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 #define USE_THE_INDEX_VARIABLE
  10 #include "cache.h"
  11 #include "abspath.h"
  12 #include "alloc.h"
  13 #include "config.h"
  14 #include "environment.h"
  15 #include "gettext.h"
  16 #include "hex.h"
  17 #include "parse-options.h"
  18 #include "builtin.h"
  19 #include "lockfile.h"
  20 #include "run-command.h"
  21 #include "hook.h"
  22 #include "diff.h"
  23 #include "diff-merges.h"
  24 #include "refs.h"
  25 #include "refspec.h"
  26 #include "commit.h"
  27 #include "diffcore.h"
  28 #include "revision.h"
  29 #include "unpack-trees.h"
  30 #include "cache-tree.h"
  31 #include "dir.h"
  32 #include "utf8.h"
  33 #include "log-tree.h"
  34 #include "color.h"
  35 #include "rerere.h"
  36 #include "help.h"
  37 #include "merge-recursive.h"
  38 #include "merge-ort-wrappers.h"
  39 #include "resolve-undo.h"
  40 #include "remote.h"
  41 #include "fmt-merge-msg.h"
  42 #include "gpg-interface.h"
  43 #include "sequencer.h"
  44 #include "string-list.h"
  45 #include "packfile.h"
  46 #include "tag.h"
  47 #include "alias.h"
  48 #include "branch.h"
  49 #include "commit-reach.h"
  50 #include "wt-status.h"
  51 #include "commit-graph.h"
  52 #include "wrapper.h"
  53
  54 #define DEFAULT_TWOHEAD (1<<0)
  55 #define DEFAULT_OCTOPUS (1<<1)
  56 #define NO_FAST_FORWARD (1<<2)
  57 #define NO_TRIVIAL      (1<<3)
  58
  59 struct strategy {
  60         const char *name;
  61         unsigned attr;
  62 };
  63
  64 static const char * const builtin_merge_usage[] = {
  65         N_("git merge [<options>] [<commit>...]"),
  66         "git merge --abort",
  67         "git merge --continue",
  68         NULL
  69 };
  70
  71 static int show_diffstat = 1, shortlog_len = -1, squash;
  72 static int option_commit = -1;
  73 static int option_edit = -1;
  74 static int allow_trivial = 1, have_message, verify_signatures;
  75 static int check_trust_level = 1;
  76 static int overwrite_ignore = 1;
  77 static struct strbuf merge_msg = STRBUF_INIT;
  78 static struct strategy **use_strategies;
  79 static size_t use_strategies_nr, use_strategies_alloc;
  80 static const char **xopts;
  81 static size_t xopts_nr, xopts_alloc;
  82 static const char *branch;
  83 static char *branch_mergeoptions;
  84 static int verbosity;
  85 static int allow_rerere_auto;
  86 static int abort_current_merge;
  87 static int quit_current_merge;
  88 static int continue_current_merge;
  89 static int allow_unrelated_histories;
  90 static int show_progress = -1;
  91 static int default_to_upstream = 1;
  92 static int signoff;
  93 static const char *sign_commit;
  94 static int autostash;
  95 static int no_verify;
  96 static char *into_name;
  97
  98 static struct strategy all_strategy[] = {
  99         { "recursive",  NO_TRIVIAL },
 100         { "octopus",    DEFAULT_OCTOPUS },
 101         { "ort",        DEFAULT_TWOHEAD | NO_TRIVIAL },
 102         { "resolve",    0 },
 103         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
 104         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
 105 };
 106
 107 static const char *pull_twohead, *pull_octopus;
 108
 109 enum ff_type {
 110         FF_NO,
 111         FF_ALLOW,
 112         FF_ONLY
 113 };
 114
 115 static enum ff_type fast_forward = FF_ALLOW;
 116
 117 static const char *cleanup_arg;
 118 static enum commit_msg_cleanup_mode cleanup_mode;
 119
 120 static int option_parse_message(const struct option *opt,
 121                                 const char *arg, int unset)
 122 {
 123         struct strbuf *buf = opt->value;
 124
 125         if (unset)
 126                 strbuf_setlen(buf, 0);
 127         else if (arg) {
 128                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
 129                 have_message = 1;
 130         } else
 131                 return error(_("switch `m' requires a value"));
 132         return 0;
 133 }
 134
 135 static enum parse_opt_result option_read_message(struct parse_opt_ctx_t *ctx,
 136                                                  const struct option *opt,
 137                                                  const char *arg_not_used,
 138                                                  int unset)
 139 {
 140         struct strbuf *buf = opt->value;
 141         const char *arg;
 142
 143         BUG_ON_OPT_ARG(arg_not_used);
 144         if (unset)
 145                 BUG("-F cannot be negated");
 146
 147         if (ctx->opt) {
 148                 arg = ctx->opt;
 149                 ctx->opt = NULL;
 150         } else if (ctx->argc > 1) {
 151                 ctx->argc--;
 152                 arg = *++ctx->argv;
 153         } else
 154                 return error(_("option `%s' requires a value"), opt->long_name);
 155
 156         if (buf->len)
 157                 strbuf_addch(buf, '\n');
 158         if (ctx->prefix && !is_absolute_path(arg))
 159                 arg = prefix_filename(ctx->prefix, arg);
 160         if (strbuf_read_file(buf, arg, 0) < 0)
 161                 return error(_("could not read file '%s'"), arg);
 162         have_message = 1;
 163
 164         return 0;
 165 }
 166
 167 static struct strategy *get_strategy(const char *name)
 168 {
 169         int i;
 170         struct strategy *ret;
 171         static struct cmdnames main_cmds, other_cmds;
 172         static int loaded;
 173         char *default_strategy = getenv("GIT_TEST_MERGE_ALGORITHM");
 174
 175         if (!name)
 176                 return NULL;
 177
 178         if (default_strategy &&
 179             !strcmp(default_strategy, "ort") &&
 180             !strcmp(name, "recursive")) {
 181                 name = "ort";
 182         }
 183
 184         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 185                 if (!strcmp(name, all_strategy[i].name))
 186                         return &all_strategy[i];
 187
 188         if (!loaded) {
 189                 struct cmdnames not_strategies;
 190                 loaded = 1;
 191
 192                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 193                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 194                 for (i = 0; i < main_cmds.cnt; i++) {
 195                         int j, found = 0;
 196                         struct cmdname *ent = main_cmds.names[i];
 197                         for (j = 0; !found && j < ARRAY_SIZE(all_strategy); j++)
 198                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 199                                                 && !all_strategy[j].name[ent->len])
 200                                         found = 1;
 201                         if (!found)
 202                                 add_cmdname(&not_strategies, ent->name, ent->len);
 203                 }
 204                 exclude_cmds(&main_cmds, &not_strategies);
 205         }
 206         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 207                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 208                 fprintf(stderr, _("Available strategies are:"));
 209                 for (i = 0; i < main_cmds.cnt; i++)
 210                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 211                 fprintf(stderr, ".\n");
 212                 if (other_cmds.cnt) {
 213                         fprintf(stderr, _("Available custom strategies are:"));
 214                         for (i = 0; i < other_cmds.cnt; i++)
 215                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 216                         fprintf(stderr, ".\n");
 217                 }
 218                 exit(1);
 219         }
 220
 221         CALLOC_ARRAY(ret, 1);
 222         ret->name = xstrdup(name);
 223         ret->attr = NO_TRIVIAL;
 224         return ret;
 225 }
 226
 227 static void append_strategy(struct strategy *s)
 228 {
 229         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 230         use_strategies[use_strategies_nr++] = s;
 231 }
 232
 233 static int option_parse_strategy(const struct option *opt,
 234                                  const char *name, int unset)
 235 {
 236         if (unset)
 237                 return 0;
 238
 239         append_strategy(get_strategy(name));
 240         return 0;
 241 }
 242
 243 static int option_parse_x(const struct option *opt,
 244                           const char *arg, int unset)
 245 {
 246         if (unset)
 247                 return 0;
 248
 249         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 250         xopts[xopts_nr++] = xstrdup(arg);
 251         return 0;
 252 }
 253
 254 static int option_parse_n(const struct option *opt,
 255                           const char *arg, int unset)
 256 {
 257         BUG_ON_OPT_ARG(arg);
 258         show_diffstat = unset;
 259         return 0;
 260 }
 261
 262 static struct option builtin_merge_options[] = {
 263         OPT_CALLBACK_F('n', NULL, NULL, NULL,
 264                 N_("do not show a diffstat at the end of the merge"),
 265                 PARSE_OPT_NOARG, option_parse_n),
 266         OPT_BOOL(0, "stat", &show_diffstat,
 267                 N_("show a diffstat at the end of the merge")),
