git.oblomov.eu Git - git/blob - builtin/merge.c

   1 /*
   2  * Builtin "git merge"
   3  *
   4  * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
   5  *
   6  * Based on git-merge.sh by Junio C Hamano.
   7  */
   8
   9 #define USE_THE_INDEX_COMPATIBILITY_MACROS
  10 #include "cache.h"
  11 #include "config.h"
  12 #include "parse-options.h"
  13 #include "builtin.h"
  14 #include "lockfile.h"
  15 #include "run-command.h"
  16 #include "diff.h"
  17 #include "refs.h"
  18 #include "refspec.h"
  19 #include "commit.h"
  20 #include "diffcore.h"
  21 #include "revision.h"
  22 #include "unpack-trees.h"
  23 #include "cache-tree.h"
  24 #include "dir.h"
  25 #include "utf8.h"
  26 #include "log-tree.h"
  27 #include "color.h"
  28 #include "rerere.h"
  29 #include "help.h"
  30 #include "merge-recursive.h"
  31 #include "resolve-undo.h"
  32 #include "remote.h"
  33 #include "fmt-merge-msg.h"
  34 #include "gpg-interface.h"
  35 #include "sequencer.h"
  36 #include "string-list.h"
  37 #include "packfile.h"
  38 #include "tag.h"
  39 #include "alias.h"
  40 #include "branch.h"
  41 #include "commit-reach.h"
  42
  43 #define DEFAULT_TWOHEAD (1<<0)
  44 #define DEFAULT_OCTOPUS (1<<1)
  45 #define NO_FAST_FORWARD (1<<2)
  46 #define NO_TRIVIAL      (1<<3)
  47
  48 struct strategy {
  49         const char *name;
  50         unsigned attr;
  51 };
  52
  53 static const char * const builtin_merge_usage[] = {
  54         N_("git merge [<options>] [<commit>...]"),
  55         N_("git merge --abort"),
  56         N_("git merge --continue"),
  57         NULL
  58 };
  59
  60 static int show_diffstat = 1, shortlog_len = -1, squash;
  61 static int option_commit = 1;
  62 static int option_edit = -1;
  63 static int allow_trivial = 1, have_message, verify_signatures;
  64 static int overwrite_ignore = 1;
  65 static struct strbuf merge_msg = STRBUF_INIT;
  66 static struct strategy **use_strategies;
  67 static size_t use_strategies_nr, use_strategies_alloc;
  68 static const char **xopts;
  69 static size_t xopts_nr, xopts_alloc;
  70 static const char *branch;
  71 static char *branch_mergeoptions;
  72 static int option_renormalize;
  73 static int verbosity;
  74 static int allow_rerere_auto;
  75 static int abort_current_merge;
  76 static int quit_current_merge;
  77 static int continue_current_merge;
  78 static int allow_unrelated_histories;
  79 static int show_progress = -1;
  80 static int default_to_upstream = 1;
  81 static int signoff;
  82 static const char *sign_commit;
  83 static int verify_msg = 1;
  84
  85 static struct strategy all_strategy[] = {
  86         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  87         { "octopus",    DEFAULT_OCTOPUS },
  88         { "resolve",    0 },
  89         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  90         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  91 };
  92
  93 static const char *pull_twohead, *pull_octopus;
  94
  95 enum ff_type {
  96         FF_NO,
  97         FF_ALLOW,
  98         FF_ONLY
  99 };
 100
 101 static enum ff_type fast_forward = FF_ALLOW;
 102
 103 static int option_parse_message(const struct option *opt,
 104                                 const char *arg, int unset)
 105 {
 106         struct strbuf *buf = opt->value;
 107
 108         if (unset)
 109                 strbuf_setlen(buf, 0);
 110         else if (arg) {
 111                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
 112                 have_message = 1;
 113         } else
 114                 return error(_("switch `m' requires a value"));
 115         return 0;
 116 }
 117
 118 static int option_read_message(struct parse_opt_ctx_t *ctx,
 119                                const struct option *opt, int unset)
 120 {
 121         struct strbuf *buf = opt->value;
 122         const char *arg;
 123
 124         if (unset)
 125                 BUG("-F cannot be negated");
 126
 127         if (ctx->opt) {
 128                 arg = ctx->opt;
 129                 ctx->opt = NULL;
 130         } else if (ctx->argc > 1) {
 131                 ctx->argc--;
 132                 arg = *++ctx->argv;
 133         } else
 134                 return error(_("option `%s' requires a value"), opt->long_name);
 135
 136         if (buf->len)
 137                 strbuf_addch(buf, '\n');
 138         if (ctx->prefix && !is_absolute_path(arg))
 139                 arg = prefix_filename(ctx->prefix, arg);
 140         if (strbuf_read_file(buf, arg, 0) < 0)
 141                 return error(_("could not read file '%s'"), arg);
 142         have_message = 1;
 143
 144         return 0;
 145 }
 146
 147 static struct strategy *get_strategy(const char *name)
 148 {
 149         int i;
 150         struct strategy *ret;
 151         static struct cmdnames main_cmds, other_cmds;
