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 "config.h"
  11 #include "parse-options.h"
  12 #include "builtin.h"
  13 #include "lockfile.h"
  14 #include "run-command.h"
  15 #include "diff.h"
  16 #include "refs.h"
  17 #include "commit.h"
  18 #include "diffcore.h"
  19 #include "revision.h"
  20 #include "unpack-trees.h"
  21 #include "cache-tree.h"
  22 #include "dir.h"
  23 #include "utf8.h"
  24 #include "log-tree.h"
  25 #include "color.h"
  26 #include "rerere.h"
  27 #include "help.h"
  28 #include "merge-recursive.h"
  29 #include "resolve-undo.h"
  30 #include "remote.h"
  31 #include "fmt-merge-msg.h"
  32 #include "gpg-interface.h"
  33 #include "sequencer.h"
  34 #include "string-list.h"
  35 #include "packfile.h"
  36 #include "tag.h"
  37
  38 #define DEFAULT_TWOHEAD (1<<0)
  39 #define DEFAULT_OCTOPUS (1<<1)
  40 #define NO_FAST_FORWARD (1<<2)
  41 #define NO_TRIVIAL      (1<<3)
  42
  43 struct strategy {
  44         const char *name;
  45         unsigned attr;
  46 };
  47
  48 static const char * const builtin_merge_usage[] = {
  49         N_("git merge [<options>] [<commit>...]"),
  50         N_("git merge --abort"),
  51         N_("git merge --continue"),
  52         NULL
  53 };
  54
  55 static int show_diffstat = 1, shortlog_len = -1, squash;
  56 static int option_commit = 1;
  57 static int option_edit = -1;
  58 static int allow_trivial = 1, have_message, verify_signatures;
  59 static int overwrite_ignore = 1;
  60 static struct strbuf merge_msg = STRBUF_INIT;
  61 static struct strategy **use_strategies;
  62 static size_t use_strategies_nr, use_strategies_alloc;
  63 static const char **xopts;
  64 static size_t xopts_nr, xopts_alloc;
  65 static const char *branch;
  66 static char *branch_mergeoptions;
  67 static int option_renormalize;
  68 static int verbosity;
  69 static int allow_rerere_auto;
  70 static int abort_current_merge;
  71 static int continue_current_merge;
  72 static int allow_unrelated_histories;
  73 static int show_progress = -1;
  74 static int default_to_upstream = 1;
  75 static int signoff;
  76 static const char *sign_commit;
  77 static int verify_msg = 1;
  78
  79 static struct strategy all_strategy[] = {
  80         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  81         { "octopus",    DEFAULT_OCTOPUS },
  82         { "resolve",    0 },
  83         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  84         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  85 };
  86
  87 static const char *pull_twohead, *pull_octopus;
  88
  89 enum ff_type {
  90         FF_NO,
  91         FF_ALLOW,
  92         FF_ONLY
  93 };
  94
  95 static enum ff_type fast_forward = FF_ALLOW;
  96
  97 static int option_parse_message(const struct option *opt,
  98                                 const char *arg, int unset)
  99 {
 100         struct strbuf *buf = opt->value;
 101
 102         if (unset)
 103                 strbuf_setlen(buf, 0);
 104         else if (arg) {
 105                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
 106                 have_message = 1;
 107         } else
 108                 return error(_("switch `m' requires a value"));
 109         return 0;
 110 }
 111
 112 static struct strategy *get_strategy(const char *name)
 113 {
 114         int i;
 115         struct strategy *ret;
 116         static struct cmdnames main_cmds, other_cmds;
 117         static int loaded;
 118
 119         if (!name)
 120                 return NULL;
 121
 122         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 123                 if (!strcmp(name, all_strategy[i].name))
 124                         return &all_strategy[i];
 125
 126         if (!loaded) {
 127                 struct cmdnames not_strategies;
 128                 loaded = 1;
 129
 130                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 131                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 132                 for (i = 0; i < main_cmds.cnt; i++) {
 133                         int j, found = 0;
 134                         struct cmdname *ent = main_cmds.names[i];
 135                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 136                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 137                                                 && !all_strategy[j].name[ent->len])
 138                                         found = 1;
 139                         if (!found)
 140                                 add_cmdname(&not_strategies, ent->name, ent->len);
 141                 }
 142                 exclude_cmds(&main_cmds, &not_strategies);
 143         }
 144         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 145                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 146                 fprintf(stderr, _("Available strategies are:"));
 147                 for (i = 0; i < main_cmds.cnt; i++)
 148                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 149                 fprintf(stderr, ".\n");
 150                 if (other_cmds.cnt) {
 151                         fprintf(stderr, _("Available custom strategies are:"));
 152                         for (i = 0; i < other_cmds.cnt; i++)
 153                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 154                         fprintf(stderr, ".\n");
 155                 }
 156                 exit(1);
 157         }
 158
 159         ret = xcalloc(1, sizeof(struct strategy));
 160         ret->name = xstrdup(name);
 161         ret->attr = NO_TRIVIAL;
 162         return ret;
 163 }
 164
 165 static void append_strategy(struct strategy *s)
 166 {
 167         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 168         use_strategies[use_strategies_nr++] = s;
 169 }
 170
 171 static int option_parse_strategy(const struct option *opt,
 172                                  const char *name, int unset)
 173 {
 174         if (unset)
 175                 return 0;
 176
 177         append_strategy(get_strategy(name));
 178         return 0;
 179 }
 180
 181 static int option_parse_x(const struct option *opt,
 182                           const char *arg, int unset)
 183 {
 184         if (unset)
 185                 return 0;
 186
 187         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 188         xopts[xopts_nr++] = xstrdup(arg);
 189         return 0;
 190 }
 191
 192 static int option_parse_n(const struct option *opt,
 193                           const char *arg, int unset)
 194 {
 195         show_diffstat = unset;
 196         return 0;
 197 }
 198
 199 static struct option builtin_merge_options[] = {
 200         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 201                 N_("do not show a diffstat at the end of the merge"),
 202                 PARSE_OPT_NOARG, option_parse_n },
 203         OPT_BOOL(0, "stat", &show_diffstat,
 204                 N_("show a diffstat at the end of the merge")),
 205         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
 206         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
 207           N_("add (at most <n>) entries from shortlog to merge commit message"),
 208           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 209         OPT_BOOL(0, "squash", &squash,
 210                 N_("create a single commit instead of doing a merge")),
 211         OPT_BOOL(0, "commit", &option_commit,
 212                 N_("perform a commit if the merge succeeds (default)")),
 213         OPT_BOOL('e', "edit", &option_edit,
 214                 N_("edit message before committing")),
 215         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
 216         { OPTION_SET_INT, 0, "ff-only", &fast_forward, NULL,