 268         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
 269         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
 270           N_("add (at most <n>) entries from shortlog to merge commit message"),
 271           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 272         OPT_BOOL(0, "squash", &squash,
 273                 N_("create a single commit instead of doing a merge")),
 274         OPT_BOOL(0, "commit", &option_commit,
 275                 N_("perform a commit if the merge succeeds (default)")),
 276         OPT_BOOL('e', "edit", &option_edit,
 277                 N_("edit message before committing")),
 278         OPT_CLEANUP(&cleanup_arg),
 279         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
 280         OPT_SET_INT_F(0, "ff-only", &fast_forward,
 281                       N_("abort if fast-forward is not possible"),
 282                       FF_ONLY, PARSE_OPT_NONEG),
 283         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 284         OPT_BOOL(0, "verify-signatures", &verify_signatures,
 285                 N_("verify that the named commit has a valid GPG signature")),
 286         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
 287                 N_("merge strategy to use"), option_parse_strategy),
 288         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
 289                 N_("option for selected merge strategy"), option_parse_x),
 290         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
 291                 N_("merge commit message (for a non-fast-forward merge)"),
 292                 option_parse_message),
 293         { OPTION_LOWLEVEL_CALLBACK, 'F', "file", &merge_msg, N_("path"),
 294                 N_("read message from file"), PARSE_OPT_NONEG,
 295                 NULL, 0, option_read_message },
 296         OPT_STRING(0, "into-name", &into_name, N_("name"),
 297                    N_("use <name> instead of the real target")),
 298         OPT__VERBOSITY(&verbosity),
 299         OPT_BOOL(0, "abort", &abort_current_merge,
 300                 N_("abort the current in-progress merge")),
 301         OPT_BOOL(0, "quit", &quit_current_merge,
 302                 N_("--abort but leave index and working tree alone")),
 303         OPT_BOOL(0, "continue", &continue_current_merge,
 304                 N_("continue the current in-progress merge")),
 305         OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
 306                  N_("allow merging unrelated histories")),
 307         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
 308         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
 309           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 310         OPT_AUTOSTASH(&autostash),
 311         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
 312         OPT_BOOL(0, "signoff", &signoff, N_("add a Signed-off-by trailer")),
 313         OPT_BOOL(0, "no-verify", &no_verify, N_("bypass pre-merge-commit and commit-msg hooks")),
 314         OPT_END()
 315 };
 316
 317 static int save_state(struct object_id *stash)
 318 {
 319         int len;
 320         struct child_process cp = CHILD_PROCESS_INIT;
 321         struct strbuf buffer = STRBUF_INIT;
 322         struct lock_file lock_file = LOCK_INIT;
 323         int fd;
 324         int rc = -1;
 325
 326         fd = repo_hold_locked_index(the_repository, &lock_file, 0);
 327         refresh_index(&the_index, REFRESH_QUIET, NULL, NULL, NULL);
 328         if (0 <= fd)
 329                 repo_update_index_if_able(the_repository, &lock_file);
 330         rollback_lock_file(&lock_file);
 331
 332         strvec_pushl(&cp.args, "stash", "create", NULL);
 333         cp.out = -1;
 334         cp.git_cmd = 1;
 335
 336         if (start_command(&cp))
 337                 die(_("could not run stash."));
 338         len = strbuf_read(&buffer, cp.out, 1024);
 339         close(cp.out);
 340
 341         if (finish_command(&cp) || len < 0)
 342                 die(_("stash failed"));
 343         else if (!len)          /* no changes */
 344                 goto out;
 345         strbuf_setlen(&buffer, buffer.len-1);
 346         if (repo_get_oid(the_repository, buffer.buf, stash))
 347                 die(_("not a valid object: %s"), buffer.buf);
 348         rc = 0;
 349 out:
 350         strbuf_release(&buffer);
 351         return rc;
 352 }
 353
 354 static void read_empty(const struct object_id *oid)
 355 {
 356         struct child_process cmd = CHILD_PROCESS_INIT;
 357
 358         strvec_pushl(&cmd.args, "read-tree", "-m", "-u", empty_tree_oid_hex(),
 359                      oid_to_hex(oid), NULL);
 360         cmd.git_cmd = 1;
 361
 362         if (run_command(&cmd))
 363                 die(_("read-tree failed"));
 364 }
 365
 366 static void reset_hard(const struct object_id *oid)
 367 {
 368         struct child_process cmd = CHILD_PROCESS_INIT;
 369
 370         strvec_pushl(&cmd.args, "read-tree", "-v", "--reset", "-u",
 371                      oid_to_hex(oid), NULL);
 372         cmd.git_cmd = 1;
 373
 374         if (run_command(&cmd))
 375                 die(_("read-tree failed"));
 376 }
 377
 378 static void restore_state(const struct object_id *head,
 379                           const struct object_id *stash)
 380 {
 381         struct child_process cmd = CHILD_PROCESS_INIT;
 382
 383         reset_hard(head);
 384
 385         if (is_null_oid(stash))
 386                 goto refresh_cache;
 387
 388         strvec_pushl(&cmd.args, "stash", "apply", "--index", "--quiet", NULL);
 389         strvec_push(&cmd.args, oid_to_hex(stash));
 390
 391         /*
 392          * It is OK to ignore error here, for example when there was
 393          * nothing to restore.
 394          */
 395         cmd.git_cmd = 1;
 396         run_command(&cmd);
 397
 398 refresh_cache:
 399         discard_index(&the_index);
 400         if (repo_read_index(the_repository) < 0)
 401                 die(_("could not read index"));
 402 }
 403
 404 /* This is called when no merge was necessary. */
 405 static void finish_up_to_date(void)
 406 {
 407         if (verbosity >= 0) {
 408                 if (squash)
 409                         puts(_("Already up to date. (nothing to squash)"));
 410                 else
 411                         puts(_("Already up to date."));
 412         }
 413         remove_merge_branch_state(the_repository);
 414 }
 415
 416 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 417 {
 418         struct rev_info rev;
 419         struct strbuf out = STRBUF_INIT;
 420         struct commit_list *j;
 421         struct pretty_print_context ctx = {0};
 422
 423         printf(_("Squash commit -- not updating HEAD\n"));
 424
 425         repo_init_revisions(the_repository, &rev, NULL);
 426         diff_merges_suppress(&rev);
 427         rev.commit_format = CMIT_FMT_MEDIUM;
 428
 429         commit->object.flags |= UNINTERESTING;
 430         add_pending_object(&rev, &commit->object, NULL);
 431
 432         for (j = remoteheads; j; j = j->next)
 433                 add_pending_object(&rev, &j->item->object, NULL);
 434
 435         setup_revisions(0, NULL, &rev, NULL);
 436         if (prepare_revision_walk(&rev))
 437                 die(_("revision walk setup failed"));
 438
 439         ctx.abbrev = rev.abbrev;
 440         ctx.date_mode = rev.date_mode;
 441         ctx.fmt = rev.commit_format;
 442
 443         strbuf_addstr(&out, "Squashed commit of the following:\n");
 444         while ((commit = get_revision(&rev)) != NULL) {
 445                 strbuf_addch(&out, '\n');
 446                 strbuf_addf(&out, "commit %s\n",
 447                         oid_to_hex(&commit->object.oid));
 448                 pretty_print_commit(&ctx, commit, &out);
 449         }
 450         write_file_buf(git_path_squash_msg(the_repository), out.buf, out.len);
 451         strbuf_release(&out);
 452         release_revisions(&rev);
 453 }
 454
 455 static void finish(struct commit *head_commit,
 456                    struct commit_list *remoteheads,
 457                    const struct object_id *new_head, const char *msg)
 458 {
 459         struct strbuf reflog_message = STRBUF_INIT;
 460         const struct object_id *head = &head_commit->object.oid;
 461
 462         if (!msg)
 463                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 464         else {
 465                 if (verbosity >= 0)
 466                         printf("%s\n", msg);
 467                 strbuf_addf(&reflog_message, "%s: %s",
 468                         getenv("GIT_REFLOG_ACTION"), msg);
 469         }
 470         if (squash) {
 471                 squash_message(head_commit, remoteheads);
 472         } else {
 473                 if (verbosity >= 0 && !merge_msg.len)
 474                         printf(_("No merge message -- not updating HEAD\n"));
 475                 else {
 476                         update_ref(reflog_message.buf, "HEAD", new_head, head,
 477                                    0, UPDATE_REFS_DIE_ON_ERR);
 478                         /*
 479                          * We ignore errors in 'gc --auto', since the
 480                          * user should see them.
