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