                 /* We are invoked directly as the first-class UI. */
1227                 head_arg = "HEAD";
1228
1229                 /*
1230                  * All the rest are the commits being merged; prepare
1231                  * the standard merge summary message to be appended
1232                  * to the given message.
1233                  */
1234                 for (i = 0; i < argc; i++)
1235                         merge_name(argv[i], &merge_names);
1236
1237                 if (!have_message || shortlog_len) {
1238                         struct fmt_merge_msg_opts opts;
1239                         memset(&opts, 0, sizeof(opts));
1240                         opts.add_title = !have_message;
1241                         opts.shortlog_len = shortlog_len;
1242
1243                         fmt_merge_msg(&merge_names, &merge_msg, &opts);
1244                         if (merge_msg.len)
1245                                 strbuf_setlen(&merge_msg, merge_msg.len - 1);
1246                 }
1247         }
1248
1249         if (!head_commit || !argc)
1250                 usage_with_options(builtin_merge_usage,
1251                         builtin_merge_options);
1252
1253         strbuf_addstr(&buf, "merge");
1254         for (i = 0; i < argc; i++)
1255                 strbuf_addf(&buf, " %s", argv[i]);
1256         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1257         strbuf_reset(&buf);
1258
1259         for (i = 0; i < argc; i++) {
1260                 struct commit *commit = get_merge_parent(argv[i]);
1261                 if (!commit)
1262                         die(_("%s - not something we can merge"), argv[i]);
1263                 remotes = &commit_list_insert(commit, remotes)->next;
1264                 strbuf_addf(&buf, "GITHEAD_%s",
1265                             sha1_to_hex(commit->object.sha1));
1266                 setenv(buf.buf, argv[i], 1);
1267                 strbuf_reset(&buf);
1268                 if (merge_remote_util(commit) &&
1269                     merge_remote_util(commit)->obj &&
1270                     merge_remote_util(commit)->obj->type == OBJ_TAG) {
1271                         option_edit = 1;
1272                         allow_fast_forward = 0;
1273                 }
1274         }
1275
1276         if (!use_strategies) {
1277                 if (!remoteheads->next)
1278                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1279                 else
1280                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1281         }
1282
1283         for (i = 0; i < use_strategies_nr; i++) {
1284                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1285                         allow_fast_forward = 0;
1286                 if (use_strategies[i]->attr & NO_TRIVIAL)
1287                         allow_trivial = 0;
1288         }
1289
1290         if (!remoteheads->next)
1291                 common = get_merge_bases(head_commit, remoteheads->item, 1);
1292         else {
1293                 struct commit_list *list = remoteheads;
1294                 commit_list_insert(head_commit, &list);
1295                 common = get_octopus_merge_bases(list);
1296                 free(list);
1297         }
1298
1299         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
1300                    NULL, 0, DIE_ON_ERR);
1301
1302         if (!common)
1303                 ; /* No common ancestors found. We need a real merge. */
1304         else if (!remoteheads->next && !common->next &&
1305                         common->item == remoteheads->item) {
1306                 /*
1307                  * If head can reach all the merge then we are up to date.
1308                  * but first the most common case of merging one remote.
1309                  */
1310                 finish_up_to_date("Already up-to-date.");
1311                 return 0;
1312         } else if (allow_fast_forward && !remoteheads->next &&
1313                         !common->next &&
1314                         !hashcmp(common->item->object.sha1, head_commit->object.sha1)) {
1315                 /* Again the most common case of merging one remote. */
1316                 struct strbuf msg = STRBUF_INIT;
1317                 struct commit *commit;
1318                 char hex[41];
1319
1320                 strcpy(hex, find_unique_abbrev(head_commit->object.sha1, DEFAULT_ABBREV));
1321
1322                 if (verbosity >= 0)
1323                         printf(_("Updating %s..%s\n"),
1324                                 hex,
1325                                 find_unique_abbrev(remoteheads->item->object.sha1,
1326                                 DEFAULT_ABBREV));
1327                 strbuf_addstr(&msg, "Fast-forward");
1328                 if (have_message)
1329                         strbuf_addstr(&msg,
1330                                 " (no commit created; -m option ignored)");
1331                 commit = remoteheads->item;
1332                 if (!commit)
1333                         return 1;
1334
1335                 if (checkout_fast_forward(head_commit->object.sha1,
1336                                           commit->object.sha1))
1337                         return 1;
1338
1339                 finish(head_commit, commit->object.sha1, msg.buf);
1340                 drop_save();
1341                 return 0;
1342         } else if (!remoteheads->next && common->next)
1343                 ;
1344                 /*
1345                  * We are not doing octopus and not fast-forward.  Need
1346                  * a real merge.
1347                  */
1348         else if (!remoteheads->next && !common->next && option_commit) {
1349                 /*
1350                  * We are not doing octopus, not fast-forward, and have
1351                  * only one common.