 481                          */
 482                         run_auto_maintenance(verbosity < 0);
 483                 }
 484         }
 485         if (new_head && show_diffstat) {
 486                 struct diff_options opts;
 487                 repo_diff_setup(the_repository, &opts);
 488                 opts.stat_width = -1; /* use full terminal width */
 489                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
 490                 opts.output_format |=
 491                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 492                 opts.detect_rename = DIFF_DETECT_RENAME;
 493                 diff_setup_done(&opts);
 494                 diff_tree_oid(head, new_head, "", &opts);
 495                 diffcore_std(&opts);
 496                 diff_flush(&opts);
 497         }
 498
 499         /* Run a post-merge hook */
 500         run_hooks_l("post-merge", squash ? "1" : "0", NULL);
 501
 502         if (new_head)
 503                 apply_autostash(git_path_merge_autostash(the_repository));
 504         strbuf_release(&reflog_message);
 505 }
 506
 507 /* Get the name for the merge commit's message. */
 508 static void merge_name(const char *remote, struct strbuf *msg)
 509 {
 510         struct commit *remote_head;
 511         struct object_id branch_head;
 512         struct strbuf bname = STRBUF_INIT;
 513         struct merge_remote_desc *desc;
 514         const char *ptr;
 515         char *found_ref = NULL;
 516         int len, early;
 517
 518         strbuf_branchname(&bname, remote, 0);
 519         remote = bname.buf;
 520
 521         oidclr(&branch_head);
 522         remote_head = get_merge_parent(remote);
 523         if (!remote_head)
 524                 die(_("'%s' does not point to a commit"), remote);
 525
 526         if (repo_dwim_ref(the_repository, remote, strlen(remote), &branch_head,
 527                           &found_ref, 0) > 0) {
 528                 if (starts_with(found_ref, "refs/heads/")) {
 529                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 530                                     oid_to_hex(&branch_head), remote);
 531                         goto cleanup;
 532                 }
 533                 if (starts_with(found_ref, "refs/tags/")) {
 534                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 535                                     oid_to_hex(&branch_head), remote);
 536                         goto cleanup;
 537                 }
 538                 if (starts_with(found_ref, "refs/remotes/")) {
 539                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 540                                     oid_to_hex(&branch_head), remote);
 541                         goto cleanup;
 542                 }
 543         }
 544
 545         /* See if remote matches <name>^^^.. or <name>~<number> */
 546         for (len = 0, ptr = remote + strlen(remote);
 547              remote < ptr && ptr[-1] == '^';
 548              ptr--)
 549                 len++;
 550         if (len)
 551                 early = 1;
 552         else {
 553                 early = 0;
 554                 ptr = strrchr(remote, '~');
 555                 if (ptr) {
 556                         int seen_nonzero = 0;
 557
 558                         len++; /* count ~ */
 559                         while (*++ptr && isdigit(*ptr)) {
 560                                 seen_nonzero |= (*ptr != '0');
 561                                 len++;
 562                         }
 563                         if (*ptr)
 564                                 len = 0; /* not ...~<number> */
 565                         else if (seen_nonzero)
 566                                 early = 1;
 567                         else if (len == 1)
 568                                 early = 1; /* "name~" is "name~1"! */
 569                 }
 570         }
 571         if (len) {
 572                 struct strbuf truname = STRBUF_INIT;
 573                 strbuf_addf(&truname, "refs/heads/%s", remote);
 574                 strbuf_setlen(&truname, truname.len - len);
 575                 if (ref_exists(truname.buf)) {
 576                         strbuf_addf(msg,
 577                                     "%s\t\tbranch '%s'%s of .\n",
 578                                     oid_to_hex(&remote_head->object.oid),
 579                                     truname.buf + 11,
 580                                     (early ? " (early part)" : ""));
 581                         strbuf_release(&truname);
 582                         goto cleanup;
 583                 }
 584                 strbuf_release(&truname);
 585         }
 586
 587         desc = merge_remote_util(remote_head);
 588         if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 589                 strbuf_addf(msg, "%s\t\t%s '%s'\n",
 590                             oid_to_hex(&desc->obj->oid),
 591                             type_name(desc->obj->type),
 592                             remote);
 593                 goto cleanup;
 594         }
 595
 596         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 597                 oid_to_hex(&remote_head->object.oid), remote);
 598 cleanup:
 599         free(found_ref);
 600         strbuf_release(&bname);
 601 }
 602
 603 static void parse_branch_merge_options(char *bmo)
 604 {
 605         const char **argv;
 606         int argc;
 607
 608         if (!bmo)
 609                 return;
 610         argc = split_cmdline(bmo, &argv);
 611         if (argc < 0)
 612                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 613                     _(split_cmdline_strerror(argc)));
 614         REALLOC_ARRAY(argv, argc + 2);
 615         MOVE_ARRAY(argv + 1, argv, argc + 1);
 616         argc++;
 617         argv[0] = "branch.*.mergeoptions";
 618         parse_options(argc, argv, NULL, builtin_merge_options,
 619                       builtin_merge_usage, 0);
 620         free(argv);
 621 }
 622
 623 static int git_merge_config(const char *k, const char *v, void *cb)
 624 {
 625         int status;
 626         const char *str;
 627
 628         if (branch &&
 629             skip_prefix(k, "branch.", &str) &&
 630             skip_prefix(str, branch, &str) &&
 631             !strcmp(str, ".mergeoptions")) {
 632                 free(branch_mergeoptions);
 633                 branch_mergeoptions = xstrdup(v);
 634                 return 0;
 635         }
 636
 637         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 638                 show_diffstat = git_config_bool(k, v);
 639         else if (!strcmp(k, "merge.verifysignatures"))
 640                 verify_signatures = git_config_bool(k, v);
 641         else if (!strcmp(k, "pull.twohead"))
 642                 return git_config_string(&pull_twohead, k, v);
 643         else if (!strcmp(k, "pull.octopus"))
 644                 return git_config_string(&pull_octopus, k, v);
 645         else if (!strcmp(k, "commit.cleanup"))
 646                 return git_config_string(&cleanup_arg, k, v);
 647         else if (!strcmp(k, "merge.ff")) {
 648                 int boolval = git_parse_maybe_bool(v);
 649                 if (0 <= boolval) {
 650                         fast_forward = boolval ? FF_ALLOW : FF_NO;
 651                 } else if (v && !strcmp(v, "only")) {
 652                         fast_forward = FF_ONLY;
 653                 } /* do not barf on values from future versions of git */
 654                 return 0;
 655         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 656                 default_to_upstream = git_config_bool(k, v);
 657                 return 0;
 658         } else if (!strcmp(k, "commit.gpgsign")) {
 659                 sign_commit = git_config_bool(k, v) ? "" : NULL;
 660                 return 0;
 661         } else if (!strcmp(k, "gpg.mintrustlevel")) {
 662                 check_trust_level = 0;
 663         } else if (!strcmp(k, "merge.autostash")) {
 664                 autostash = git_config_bool(k, v);
 665                 return 0;
 666         }
 667
 668         status = fmt_merge_msg_config(k, v, cb);