 217                 N_("abort if fast-forward is not possible"),
 218                 PARSE_OPT_NOARG | PARSE_OPT_NONEG, NULL, FF_ONLY },
 219         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 220         OPT_BOOL(0, "verify-signatures", &verify_signatures,
 221                 N_("verify that the named commit has a valid GPG signature")),
 222         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
 223                 N_("merge strategy to use"), option_parse_strategy),
 224         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
 225                 N_("option for selected merge strategy"), option_parse_x),
 226         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
 227                 N_("merge commit message (for a non-fast-forward merge)"),
 228                 option_parse_message),
 229         OPT__VERBOSITY(&verbosity),
 230         OPT_BOOL(0, "abort", &abort_current_merge,
 231                 N_("abort the current in-progress merge")),
 232         OPT_BOOL(0, "continue", &continue_current_merge,
 233                 N_("continue the current in-progress merge")),
 234         OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
 235                  N_("allow merging unrelated histories")),
 236         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
 237         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
 238           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 239         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
 240         OPT_BOOL(0, "signoff", &signoff, N_("add Signed-off-by:")),
 241         OPT_BOOL(0, "verify", &verify_msg, N_("verify commit-msg hook")),
 242         OPT_END()
 243 };
 244
 245 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 246 static void drop_save(void)
 247 {
 248         unlink(git_path_merge_head());
 249         unlink(git_path_merge_msg());
 250         unlink(git_path_merge_mode());
 251 }
 252
 253 static int save_state(struct object_id *stash)
 254 {
 255         int len;
 256         struct child_process cp = CHILD_PROCESS_INIT;
 257         struct strbuf buffer = STRBUF_INIT;
 258         const char *argv[] = {"stash", "create", NULL};
 259         int rc = -1;
 260
 261         cp.argv = argv;
 262         cp.out = -1;
 263         cp.git_cmd = 1;
 264
 265         if (start_command(&cp))
 266                 die(_("could not run stash."));
 267         len = strbuf_read(&buffer, cp.out, 1024);
 268         close(cp.out);
 269
 270         if (finish_command(&cp) || len < 0)
 271                 die(_("stash failed"));
 272         else if (!len)          /* no changes */
 273                 goto out;
 274         strbuf_setlen(&buffer, buffer.len-1);
 275         if (get_oid(buffer.buf, stash))
 276                 die(_("not a valid object: %s"), buffer.buf);
 277         rc = 0;
 278 out:
 279         strbuf_release(&buffer);
 280         return rc;
 281 }
 282
 283 static void read_empty(unsigned const char *sha1, int verbose)
 284 {
 285         int i = 0;
 286         const char *args[7];
 287
 288         args[i++] = "read-tree";
 289         if (verbose)
 290                 args[i++] = "-v";
 291         args[i++] = "-m";
 292         args[i++] = "-u";
 293         args[i++] = EMPTY_TREE_SHA1_HEX;
 294         args[i++] = sha1_to_hex(sha1);
 295         args[i] = NULL;
 296
 297         if (run_command_v_opt(args, RUN_GIT_CMD))
 298                 die(_("read-tree failed"));
 299 }
 300
 301 static void reset_hard(unsigned const char *sha1, int verbose)
 302 {
 303         int i = 0;
 304         const char *args[6];
 305
 306         args[i++] = "read-tree";
 307         if (verbose)
 308                 args[i++] = "-v";
 309         args[i++] = "--reset";
 310         args[i++] = "-u";
 311         args[i++] = sha1_to_hex(sha1);
 312         args[i] = NULL;
 313
 314         if (run_command_v_opt(args, RUN_GIT_CMD))
 315                 die(_("read-tree failed"));
 316 }
 317
 318 static void restore_state(const struct object_id *head,
 319                           const struct object_id *stash)
 320 {
 321         struct strbuf sb = STRBUF_INIT;
 322         const char *args[] = { "stash", "apply", NULL, NULL };
 323
 324         if (is_null_oid(stash))
 325                 return;
 326
 327         reset_hard(head->hash, 1);
 328
 329         args[2] = oid_to_hex(stash);
 330
 331         /*
 332          * It is OK to ignore error here, for example when there was
 333          * nothing to restore.
 334          */
 335         run_command_v_opt(args, RUN_GIT_CMD);
 336
 337         strbuf_release(&sb);
 338         refresh_cache(REFRESH_QUIET);
 339 }
 340
 341 /* This is called when no merge was necessary. */
 342 static void finish_up_to_date(const char *msg)
 343 {
 344         if (verbosity >= 0)
 345                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 346         drop_save();
 347 }
 348
 349 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 350 {
 351         struct rev_info rev;
 352         struct strbuf out = STRBUF_INIT;
 353         struct commit_list *j;
 354         struct pretty_print_context ctx = {0};
 355
 356         printf(_("Squash commit -- not updating HEAD\n"));
 357
 358         init_revisions(&rev, NULL);
 359         rev.ignore_merges = 1;
 360         rev.commit_format = CMIT_FMT_MEDIUM;
 361
 362         commit->object.flags |= UNINTERESTING;
 363         add_pending_object(&rev, &commit->object, NULL);
 364
 365         for (j = remoteheads; j; j = j->next)
 366                 add_pending_object(&rev, &j->item->object, NULL);
 367
 368         setup_revisions(0, NULL, &rev, NULL);
 369         if (prepare_revision_walk(&rev))
 370                 die(_("revision walk setup failed"));
 371
 372         ctx.abbrev = rev.abbrev;
 373         ctx.date_mode = rev.date_mode;
 374         ctx.fmt = rev.commit_format;
 375
 376         strbuf_addstr(&out, "Squashed commit of the following:\n");
 377         while ((commit = get_revision(&rev)) != NULL) {
 378                 strbuf_addch(&out, '\n');
 379                 strbuf_addf(&out, "commit %s\n",
 380                         oid_to_hex(&commit->object.oid));
 381                 pretty_print_commit(&ctx, commit, &out);
 382         }
 383         write_file_buf(git_path_squash_msg(), out.buf, out.len);
 384         strbuf_release(&out);
 385 }
 386
 387 static void finish(struct commit *head_commit,
 388                    struct commit_list *remoteheads,
 389                    const struct object_id *new_head, const char *msg)
 390 {
 391         struct strbuf reflog_message = STRBUF_INIT;
 392         const struct object_id *head = &head_commit->object.oid;
 393
 394         if (!msg)
 395                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 396         else {
 397                 if (verbosity >= 0)
 398                         printf("%s\n", msg);
 399                 strbuf_addf(&reflog_message, "%s: %s",
 400                         getenv("GIT_REFLOG_ACTION"), msg);
 401         }
 402         if (squash) {
 403                 squash_message(head_commit, remoteheads);
 404         } else {
 405                 if (verbosity >= 0 && !merge_msg.len)
 406                         printf(_("No merge message -- not updating HEAD\n"));
 407                 else {
 408                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 409                         update_ref(reflog_message.buf, "HEAD", new_head, head,
 410                                    0, UPDATE_REFS_DIE_ON_ERR);
 411                         /*
 412                          * We ignore errors in 'gc --auto', since the
 413                          * user should see them.
