builtin/merge.c

   1 /*
   2  * Builtin "git merge"
   3  *
   4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
   5  *
   6  * Based on git-merge.sh by Junio C Hamano.
   7  */
   8
   9 #include "cache.h"
  10 #include "parse-options.h"
  11 #include "builtin.h"
  12 #include "run-command.h"
  13 #include "diff.h"
  14 #include "refs.h"
  15 #include "commit.h"
  16 #include "diffcore.h"
  17 #include "revision.h"
  18 #include "unpack-trees.h"
  19 #include "cache-tree.h"
  20 #include "dir.h"
  21 #include "utf8.h"
  22 #include "log-tree.h"
  23 #include "color.h"
  24 #include "rerere.h"
  25 #include "help.h"
  26 #include "merge-recursive.h"
  27 #include "resolve-undo.h"
  28 #include "remote.h"
  29 #include "fmt-merge-msg.h"
  30 #include "gpg-interface.h"
  31
  32 #define DEFAULT_TWOHEAD (1<<0)
  33 #define DEFAULT_OCTOPUS (1<<1)
  34 #define NO_FAST_FORWARD (1<<2)
  35 #define NO_TRIVIAL      (1<<3)
  36
  37 struct strategy {
  38         const char *name;
  39         unsigned attr;
  40 };
  41
  42 static const char * const builtin_merge_usage[] = {
  43         N_("git merge [options] [<commit>...]"),
  44         N_("git merge [options] <msg> HEAD <commit>"),
  45         N_("git merge --abort"),
  46         NULL
  47 };
  48
  49 static int show_diffstat = 1, shortlog_len = -1, squash;
  50 static int option_commit = 1;
  51 static int option_edit = -1;
  52 static int allow_trivial = 1, have_message, verify_signatures;
  53 static int overwrite_ignore = 1;
  54 static struct strbuf merge_msg = STRBUF_INIT;
  55 static struct strategy **use_strategies;
  56 static size_t use_strategies_nr, use_strategies_alloc;
  57 static const char **xopts;
  58 static size_t xopts_nr, xopts_alloc;
  59 static const char *branch;
  60 static char *branch_mergeoptions;
  61 static int option_renormalize;
  62 static int verbosity;
  63 static int allow_rerere_auto;
  64 static int abort_current_merge;
  65 static int show_progress = -1;
  66 static int default_to_upstream;
  67 static const char *sign_commit;
  68
  69 static struct strategy all_strategy[] = {
  70         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  71         { "octopus",    DEFAULT_OCTOPUS },
  72         { "resolve",    0 },
  73         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  74         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  75 };
  76
  77 static const char *pull_twohead, *pull_octopus;
  78
  79 enum ff_type {
  80         FF_NO,
  81         FF_ALLOW,
  82         FF_ONLY
  83 };
  84
  85 static enum ff_type fast_forward = FF_ALLOW;
  86
  87 static int option_parse_message(const struct option *opt,
  88                                 const char *arg, int unset)
  89 {
  90         struct strbuf *buf = opt->value;
  91
  92         if (unset)
  93                 strbuf_setlen(buf, 0);
  94         else if (arg) {
  95                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  96                 have_message = 1;
  97         } else
  98                 return error(_("switch `m' requires a value"));
  99         return 0;
 100 }
 101
 102 static struct strategy *get_strategy(const char *name)
 103 {
 104         int i;
 105         struct strategy *ret;
 106         static struct cmdnames main_cmds, other_cmds;
 107         static int loaded;
 108
 109         if (!name)
 110                 return NULL;
 111
 112         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 113                 if (!strcmp(name, all_strategy[i].name))
 114                         return &all_strategy[i];
 115
 116         if (!loaded) {
 117                 struct cmdnames not_strategies;
 118                 loaded = 1;
 119
 120                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 121                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 122                 for (i = 0; i < main_cmds.cnt; i++) {
 123                         int j, found = 0;
 124                         struct cmdname *ent = main_cmds.names[i];
 125                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 126                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 127                                                 && !all_strategy[j].name[ent->len])
 128                                         found = 1;
 129                         if (!found)
 130                                 add_cmdname(&not_strategies, ent->name, ent->len);
 131                 }
 132                 exclude_cmds(&main_cmds, &not_strategies);
 133         }
 134         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 135                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 136                 fprintf(stderr, _("Available strategies are:"));
 137                 for (i = 0; i < main_cmds.cnt; i++)
 138                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 139                 fprintf(stderr, ".\n");
 140                 if (other_cmds.cnt) {
 141                         fprintf(stderr, _("Available custom strategies are:"));
 142                         for (i = 0; i < other_cmds.cnt; i++)
 143                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 144                         fprintf(stderr, ".\n");
 145                 }
 146                 exit(1);
 147         }
 148
 149         ret = xcalloc(1, sizeof(struct strategy));
 150         ret->name = xstrdup(name);
 151         ret->attr = NO_TRIVIAL;
 152         return ret;
 153 }
 154
 155 static void append_strategy(struct strategy *s)
 156 {
 157         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 158         use_strategies[use_strategies_nr++] = s;
 159 }
 160
 161 static int option_parse_strategy(const struct option *opt,
 162                                  const char *name, int unset)
 163 {
 164         if (unset)
 165                 return 0;
 166
 167         append_strategy(get_strategy(name));
 168         return 0;
 169 }
 170
 171 static int option_parse_x(const struct option *opt,
 172                           const char *arg, int unset)
 173 {
 174         if (unset)
 175                 return 0;
 176
 177         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 178         xopts[xopts_nr++] = xstrdup(arg);
 179         return 0;
 180 }
 181
 182 static int option_parse_n(const struct option *opt,
 183                           const char *arg, int unset)
 184 {
 185         show_diffstat = unset;
 186         return 0;
 187 }
 188
 189 static struct option builtin_merge_options[] = {
 190         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 191                 N_("do not show a diffstat at the end of the merge"),
 192                 PARSE_OPT_NOARG, option_parse_n },
 193         OPT_BOOL(0, "stat", &show_diffstat,
 194                 N_("show a diffstat at the end of the merge")),
 195         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
 196         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
 197           N_("add (at most <n>) entries from shortlog to merge commit message"),
 198           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 199         OPT_BOOL(0, "squash", &squash,
 200                 N_("create a single commit instead of doing a merge")),
 201         OPT_BOOL(0, "commit", &option_commit,
 202                 N_("perform a commit if the merge succeeds (default)")),
 203         OPT_BOOL('e', "edit", &option_edit,
 204                 N_("edit message before committing")),
 205         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
 206         { OPTION_SET_INT, 0, "ff-only", &fast_forward, NULL,