 669         if (status)
 670                 return status;
 671         return git_diff_ui_config(k, v, cb);
 672 }
 673
 674 static int read_tree_trivial(struct object_id *common, struct object_id *head,
 675                              struct object_id *one)
 676 {
 677         int i, nr_trees = 0;
 678         struct tree *trees[MAX_UNPACK_TREES];
 679         struct tree_desc t[MAX_UNPACK_TREES];
 680         struct unpack_trees_options opts;
 681
 682         memset(&opts, 0, sizeof(opts));
 683         opts.head_idx = 2;
 684         opts.src_index = &the_index;
 685         opts.dst_index = &the_index;
 686         opts.update = 1;
 687         opts.verbose_update = 1;
 688         opts.trivial_merges_only = 1;
 689         opts.merge = 1;
 690         opts.preserve_ignored = 0; /* FIXME: !overwrite_ignore */
 691         trees[nr_trees] = parse_tree_indirect(common);
 692         if (!trees[nr_trees++])
 693                 return -1;
 694         trees[nr_trees] = parse_tree_indirect(head);
 695         if (!trees[nr_trees++])
 696                 return -1;
 697         trees[nr_trees] = parse_tree_indirect(one);
 698         if (!trees[nr_trees++])
 699                 return -1;
 700         opts.fn = threeway_merge;
 701         cache_tree_free(&the_index.cache_tree);
 702         for (i = 0; i < nr_trees; i++) {
 703                 parse_tree(trees[i]);
 704                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 705         }
 706         if (unpack_trees(nr_trees, t, &opts))
 707                 return -1;
 708         return 0;
 709 }
 710
 711 static void write_tree_trivial(struct object_id *oid)
 712 {
 713         if (write_index_as_tree(oid, &the_index, get_index_file(), 0, NULL))
 714                 die(_("git write-tree failed to write a tree"));
 715 }
 716
 717 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 718                               struct commit_list *remoteheads,
 719                               struct commit *head)
 720 {
 721         const char *head_arg = "HEAD";
 722
 723         if (repo_refresh_and_write_index(the_repository, REFRESH_QUIET,
 724                                          SKIP_IF_UNCHANGED, 0, NULL, NULL,
 725                                          NULL) < 0)
 726                 return error(_("Unable to write index."));
 727
 728         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree") ||
 729             !strcmp(strategy, "ort")) {
 730                 struct lock_file lock = LOCK_INIT;
 731                 int clean, x;
 732                 struct commit *result;
 733                 struct commit_list *reversed = NULL;
 734                 struct merge_options o;
 735                 struct commit_list *j;
 736
 737                 if (remoteheads->next) {
 738                         error(_("Not handling anything other than two heads merge."));
 739                         return 2;
 740                 }
 741
 742                 init_merge_options(&o, the_repository);
 743                 if (!strcmp(strategy, "subtree"))
 744                         o.subtree_shift = "";
 745
 746                 o.show_rename_progress =
 747                         show_progress == -1 ? isatty(2) : show_progress;
 748
 749                 for (x = 0; x < xopts_nr; x++)
 750                         if (parse_merge_opt(&o, xopts[x]))
 751                                 die(_("unknown strategy option: -X%s"), xopts[x]);
 752
 753                 o.branch1 = head_arg;
 754                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 755
 756                 for (j = common; j; j = j->next)
 757                         commit_list_insert(j->item, &reversed);
 758
 759                 repo_hold_locked_index(the_repository, &lock,
 760                                        LOCK_DIE_ON_ERROR);
 761                 if (!strcmp(strategy, "ort"))
 762                         clean = merge_ort_recursive(&o, head, remoteheads->item,
 763                                                     reversed, &result);
 764                 else
 765                         clean = merge_recursive(&o, head, remoteheads->item,
 766                                                 reversed, &result);
 767                 if (clean < 0) {
 768                         rollback_lock_file(&lock);
 769                         return 2;
 770                 }
 771                 if (write_locked_index(&the_index, &lock,
 772                                        COMMIT_LOCK | SKIP_IF_UNCHANGED))
 773                         die(_("unable to write %s"), get_index_file());
 774                 return clean ? 0 : 1;
 775         } else {
 776                 return try_merge_command(the_repository,
 777                                          strategy, xopts_nr, xopts,
 778                                          common, head_arg, remoteheads);
 779         }
 780 }
 781
 782 static void count_diff_files(struct diff_queue_struct *q,
 783                              struct diff_options *opt UNUSED, void *data)
 784 {
 785         int *count = data;
 786
 787         (*count) += q->nr;
 788 }
 789
 790 static int count_unmerged_entries(void)
 791 {
 792         int i, ret = 0;
 793
 794         for (i = 0; i < the_index.cache_nr; i++)
 795                 if (ce_stage(the_index.cache[i]))
 796                         ret++;
 797
 798         return ret;
 799 }
 800
 801 static void add_strategies(const char *string, unsigned attr)
 802 {
 803         int i;
 804
 805         if (string) {
 806                 struct string_list list = STRING_LIST_INIT_DUP;
 807                 struct string_list_item *item;
 808                 string_list_split(&list, string, ' ', -1);
 809                 for_each_string_list_item(item, &list)
 810                         append_strategy(get_strategy(item->string));
 811                 string_list_clear(&list, 0);
 812                 return;
 813         }
 814         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 815                 if (all_strategy[i].attr & attr)
 816                         append_strategy(&all_strategy[i]);
 817
 818 }
 819
 820 static void read_merge_msg(struct strbuf *msg)
 821 {
 822         const char *filename = git_path_merge_msg(the_repository);
 823         strbuf_reset(msg);
 824         if (strbuf_read_file(msg, filename, 0) < 0)
 825                 die_errno(_("Could not read from '%s'"), filename);
 826 }
 827
 828 static void write_merge_state(struct commit_list *);
 829 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
 830 {
 831         if (err_msg)
 832                 error("%s", err_msg);
 833         fprintf(stderr,
 834                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 835         write_merge_state(remoteheads);
 836         exit(1);
 837 }
 838
 839 static const char merge_editor_comment[] =
 840 N_("Please enter a commit message to explain why this merge is necessary,\n"
 841    "especially if it merges an updated upstream into a topic branch.\n"
 842    "\n");
 843
 844 static const char scissors_editor_comment[] =
 845 N_("An empty message aborts the commit.\n");
 846
 847 static const char no_scissors_editor_comment[] =
 848 N_("Lines starting with '%c' will be ignored, and an empty message aborts\n"
 849    "the commit.\n");
 850
 851 static void write_merge_heads(struct commit_list *);
 852 static void prepare_to_commit(struct commit_list *remoteheads)
 853 {
 854         struct strbuf msg = STRBUF_INIT;
 855         const char *index_file = get_index_file();
 856
 857         if (!no_verify) {
 858                 int invoked_hook;
 859
 860                 if (run_commit_hook(0 < option_edit, index_file, &invoked_hook,
 861                                     "pre-merge-commit", NULL))
 862                         abort_commit(remoteheads, NULL);
 863                 /*
 864                  * Re-read the index as pre-merge-commit hook could have updated it,
 865                  * and write it out as a tree.  We must do this before we invoke
 866                  * the editor and after we invoke run_status above.