 414                          */
 415                         close_all_packs();
 416                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 417                 }
 418         }
 419         if (new_head && show_diffstat) {
 420                 struct diff_options opts;
 421                 diff_setup(&opts);
 422                 opts.stat_width = -1; /* use full terminal width */
 423                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
 424                 opts.output_format |=
 425                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 426                 opts.detect_rename = DIFF_DETECT_RENAME;
 427                 diff_setup_done(&opts);
 428                 diff_tree_oid(head, new_head, "", &opts);
 429                 diffcore_std(&opts);
 430                 diff_flush(&opts);
 431         }
 432
 433         /* Run a post-merge hook */
 434         run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
 435
 436         strbuf_release(&reflog_message);
 437 }
 438
 439 /* Get the name for the merge commit's message. */
 440 static void merge_name(const char *remote, struct strbuf *msg)
 441 {
 442         struct commit *remote_head;
 443         struct object_id branch_head;
 444         struct strbuf buf = STRBUF_INIT;
 445         struct strbuf bname = STRBUF_INIT;
 446         const char *ptr;
 447         char *found_ref;
 448         int len, early;
 449
 450         strbuf_branchname(&bname, remote, 0);
 451         remote = bname.buf;
 452
 453         oidclr(&branch_head);
 454         remote_head = get_merge_parent(remote);
 455         if (!remote_head)
 456                 die(_("'%s' does not point to a commit"), remote);
 457
 458         if (dwim_ref(remote, strlen(remote), &branch_head, &found_ref) > 0) {
 459                 if (starts_with(found_ref, "refs/heads/")) {
 460                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 461                                     oid_to_hex(&branch_head), remote);
 462                         goto cleanup;
 463                 }
 464                 if (starts_with(found_ref, "refs/tags/")) {
 465                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 466                                     oid_to_hex(&branch_head), remote);
 467                         goto cleanup;
 468                 }
 469                 if (starts_with(found_ref, "refs/remotes/")) {
 470                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 471                                     oid_to_hex(&branch_head), remote);
 472                         goto cleanup;
 473                 }
 474         }
 475
 476         /* See if remote matches <name>^^^.. or <name>~<number> */
 477         for (len = 0, ptr = remote + strlen(remote);
 478              remote < ptr && ptr[-1] == '^';
 479              ptr--)
 480                 len++;
 481         if (len)
 482                 early = 1;
 483         else {
 484                 early = 0;
 485                 ptr = strrchr(remote, '~');
 486                 if (ptr) {
 487                         int seen_nonzero = 0;
 488
 489                         len++; /* count ~ */
 490                         while (*++ptr && isdigit(*ptr)) {
 491                                 seen_nonzero |= (*ptr != '0');
 492                                 len++;
 493                         }
 494                         if (*ptr)
 495                                 len = 0; /* not ...~<number> */
 496                         else if (seen_nonzero)
 497                                 early = 1;
 498                         else if (len == 1)
 499                                 early = 1; /* "name~" is "name~1"! */
 500                 }
 501         }
 502         if (len) {
 503                 struct strbuf truname = STRBUF_INIT;
 504                 strbuf_addf(&truname, "refs/heads/%s", remote);
 505                 strbuf_setlen(&truname, truname.len - len);
 506                 if (ref_exists(truname.buf)) {
 507                         strbuf_addf(msg,
 508                                     "%s\t\tbranch '%s'%s of .\n",
 509                                     oid_to_hex(&remote_head->object.oid),
 510                                     truname.buf + 11,
 511                                     (early ? " (early part)" : ""));
 512                         strbuf_release(&truname);
 513                         goto cleanup;
 514                 }
 515                 strbuf_release(&truname);
 516         }
 517
 518         if (remote_head->util) {
 519                 struct merge_remote_desc *desc;
 520                 desc = merge_remote_util(remote_head);
 521                 if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 522                         strbuf_addf(msg, "%s\t\t%s '%s'\n",
 523                                     oid_to_hex(&desc->obj->oid),
 524                                     type_name(desc->obj->type),
 525                                     remote);
 526                         goto cleanup;
 527                 }
 528         }
 529
 530         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 531                 oid_to_hex(&remote_head->object.oid), remote);
 532 cleanup:
 533         strbuf_release(&buf);
 534         strbuf_release(&bname);
 535 }
 536
 537 static void parse_branch_merge_options(char *bmo)
 538 {
 539         const char **argv;
 540         int argc;
 541
 542         if (!bmo)
 543                 return;
 544         argc = split_cmdline(bmo, &argv);
 545         if (argc < 0)
 546                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 547                     split_cmdline_strerror(argc));
 548         REALLOC_ARRAY(argv, argc + 2);
 549         MOVE_ARRAY(argv + 1, argv, argc + 1);
 550         argc++;
 551         argv[0] = "branch.*.mergeoptions";
 552         parse_options(argc, argv, NULL, builtin_merge_options,
 553                       builtin_merge_usage, 0);
 554         free(argv);
 555 }
 556
 557 static int git_merge_config(const char *k, const char *v, void *cb)
 558 {
 559         int status;
 560
 561         if (branch && starts_with(k, "branch.") &&
 562                 starts_with(k + 7, branch) &&
 563                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 564                 free(branch_mergeoptions);
 565                 branch_mergeoptions = xstrdup(v);
 566                 return 0;
 567         }
 568
 569         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 570                 show_diffstat = git_config_bool(k, v);
 571         else if (!strcmp(k, "merge.verifysignatures"))
 572                 verify_signatures = git_config_bool(k, v);
 573         else if (!strcmp(k, "pull.twohead"))
 574                 return git_config_string(&pull_twohead, k, v);
 575         else if (!strcmp(k, "pull.octopus"))
 576                 return git_config_string(&pull_octopus, k, v);
 577         else if (!strcmp(k, "merge.renormalize"))
 578                 option_renormalize = git_config_bool(k, v);
 579         else if (!strcmp(k, "merge.ff")) {
 580                 int boolval = git_parse_maybe_bool(v);
 581                 if (0 <= boolval) {
 582                         fast_forward = boolval ? FF_ALLOW : FF_NO;
 583                 } else if (v && !strcmp(v, "only")) {
 584                         fast_forward = FF_ONLY;
 585                 } /* do not barf on values from future versions of git */
 586                 return 0;
 587         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 588                 default_to_upstream = git_config_bool(k, v);
 589                 return 0;
 590         } else if (!strcmp(k, "commit.gpgsign")) {
 591                 sign_commit = git_config_bool(k, v) ? "" : NULL;
 592                 return 0;
 593         }
 594
 595         status = fmt_merge_msg_config(k, v, cb);
 596         if (status)
 597                 return status;
 598         status = git_gpg_config(k, v, NULL);
 599         if (status)
 600                 return status;
 601         return git_diff_ui_config(k, v, cb);
 602 }
 603
 604 static int read_tree_trivial(struct object_id *common, struct object_id *head,
 605                              struct object_id *one)
 606 {
 607         int i, nr_trees = 0;
 608         struct tree *trees[MAX_UNPACK_TREES];
 609         struct tree_desc t[MAX_UNPACK_TREES];
 610         struct unpack_trees_options opts;
 611
 612         memset(&opts, 0, sizeof(opts));
 613         opts.head_idx = 2;
 614         opts.src_index = &the_index;
 615         opts.dst_index = &the_index;
 616         opts.update = 1;
 617         opts.verbose_update = 1;
 618         opts.trivial_merges_only = 1;
 619         opts.merge = 1;
 620         trees[nr_trees] = parse_tree_indirect(common);
 621         if (!trees[nr_trees++])
 622                 return -1;
 623         trees[nr_trees] = parse_tree_indirect(head);
 624         if (!trees[nr_trees++])
 625                 return -1;
 626         trees[nr_trees] = parse_tree_indirect(one);
 627         if (!trees[nr_trees++])
 628                 return -1;
 629         opts.fn = threeway_merge;
 630         cache_tree_free(&active_cache_tree);
 631         for (i = 0; i < nr_trees; i++) {
 632                 parse_tree(trees[i]);
 633                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 634         }
 635         if (unpack_trees(nr_trees, t, &opts))
 636                 return -1;
 637         return 0;
 638 }
 639
 640 static void write_tree_trivial(struct object_id *oid)
 641 {
 642         if (write_cache_as_tree(oid->hash, 0, NULL))
 643                 die(_("git write-tree failed to write a tree"));
 644 }
 645
 646 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 647                               struct commit_list *remoteheads,