 207                 N_("abort if fast-forward is not possible"),
 208                 PARSE_OPT_NOARG | PARSE_OPT_NONEG, NULL, FF_ONLY },
 209         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 210         OPT_BOOL(0, "verify-signatures", &verify_signatures,
 211                 N_("Verify that the named commit has a valid GPG signature")),
 212         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
 213                 N_("merge strategy to use"), option_parse_strategy),
 214         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
 215                 N_("option for selected merge strategy"), option_parse_x),
 216         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
 217                 N_("merge commit message (for a non-fast-forward merge)"),
 218                 option_parse_message),
 219         OPT__VERBOSITY(&verbosity),
 220         OPT_BOOL(0, "abort", &abort_current_merge,
 221                 N_("abort the current in-progress merge")),
 222         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
 223         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
 224           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 225         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
 226         OPT_END()
 227 };
 228
 229 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 230 static void drop_save(void)
 231 {
 232         unlink(git_path("MERGE_HEAD"));
 233         unlink(git_path("MERGE_MSG"));
 234         unlink(git_path("MERGE_MODE"));
 235 }
 236
 237 static int save_state(unsigned char *stash)
 238 {
 239         int len;
 240         struct child_process cp;
 241         struct strbuf buffer = STRBUF_INIT;
 242         const char *argv[] = {"stash", "create", NULL};
 243
 244         memset(&cp, 0, sizeof(cp));
 245         cp.argv = argv;
 246         cp.out = -1;
 247         cp.git_cmd = 1;
 248
 249         if (start_command(&cp))
 250                 die(_("could not run stash."));
 251         len = strbuf_read(&buffer, cp.out, 1024);
 252         close(cp.out);
 253
 254         if (finish_command(&cp) || len < 0)
 255                 die(_("stash failed"));
 256         else if (!len)          /* no changes */
 257                 return -1;
 258         strbuf_setlen(&buffer, buffer.len-1);
 259         if (get_sha1(buffer.buf, stash))
 260                 die(_("not a valid object: %s"), buffer.buf);
 261         return 0;
 262 }
 263
 264 static void read_empty(unsigned const char *sha1, int verbose)
 265 {
 266         int i = 0;
 267         const char *args[7];
 268
 269         args[i++] = "read-tree";
 270         if (verbose)
 271                 args[i++] = "-v";
 272         args[i++] = "-m";
 273         args[i++] = "-u";
 274         args[i++] = EMPTY_TREE_SHA1_HEX;
 275         args[i++] = sha1_to_hex(sha1);
 276         args[i] = NULL;
 277
 278         if (run_command_v_opt(args, RUN_GIT_CMD))
 279                 die(_("read-tree failed"));
 280 }
 281
 282 static void reset_hard(unsigned const char *sha1, int verbose)
 283 {
 284         int i = 0;
 285         const char *args[6];
 286
 287         args[i++] = "read-tree";
 288         if (verbose)
 289                 args[i++] = "-v";
 290         args[i++] = "--reset";
 291         args[i++] = "-u";
 292         args[i++] = sha1_to_hex(sha1);
 293         args[i] = NULL;
 294
 295         if (run_command_v_opt(args, RUN_GIT_CMD))
 296                 die(_("read-tree failed"));
 297 }
 298
 299 static void restore_state(const unsigned char *head,
 300                           const unsigned char *stash)
 301 {
 302         struct strbuf sb = STRBUF_INIT;
 303         const char *args[] = { "stash", "apply", NULL, NULL };
 304
 305         if (is_null_sha1(stash))
 306                 return;
 307
 308         reset_hard(head, 1);
 309
 310         args[2] = sha1_to_hex(stash);
 311
 312         /*
 313          * It is OK to ignore error here, for example when there was
 314          * nothing to restore.
 315          */
 316         run_command_v_opt(args, RUN_GIT_CMD);
 317
 318         strbuf_release(&sb);
 319         refresh_cache(REFRESH_QUIET);
 320 }
 321
 322 /* This is called when no merge was necessary. */
 323 static void finish_up_to_date(const char *msg)
 324 {
 325         if (verbosity >= 0)
 326                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 327         drop_save();
 328 }
 329
 330 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 331 {
 332         struct rev_info rev;
 333         struct strbuf out = STRBUF_INIT;
 334         struct commit_list *j;
 335         const char *filename;
 336         int fd;
 337         struct pretty_print_context ctx = {0};
 338
 339         printf(_("Squash commit -- not updating HEAD\n"));
 340         filename = git_path("SQUASH_MSG");
 341         fd = open(filename, O_WRONLY | O_CREAT, 0666);
 342         if (fd < 0)
 343                 die_errno(_("Could not write to '%s'"), filename);
 344
 345         init_revisions(&rev, NULL);
 346         rev.ignore_merges = 1;
 347         rev.commit_format = CMIT_FMT_MEDIUM;
 348
 349         commit->object.flags |= UNINTERESTING;
 350         add_pending_object(&rev, &commit->object, NULL);
 351
 352         for (j = remoteheads; j; j = j->next)
 353                 add_pending_object(&rev, &j->item->object, NULL);
 354
 355         setup_revisions(0, NULL, &rev, NULL);
 356         if (prepare_revision_walk(&rev))
 357                 die(_("revision walk setup failed"));
 358
 359         ctx.abbrev = rev.abbrev;
 360         ctx.date_mode = rev.date_mode;
 361         ctx.fmt = rev.commit_format;
 362
 363         strbuf_addstr(&out, "Squashed commit of the following:\n");
 364         while ((commit = get_revision(&rev)) != NULL) {
 365                 strbuf_addch(&out, '\n');
 366                 strbuf_addf(&out, "commit %s\n",
 367                         sha1_to_hex(commit->object.sha1));
 368                 pretty_print_commit(&ctx, commit, &out);
 369         }
 370         if (write_in_full(fd, out.buf, out.len) != out.len)
 371                 die_errno(_("Writing SQUASH_MSG"));
 372         if (close(fd))
 373                 die_errno(_("Finishing SQUASH_MSG"));
 374         strbuf_release(&out);
 375 }
 376
 377 static void finish(struct commit *head_commit,
 378                    struct commit_list *remoteheads,
 379                    const unsigned char *new_head, const char *msg)
 380 {
 381         struct strbuf reflog_message = STRBUF_INIT;
 382         const unsigned char *head = head_commit->object.sha1;
 383
 384         if (!msg)
 385                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 386         else {
 387                 if (verbosity >= 0)
 388                         printf("%s\n", msg);
 389                 strbuf_addf(&reflog_message, "%s: %s",
 390                         getenv("GIT_REFLOG_ACTION"), msg);
 391         }
 392         if (squash) {
 393                 squash_message(head_commit, remoteheads);
 394         } else {
 395                 if (verbosity >= 0 && !merge_msg.len)
 396                         printf(_("No merge message -- not updating HEAD\n"));
 397                 else {
 398                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 399                         update_ref(reflog_message.buf, "HEAD",
 400                                 new_head, head, 0,
 401                                 DIE_ON_ERR);
 402                         /*
 403                          * We ignore errors in 'gc --auto', since the
 404                          * user should see them.