 867                  */
 868                 if (invoked_hook)
 869                         discard_index(&the_index);
 870         }
 871         read_index_from(&the_index, index_file, get_git_dir());
 872         strbuf_addbuf(&msg, &merge_msg);
 873         if (squash)
 874                 BUG("the control must not reach here under --squash");
 875         if (0 < option_edit) {
 876                 strbuf_addch(&msg, '\n');
 877                 if (cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS) {
 878                         wt_status_append_cut_line(&msg);
 879                         strbuf_commented_addf(&msg, "\n");
 880                 }
 881                 strbuf_commented_addf(&msg, _(merge_editor_comment));
 882                 if (cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS)
 883                         strbuf_commented_addf(&msg, _(scissors_editor_comment));
 884                 else
 885                         strbuf_commented_addf(&msg,
 886                                 _(no_scissors_editor_comment), comment_line_char);
 887         }
 888         if (signoff)
 889                 append_signoff(&msg, ignore_non_trailer(msg.buf, msg.len), 0);
 890         write_merge_heads(remoteheads);
 891         write_file_buf(git_path_merge_msg(the_repository), msg.buf, msg.len);
 892         if (run_commit_hook(0 < option_edit, get_index_file(), NULL,
 893                             "prepare-commit-msg",
 894                             git_path_merge_msg(the_repository), "merge", NULL))
 895                 abort_commit(remoteheads, NULL);
 896         if (0 < option_edit) {
 897                 if (launch_editor(git_path_merge_msg(the_repository), NULL, NULL))
 898                         abort_commit(remoteheads, NULL);
 899         }
 900
 901         if (!no_verify && run_commit_hook(0 < option_edit, get_index_file(),
 902                                           NULL, "commit-msg",
 903                                           git_path_merge_msg(the_repository), NULL))
 904                 abort_commit(remoteheads, NULL);
 905
 906         read_merge_msg(&msg);
 907         cleanup_message(&msg, cleanup_mode, 0);
 908         if (!msg.len)
 909                 abort_commit(remoteheads, _("Empty commit message."));
 910         strbuf_release(&merge_msg);
 911         strbuf_addbuf(&merge_msg, &msg);
 912         strbuf_release(&msg);
 913 }
 914
 915 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 916 {
 917         struct object_id result_tree, result_commit;
 918         struct commit_list *parents, **pptr = &parents;
 919
 920         if (repo_refresh_and_write_index(the_repository, REFRESH_QUIET,
 921                                          SKIP_IF_UNCHANGED, 0, NULL, NULL,
 922                                          NULL) < 0)
 923                 return error(_("Unable to write index."));
 924
 925         write_tree_trivial(&result_tree);
 926         printf(_("Wonderful.\n"));
 927         pptr = commit_list_append(head, pptr);
 928         pptr = commit_list_append(remoteheads->item, pptr);
 929         prepare_to_commit(remoteheads);
 930         if (commit_tree(merge_msg.buf, merge_msg.len, &result_tree, parents,
 931                         &result_commit, NULL, sign_commit))
 932                 die(_("failed to write commit object"));
 933         finish(head, remoteheads, &result_commit, "In-index merge");
 934         remove_merge_branch_state(the_repository);
 935         return 0;
 936 }
 937
 938 static int finish_automerge(struct commit *head,
 939                             int head_subsumed,
 940                             struct commit_list *common,
 941                             struct commit_list *remoteheads,
 942                             struct object_id *result_tree,
 943                             const char *wt_strategy)
 944 {
 945         struct commit_list *parents = NULL;
 946         struct strbuf buf = STRBUF_INIT;
 947         struct object_id result_commit;
 948
 949         write_tree_trivial(result_tree);
 950         free_commit_list(common);
 951         parents = remoteheads;
 952         if (!head_subsumed || fast_forward == FF_NO)
 953                 commit_list_insert(head, &parents);
 954         prepare_to_commit(remoteheads);
 955         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 956                         &result_commit, NULL, sign_commit))
 957                 die(_("failed to write commit object"));
 958         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 959         finish(head, remoteheads, &result_commit, buf.buf);
 960         strbuf_release(&buf);
 961         remove_merge_branch_state(the_repository);
 962         return 0;
 963 }
 964
 965 static int suggest_conflicts(void)
 966 {
 967         const char *filename;
 968         FILE *fp;
 969         struct strbuf msgbuf = STRBUF_INIT;
 970
 971         filename = git_path_merge_msg(the_repository);
 972         fp = xfopen(filename, "a");
 973
 974         /*
 975          * We can't use cleanup_mode because if we're not using the editor,
 976          * get_cleanup_mode will return COMMIT_MSG_CLEANUP_SPACE instead, even
 977          * though the message is meant to be processed later by git-commit.
 978          * Thus, we will get the cleanup mode which is returned when we _are_
 979          * using an editor.
 980          */
 981         append_conflicts_hint(&the_index, &msgbuf,
 982                               get_cleanup_mode(cleanup_arg, 1));
 983         fputs(msgbuf.buf, fp);
 984         strbuf_release(&msgbuf);
 985         fclose(fp);
 986         repo_rerere(the_repository, allow_rerere_auto);
 987         printf(_("Automatic merge failed; "
 988                         "fix conflicts and then commit the result.\n"));
 989         return 1;
 990 }
 991
 992 static int evaluate_result(void)
 993 {
 994         int cnt = 0;
 995         struct rev_info rev;
 996
 997         /* Check how many files differ. */
 998         repo_init_revisions(the_repository, &rev, "");
 999         setup_revisions(0, NULL, &rev, NULL);
1000         rev.diffopt.output_format |=
1001                 DIFF_FORMAT_CALLBACK;
1002         rev.diffopt.format_callback = count_diff_files;
1003         rev.diffopt.format_callback_data = &cnt;
1004         run_diff_files(&rev, 0);
1005
1006         /*
1007          * Check how many unmerged entries are
1008          * there.
1009          */
1010         cnt += count_unmerged_entries();
1011
1012         release_revisions(&rev);
1013         return cnt;
1014 }
1015
1016 /*
1017  * Pretend as if the user told us to merge with the remote-tracking
1018  * branch we have for the upstream of the current branch
1019  */
1020 static int setup_with_upstream(const char ***argv)
1021 {
1022         struct branch *branch = branch_get(NULL);
1023         int i;
1024         const char **args;
1025
1026         if (!branch)
1027                 die(_("No current branch."));
1028         if (!branch->remote_name)
1029                 die(_("No remote for the current branch."));
1030         if (!branch->merge_nr)
1031                 die(_("No default upstream defined for the current branch."));
1032
1033         args = xcalloc(st_add(branch->merge_nr, 1), sizeof(char *));
1034         for (i = 0; i < branch->merge_nr; i++) {
1035                 if (!branch->merge[i]->dst)
1036                         die(_("No remote-tracking branch for %s from %s"),
1037                             branch->merge[i]->src, branch->remote_name);
1038                 args[i] = branch->merge[i]->dst;
1039         }
1040         args[i] = NULL;
1041         *argv = args;
1042         return i;
1043 }
1044
1045 static void write_merge_heads(struct commit_list *remoteheads)
1046 {
1047         struct commit_list *j;
1048         struct strbuf buf = STRBUF_INIT;
1049
1050         for (j = remoteheads; j; j = j->next) {
1051                 struct object_id *oid;
1052                 struct commit *c = j->item;
1053                 struct merge_remote_desc *desc;
1054
1055                 desc = merge_remote_util(c);
1056                 if (desc && desc->obj) {
1057                         oid = &desc->obj->oid;
1058                 } else {
1059                         oid = &c->object.oid;
1060                 }
1061                 strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
1062         }
1063         write_file_buf(git_path_merge_head(the_repository), buf.buf, buf.len);
1064
1065         strbuf_reset(&buf);
1066         if (fast_forward == FF_NO)
1067                 strbuf_addstr(&buf, "no-ff");
1068         write_file_buf(git_path_merge_mode(the_repository), buf.buf, buf.len);
1069         strbuf_release(&buf);
1070 }
1071
1072 static void write_merge_state(struct commit_list *remoteheads)
1073 {
1074         write_merge_heads(remoteheads);
1075         strbuf_addch(&merge_msg, '\n');
1076         write_file_buf(git_path_merge_msg(the_repository), merge_msg.buf,
1077                        merge_msg.len);
1078 }
1079
1080 static int default_edit_option(void)
1081 {
1082         static const char name[] = "GIT_MERGE_AUTOEDIT";
1083         const char *e = getenv(name);
1084         struct stat st_stdin, st_stdout;
1085
1086         if (have_message)
1087                 /* an explicit -m msg without --[no-]edit */
1088                 return 0;
1089
1090         if (e) {
1091                 int v = git_parse_maybe_bool(e);
1092                 if (v < 0)
1093                         die(_("Bad value '%s' in environment '%s'"), e, name);
1094                 return v;
1095         }
1096
1097         /* Use editor if stdin and stdout are the same and is a tty */
1098         return (!fstat(0, &st_stdin) &&
1099                 !fstat(1, &st_stdout) &&
1100                 isatty(0) && isatty(1) &&
1101                 st_stdin.st_dev == st_stdout.st_dev &&
1102                 st_stdin.st_ino == st_stdout.st_ino &&
1103                 st_stdin.st_mode == st_stdout.st_mode);
1104 }
1105
1106 static struct commit_list *reduce_parents(struct commit *head_commit,
1107                                           int *head_subsumed,
1108                                           struct commit_list *remoteheads)
1109 {
1110         struct commit_list *parents, **remotes;
1111
1112         /*
1113          * Is the current HEAD reachable from another commit being
1114          * merged?  If so we do not want to record it as a parent of
1115          * the resulting merge, unless --no-ff is given.  We will flip
1116          * this variable to 0 when we find HEAD among the independent
1117          * tips being merged.