 648                               struct commit *head)
 649 {
 650         static struct lock_file lock;
 651         const char *head_arg = "HEAD";
 652
 653         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 654         refresh_cache(REFRESH_QUIET);
 655         if (write_locked_index(&the_index, &lock,
 656                                COMMIT_LOCK | SKIP_IF_UNCHANGED))
 657                 return error(_("Unable to write index."));
 658
 659         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 660                 int clean, x;
 661                 struct commit *result;
 662                 struct commit_list *reversed = NULL;
 663                 struct merge_options o;
 664                 struct commit_list *j;
 665
 666                 if (remoteheads->next) {
 667                         error(_("Not handling anything other than two heads merge."));
 668                         return 2;
 669                 }
 670
 671                 init_merge_options(&o);
 672                 if (!strcmp(strategy, "subtree"))
 673                         o.subtree_shift = "";
 674
 675                 o.renormalize = option_renormalize;
 676                 o.show_rename_progress =
 677                         show_progress == -1 ? isatty(2) : show_progress;
 678
 679                 for (x = 0; x < xopts_nr; x++)
 680                         if (parse_merge_opt(&o, xopts[x]))
 681                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 682
 683                 o.branch1 = head_arg;
 684                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 685
 686                 for (j = common; j; j = j->next)
 687                         commit_list_insert(j->item, &reversed);
 688
 689                 hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 690                 clean = merge_recursive(&o, head,
 691                                 remoteheads->item, reversed, &result);
 692                 if (clean < 0)
 693                         exit(128);
 694                 if (write_locked_index(&the_index, &lock,
 695                                        COMMIT_LOCK | SKIP_IF_UNCHANGED))
 696                         die (_("unable to write %s"), get_index_file());
 697                 return clean ? 0 : 1;
 698         } else {
 699                 return try_merge_command(strategy, xopts_nr, xopts,
 700                                                 common, head_arg, remoteheads);
 701         }
 702 }
 703
 704 static void count_diff_files(struct diff_queue_struct *q,
 705                              struct diff_options *opt, void *data)
 706 {
 707         int *count = data;
 708
 709         (*count) += q->nr;
 710 }
 711
 712 static int count_unmerged_entries(void)
 713 {
 714         int i, ret = 0;
 715
 716         for (i = 0; i < active_nr; i++)
 717                 if (ce_stage(active_cache[i]))
 718                         ret++;
 719
 720         return ret;
 721 }
 722
 723 static void add_strategies(const char *string, unsigned attr)
 724 {
 725         int i;
 726
 727         if (string) {
 728                 struct string_list list = STRING_LIST_INIT_DUP;
 729                 struct string_list_item *item;
 730                 string_list_split(&list, string, ' ', -1);
 731                 for_each_string_list_item(item, &list)
 732                         append_strategy(get_strategy(item->string));
 733                 string_list_clear(&list, 0);
 734                 return;
 735         }
 736         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 737                 if (all_strategy[i].attr & attr)
 738                         append_strategy(&all_strategy[i]);
 739
 740 }
 741
 742 static void read_merge_msg(struct strbuf *msg)
 743 {
 744         const char *filename = git_path_merge_msg();
 745         strbuf_reset(msg);
 746         if (strbuf_read_file(msg, filename, 0) < 0)
 747                 die_errno(_("Could not read from '%s'"), filename);
 748 }
 749
 750 static void write_merge_state(struct commit_list *);
 751 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
 752 {
 753         if (err_msg)
 754                 error("%s", err_msg);
 755         fprintf(stderr,
 756                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 757         write_merge_state(remoteheads);
 758         exit(1);
 759 }
 760
 761 static const char merge_editor_comment[] =
 762 N_("Please enter a commit message to explain why this merge is necessary,\n"
 763    "especially if it merges an updated upstream into a topic branch.\n"
 764    "\n"
 765    "Lines starting with '%c' will be ignored, and an empty message aborts\n"
 766    "the commit.\n");
 767
 768 static void write_merge_heads(struct commit_list *);
 769 static void prepare_to_commit(struct commit_list *remoteheads)
 770 {
 771         struct strbuf msg = STRBUF_INIT;
 772         strbuf_addbuf(&msg, &merge_msg);
 773         strbuf_addch(&msg, '\n');
 774         if (squash)
 775                 BUG("the control must not reach here under --squash");
 776         if (0 < option_edit)
 777                 strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
 778         if (signoff)
 779                 append_signoff(&msg, ignore_non_trailer(msg.buf, msg.len), 0);
 780         write_merge_heads(remoteheads);
 781         write_file_buf(git_path_merge_msg(), msg.buf, msg.len);
 782         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
 783                             git_path_merge_msg(), "merge", NULL))
 784                 abort_commit(remoteheads, NULL);
 785         if (0 < option_edit) {
 786                 if (launch_editor(git_path_merge_msg(), NULL, NULL))
 787                         abort_commit(remoteheads, NULL);
 788         }
 789
 790         if (verify_msg && run_commit_hook(0 < option_edit, get_index_file(),
 791                                           "commit-msg",
 792                                           git_path_merge_msg(), NULL))
 793                 abort_commit(remoteheads, NULL);
 794
 795         read_merge_msg(&msg);
 796         strbuf_stripspace(&msg, 0 < option_edit);
 797         if (!msg.len)
 798                 abort_commit(remoteheads, _("Empty commit message."));
 799         strbuf_release(&merge_msg);
 800         strbuf_addbuf(&merge_msg, &msg);
 801         strbuf_release(&msg);
 802 }
 803
 804 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 805 {
 806         struct object_id result_tree, result_commit;
 807         struct commit_list *parents, **pptr = &parents;
 808         static struct lock_file lock;
 809
 810         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 811         refresh_cache(REFRESH_QUIET);
 812         if (write_locked_index(&the_index, &lock,
 813                                COMMIT_LOCK | SKIP_IF_UNCHANGED))
 814                 return error(_("Unable to write index."));
 815
 816         write_tree_trivial(&result_tree);
 817         printf(_("Wonderful.\n"));
 818         pptr = commit_list_append(head, pptr);
 819         pptr = commit_list_append(remoteheads->item, pptr);
 820         prepare_to_commit(remoteheads);
 821         if (commit_tree(merge_msg.buf, merge_msg.len, &result_tree, parents,
 822                         &result_commit, NULL, sign_commit))
 823                 die(_("failed to write commit object"));
 824         finish(head, remoteheads, &result_commit, "In-index merge");
 825         drop_save();
 826         return 0;
 827 }
 828
 829 static int finish_automerge(struct commit *head,
 830                             int head_subsumed,
 831                             struct commit_list *common,
 832                             struct commit_list *remoteheads,
 833                             struct object_id *result_tree,
 834                             const char *wt_strategy)
 835 {
 836         struct commit_list *parents = NULL;
 837         struct strbuf buf = STRBUF_INIT;
 838         struct object_id result_commit;
 839
 840         free_commit_list(common);
 841         parents = remoteheads;
 842         if (!head_subsumed || fast_forward == FF_NO)
 843                 commit_list_insert(head, &parents);
 844         strbuf_addch(&merge_msg, '\n');
 845         prepare_to_commit(remoteheads);
 846         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 847                         &result_commit, NULL, sign_commit))
 848                 die(_("failed to write commit object"));
 849         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 850         finish(head, remoteheads, &result_commit, buf.buf);
 851         strbuf_release(&buf);
 852         drop_save();
 853         return 0;
 854 }
 855
 856 static int suggest_conflicts(void)
 857 {
 858         const char *filename;
 859         FILE *fp;
 860         struct strbuf msgbuf = STRBUF_INIT;
 861
 862         filename = git_path_merge_msg();
 863         fp = xfopen(filename, "a");
 864
 865         append_conflicts_hint(&msgbuf);
 866         fputs(msgbuf.buf, fp);
 867         strbuf_release(&msgbuf);
 868         fclose(fp);
 869         rerere(allow_rerere_auto);
 870         printf(_("Automatic merge failed; "
 871                         "fix conflicts and then commit the result.\n"));
 872         return 1;
 873 }
 874
 875 static int evaluate_result(void)
 876 {
 877         int cnt = 0;
 878         struct rev_info rev;
 879
 880         /* Check how many files differ. */
 881         init_revisions(&rev, "");
 882         setup_revisions(0, NULL, &rev, NULL);
 883         rev.diffopt.output_format |=
 884                 DIFF_FORMAT_CALLBACK;
 885         rev.diffopt.format_callback = count_diff_files;
 886         rev.diffopt.format_callback_data = &cnt;
 887         run_diff_files(&rev, 0);
 888
 889         /*
 890          * Check how many unmerged entries are
 891          * there.