 405                          */
 406                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 407                 }
 408         }
 409         if (new_head && show_diffstat) {
 410                 struct diff_options opts;
 411                 diff_setup(&opts);
 412                 opts.stat_width = -1; /* use full terminal width */
 413                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
 414                 opts.output_format |=
 415                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 416                 opts.detect_rename = DIFF_DETECT_RENAME;
 417                 diff_setup_done(&opts);
 418                 diff_tree_sha1(head, new_head, "", &opts);
 419                 diffcore_std(&opts);
 420                 diff_flush(&opts);
 421         }
 422
 423         /* Run a post-merge hook */
 424         run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
 425
 426         strbuf_release(&reflog_message);
 427 }
 428
 429 /* Get the name for the merge commit's message. */
 430 static void merge_name(const char *remote, struct strbuf *msg)
 431 {
 432         struct commit *remote_head;
 433         unsigned char branch_head[20];
 434         struct strbuf buf = STRBUF_INIT;
 435         struct strbuf bname = STRBUF_INIT;
 436         const char *ptr;
 437         char *found_ref;
 438         int len, early;
 439
 440         strbuf_branchname(&bname, remote);
 441         remote = bname.buf;
 442
 443         memset(branch_head, 0, sizeof(branch_head));
 444         remote_head = get_merge_parent(remote);
 445         if (!remote_head)
 446                 die(_("'%s' does not point to a commit"), remote);
 447
 448         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 449                 if (starts_with(found_ref, "refs/heads/")) {
 450                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 451                                     sha1_to_hex(branch_head), remote);
 452                         goto cleanup;
 453                 }
 454                 if (starts_with(found_ref, "refs/tags/")) {
 455                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 456                                     sha1_to_hex(branch_head), remote);
 457                         goto cleanup;
 458                 }
 459                 if (starts_with(found_ref, "refs/remotes/")) {
 460                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 461                                     sha1_to_hex(branch_head), remote);
 462                         goto cleanup;
 463                 }
 464         }
 465
 466         /* See if remote matches <name>^^^.. or <name>~<number> */
 467         for (len = 0, ptr = remote + strlen(remote);
 468              remote < ptr && ptr[-1] == '^';
 469              ptr--)
 470                 len++;
 471         if (len)
 472                 early = 1;
 473         else {
 474                 early = 0;
 475                 ptr = strrchr(remote, '~');
 476                 if (ptr) {
 477                         int seen_nonzero = 0;
 478
 479                         len++; /* count ~ */
 480                         while (*++ptr && isdigit(*ptr)) {
 481                                 seen_nonzero |= (*ptr != '0');
 482                                 len++;
 483                         }
 484                         if (*ptr)
 485                                 len = 0; /* not ...~<number> */
 486                         else if (seen_nonzero)
 487                                 early = 1;
 488                         else if (len == 1)
 489                                 early = 1; /* "name~" is "name~1"! */
 490                 }
 491         }
 492         if (len) {
 493                 struct strbuf truname = STRBUF_INIT;
 494                 strbuf_addstr(&truname, "refs/heads/");
 495                 strbuf_addstr(&truname, remote);
 496                 strbuf_setlen(&truname, truname.len - len);
 497                 if (ref_exists(truname.buf)) {
 498                         strbuf_addf(msg,
 499                                     "%s\t\tbranch '%s'%s of .\n",
 500                                     sha1_to_hex(remote_head->object.sha1),
 501                                     truname.buf + 11,
 502                                     (early ? " (early part)" : ""));
 503                         strbuf_release(&truname);
 504                         goto cleanup;
 505                 }
 506         }
 507
 508         if (!strcmp(remote, "FETCH_HEAD") &&
 509                         !access(git_path("FETCH_HEAD"), R_OK)) {
 510                 const char *filename;
 511                 FILE *fp;
 512                 struct strbuf line = STRBUF_INIT;
 513                 char *ptr;
 514
 515                 filename = git_path("FETCH_HEAD");
 516                 fp = fopen(filename, "r");
 517                 if (!fp)
 518                         die_errno(_("could not open '%s' for reading"),
 519                                   filename);
 520                 strbuf_getline(&line, fp, '\n');
 521                 fclose(fp);
 522                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 523                 if (ptr)
 524                         strbuf_remove(&line, ptr-line.buf+1, 13);
 525                 strbuf_addbuf(msg, &line);
 526                 strbuf_release(&line);
 527                 goto cleanup;
 528         }
 529
 530         if (remote_head->util) {
 531                 struct merge_remote_desc *desc;
 532                 desc = merge_remote_util(remote_head);
 533                 if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 534                         strbuf_addf(msg, "%s\t\t%s '%s'\n",
 535                                     sha1_to_hex(desc->obj->sha1),
 536                                     typename(desc->obj->type),
 537                                     remote);
 538                         goto cleanup;
 539                 }
 540         }
 541
 542         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 543                 sha1_to_hex(remote_head->object.sha1), remote);
 544 cleanup:
 545         strbuf_release(&buf);
 546         strbuf_release(&bname);
 547 }
 548
 549 static void parse_branch_merge_options(char *bmo)
 550 {
 551         const char **argv;
 552         int argc;
 553
 554         if (!bmo)
 555                 return;
 556         argc = split_cmdline(bmo, &argv);
 557         if (argc < 0)
 558                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 559                     split_cmdline_strerror(argc));
 560         argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 561         memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 562         argc++;
 563         argv[0] = "branch.*.mergeoptions";
 564         parse_options(argc, argv, NULL, builtin_merge_options,
 565                       builtin_merge_usage, 0);
 566         free(argv);
 567 }
 568
 569 static int git_merge_config(const char *k, const char *v, void *cb)
 570 {
 571         int status;
 572
 573         if (branch && starts_with(k, "branch.") &&
 574                 starts_with(k + 7, branch) &&
 575                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 576                 free(branch_mergeoptions);
 577                 branch_mergeoptions = xstrdup(v);
 578                 return 0;
 579         }
 580
 581         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 582                 show_diffstat = git_config_bool(k, v);