1118          */
1119         *head_subsumed = 1;
1120
1121         /* Find what parents to record by checking independent ones. */
1122         parents = reduce_heads(remoteheads);
1123         free_commit_list(remoteheads);
1124
1125         remoteheads = NULL;
1126         remotes = &remoteheads;
1127         while (parents) {
1128                 struct commit *commit = pop_commit(&parents);
1129                 if (commit == head_commit)
1130                         *head_subsumed = 0;
1131                 else
1132                         remotes = &commit_list_insert(commit, remotes)->next;
1133         }
1134         return remoteheads;
1135 }
1136
1137 static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
1138 {
1139         struct fmt_merge_msg_opts opts;
1140
1141         memset(&opts, 0, sizeof(opts));
1142         opts.add_title = !have_message;
1143         opts.shortlog_len = shortlog_len;
1144         opts.credit_people = (0 < option_edit);
1145         opts.into_name = into_name;
1146
1147         fmt_merge_msg(merge_names, merge_msg, &opts);
1148         if (merge_msg->len)
1149                 strbuf_setlen(merge_msg, merge_msg->len - 1);
1150 }
1151
1152 static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1153 {
1154         const char *filename;
1155         int fd, pos, npos;
1156         struct strbuf fetch_head_file = STRBUF_INIT;
1157         const unsigned hexsz = the_hash_algo->hexsz;
1158
1159         if (!merge_names)
1160                 merge_names = &fetch_head_file;
1161
1162         filename = git_path_fetch_head(the_repository);
1163         fd = xopen(filename, O_RDONLY);
1164
1165         if (strbuf_read(merge_names, fd, 0) < 0)
1166                 die_errno(_("could not read '%s'"), filename);
1167         if (close(fd) < 0)
1168                 die_errno(_("could not close '%s'"), filename);
1169
1170         for (pos = 0; pos < merge_names->len; pos = npos) {
1171                 struct object_id oid;
1172                 char *ptr;
1173                 struct commit *commit;
1174
1175                 ptr = strchr(merge_names->buf + pos, '\n');
1176                 if (ptr)
1177                         npos = ptr - merge_names->buf + 1;
1178                 else
1179                         npos = merge_names->len;
1180
1181                 if (npos - pos < hexsz + 2 ||
1182                     get_oid_hex(merge_names->buf + pos, &oid))
1183                         commit = NULL; /* bad */
1184                 else if (memcmp(merge_names->buf + pos + hexsz, "\t\t", 2))
1185                         continue; /* not-for-merge */
1186                 else {
1187                         char saved = merge_names->buf[pos + hexsz];
1188                         merge_names->buf[pos + hexsz] = '\0';
1189                         commit = get_merge_parent(merge_names->buf + pos);
1190                         merge_names->buf[pos + hexsz] = saved;
1191                 }
1192                 if (!commit) {
1193                         if (ptr)
1194                                 *ptr = '\0';
1195                         die(_("not something we can merge in %s: %s"),
1196                             filename, merge_names->buf + pos);
1197                 }
1198                 remotes = &commit_list_insert(commit, remotes)->next;
1199         }
1200
1201         if (merge_names == &fetch_head_file)
1202                 strbuf_release(&fetch_head_file);
1203 }
1204
1205 static struct commit_list *collect_parents(struct commit *head_commit,
1206                                            int *head_subsumed,
1207                                            int argc, const char **argv,
1208                                            struct strbuf *merge_msg)
1209 {
1210         int i;
1211         struct commit_list *remoteheads = NULL;
1212         struct commit_list **remotes = &remoteheads;
1213         struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1214
1215         if (merge_msg && (!have_message || shortlog_len))
1216                 autogen = &merge_names;
1217
1218         if (head_commit)
1219                 remotes = &commit_list_insert(head_commit, remotes)->next;
1220
1221         if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1222                 handle_fetch_head(remotes, autogen);
1223                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1224         } else {
1225                 for (i = 0; i < argc; i++) {
1226                         struct commit *commit = get_merge_parent(argv[i]);
1227                         if (!commit)
1228                                 help_unknown_ref(argv[i], "merge",
1229                                                  _("not something we can merge"));
1230                         remotes = &commit_list_insert(commit, remotes)->next;
1231                 }
1232                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1233                 if (autogen) {
1234                         struct commit_list *p;
1235                         for (p = remoteheads; p; p = p->next)
1236                                 merge_name(merge_remote_util(p->item)->name, autogen);
1237                 }
1238         }
1239
1240         if (autogen) {
1241                 prepare_merge_message(autogen, merge_msg);
1242                 strbuf_release(autogen);
1243         }
1244
1245         return remoteheads;
1246 }
1247
1248 static int merging_a_throwaway_tag(struct commit *commit)
1249 {
1250         char *tag_ref;
1251         struct object_id oid;
1252         int is_throwaway_tag = 0;
1253
1254         /* Are we merging a tag? */
1255         if (!merge_remote_util(commit) ||
1256             !merge_remote_util(commit)->obj ||
1257             merge_remote_util(commit)->obj->type != OBJ_TAG)
1258                 return is_throwaway_tag;
1259
1260         /*
1261          * Now we know we are merging a tag object.  Are we downstream
1262          * and following the tags from upstream?  If so, we must have
1263          * the tag object pointed at by "refs/tags/$T" where $T is the
1264          * tagname recorded in the tag object.  We want to allow such
1265          * a "just to catch up" merge to fast-forward.
1266          *
1267          * Otherwise, we are playing an integrator's role, making a
1268          * merge with a throw-away tag from a contributor with
1269          * something like "git pull $contributor $signed_tag".
1270          * We want to forbid such a merge from fast-forwarding
1271          * by default; otherwise we would not keep the signature
1272          * anywhere.
1273          */
1274         tag_ref = xstrfmt("refs/tags/%s",
1275                           ((struct tag *)merge_remote_util(commit)->obj)->tag);
1276         if (!read_ref(tag_ref, &oid) &&
1277             oideq(&oid, &merge_remote_util(commit)->obj->oid))
1278                 is_throwaway_tag = 0;
1279         else
1280                 is_throwaway_tag = 1;
1281         free(tag_ref);
1282         return is_throwaway_tag;
1283 }
1284
1285 int cmd_merge(int argc, const char **argv, const char *prefix)
1286 {
1287         struct object_id result_tree, stash, head_oid;
1288         struct commit *head_commit;
1289         struct strbuf buf = STRBUF_INIT;
1290         int i, ret = 0, head_subsumed;
1291         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1292         struct commit_list *common = NULL;
1293         const char *best_strategy = NULL, *wt_strategy = NULL;
1294         struct commit_list *remoteheads = NULL, *p;
1295         void *branch_to_free;
1296         int orig_argc = argc;
1297
1298         if (argc == 2 && !strcmp(argv[1], "-h"))
1299                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1300
1301         prepare_repo_settings(the_repository);
1302         the_repository->settings.command_requires_full_index = 0;
1303
1304         /*
1305          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1306          * current branch.