 892          */
 893         cnt += count_unmerged_entries();
 894
 895         return cnt;
 896 }
 897
 898 /*
 899  * Pretend as if the user told us to merge with the remote-tracking
 900  * branch we have for the upstream of the current branch
 901  */
 902 static int setup_with_upstream(const char ***argv)
 903 {
 904         struct branch *branch = branch_get(NULL);
 905         int i;
 906         const char **args;
 907
 908         if (!branch)
 909                 die(_("No current branch."));
 910         if (!branch->remote_name)
 911                 die(_("No remote for the current branch."));
 912         if (!branch->merge_nr)
 913                 die(_("No default upstream defined for the current branch."));
 914
 915         args = xcalloc(st_add(branch->merge_nr, 1), sizeof(char *));
 916         for (i = 0; i < branch->merge_nr; i++) {
 917                 if (!branch->merge[i]->dst)
 918                         die(_("No remote-tracking branch for %s from %s"),
 919                             branch->merge[i]->src, branch->remote_name);
 920                 args[i] = branch->merge[i]->dst;
 921         }
 922         args[i] = NULL;
 923         *argv = args;
 924         return i;
 925 }
 926
 927 static void write_merge_heads(struct commit_list *remoteheads)
 928 {
 929         struct commit_list *j;
 930         struct strbuf buf = STRBUF_INIT;
 931
 932         for (j = remoteheads; j; j = j->next) {
 933                 struct object_id *oid;
 934                 struct commit *c = j->item;
 935                 if (c->util && merge_remote_util(c)->obj) {
 936                         oid = &merge_remote_util(c)->obj->oid;
 937                 } else {
 938                         oid = &c->object.oid;
 939                 }
 940                 strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
 941         }
 942         write_file_buf(git_path_merge_head(), buf.buf, buf.len);
 943
 944         strbuf_reset(&buf);
 945         if (fast_forward == FF_NO)
 946                 strbuf_addstr(&buf, "no-ff");
 947         write_file_buf(git_path_merge_mode(), buf.buf, buf.len);
 948         strbuf_release(&buf);
 949 }
 950
 951 static void write_merge_state(struct commit_list *remoteheads)
 952 {
 953         write_merge_heads(remoteheads);
 954         strbuf_addch(&merge_msg, '\n');
 955         write_file_buf(git_path_merge_msg(), merge_msg.buf, merge_msg.len);
 956 }
 957
 958 static int default_edit_option(void)
 959 {
 960         static const char name[] = "GIT_MERGE_AUTOEDIT";
 961         const char *e = getenv(name);
 962         struct stat st_stdin, st_stdout;
 963
 964         if (have_message)
 965                 /* an explicit -m msg without --[no-]edit */
 966                 return 0;
 967
 968         if (e) {
 969                 int v = git_parse_maybe_bool(e);
 970                 if (v < 0)
 971                         die(_("Bad value '%s' in environment '%s'"), e, name);
 972                 return v;
 973         }
 974
 975         /* Use editor if stdin and stdout are the same and is a tty */
 976         return (!fstat(0, &st_stdin) &&
 977                 !fstat(1, &st_stdout) &&
 978                 isatty(0) && isatty(1) &&
 979                 st_stdin.st_dev == st_stdout.st_dev &&
 980                 st_stdin.st_ino == st_stdout.st_ino &&
 981                 st_stdin.st_mode == st_stdout.st_mode);
 982 }
 983
 984 static struct commit_list *reduce_parents(struct commit *head_commit,
 985                                           int *head_subsumed,
 986                                           struct commit_list *remoteheads)
 987 {
 988         struct commit_list *parents, **remotes;
 989
 990         /*
 991          * Is the current HEAD reachable from another commit being
 992          * merged?  If so we do not want to record it as a parent of
 993          * the resulting merge, unless --no-ff is given.  We will flip
 994          * this variable to 0 when we find HEAD among the independent
 995          * tips being merged.