 583         else if (!strcmp(k, "pull.twohead"))
 584                 return git_config_string(&pull_twohead, k, v);
 585         else if (!strcmp(k, "pull.octopus"))
 586                 return git_config_string(&pull_octopus, k, v);
 587         else if (!strcmp(k, "merge.renormalize"))
 588                 option_renormalize = git_config_bool(k, v);
 589         else if (!strcmp(k, "merge.ff")) {
 590                 int boolval = git_config_maybe_bool(k, v);
 591                 if (0 <= boolval) {
 592                         fast_forward = boolval ? FF_ALLOW : FF_NO;
 593                 } else if (v && !strcmp(v, "only")) {
 594                         fast_forward = FF_ONLY;
 595                 } /* do not barf on values from future versions of git */
 596                 return 0;
 597         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 598                 default_to_upstream = git_config_bool(k, v);
 599                 return 0;
 600         } else if (!strcmp(k, "commit.gpgsign")) {
 601                 sign_commit = git_config_bool(k, v) ? "" : NULL;
 602                 return 0;
 603         }
 604
 605         status = fmt_merge_msg_config(k, v, cb);
 606         if (status)
 607                 return status;
 608         status = git_gpg_config(k, v, NULL);
 609         if (status)
 610                 return status;
 611         return git_diff_ui_config(k, v, cb);
 612 }
 613
 614 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 615                              unsigned char *one)
 616 {
 617         int i, nr_trees = 0;
 618         struct tree *trees[MAX_UNPACK_TREES];
 619         struct tree_desc t[MAX_UNPACK_TREES];
 620         struct unpack_trees_options opts;
 621
 622         memset(&opts, 0, sizeof(opts));
 623         opts.head_idx = 2;
 624         opts.src_index = &the_index;
 625         opts.dst_index = &the_index;
 626         opts.update = 1;
 627         opts.verbose_update = 1;
 628         opts.trivial_merges_only = 1;
 629         opts.merge = 1;
 630         trees[nr_trees] = parse_tree_indirect(common);
 631         if (!trees[nr_trees++])
 632                 return -1;
 633         trees[nr_trees] = parse_tree_indirect(head);
 634         if (!trees[nr_trees++])
 635                 return -1;
 636         trees[nr_trees] = parse_tree_indirect(one);
 637         if (!trees[nr_trees++])
 638                 return -1;
 639         opts.fn = threeway_merge;
 640         cache_tree_free(&active_cache_tree);
 641         for (i = 0; i < nr_trees; i++) {
 642                 parse_tree(trees[i]);
 643                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 644         }
 645         if (unpack_trees(nr_trees, t, &opts))
 646                 return -1;
 647         return 0;
 648 }
 649
 650 static void write_tree_trivial(unsigned char *sha1)
 651 {
 652         if (write_cache_as_tree(sha1, 0, NULL))
 653                 die(_("git write-tree failed to write a tree"));
 654 }
 655
 656 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 657                               struct commit_list *remoteheads,
 658                               struct commit *head, const char *head_arg)
 659 {
 660         int index_fd;
 661         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 662
 663         index_fd = hold_locked_index(lock, 1);
 664         refresh_cache(REFRESH_QUIET);
 665         if (active_cache_changed &&
 666                         (write_cache(index_fd, active_cache, active_nr) ||
 667                          commit_locked_index(lock)))
 668                 return error(_("Unable to write index."));
 669         rollback_lock_file(lock);
 670
 671         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 672                 int clean, x;
 673                 struct commit *result;
 674                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 675                 int index_fd;
 676                 struct commit_list *reversed = NULL;
 677                 struct merge_options o;
 678                 struct commit_list *j;
 679
 680                 if (remoteheads->next) {
 681                         error(_("Not handling anything other than two heads merge."));
 682                         return 2;
 683                 }
 684
 685                 init_merge_options(&o);
 686                 if (!strcmp(strategy, "subtree"))
 687                         o.subtree_shift = "";
 688
 689                 o.renormalize = option_renormalize;
 690                 o.show_rename_progress =
 691                         show_progress == -1 ? isatty(2) : show_progress;
 692
 693                 for (x = 0; x < xopts_nr; x++)
 694                         if (parse_merge_opt(&o, xopts[x]))
 695                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 696
 697                 o.branch1 = head_arg;
 698                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 699
 700                 for (j = common; j; j = j->next)
 701                         commit_list_insert(j->item, &reversed);
 702
 703                 index_fd = hold_locked_index(lock, 1);
 704                 clean = merge_recursive(&o, head,
 705                                 remoteheads->item, reversed, &result);
 706                 if (active_cache_changed &&
 707                                 (write_cache(index_fd, active_cache, active_nr) ||
 708                                  commit_locked_index(lock)))
 709                         die (_("unable to write %s"), get_index_file());
 710                 rollback_lock_file(lock);
 711                 return clean ? 0 : 1;
 712         } else {
 713                 return try_merge_command(strategy, xopts_nr, xopts,
 714                                                 common, head_arg, remoteheads);
 715         }
 716 }
 717
 718 static void count_diff_files(struct diff_queue_struct *q,
 719                              struct diff_options *opt, void *data)
 720 {
 721         int *count = data;
 722
 723         (*count) += q->nr;
 724 }
 725
 726 static int count_unmerged_entries(void)
 727 {
 728         int i, ret = 0;
 729
 730         for (i = 0; i < active_nr; i++)
 731                 if (ce_stage(active_cache[i]))
 732                         ret++;
 733
 734         return ret;
 735 }
 736
 737 static void split_merge_strategies(const char *string, struct strategy **list,
 738                                    int *nr, int *alloc)
 739 {
 740         char *p, *q, *buf;
 741
 742         if (!string)
 743                 return;
 744
 745         buf = xstrdup(string);
 746         q = buf;
 747         for (;;) {
 748                 p = strchr(q, ' ');
 749                 if (!p) {
 750                         ALLOC_GROW(*list, *nr + 1, *alloc);
 751                         (*list)[(*nr)++].name = xstrdup(q);
 752                         free(buf);
 753                         return;
 754                 } else {
 755                         *p = '\0';
 756                         ALLOC_GROW(*list, *nr + 1, *alloc);
 757                         (*list)[(*nr)++].name = xstrdup(q);
 758                         q = ++p;
 759                 }
 760         }
 761 }
 762
 763 static void add_strategies(const char *string, unsigned attr)
 764 {
 765         struct strategy *list = NULL;
 766         int list_alloc = 0, list_nr = 0, i;
 767
 768         memset(&list, 0, sizeof(list));