1352                  */
1353                 refresh_cache(REFRESH_QUIET);
1354                 if (allow_trivial && !fast_forward_only) {
1355                         /* See if it is really trivial. */
1356                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1357                         printf(_("Trying really trivial in-index merge...\n"));
1358                         if (!read_tree_trivial(common->item->object.sha1,
1359                                         head_commit->object.sha1, remoteheads->item->object.sha1))
1360                                 return merge_trivial(head_commit);
1361                         printf(_("Nope.\n"));
1362                 }
1363         } else {
1364                 /*
1365                  * An octopus.  If we can reach all the remote we are up
1366                  * to date.
1367                  */
1368                 int up_to_date = 1;
1369                 struct commit_list *j;
1370
1371                 for (j = remoteheads; j; j = j->next) {
1372                         struct commit_list *common_one;
1373
1374                         /*
1375                          * Here we *have* to calculate the individual
1376                          * merge_bases again, otherwise "git merge HEAD^
1377                          * HEAD^^" would be missed.
1378                          */
1379                         common_one = get_merge_bases(head_commit, j->item, 1);
1380                         if (hashcmp(common_one->item->object.sha1,
1381                                 j->item->object.sha1)) {
1382                                 up_to_date = 0;
1383                                 break;
1384                         }
1385                 }
1386                 if (up_to_date) {
1387                         finish_up_to_date("Already up-to-date. Yeeah!");
1388                         return 0;
1389                 }
1390         }
1391
1392         if (fast_forward_only)
1393                 die(_("Not possible to fast-forward, aborting."));
1394
1395         /* We are going to make a new commit. */
1396         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1397
1398         /*
1399          * At this point, we need a real merge.  No matter what strategy
1400          * we use, it would operate on the index, possibly affecting the
1401          * working tree, and when resolved cleanly, have the desired
1402          * tree in the index -- this means that the index must be in
1403          * sync with the head commit.  The strategies are responsible
1404          * to ensure this.
1405          */
1406         if (use_strategies_nr == 1 ||
1407             /*
1408              * Stash away the local changes so that we can try more than one.
1409              */
1410             save_state(stash))
1411                 hashcpy(stash, null_sha1);
1412
1413         for (i = 0; i < use_strategies_nr; i++) {
1414                 int ret;
1415                 if (i) {
1416                         printf(_("Rewinding the tree to pristine...\n"));
1417                         restore_state(head_commit->object.sha1, stash);
1418                 }
1419                 if (use_strategies_nr != 1)
1420                         printf(_("Trying merge strategy %s...\n"),
1421                                 use_strategies[i]->name);
1422                 /*
1423                  * Remember which strategy left the state in the working
1424                  * tree.
1425                  */
1426                 wt_strategy = use_strategies[i]->name;
1427
1428                 ret = try_merge_strategy(use_strategies[i]->name,
1429                                          common, head_commit, head_arg);
1430                 if (!option_commit && !ret) {
1431                         merge_was_ok = 1;
1432                         /*
1433                          * This is necessary here just to avoid writing
1434                          * the tree, but later we will *not* exit with
1435                          * status code 1 because merge_was_ok is set.
1436                          */
1437                         ret = 1;
1438                 }
1439
1440                 if (ret) {
1441                         /*
1442                          * The backend exits with 1 when conflicts are
1443                          * left to be resolved, with 2 when it does not
1444                          * handle the given merge at all.
1445                          */
1446                         if (ret == 1) {
1447                                 int cnt = evaluate_result();
1448
1449                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1450                                         best_strategy = use_strategies[i]->name;
1451                                         best_cnt = cnt;
1452                                 }
1453                         }
1454                         if (merge_was_ok)
1455                                 break;
1456                         else
1457                                 continue;
1458                 }
1459
1460                 /* Automerge succeeded. */
1461                 write_tree_trivial(result_tree);
1462                 automerge_was_ok = 1;
1463                 break;
1464         }
1465
1466         /*
1467          * If we have a resulting tree, that means the strategy module
1468          * auto resolved the merge cleanly.
1469          */
1470         if (automerge_was_ok)
1471                 return finish_automerge(head_commit, common, result_tree,
1472                                         wt_strategy);
1473
1474         /*
1475          * Pick the result from the best strategy and have the user fix
1476          * it up.
1477          */
1478         if (!best_strategy) {
1479                 restore_state(head_commit->object.sha1, stash);
1480                 if (use_strategies_nr > 1)
1481                         fprintf(stderr,
1482                                 _("No merge strategy handled the merge.\n"));
1483                 else
1484                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1485                                 use_strategies[0]->name);
1486                 return 2;
1487         } else if (best_strategy == wt_strategy)
1488                 ; /* We already have its result in the working tree. */
1489         else {
1490                 printf(_("Rewinding the tree to pristine...\n"));
1491                 restore_state(head_commit->object.sha1, stash);
1492                 printf(_("Using the %s to prepare resolving by hand.\n"),
1493                         best_strategy);
1494                 try_merge_strategy(best_strategy, common, head_commit, head_arg);
1495         }
1496
1497         if (squash)
1498                 finish(head_commit, NULL, NULL);
1499         else
1500                 write_merge_state();
1501
1502         if (merge_was_ok) {
1503                 fprintf(stderr, _("Automatic merge went well; "
1504                         "stopped before committing as requested\n"));
1505                 return 0;
1506         } else
1507                 return suggest_conflicts(option_renormalize);
1508 }