 996          */
 997         *head_subsumed = 1;
 998
 999         /* Find what parents to record by checking independent ones. */
1000         parents = reduce_heads(remoteheads);
1001         free_commit_list(remoteheads);
1002
1003         remoteheads = NULL;
1004         remotes = &remoteheads;
1005         while (parents) {
1006                 struct commit *commit = pop_commit(&parents);
1007                 if (commit == head_commit)
1008                         *head_subsumed = 0;
1009                 else
1010                         remotes = &commit_list_insert(commit, remotes)->next;
1011         }
1012         return remoteheads;
1013 }
1014
1015 static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
1016 {
1017         struct fmt_merge_msg_opts opts;
1018
1019         memset(&opts, 0, sizeof(opts));
1020         opts.add_title = !have_message;
1021         opts.shortlog_len = shortlog_len;
1022         opts.credit_people = (0 < option_edit);
1023
1024         fmt_merge_msg(merge_names, merge_msg, &opts);
1025         if (merge_msg->len)
1026                 strbuf_setlen(merge_msg, merge_msg->len - 1);
1027 }
1028
1029 static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1030 {
1031         const char *filename;
1032         int fd, pos, npos;
1033         struct strbuf fetch_head_file = STRBUF_INIT;
1034
1035         if (!merge_names)
1036                 merge_names = &fetch_head_file;
1037
1038         filename = git_path_fetch_head();
1039         fd = open(filename, O_RDONLY);
1040         if (fd < 0)
1041                 die_errno(_("could not open '%s' for reading"), filename);
1042
1043         if (strbuf_read(merge_names, fd, 0) < 0)
1044                 die_errno(_("could not read '%s'"), filename);
1045         if (close(fd) < 0)
1046                 die_errno(_("could not close '%s'"), filename);
1047
1048         for (pos = 0; pos < merge_names->len; pos = npos) {
1049                 struct object_id oid;
1050                 char *ptr;
1051                 struct commit *commit;
1052
1053                 ptr = strchr(merge_names->buf + pos, '\n');
1054                 if (ptr)
1055                         npos = ptr - merge_names->buf + 1;
1056                 else
1057                         npos = merge_names->len;
1058
1059                 if (npos - pos < GIT_SHA1_HEXSZ + 2 ||
1060                     get_oid_hex(merge_names->buf + pos, &oid))
1061                         commit = NULL; /* bad */
1062                 else if (memcmp(merge_names->buf + pos + GIT_SHA1_HEXSZ, "\t\t", 2))
1063                         continue; /* not-for-merge */
1064                 else {
1065                         char saved = merge_names->buf[pos + GIT_SHA1_HEXSZ];
1066                         merge_names->buf[pos + GIT_SHA1_HEXSZ] = '\0';
1067                         commit = get_merge_parent(merge_names->buf + pos);
1068                         merge_names->buf[pos + GIT_SHA1_HEXSZ] = saved;
1069                 }
1070                 if (!commit) {
1071                         if (ptr)
1072                                 *ptr = '\0';
1073                         die(_("not something we can merge in %s: %s"),
1074                             filename, merge_names->buf + pos);
1075                 }
1076                 remotes = &commit_list_insert(commit, remotes)->next;
1077         }
1078
1079         if (merge_names == &fetch_head_file)
1080                 strbuf_release(&fetch_head_file);
1081 }
1082
1083 static struct commit_list *collect_parents(struct commit *head_commit,
1084                                            int *head_subsumed,
1085                                            int argc, const char **argv,
1086                                            struct strbuf *merge_msg)
1087 {
1088         int i;
1089         struct commit_list *remoteheads = NULL;
1090         struct commit_list **remotes = &remoteheads;
1091         struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1092
1093         if (merge_msg && (!have_message || shortlog_len))
1094                 autogen = &merge_names;
1095
1096         if (head_commit)
1097                 remotes = &commit_list_insert(head_commit, remotes)->next;
1098
1099         if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1100                 handle_fetch_head(remotes, autogen);
1101                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1102         } else {
1103                 for (i = 0; i < argc; i++) {
1104                         struct commit *commit = get_merge_parent(argv[i]);
1105                         if (!commit)
1106                                 help_unknown_ref(argv[i], "merge",
1107                                                  _("not something we can merge"));
1108                         remotes = &commit_list_insert(commit, remotes)->next;
1109                 }
1110                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1111                 if (autogen) {
1112                         struct commit_list *p;
1113                         for (p = remoteheads; p; p = p->next)
1114                                 merge_name(merge_remote_util(p->item)->name, autogen);
1115                 }
1116         }
1117
1118         if (autogen) {
1119                 prepare_merge_message(autogen, merge_msg);
1120                 strbuf_release(autogen);
1121         }
1122
1123         return remoteheads;
1124 }
1125
1126 static int merging_a_throwaway_tag(struct commit *commit)
1127 {
1128         char *tag_ref;
1129         struct object_id oid;
1130         int is_throwaway_tag = 0;
1131
1132         /* Are we merging a tag? */
1133         if (!merge_remote_util(commit) ||
1134             !merge_remote_util(commit)->obj ||
1135             merge_remote_util(commit)->obj->type != OBJ_TAG)
1136                 return is_throwaway_tag;
1137
1138         /*
1139          * Now we know we are merging a tag object.  Are we downstream
1140          * and following the tags from upstream?  If so, we must have
1141          * the tag object pointed at by "refs/tags/$T" where $T is the
1142          * tagname recorded in the tag object.  We want to allow such
1143          * a "just to catch up" merge to fast-forward.
1144          *
1145          * Otherwise, we are playing an integrator's role, making a
1146          * merge with a throw-away tag from a contributor with
1147          * something like "git pull $contributor $signed_tag".
1148          * We want to forbid such a merge from fast-forwarding
1149          * by default; otherwise we would not keep the signature
1150          * anywhere.
1151          */
1152         tag_ref = xstrfmt("refs/tags/%s",
1153                           ((struct tag *)merge_remote_util(commit)->obj)->tag);
1154         if (!read_ref(tag_ref, &oid) &&
1155             !oidcmp(&oid, &merge_remote_util(commit)->obj->oid))
1156                 is_throwaway_tag = 0;
1157         else
1158                 is_throwaway_tag = 1;
1159         free(tag_ref);
1160         return is_throwaway_tag;
1161 }
1162
1163 int cmd_merge(int argc, const char **argv, const char *prefix)
1164 {
1165         struct object_id result_tree, stash, head_oid;
1166         struct commit *head_commit;
1167         struct strbuf buf = STRBUF_INIT;
1168         int i, ret = 0, head_subsumed;
1169         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1170         struct commit_list *common = NULL;
1171         const char *best_strategy = NULL, *wt_strategy = NULL;
1172         struct commit_list *remoteheads, *p;
1173         void *branch_to_free;
1174         int orig_argc = argc;
1175
1176         if (argc == 2 && !strcmp(argv[1], "-h"))
1177                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1178
1179         /*
1180          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1181          * current branch.
1182          */
1183         branch = branch_to_free = resolve_refdup("HEAD", 0, &head_oid, NULL);
1184         if (branch)
1185                 skip_prefix(branch, "refs/heads/", &branch);
1186         if (!branch || is_null_oid(&head_oid))
1187                 head_commit = NULL;
1188         else
1189                 head_commit = lookup_commit_or_die(&head_oid, "HEAD");
1190
1191         init_diff_ui_defaults();
1192         git_config(git_merge_config, NULL);
1193
1194         if (branch_mergeoptions)
1195                 parse_branch_merge_options(branch_mergeoptions);
1196         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1197                         builtin_merge_usage, 0);
1198         if (shortlog_len < 0)
1199                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1200
1201         if (verbosity < 0 && show_progress == -1)
1202                 show_progress = 0;
1203
1204         if (abort_current_merge) {
1205                 int nargc = 2;
1206                 const char *nargv[] = {"reset", "--merge", NULL};
1207
1208                 if (orig_argc != 2)
1209                         usage_msg_opt(_("--abort expects no arguments"),
1210                               builtin_merge_usage, builtin_merge_options);
1211
1212                 if (!file_exists(git_path_merge_head()))
1213                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1214
1215                 /* Invoke 'git reset --merge' */
1216                 ret = cmd_reset(nargc, nargv, prefix);
1217                 goto done;
1218         }
1219
1220         if (continue_current_merge) {
1221                 int nargc = 1;
1222                 const char *nargv[] = {"commit", NULL};
1223
1224                 if (orig_argc != 2)
1225                         usage_msg_opt(_("--continue expects no arguments"),
1226                               builtin_merge_usage, builtin_merge_options);
1227
1228                 if (!file_exists(git_path_merge_head()))
1229                         die(_("There is no merge in progress (MERGE_HEAD missing)."));
1230
1231                 /* Invoke 'git commit' */
1232                 ret = cmd_commit(nargc, nargv, prefix);
1233                 goto done;
1234         }
1235
1236         if (read_cache_unmerged())
1237                 die_resolve_conflict("merge");
1238
1239         if (file_exists(git_path_merge_head())) {
1240                 /*
1241                  * There is no unmerged entry, don't advise 'git
1242                  * add/rm <file>', just 'git commit'.