 769         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 770         if (list) {
 771                 for (i = 0; i < list_nr; i++)
 772                         append_strategy(get_strategy(list[i].name));
 773                 return;
 774         }
 775         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 776                 if (all_strategy[i].attr & attr)
 777                         append_strategy(&all_strategy[i]);
 778
 779 }
 780
 781 static void write_merge_msg(struct strbuf *msg)
 782 {
 783         const char *filename = git_path("MERGE_MSG");
 784         int fd = open(filename, O_WRONLY | O_CREAT, 0666);
 785         if (fd < 0)
 786                 die_errno(_("Could not open '%s' for writing"),
 787                           filename);
 788         if (write_in_full(fd, msg->buf, msg->len) != msg->len)
 789                 die_errno(_("Could not write to '%s'"), filename);
 790         close(fd);
 791 }
 792
 793 static void read_merge_msg(struct strbuf *msg)
 794 {
 795         const char *filename = git_path("MERGE_MSG");
 796         strbuf_reset(msg);
 797         if (strbuf_read_file(msg, filename, 0) < 0)
 798                 die_errno(_("Could not read from '%s'"), filename);
 799 }
 800
 801 static void write_merge_state(struct commit_list *);
 802 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
 803 {
 804         if (err_msg)
 805                 error("%s", err_msg);
 806         fprintf(stderr,
 807                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 808         write_merge_state(remoteheads);
 809         exit(1);
 810 }
 811
 812 static const char merge_editor_comment[] =
 813 N_("Please enter a commit message to explain why this merge is necessary,\n"
 814    "especially if it merges an updated upstream into a topic branch.\n"
 815    "\n"
 816    "Lines starting with '%c' will be ignored, and an empty message aborts\n"
 817    "the commit.\n");
 818
 819 static void prepare_to_commit(struct commit_list *remoteheads)
 820 {
 821         struct strbuf msg = STRBUF_INIT;
 822         strbuf_addbuf(&msg, &merge_msg);
 823         strbuf_addch(&msg, '\n');
 824         if (0 < option_edit)
 825                 strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
 826         write_merge_msg(&msg);
 827         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
 828                             git_path("MERGE_MSG"), "merge", NULL))
 829                 abort_commit(remoteheads, NULL);
 830         if (0 < option_edit) {
 831                 if (launch_editor(git_path("MERGE_MSG"), NULL, NULL))
 832                         abort_commit(remoteheads, NULL);
 833         }
 834         read_merge_msg(&msg);
 835         stripspace(&msg, 0 < option_edit);
 836         if (!msg.len)
 837                 abort_commit(remoteheads, _("Empty commit message."));
 838         strbuf_release(&merge_msg);
 839         strbuf_addbuf(&merge_msg, &msg);
 840         strbuf_release(&msg);
 841 }
 842
 843 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 844 {
 845         unsigned char result_tree[20], result_commit[20];
 846         struct commit_list *parent = xmalloc(sizeof(*parent));
 847
 848         write_tree_trivial(result_tree);
 849         printf(_("Wonderful.\n"));
 850         parent->item = head;
 851         parent->next = xmalloc(sizeof(*parent->next));
 852         parent->next->item = remoteheads->item;
 853         parent->next->next = NULL;
 854         prepare_to_commit(remoteheads);
 855         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parent,
 856                         result_commit, NULL, sign_commit))
 857                 die(_("failed to write commit object"));
 858         finish(head, remoteheads, result_commit, "In-index merge");
 859         drop_save();
 860         return 0;
 861 }
 862
 863 static int finish_automerge(struct commit *head,
 864                             int head_subsumed,
 865                             struct commit_list *common,
 866                             struct commit_list *remoteheads,
 867                             unsigned char *result_tree,
 868                             const char *wt_strategy)
 869 {
 870         struct commit_list *parents = NULL;
 871         struct strbuf buf = STRBUF_INIT;
 872         unsigned char result_commit[20];
 873
 874         free_commit_list(common);
 875         parents = remoteheads;
 876         if (!head_subsumed || fast_forward == FF_NO)
 877                 commit_list_insert(head, &parents);
 878         strbuf_addch(&merge_msg, '\n');
 879         prepare_to_commit(remoteheads);
 880         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 881                         result_commit, NULL, sign_commit))
 882                 die(_("failed to write commit object"));
 883         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 884         finish(head, remoteheads, result_commit, buf.buf);
 885         strbuf_release(&buf);
 886         drop_save();
 887         return 0;
 888 }
 889
 890 static int suggest_conflicts(int renormalizing)
 891 {
 892         const char *filename;
 893         FILE *fp;
 894         int pos;
 895
 896         filename = git_path("MERGE_MSG");
 897         fp = fopen(filename, "a");
 898         if (!fp)
 899                 die_errno(_("Could not open '%s' for writing"), filename);
 900         fprintf(fp, "\nConflicts:\n");
 901         for (pos = 0; pos < active_nr; pos++) {
 902                 const struct cache_entry *ce = active_cache[pos];
 903
 904                 if (ce_stage(ce)) {
 905                         fprintf(fp, "\t%s\n", ce->name);
 906                         while (pos + 1 < active_nr &&
 907                                         !strcmp(ce->name,
 908                                                 active_cache[pos + 1]->name))
 909                                 pos++;
 910                 }
 911         }
 912         fclose(fp);
 913         rerere(allow_rerere_auto);
 914         printf(_("Automatic merge failed; "
 915                         "fix conflicts and then commit the result.\n"));
 916         return 1;
 917 }
 918
 919 static struct commit *is_old_style_invocation(int argc, const char **argv,
 920                                               const unsigned char *head)
 921 {
 922         struct commit *second_token = NULL;
 923         if (argc > 2) {
 924                 unsigned char second_sha1[20];
 925
 926                 if (get_sha1(argv[1], second_sha1))
 927                         return NULL;
 928                 second_token = lookup_commit_reference_gently(second_sha1, 0);
 929                 if (!second_token)
 930                         die(_("'%s' is not a commit"), argv[1]);
 931                 if (hashcmp(second_token->object.sha1, head))
 932                         return NULL;
 933         }
 934         return second_token;
 935 }
 936
 937 static int evaluate_result(void)
 938 {
 939         int cnt = 0;
 940         struct rev_info rev;
 941
 942         /* Check how many files differ. */
 943         init_revisions(&rev, "");
 944         setup_revisions(0, NULL, &rev, NULL);
 945         rev.diffopt.output_format |=
 946                 DIFF_FORMAT_CALLBACK;
 947         rev.diffopt.format_callback = count_diff_files;
 948         rev.diffopt.format_callback_data = &cnt;
 949         run_diff_files(&rev, 0);
 950
 951         /*
 952          * Check how many unmerged entries are
 953          * there.