1307          */
1308         branch = branch_to_free = resolve_refdup("HEAD", 0, &head_oid, NULL);
1309         if (branch)
1310                 skip_prefix(branch, "refs/heads/", &branch);
1311
1312         if (!pull_twohead) {
1313                 char *default_strategy = getenv("GIT_TEST_MERGE_ALGORITHM");
1314                 if (default_strategy && !strcmp(default_strategy, "ort"))
1315                         pull_twohead = "ort";
1316         }
1317
1318         init_diff_ui_defaults();
1319         git_config(git_merge_config, NULL);
1320
1321         if (!branch || is_null_oid(&head_oid))
1322                 head_commit = NULL;
1323         else
1324                 head_commit = lookup_commit_or_die(&head_oid, "HEAD");
1325
1326         if (branch_mergeoptions)
1327                 parse_branch_merge_options(branch_mergeoptions);
1328         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1329                         builtin_merge_usage, 0);
1330         if (shortlog_len < 0)
1331                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1332
1333         if (verbosity < 0 && show_progress == -1)
1334                 show_progress = 0;
1335
1336         if (abort_current_merge) {
1337                 int nargc = 2;
1338                 const char *nargv[] = {"reset", "--merge", NULL};
1339                 struct strbuf stash_oid = STRBUF_INIT;
1340
1341                 if (orig_argc != 2)
1342                         usage_msg_opt(_("--abort expects no arguments"),
1343                               builtin_merge_usage, builtin_merge_options);
1344
1345                 if (!file_exists(git_path_merge_head(the_repository)))
1346                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1347
1348                 if (read_oneliner(&stash_oid, git_path_merge_autostash(the_repository),
1349                     READ_ONELINER_SKIP_IF_EMPTY))
1350                         unlink(git_path_merge_autostash(the_repository));
1351
1352                 /* Invoke 'git reset --merge' */
1353                 ret = cmd_reset(nargc, nargv, prefix);
1354
1355                 if (stash_oid.len)
1356                         apply_autostash_oid(stash_oid.buf);
1357
1358                 strbuf_release(&stash_oid);
1359                 goto done;
1360         }
1361
1362         if (quit_current_merge) {
1363                 if (orig_argc != 2)
1364                         usage_msg_opt(_("--quit expects no arguments"),
1365                                       builtin_merge_usage,
1366                                       builtin_merge_options);
1367
1368                 remove_merge_branch_state(the_repository);
1369                 goto done;
1370         }
1371
1372         if (continue_current_merge) {
1373                 int nargc = 1;
1374                 const char *nargv[] = {"commit", NULL};
1375
1376                 if (orig_argc != 2)
1377                         usage_msg_opt(_("--continue expects no arguments"),
1378                               builtin_merge_usage, builtin_merge_options);
1379
1380                 if (!file_exists(git_path_merge_head(the_repository)))
1381                         die(_("There is no merge in progress (MERGE_HEAD missing)."));
1382
1383                 /* Invoke 'git commit' */
1384                 ret = cmd_commit(nargc, nargv, prefix);
1385                 goto done;
1386         }
1387
1388         if (repo_read_index_unmerged(the_repository))
1389                 die_resolve_conflict("merge");
1390
1391         if (file_exists(git_path_merge_head(the_repository))) {
1392                 /*
1393                  * There is no unmerged entry, don't advise 'git
1394                  * add/rm <file>', just 'git commit'.
1395                  */
1396                 if (advice_enabled(ADVICE_RESOLVE_CONFLICT))
1397                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1398                                   "Please, commit your changes before you merge."));
1399                 else
1400                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1401         }
1402         if (ref_exists("CHERRY_PICK_HEAD")) {
1403                 if (advice_enabled(ADVICE_RESOLVE_CONFLICT))
1404                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1405                             "Please, commit your changes before you merge."));
1406                 else
1407                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1408         }
1409         resolve_undo_clear_index(&the_index);
1410
1411         if (option_edit < 0)
1412                 option_edit = default_edit_option();
1413
1414         cleanup_mode = get_cleanup_mode(cleanup_arg, 0 < option_edit);
1415
1416         if (verbosity < 0)
1417                 show_diffstat = 0;
1418
1419         if (squash) {
1420                 if (fast_forward == FF_NO)
1421                         die(_("options '%s' and '%s' cannot be used together"), "--squash", "--no-ff.");
1422                 if (option_commit > 0)
1423                         die(_("options '%s' and '%s' cannot be used together"), "--squash", "--commit.");
1424                 /*
1425                  * squash can now silently disable option_commit - this is not
1426                  * a problem as it is only overriding the default, not a user
1427                  * supplied option.
1428                  */
1429                 option_commit = 0;
1430         }
1431
1432         if (option_commit < 0)
1433                 option_commit = 1;
1434
1435         if (!argc) {
1436                 if (default_to_upstream)
1437                         argc = setup_with_upstream(&argv);
1438                 else
1439                         die(_("No commit specified and merge.defaultToUpstream not set."));
1440         } else if (argc == 1 && !strcmp(argv[0], "-")) {
1441                 argv[0] = "@{-1}";
1442         }
1443
1444         if (!argc)
1445                 usage_with_options(builtin_merge_usage,
1446                         builtin_merge_options);
1447
1448         if (!head_commit) {
1449                 /*
1450                  * If the merged head is a valid one there is no reason
1451                  * to forbid "git merge" into a branch yet to be born.
1452                  * We do the same for "git pull".
1453                  */
1454                 struct object_id *remote_head_oid;
1455                 if (squash)
1456                         die(_("Squash commit into empty head not supported yet"));
1457                 if (fast_forward == FF_NO)
1458                         die(_("Non-fast-forward commit does not make sense into "
1459                             "an empty head"));
1460                 remoteheads = collect_parents(head_commit, &head_subsumed,
1461                                               argc, argv, NULL);
1462                 if (!remoteheads)
1463                         die(_("%s - not something we can merge"), argv[0]);
1464                 if (remoteheads->next)
1465                         die(_("Can merge only exactly one commit into empty head"));
1466
1467                 if (verify_signatures)
1468                         verify_merge_signature(remoteheads->item, verbosity,
1469                                                check_trust_level);
1470
1471                 remote_head_oid = &remoteheads->item->object.oid;
1472                 read_empty(remote_head_oid);
1473                 update_ref("initial pull", "HEAD", remote_head_oid, NULL, 0,
1474                            UPDATE_REFS_DIE_ON_ERR);
1475                 goto done;
1476         }
1477
1478         /*
1479          * All the rest are the commits being merged; prepare
1480          * the standard merge summary message to be appended
1481          * to the given message.
1482          */
1483         remoteheads = collect_parents(head_commit, &head_subsumed,
1484                                       argc, argv, &merge_msg);
1485
1486         if (!head_commit || !argc)
1487                 usage_with_options(builtin_merge_usage,
1488                         builtin_merge_options);
1489
1490         if (verify_signatures) {
1491                 for (p = remoteheads; p; p = p->next) {
1492                         verify_merge_signature(p->item, verbosity,
1493                                                check_trust_level);
1494                 }
1495         }
1496
1497         strbuf_addstr(&buf, "merge");
1498         for (p = remoteheads; p; p = p->next)
1499                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1500         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1501         strbuf_reset(&buf);
1502
1503         for (p = remoteheads; p; p = p->next) {
1504                 struct commit *commit = p->item;
1505                 strbuf_addf(&buf, "GITHEAD_%s",
1506                             oid_to_hex(&commit->object.oid));
1507                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1508                 strbuf_reset(&buf);
1509                 if (fast_forward != FF_ONLY && merging_a_throwaway_tag(commit))
1510                         fast_forward = FF_NO;
1511         }
1512
1513         if (!use_strategies && !pull_twohead &&
1514             remoteheads && !remoteheads->next) {
1515                 char *default_strategy = getenv("GIT_TEST_MERGE_ALGORITHM");
1516                 if (default_strategy)
1517                         append_strategy(get_strategy(default_strategy));
1518         }
1519         if (!use_strategies) {
1520                 if (!remoteheads)
1521                         ; /* already up-to-date */
1522                 else if (!remoteheads->next)
1523                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1524                 else
1525                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1526         }
1527
1528         for (i = 0; i < use_strategies_nr; i++) {
1529                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1530                         fast_forward = FF_NO;
1531                 if (use_strategies[i]->attr & NO_TRIVIAL)
1532                         allow_trivial = 0;
1533         }
1534
1535         if (!remoteheads)
1536                 ; /* already up-to-date */
1537         else if (!remoteheads->next)
1538                 common = repo_get_merge_bases(the_repository, head_commit,
1539                                               remoteheads->item);
1540         else {
1541                 struct commit_list *list = remoteheads;
1542                 commit_list_insert(head_commit, &list);
1543                 common = get_octopus_merge_bases(list);
1544                 free(list);
1545         }
1546
1547         update_ref("updating ORIG_HEAD", "ORIG_HEAD",
1548                    &head_commit->object.oid, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1549
1550         if (remoteheads && !common) {
1551                 /* No common ancestors found. */
1552                 if (!allow_unrelated_histories)
1553                         die(_("refusing to merge unrelated histories"));
1554                 /* otherwise, we need a real merge. */
1555         } else if (!remoteheads ||
1556                  (!remoteheads->next && !common->next &&
1557                   common->item == remoteheads->item)) {
1558                 /*
1559                  * If head can reach all the merge then we are up to date.
1560                  * but first the most common case of merging one remote.
1561                  */
1562                 finish_up_to_date();
1563                 goto done;
1564         } else if (fast_forward != FF_NO && !remoteheads->next &&
1565                         !common->next &&
1566                         oideq(&common->item->object.oid, &head_commit->object.oid)) {
1567                 /* Again the most common case of merging one remote. */
1568                 const char *msg = have_message ?