1243                  */
1244                 if (advice_resolve_conflict)
1245                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1246                                   "Please, commit your changes before you merge."));
1247                 else
1248                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1249         }
1250         if (file_exists(git_path_cherry_pick_head())) {
1251                 if (advice_resolve_conflict)
1252                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1253                             "Please, commit your changes before you merge."));
1254                 else
1255                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1256         }
1257         resolve_undo_clear();
1258
1259         if (verbosity < 0)
1260                 show_diffstat = 0;
1261
1262         if (squash) {
1263                 if (fast_forward == FF_NO)
1264                         die(_("You cannot combine --squash with --no-ff."));
1265                 option_commit = 0;
1266         }
1267
1268         if (!argc) {
1269                 if (default_to_upstream)
1270                         argc = setup_with_upstream(&argv);
1271                 else
1272                         die(_("No commit specified and merge.defaultToUpstream not set."));
1273         } else if (argc == 1 && !strcmp(argv[0], "-")) {
1274                 argv[0] = "@{-1}";
1275         }
1276
1277         if (!argc)
1278                 usage_with_options(builtin_merge_usage,
1279                         builtin_merge_options);
1280
1281         if (!head_commit) {
1282                 /*
1283                  * If the merged head is a valid one there is no reason
1284                  * to forbid "git merge" into a branch yet to be born.
1285                  * We do the same for "git pull".
1286                  */
1287                 struct object_id *remote_head_oid;
1288                 if (squash)
1289                         die(_("Squash commit into empty head not supported yet"));
1290                 if (fast_forward == FF_NO)
1291                         die(_("Non-fast-forward commit does not make sense into "
1292                             "an empty head"));
1293                 remoteheads = collect_parents(head_commit, &head_subsumed,
1294                                               argc, argv, NULL);
1295                 if (!remoteheads)
1296                         die(_("%s - not something we can merge"), argv[0]);
1297                 if (remoteheads->next)
1298                         die(_("Can merge only exactly one commit into empty head"));
1299                 remote_head_oid = &remoteheads->item->object.oid;
1300                 read_empty(remote_head_oid->hash, 0);
1301                 update_ref("initial pull", "HEAD", remote_head_oid, NULL, 0,
1302                            UPDATE_REFS_DIE_ON_ERR);
1303                 goto done;
1304         }
1305
1306         /*
1307          * All the rest are the commits being merged; prepare
1308          * the standard merge summary message to be appended
1309          * to the given message.
1310          */
1311         remoteheads = collect_parents(head_commit, &head_subsumed,
1312                                       argc, argv, &merge_msg);
1313
1314         if (!head_commit || !argc)
1315                 usage_with_options(builtin_merge_usage,
1316                         builtin_merge_options);
1317
1318         if (verify_signatures) {
1319                 for (p = remoteheads; p; p = p->next) {
1320                         struct commit *commit = p->item;
1321                         char hex[GIT_MAX_HEXSZ + 1];
1322                         struct signature_check signature_check;
1323                         memset(&signature_check, 0, sizeof(signature_check));
1324
1325                         check_commit_signature(commit, &signature_check);
1326
1327                         find_unique_abbrev_r(hex, commit->object.oid.hash, DEFAULT_ABBREV);
1328                         switch (signature_check.result) {
1329                         case 'G':
1330                                 break;
1331                         case 'U':
1332                                 die(_("Commit %s has an untrusted GPG signature, "
1333                                       "allegedly by %s."), hex, signature_check.signer);
1334                         case 'B':
1335                                 die(_("Commit %s has a bad GPG signature "
1336                                       "allegedly by %s."), hex, signature_check.signer);
1337                         default: /* 'N' */
1338                                 die(_("Commit %s does not have a GPG signature."), hex);
1339                         }
1340                         if (verbosity >= 0 && signature_check.result == 'G')
1341                                 printf(_("Commit %s has a good GPG signature by %s\n"),
1342                                        hex, signature_check.signer);
1343
1344                         signature_check_clear(&signature_check);
1345                 }
1346         }
1347
1348         strbuf_addstr(&buf, "merge");
1349         for (p = remoteheads; p; p = p->next)
1350                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1351         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1352         strbuf_reset(&buf);
1353
1354         for (p = remoteheads; p; p = p->next) {
1355                 struct commit *commit = p->item;
1356                 strbuf_addf(&buf, "GITHEAD_%s",
1357                             oid_to_hex(&commit->object.oid));
1358                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1359                 strbuf_reset(&buf);
1360                 if (fast_forward != FF_ONLY && merging_a_throwaway_tag(commit))
1361                         fast_forward = FF_NO;
1362         }
1363
1364         if (option_edit < 0)
1365                 option_edit = default_edit_option();
1366
1367         if (!use_strategies) {
1368                 if (!remoteheads)
1369                         ; /* already up-to-date */
1370                 else if (!remoteheads->next)
1371                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1372                 else
1373                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1374         }
1375
1376         for (i = 0; i < use_strategies_nr; i++) {
1377                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1378                         fast_forward = FF_NO;
1379                 if (use_strategies[i]->attr & NO_TRIVIAL)
1380                         allow_trivial = 0;
1381         }
1382
1383         if (!remoteheads)
1384                 ; /* already up-to-date */
1385         else if (!remoteheads->next)
1386                 common = get_merge_bases(head_commit, remoteheads->item);
1387         else {
1388                 struct commit_list *list = remoteheads;
1389                 commit_list_insert(head_commit, &list);
1390                 common = get_octopus_merge_bases(list);
1391                 free(list);
1392         }
1393
1394         update_ref("updating ORIG_HEAD", "ORIG_HEAD",
1395                    &head_commit->object.oid, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1396
1397         if (remoteheads && !common) {
1398                 /* No common ancestors found. */
1399                 if (!allow_unrelated_histories)
1400                         die(_("refusing to merge unrelated histories"));
1401                 /* otherwise, we need a real merge. */
1402         } else if (!remoteheads ||
1403                  (!remoteheads->next && !common->next &&
1404                   common->item == remoteheads->item)) {
1405                 /*
1406                  * If head can reach all the merge then we are up to date.
1407                  * but first the most common case of merging one remote.