 954          */
 955         cnt += count_unmerged_entries();
 956
 957         return cnt;
 958 }
 959
 960 /*
 961  * Pretend as if the user told us to merge with the remote-tracking
 962  * branch we have for the upstream of the current branch
 963  */
 964 static int setup_with_upstream(const char ***argv)
 965 {
 966         struct branch *branch = branch_get(NULL);
 967         int i;
 968         const char **args;
 969
 970         if (!branch)
 971                 die(_("No current branch."));
 972         if (!branch->remote)
 973                 die(_("No remote for the current branch."));
 974         if (!branch->merge_nr)
 975                 die(_("No default upstream defined for the current branch."));
 976
 977         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
 978         for (i = 0; i < branch->merge_nr; i++) {
 979                 if (!branch->merge[i]->dst)
 980                         die(_("No remote-tracking branch for %s from %s"),
 981                             branch->merge[i]->src, branch->remote_name);
 982                 args[i] = branch->merge[i]->dst;
 983         }
 984         args[i] = NULL;
 985         *argv = args;
 986         return i;
 987 }
 988
 989 static void write_merge_state(struct commit_list *remoteheads)
 990 {
 991         const char *filename;
 992         int fd;
 993         struct commit_list *j;
 994         struct strbuf buf = STRBUF_INIT;
 995
 996         for (j = remoteheads; j; j = j->next) {
 997                 unsigned const char *sha1;
 998                 struct commit *c = j->item;
 999                 if (c->util && merge_remote_util(c)->obj) {
1000                         sha1 = merge_remote_util(c)->obj->sha1;
1001                 } else {
1002                         sha1 = c->object.sha1;
1003                 }
1004                 strbuf_addf(&buf, "%s\n", sha1_to_hex(sha1));
1005         }
1006         filename = git_path("MERGE_HEAD");
1007         fd = open(filename, O_WRONLY | O_CREAT, 0666);
1008         if (fd < 0)
1009                 die_errno(_("Could not open '%s' for writing"), filename);
1010         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1011                 die_errno(_("Could not write to '%s'"), filename);
1012         close(fd);
1013         strbuf_addch(&merge_msg, '\n');
1014         write_merge_msg(&merge_msg);
1015
1016         filename = git_path("MERGE_MODE");
1017         fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
1018         if (fd < 0)
1019                 die_errno(_("Could not open '%s' for writing"), filename);
1020         strbuf_reset(&buf);
1021         if (fast_forward == FF_NO)
1022                 strbuf_addf(&buf, "no-ff");
1023         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1024                 die_errno(_("Could not write to '%s'"), filename);
1025         close(fd);
1026 }
1027
1028 static int default_edit_option(void)
1029 {
1030         static const char name[] = "GIT_MERGE_AUTOEDIT";
1031         const char *e = getenv(name);
1032         struct stat st_stdin, st_stdout;
1033
1034         if (have_message)
1035                 /* an explicit -m msg without --[no-]edit */
1036                 return 0;
1037
1038         if (e) {
1039                 int v = git_config_maybe_bool(name, e);
1040                 if (v < 0)
1041                         die("Bad value '%s' in environment '%s'", e, name);
1042                 return v;
1043         }
1044
1045         /* Use editor if stdin and stdout are the same and is a tty */
1046         return (!fstat(0, &st_stdin) &&
1047                 !fstat(1, &st_stdout) &&
1048                 isatty(0) && isatty(1) &&
1049                 st_stdin.st_dev == st_stdout.st_dev &&
1050                 st_stdin.st_ino == st_stdout.st_ino &&
1051                 st_stdin.st_mode == st_stdout.st_mode);
1052 }
1053
1054 static struct commit_list *collect_parents(struct commit *head_commit,
1055                                            int *head_subsumed,
1056                                            int argc, const char **argv)
1057 {
1058         int i;
1059         struct commit_list *remoteheads = NULL, *parents, *next;
1060         struct commit_list **remotes = &remoteheads;
1061
1062         if (head_commit)
1063                 remotes = &commit_list_insert(head_commit, remotes)->next;
1064         for (i = 0; i < argc; i++) {
1065                 struct commit *commit = get_merge_parent(argv[i]);
1066                 if (!commit)
1067                         help_unknown_ref(argv[i], "merge",
1068                                          "not something we can merge");
1069                 remotes = &commit_list_insert(commit, remotes)->next;
1070         }
1071         *remotes = NULL;
1072
1073         parents = reduce_heads(remoteheads);
1074
1075         *head_subsumed = 1; /* we will flip this to 0 when we find it */
1076         for (remoteheads = NULL, remotes = &remoteheads;
1077              parents;
1078              parents = next) {
1079                 struct commit *commit = parents->item;
1080                 next = parents->next;
1081                 if (commit == head_commit)
1082                         *head_subsumed = 0;
1083                 else
1084                         remotes = &commit_list_insert(commit, remotes)->next;
1085         }
1086         return remoteheads;
1087 }
1088
1089 int cmd_merge(int argc, const char **argv, const char *prefix)
1090 {
1091         unsigned char result_tree[20];
1092         unsigned char stash[20];
1093         unsigned char head_sha1[20];
1094         struct commit *head_commit;
1095         struct strbuf buf = STRBUF_INIT;
1096         const char *head_arg;
1097         int flag, i, ret = 0, head_subsumed;
1098         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1099         struct commit_list *common = NULL;
1100         const char *best_strategy = NULL, *wt_strategy = NULL;
1101         struct commit_list *remoteheads, *p;
1102         void *branch_to_free;
1103
1104         if (argc == 2 && !strcmp(argv[1], "-h"))
1105                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1106
1107         /*
1108          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1109          * current branch.
1110          */
1111         branch = branch_to_free = resolve_refdup("HEAD", head_sha1, 0, &flag);
1112         if (branch && starts_with(branch, "refs/heads/"))
1113                 branch += 11;
1114         if (!branch || is_null_sha1(head_sha1))
1115                 head_commit = NULL;
1116         else
1117                 head_commit = lookup_commit_or_die(head_sha1, "HEAD");
1118
1119         git_config(git_merge_config, NULL);
1120
1121         if (branch_mergeoptions)
1122                 parse_branch_merge_options(branch_mergeoptions);
1123         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1124                         builtin_merge_usage, 0);
1125         if (shortlog_len < 0)
1126                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1127
1128         if (verbosity < 0 && show_progress == -1)
1129                 show_progress = 0;
1130
1131         if (abort_current_merge) {
1132                 int nargc = 2;
1133                 const char *nargv[] = {"reset", "--merge", NULL};
1134
1135                 if (!file_exists(git_path("MERGE_HEAD")))
1136                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1137
1138                 /* Invoke 'git reset --merge' */
1139                 ret = cmd_reset(nargc, nargv, prefix);
1140                 goto done;
1141         }
1142
1143         if (read_cache_unmerged())
1144                 die_resolve_conflict("merge");
1145
1146         if (file_exists(git_path("MERGE_HEAD"))) {
1147                 /*
1148                  * There is no unmerged entry, don't advise 'git
1149                  * add/rm <file>', just 'git commit'.
1150                  */
1151                 if (advice_resolve_conflict)
1152                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1153                                   "Please, commit your changes before you can merge."));
1154                 else
1155                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1156         }
1157         if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1158                 if (advice_resolve_conflict)
1159                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1160                             "Please, commit your changes before you can merge."));
1161                 else
1162                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1163         }
1164         resolve_undo_clear();
1165
1166         if (verbosity < 0)
1167                 show_diffstat = 0;
1168
1169         if (squash) {
1170                 if (fast_forward == FF_NO)
1171                         die(_("You cannot combine --squash with --no-ff."));
1172                 option_commit = 0;
1173         }
1174
1175         if (!abort_current_merge) {
1176                 if (!argc) {
1177                         if (default_to_upstream)
1178                                 argc = setup_with_upstream(&argv);
1179                         else
1180                                 die(_("No commit specified and merge.defaultToUpstream not set."));
1181                 } else if (argc == 1 && !strcmp(argv[0], "-"))
1182                         argv[0] = "@{-1}";
1183         }
1184         if (!argc)
1185                 usage_with_options(builtin_merge_usage,
1186                         builtin_merge_options);
1187
1188         /*
1189          * This could be traditional "merge <msg> HEAD <commit>..."  and
1190          * the way we can tell it is to see if the second token is HEAD,
1191          * but some people might have misused the interface and used a
1192          * commit-ish that is the same as HEAD there instead.