1569                         "Fast-forward (no commit created; -m option ignored)" :
1570                         "Fast-forward";
1571                 struct commit *commit;
1572
1573                 if (verbosity >= 0) {
1574                         printf(_("Updating %s..%s\n"),
1575                                repo_find_unique_abbrev(the_repository, &head_commit->object.oid,
1576                                                        DEFAULT_ABBREV),
1577                                repo_find_unique_abbrev(the_repository, &remoteheads->item->object.oid,
1578                                                        DEFAULT_ABBREV));
1579                 }
1580                 commit = remoteheads->item;
1581                 if (!commit) {
1582                         ret = 1;
1583                         goto done;
1584                 }
1585
1586                 if (autostash)
1587                         create_autostash(the_repository,
1588                                          git_path_merge_autostash(the_repository));
1589                 if (checkout_fast_forward(the_repository,
1590                                           &head_commit->object.oid,
1591                                           &commit->object.oid,
1592                                           overwrite_ignore)) {
1593                         apply_autostash(git_path_merge_autostash(the_repository));
1594                         ret = 1;
1595                         goto done;
1596                 }
1597
1598                 finish(head_commit, remoteheads, &commit->object.oid, msg);
1599                 remove_merge_branch_state(the_repository);
1600                 goto done;
1601         } else if (!remoteheads->next && common->next)
1602                 ;
1603                 /*
1604                  * We are not doing octopus and not fast-forward.  Need
1605                  * a real merge.
1606                  */
1607         else if (!remoteheads->next && !common->next && option_commit) {
1608                 /*
1609                  * We are not doing octopus, not fast-forward, and have
1610                  * only one common.
1611                  */
1612                 refresh_index(&the_index, REFRESH_QUIET, NULL, NULL, NULL);
1613                 if (allow_trivial && fast_forward != FF_ONLY) {
1614                         /*
1615                          * Must first ensure that index matches HEAD before
1616                          * attempting a trivial merge.
1617                          */
1618                         struct tree *head_tree = repo_get_commit_tree(the_repository,
1619                                                                       head_commit);
1620                         struct strbuf sb = STRBUF_INIT;
1621
1622                         if (repo_index_has_changes(the_repository, head_tree,
1623                                                    &sb)) {
1624                                 error(_("Your local changes to the following files would be overwritten by merge:\n  %s"),
1625                                       sb.buf);
1626                                 strbuf_release(&sb);
1627                                 ret = 2;
1628                                 goto done;
1629                         }
1630
1631                         /* See if it is really trivial. */
1632                         git_committer_info(IDENT_STRICT);
1633                         printf(_("Trying really trivial in-index merge...\n"));
1634                         if (!read_tree_trivial(&common->item->object.oid,
1635                                                &head_commit->object.oid,
1636                                                &remoteheads->item->object.oid)) {
1637                                 ret = merge_trivial(head_commit, remoteheads);
1638                                 goto done;
1639                         }
1640                         printf(_("Nope.\n"));
1641                 }
1642         } else {
1643                 /*
1644                  * An octopus.  If we can reach all the remote we are up
1645                  * to date.
1646                  */
1647                 int up_to_date = 1;
1648                 struct commit_list *j;
1649
1650                 for (j = remoteheads; j; j = j->next) {
1651                         struct commit_list *common_one;
1652
1653                         /*
1654                          * Here we *have* to calculate the individual
1655                          * merge_bases again, otherwise "git merge HEAD^
1656                          * HEAD^^" would be missed.
1657                          */
1658                         common_one = repo_get_merge_bases(the_repository,
1659                                                           head_commit,
1660                                                           j->item);
1661                         if (!oideq(&common_one->item->object.oid, &j->item->object.oid)) {
1662                                 up_to_date = 0;
1663                                 break;
1664                         }
1665                 }
1666                 if (up_to_date) {
1667                         finish_up_to_date();
1668                         goto done;
1669                 }
1670         }
1671
1672         if (fast_forward == FF_ONLY)
1673                 die_ff_impossible();
1674
1675         if (autostash)
1676                 create_autostash(the_repository,
1677                                  git_path_merge_autostash(the_repository));
1678
1679         /* We are going to make a new commit. */
1680         git_committer_info(IDENT_STRICT);
1681
1682         /*
1683          * At this point, we need a real merge.  No matter what strategy
1684          * we use, it would operate on the index, possibly affecting the
1685          * working tree, and when resolved cleanly, have the desired
1686          * tree in the index -- this means that the index must be in
1687          * sync with the head commit.  The strategies are responsible
1688          * to ensure this.
1689          *
1690          * Stash away the local changes so that we can try more than one
1691          * and/or recover from merge strategies bailing while leaving the
1692          * index and working tree polluted.
1693          */
1694         if (save_state(&stash))
1695                 oidclr(&stash);
1696
1697         for (i = 0; i < use_strategies_nr; i++) {
1698                 int ret, cnt;
1699                 if (i) {
1700                         printf(_("Rewinding the tree to pristine...\n"));
1701                         restore_state(&head_commit->object.oid, &stash);
1702                 }
1703                 if (use_strategies_nr != 1)
1704                         printf(_("Trying merge strategy %s...\n"),
1705                                 use_strategies[i]->name);
1706                 /*
1707                  * Remember which strategy left the state in the working
1708                  * tree.
1709                  */
1710                 wt_strategy = use_strategies[i]->name;
1711
1712                 ret = try_merge_strategy(wt_strategy,
1713                                          common, remoteheads,
1714                                          head_commit);
1715                 /*
1716                  * The backend exits with 1 when conflicts are
1717                  * left to be resolved, with 2 when it does not
1718                  * handle the given merge at all.
1719                  */
1720                 if (ret < 2) {
1721                         if (!ret) {
1722                                 /*
1723                                  * This strategy worked; no point in trying
1724                                  * another.
1725                                  */
1726                                 merge_was_ok = 1;
1727                                 best_strategy = wt_strategy;
1728                                 break;
1729                         }
1730                         cnt = (use_strategies_nr > 1) ? evaluate_result() : 0;
1731                         if (best_cnt <= 0 || cnt <= best_cnt) {
1732                                 best_strategy = wt_strategy;
1733                                 best_cnt = cnt;
1734                         }
1735                 }
1736         }
1737
1738         /*
1739          * If we have a resulting tree, that means the strategy module
1740          * auto resolved the merge cleanly.
1741          */
1742         if (merge_was_ok && option_commit) {
1743                 automerge_was_ok = 1;
1744                 ret = finish_automerge(head_commit, head_subsumed,
1745                                        common, remoteheads,
1746                                        &result_tree, wt_strategy);
1747                 goto done;
1748         }
1749
1750         /*
1751          * Pick the result from the best strategy and have the user fix
1752          * it up.
1753          */
1754         if (!best_strategy) {
1755                 restore_state(&head_commit->object.oid, &stash);
1756                 if (use_strategies_nr > 1)
1757                         fprintf(stderr,
1758                                 _("No merge strategy handled the merge.\n"));
1759                 else
1760                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1761                                 use_strategies[0]->name);
1762                 apply_autostash(git_path_merge_autostash(the_repository));
1763                 ret = 2;
1764                 goto done;
1765         } else if (best_strategy == wt_strategy)
1766                 ; /* We already have its result in the working tree. */
1767         else {
1768                 printf(_("Rewinding the tree to pristine...\n"));
1769                 restore_state(&head_commit->object.oid, &stash);
1770                 printf(_("Using the %s strategy to prepare resolving by hand.\n"),
1771                         best_strategy);
1772                 try_merge_strategy(best_strategy, common, remoteheads,
1773                                    head_commit);
1774         }
1775
1776         if (squash) {
1777                 finish(head_commit, remoteheads, NULL, NULL);
1778
1779                 git_test_write_commit_graph_or_die();
1780         } else
1781                 write_merge_state(remoteheads);
1782
1783         if (merge_was_ok)
1784                 fprintf(stderr, _("Automatic merge went well; "
1785                         "stopped before committing as requested\n"));
1786         else
1787                 ret = suggest_conflicts();
1788         if (autostash)
1789                 printf(_("When finished, apply stashed changes with `git stash pop`\n"));
1790
1791 done:
1792         if (!automerge_was_ok) {
1793                 free_commit_list(common);
1794                 free_commit_list(remoteheads);
1795         }
1796         strbuf_release(&buf);
1797         free(branch_to_free);
1798         discard_index(&the_index);
1799         return ret;
1800 }