1408                  */
1409                 finish_up_to_date(_("Already up to date."));
1410                 goto done;
1411         } else if (fast_forward != FF_NO && !remoteheads->next &&
1412                         !common->next &&
1413                         !oidcmp(&common->item->object.oid, &head_commit->object.oid)) {
1414                 /* Again the most common case of merging one remote. */
1415                 struct strbuf msg = STRBUF_INIT;
1416                 struct commit *commit;
1417
1418                 if (verbosity >= 0) {
1419                         printf(_("Updating %s..%s\n"),
1420                                find_unique_abbrev(head_commit->object.oid.hash,
1421                                                   DEFAULT_ABBREV),
1422                                find_unique_abbrev(remoteheads->item->object.oid.hash,
1423                                                   DEFAULT_ABBREV));
1424                 }
1425                 strbuf_addstr(&msg, "Fast-forward");
1426                 if (have_message)
1427                         strbuf_addstr(&msg,
1428                                 " (no commit created; -m option ignored)");
1429                 commit = remoteheads->item;
1430                 if (!commit) {
1431                         ret = 1;
1432                         goto done;
1433                 }
1434
1435                 if (checkout_fast_forward(&head_commit->object.oid,
1436                                           &commit->object.oid,
1437                                           overwrite_ignore)) {
1438                         ret = 1;
1439                         goto done;
1440                 }
1441
1442                 finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
1443                 drop_save();
1444                 goto done;
1445         } else if (!remoteheads->next && common->next)
1446                 ;
1447                 /*
1448                  * We are not doing octopus and not fast-forward.  Need
1449                  * a real merge.
1450                  */
1451         else if (!remoteheads->next && !common->next && option_commit) {
1452                 /*
1453                  * We are not doing octopus, not fast-forward, and have
1454                  * only one common.
1455                  */
1456                 refresh_cache(REFRESH_QUIET);
1457                 if (allow_trivial && fast_forward != FF_ONLY) {
1458                         /* See if it is really trivial. */
1459                         git_committer_info(IDENT_STRICT);
1460                         printf(_("Trying really trivial in-index merge...\n"));
1461                         if (!read_tree_trivial(&common->item->object.oid,
1462                                                &head_commit->object.oid,
1463                                                &remoteheads->item->object.oid)) {
1464                                 ret = merge_trivial(head_commit, remoteheads);
1465                                 goto done;
1466                         }
1467                         printf(_("Nope.\n"));
1468                 }
1469         } else {
1470                 /*
1471                  * An octopus.  If we can reach all the remote we are up
1472                  * to date.
1473                  */
1474                 int up_to_date = 1;
1475                 struct commit_list *j;
1476
1477                 for (j = remoteheads; j; j = j->next) {
1478                         struct commit_list *common_one;
1479
1480                         /*
1481                          * Here we *have* to calculate the individual
1482                          * merge_bases again, otherwise "git merge HEAD^
1483                          * HEAD^^" would be missed.
1484                          */
1485                         common_one = get_merge_bases(head_commit, j->item);
1486                         if (oidcmp(&common_one->item->object.oid, &j->item->object.oid)) {
1487                                 up_to_date = 0;
1488                                 break;
1489                         }
1490                 }
1491                 if (up_to_date) {
1492                         finish_up_to_date(_("Already up to date. Yeeah!"));
1493                         goto done;
1494                 }
1495         }
1496
1497         if (fast_forward == FF_ONLY)
1498                 die(_("Not possible to fast-forward, aborting."));
1499
1500         /* We are going to make a new commit. */
1501         git_committer_info(IDENT_STRICT);
1502
1503         /*
1504          * At this point, we need a real merge.  No matter what strategy
1505          * we use, it would operate on the index, possibly affecting the
1506          * working tree, and when resolved cleanly, have the desired
1507          * tree in the index -- this means that the index must be in
1508          * sync with the head commit.  The strategies are responsible
1509          * to ensure this.
1510          */
1511         if (use_strategies_nr == 1 ||
1512             /*
1513              * Stash away the local changes so that we can try more than one.
1514              */
1515             save_state(&stash))
1516                 oidclr(&stash);
1517
1518         for (i = 0; i < use_strategies_nr; i++) {
1519                 int ret;
1520                 if (i) {
1521                         printf(_("Rewinding the tree to pristine...\n"));
1522                         restore_state(&head_commit->object.oid, &stash);
1523                 }
1524                 if (use_strategies_nr != 1)
1525                         printf(_("Trying merge strategy %s...\n"),
1526                                 use_strategies[i]->name);
1527                 /*
1528                  * Remember which strategy left the state in the working
1529                  * tree.
1530                  */
1531                 wt_strategy = use_strategies[i]->name;
1532
1533                 ret = try_merge_strategy(use_strategies[i]->name,
1534                                          common, remoteheads,
1535                                          head_commit);
1536                 if (!option_commit && !ret) {
1537                         merge_was_ok = 1;
1538                         /*
1539                          * This is necessary here just to avoid writing
1540                          * the tree, but later we will *not* exit with
1541                          * status code 1 because merge_was_ok is set.
1542                          */
1543                         ret = 1;
1544                 }
1545
1546                 if (ret) {
1547                         /*
1548                          * The backend exits with 1 when conflicts are
1549                          * left to be resolved, with 2 when it does not
1550                          * handle the given merge at all.
1551                          */
1552                         if (ret == 1) {
1553                                 int cnt = evaluate_result();
1554
1555                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1556                                         best_strategy = use_strategies[i]->name;
1557                                         best_cnt = cnt;
1558                                 }
1559                         }
1560                         if (merge_was_ok)
1561                                 break;
1562                         else
1563                                 continue;
1564                 }
1565
1566                 /* Automerge succeeded. */
1567                 write_tree_trivial(&result_tree);
1568                 automerge_was_ok = 1;
1569                 break;
1570         }
1571
1572         /*
1573          * If we have a resulting tree, that means the strategy module
1574          * auto resolved the merge cleanly.
1575          */
1576         if (automerge_was_ok) {
1577                 ret = finish_automerge(head_commit, head_subsumed,
1578                                        common, remoteheads,
1579                                        &result_tree, wt_strategy);
1580                 goto done;
1581         }
1582
1583         /*
1584          * Pick the result from the best strategy and have the user fix
1585          * it up.
1586          */
1587         if (!best_strategy) {
1588                 restore_state(&head_commit->object.oid, &stash);
1589                 if (use_strategies_nr > 1)
1590                         fprintf(stderr,
1591                                 _("No merge strategy handled the merge.\n"));
1592                 else
1593                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1594                                 use_strategies[0]->name);
1595                 ret = 2;
1596                 goto done;
1597         } else if (best_strategy == wt_strategy)
1598                 ; /* We already have its result in the working tree. */
1599         else {
1600                 printf(_("Rewinding the tree to pristine...\n"));
1601                 restore_state(&head_commit->object.oid, &stash);
1602                 printf(_("Using the %s to prepare resolving by hand.\n"),
1603                         best_strategy);
1604                 try_merge_strategy(best_strategy, common, remoteheads,
1605                                    head_commit);
1606         }
1607
1608         if (squash)
1609                 finish(head_commit, remoteheads, NULL, NULL);
1610         else
1611                 write_merge_state(remoteheads);
1612
1613         if (merge_was_ok)
1614                 fprintf(stderr, _("Automatic merge went well; "
1615                         "stopped before committing as requested\n"));
1616         else
1617                 ret = suggest_conflicts();
1618
1619 done:
1620         free(branch_to_free);
1621         return ret;
1622 }