1193          * Traditional format never would have "-m" so it is an
1194          * additional safety measure to check for it.
1195          */
1196
1197         if (!have_message && head_commit &&
1198             is_old_style_invocation(argc, argv, head_commit->object.sha1)) {
1199                 strbuf_addstr(&merge_msg, argv[0]);
1200                 head_arg = argv[1];
1201                 argv += 2;
1202                 argc -= 2;
1203                 remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
1204         } else if (!head_commit) {
1205                 struct commit *remote_head;
1206                 /*
1207                  * If the merged head is a valid one there is no reason
1208                  * to forbid "git merge" into a branch yet to be born.
1209                  * We do the same for "git pull".
1210                  */
1211                 if (argc != 1)
1212                         die(_("Can merge only exactly one commit into "
1213                                 "empty head"));
1214                 if (squash)
1215                         die(_("Squash commit into empty head not supported yet"));
1216                 if (fast_forward == FF_NO)
1217                         die(_("Non-fast-forward commit does not make sense into "
1218                             "an empty head"));
1219                 remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
1220                 remote_head = remoteheads->item;
1221                 if (!remote_head)
1222                         die(_("%s - not something we can merge"), argv[0]);
1223                 read_empty(remote_head->object.sha1, 0);
1224                 update_ref("initial pull", "HEAD", remote_head->object.sha1,
1225                            NULL, 0, DIE_ON_ERR);
1226                 goto done;
1227         } else {
1228                 struct strbuf merge_names = STRBUF_INIT;
1229
1230                 /* We are invoked directly as the first-class UI. */
1231                 head_arg = "HEAD";
1232
1233                 /*
1234                  * All the rest are the commits being merged; prepare
1235                  * the standard merge summary message to be appended
1236                  * to the given message.
1237                  */
1238                 remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
1239                 for (p = remoteheads; p; p = p->next)
1240                         merge_name(merge_remote_util(p->item)->name, &merge_names);
1241
1242                 if (!have_message || shortlog_len) {
1243                         struct fmt_merge_msg_opts opts;
1244                         memset(&opts, 0, sizeof(opts));
1245                         opts.add_title = !have_message;
1246                         opts.shortlog_len = shortlog_len;
1247                         opts.credit_people = (0 < option_edit);
1248
1249                         fmt_merge_msg(&merge_names, &merge_msg, &opts);
1250                         if (merge_msg.len)
1251                                 strbuf_setlen(&merge_msg, merge_msg.len - 1);
1252                 }
1253         }
1254
1255         if (!head_commit || !argc)
1256                 usage_with_options(builtin_merge_usage,
1257                         builtin_merge_options);
1258
1259         if (verify_signatures) {
1260                 for (p = remoteheads; p; p = p->next) {
1261                         struct commit *commit = p->item;
1262                         char hex[41];
1263                         struct signature_check signature_check;
1264                         memset(&signature_check, 0, sizeof(signature_check));
1265
1266                         check_commit_signature(commit, &signature_check);
1267
1268                         strcpy(hex, find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
1269                         switch (signature_check.result) {
1270                         case 'G':
1271                                 break;
1272                         case 'U':
1273                                 die(_("Commit %s has an untrusted GPG signature, "
1274                                       "allegedly by %s."), hex, signature_check.signer);
1275                         case 'B':
1276                                 die(_("Commit %s has a bad GPG signature "
1277                                       "allegedly by %s."), hex, signature_check.signer);
1278                         default: /* 'N' */
1279                                 die(_("Commit %s does not have a GPG signature."), hex);
1280                         }
1281                         if (verbosity >= 0 && signature_check.result == 'G')
1282                                 printf(_("Commit %s has a good GPG signature by %s\n"),
1283                                        hex, signature_check.signer);
1284
1285                         free(signature_check.gpg_output);
1286                         free(signature_check.gpg_status);
1287                         free(signature_check.signer);
1288                         free(signature_check.key);
1289                 }
1290         }
1291
1292         strbuf_addstr(&buf, "merge");
1293         for (p = remoteheads; p; p = p->next)
1294                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1295         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1296         strbuf_reset(&buf);
1297
1298         for (p = remoteheads; p; p = p->next) {
1299                 struct commit *commit = p->item;
1300                 strbuf_addf(&buf, "GITHEAD_%s",
1301                             sha1_to_hex(commit->object.sha1));
1302                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1303                 strbuf_reset(&buf);
1304                 if (fast_forward != FF_ONLY &&
1305                     merge_remote_util(commit) &&
1306                     merge_remote_util(commit)->obj &&
1307                     merge_remote_util(commit)->obj->type == OBJ_TAG)
1308                         fast_forward = FF_NO;
1309         }
1310
1311         if (option_edit < 0)
1312                 option_edit = default_edit_option();
1313
1314         if (!use_strategies) {
1315                 if (!remoteheads)
1316                         ; /* already up-to-date */
1317                 else if (!remoteheads->next)
1318                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1319                 else
1320                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1321         }
1322
1323         for (i = 0; i < use_strategies_nr; i++) {
1324                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1325                         fast_forward = FF_NO;
1326                 if (use_strategies[i]->attr & NO_TRIVIAL)
1327                         allow_trivial = 0;
1328         }
1329
1330         if (!remoteheads)
1331                 ; /* already up-to-date */
1332         else if (!remoteheads->next)
1333                 common = get_merge_bases(head_commit, remoteheads->item, 1);
1334         else {
1335                 struct commit_list *list = remoteheads;
1336                 commit_list_insert(head_commit, &list);
1337                 common = get_octopus_merge_bases(list);
1338                 free(list);
1339         }
1340
1341         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
1342                    NULL, 0, DIE_ON_ERR);
1343
1344         if (remoteheads && !common)
1345                 ; /* No common ancestors found. We need a real merge. */
1346         else if (!remoteheads ||
1347                  (!remoteheads->next && !common->next &&
1348                   common->item == remoteheads->item)) {
1349                 /*
1350                  * If head can reach all the merge then we are up to date.
1351                  * but first the most common case of merging one remote.
1352                  */
1353                 finish_up_to_date("Already up-to-date.");
1354                 goto done;
1355         } else if (fast_forward != FF_NO && !remoteheads->next &&
1356                         !common->next &&
1357                         !hashcmp(common->item->object.sha1, head_commit->object.sha1)) {
1358                 /* Again the most common case of merging one remote. */
1359                 struct strbuf msg = STRBUF_INIT;
1360                 struct commit *commit;
1361                 char hex[41];
1362
1363                 strcpy(hex, find_unique_abbrev(head_commit->object.sha1, DEFAULT_ABBREV));
1364
1365                 if (verbosity >= 0)
1366                         printf(_("Updating %s..%s\n"),
1367                                 hex,
1368                                 find_unique_abbrev(remoteheads->item->object.sha1,
1369                                 DEFAULT_ABBREV));
1370                 strbuf_addstr(&msg, "Fast-forward");
1371                 if (have_message)
1372                         strbuf_addstr(&msg,
1373                                 " (no commit created; -m option ignored)");
1374                 commit = remoteheads->item;
1375                 if (!commit) {
1376                         ret = 1;
1377                         goto done;
1378                 }
1379
1380                 if (checkout_fast_forward(head_commit->object.sha1,
1381                                           commit->object.sha1,
1382                                           overwrite_ignore)) {
1383                         ret = 1;
1384                         goto done;
1385                 }
1386
1387                 finish(head_commit, remoteheads, commit->object.sha1, msg.buf);
1388                 drop_save();
1389                 goto done;
1390         } else if (!remoteheads->next && common->next)
1391                 ;
1392                 /*
1393                  * We are not doing octopus and not fast-forward.  Need
1394                  * a real merge.
1395                  */
1396         else if (!remoteheads->next && !common->next && option_commit) {
1397                 /*
1398                  * We are not doing octopus, not fast-forward, and have
1399                  * only one common.
1400                  */
1401                 refresh_cache(REFRESH_QUIET);
1402                 if (allow_trivial && fast_forward != FF_ONLY) {
1403                         /* See if it is really trivial. */
1404                         git_committer_info(IDENT_STRICT);
1405                         printf(_("Trying really trivial in-index merge...\n"));
1406                         if (!read_tree_trivial(common->item->object.sha1,
1407                                                head_commit->object.sha1,
1408                                                remoteheads->item->object.sha1)) {
1409                                 ret = merge_trivial(head_commit, remoteheads);
1410                                 goto done;
1411                         }
1412                         printf(_("Nope.\n"));
1413                 }
1414         } else {
1415                 /*
1416                  * An octopus.  If we can reach all the remote we are up
1417                  * to date.
1418                  */
1419                 int up_to_date = 1;
1420                 struct commit_list *j;
1421
1422                 for (j = remoteheads; j; j = j->next) {
1423                         struct commit_list *common_one;
1424
1425                         /*
1426                          * Here we *have* to calculate the individual
1427                          * merge_bases again, otherwise "git merge HEAD^
1428                          * HEAD^^" would be missed.
1429                          */
1430                         common_one = get_merge_bases(head_commit, j->item, 1);
1431                         if (hashcmp(common_one->item->object.sha1,
1432                                 j->item->object.sha1)) {
1433                                 up_to_date = 0;
1434                                 break;
1435                         }
1436                 }
1437                 if (up_to_date) {
1438                         finish_up_to_date("Already up-to-date. Yeeah!");
1439                         goto done;
1440                 }
1441         }
1442
1443         if (fast_forward == FF_ONLY)
1444                 die(_("Not possible to fast-forward, aborting."));
1445
1446         /* We are going to make a new commit. */
1447         git_committer_info(IDENT_STRICT);
1448
1449         /*
1450          * At this point, we need a real merge.  No matter what strategy
1451          * we use, it would operate on the index, possibly affecting the
1452          * working tree, and when resolved cleanly, have the desired
1453          * tree in the index -- this means that the index must be in
1454          * sync with the head commit.  The strategies are responsible
1455          * to ensure this.
1456          */
1457         if (use_strategies_nr == 1 ||
1458             /*
1459              * Stash away the local changes so that we can try more than one.
1460              */
1461             save_state(stash))
1462                 hashcpy(stash, null_sha1);
1463
1464         for (i = 0; i < use_strategies_nr; i++) {
1465                 int ret;
1466                 if (i) {
1467                         printf(_("Rewinding the tree to pristine...\n"));
1468                         restore_state(head_commit->object.sha1, stash);
1469                 }
1470                 if (use_strategies_nr != 1)
1471                         printf(_("Trying merge strategy %s...\n"),
1472                                 use_strategies[i]->name);
1473                 /*
1474                  * Remember which strategy left the state in the working
1475                  * tree.
1476                  */
1477                 wt_strategy = use_strategies[i]->name;
1478
1479                 ret = try_merge_strategy(use_strategies[i]->name,
1480                                          common, remoteheads,
1481                                          head_commit, head_arg);
1482                 if (!option_commit && !ret) {
1483                         merge_was_ok = 1;
1484                         /*
1485                          * This is necessary here just to avoid writing
1486                          * the tree, but later we will *not* exit with
1487                          * status code 1 because merge_was_ok is set.
1488                          */
1489                         ret = 1;
1490                 }
1491
1492                 if (ret) {
1493                         /*
1494                          * The backend exits with 1 when conflicts are
1495                          * left to be resolved, with 2 when it does not
1496                          * handle the given merge at all.
1497                          */
1498                         if (ret == 1) {
1499                                 int cnt = evaluate_result();
1500
1501                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1502                                         best_strategy = use_strategies[i]->name;
1503                                         best_cnt = cnt;
1504                                 }
1505                         }
1506                         if (merge_was_ok)
1507                                 break;
1508                         else
1509                                 continue;
1510                 }
1511
1512                 /* Automerge succeeded. */
1513                 write_tree_trivial(result_tree);
1514                 automerge_was_ok = 1;
1515                 break;
1516         }
1517
1518         /*
1519          * If we have a resulting tree, that means the strategy module
1520          * auto resolved the merge cleanly.
1521          */
1522         if (automerge_was_ok) {
1523                 ret = finish_automerge(head_commit, head_subsumed,
1524                                        common, remoteheads,
1525                                        result_tree, wt_strategy);
1526                 goto done;
1527         }
1528
1529         /*
1530          * Pick the result from the best strategy and have the user fix
1531          * it up.
1532          */
1533         if (!best_strategy) {
1534                 restore_state(head_commit->object.sha1, stash);
1535                 if (use_strategies_nr > 1)
1536                         fprintf(stderr,
1537                                 _("No merge strategy handled the merge.\n"));
1538                 else
1539                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1540                                 use_strategies[0]->name);
1541                 ret = 2;
1542                 goto done;
1543         } else if (best_strategy == wt_strategy)
1544                 ; /* We already have its result in the working tree. */
1545         else {
1546                 printf(_("Rewinding the tree to pristine...\n"));
1547                 restore_state(head_commit->object.sha1, stash);
1548                 printf(_("Using the %s to prepare resolving by hand.\n"),
1549                         best_strategy);
1550                 try_merge_strategy(best_strategy, common, remoteheads,
1551                                    head_commit, head_arg);
1552         }
1553
1554         if (squash)
1555                 finish(head_commit, remoteheads, NULL, NULL);
1556         else
1557                 write_merge_state(remoteheads);
1558
1559         if (merge_was_ok)
1560                 fprintf(stderr, _("Automatic merge went well; "
1561                         "stopped before committing as requested\n"));
1562         else
1563                 ret = suggest_conflicts(option_renormalize);
1564
1565 done:
1566         free(branch_to_free);
1567         return ret;
1568 }