 152         static int loaded;
 153
 154         if (!name)
 155                 return NULL;
 156
 157         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 158                 if (!strcmp(name, all_strategy[i].name))
 159                         return &all_strategy[i];
 160
 161         if (!loaded) {
 162                 struct cmdnames not_strategies;
 163                 loaded = 1;
 164
 165                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 166                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 167                 for (i = 0; i < main_cmds.cnt; i++) {
 168                         int j, found = 0;
 169                         struct cmdname *ent = main_cmds.names[i];
 170                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 171                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 172                                                 && !all_strategy[j].name[ent->len])
 173                                         found = 1;
 174                         if (!found)
 175                                 add_cmdname(&not_strategies, ent->name, ent->len);
 176                 }
 177                 exclude_cmds(&main_cmds, &not_strategies);
 178         }
 179         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 180                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 181                 fprintf(stderr, _("Available strategies are:"));
 182                 for (i = 0; i < main_cmds.cnt; i++)
 183                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 184                 fprintf(stderr, ".\n");
 185                 if (other_cmds.cnt) {
 186                         fprintf(stderr, _("Available custom strategies are:"));
 187                         for (i = 0; i < other_cmds.cnt; i++)
 188                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 189                         fprintf(stderr, ".\n");
 190                 }
 191                 exit(1);
 192         }
 193
 194         ret = xcalloc(1, sizeof(struct strategy));
 195         ret->name = xstrdup(name);
 196         ret->attr = NO_TRIVIAL;
 197         return ret;
 198 }
 199
 200 static void append_strategy(struct strategy *s)
 201 {
 202         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 203         use_strategies[use_strategies_nr++] = s;
 204 }
 205
 206 static int option_parse_strategy(const struct option *opt,
 207                                  const char *name, int unset)
 208 {
 209         if (unset)
 210                 return 0;
 211
 212         append_strategy(get_strategy(name));
 213         return 0;
 214 }
 215
 216 static int option_parse_x(const struct option *opt,
 217                           const char *arg, int unset)
 218 {
 219         if (unset)
 220                 return 0;
 221
 222         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 223         xopts[xopts_nr++] = xstrdup(arg);
 224         return 0;
 225 }
 226
 227 static int option_parse_n(const struct option *opt,
 228                           const char *arg, int unset)
 229 {
 230         BUG_ON_OPT_ARG(arg);
 231         show_diffstat = unset;
 232         return 0;
 233 }
 234
 235 static struct option builtin_merge_options[] = {
 236         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 237                 N_("do not show a diffstat at the end of the merge"),
 238                 PARSE_OPT_NOARG, option_parse_n },
 239         OPT_BOOL(0, "stat", &show_diffstat,
 240                 N_("show a diffstat at the end of the merge")),
 241         OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
 242         { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
 243           N_("add (at most <n>) entries from shortlog to merge commit message"),
 244           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 245         OPT_BOOL(0, "squash", &squash,
 246                 N_("create a single commit instead of doing a merge")),
 247         OPT_BOOL(0, "commit", &option_commit,
 248                 N_("perform a commit if the merge succeeds (default)")),
 249         OPT_BOOL('e', "edit", &option_edit,
 250                 N_("edit message before committing")),
 251         OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
 252         OPT_SET_INT_F(0, "ff-only", &fast_forward,
 253                       N_("abort if fast-forward is not possible"),
 254                       FF_ONLY, PARSE_OPT_NONEG),
 255         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 256         OPT_BOOL(0, "verify-signatures", &verify_signatures,
 257                 N_("verify that the named commit has a valid GPG signature")),
 258         OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
 259                 N_("merge strategy to use"), option_parse_strategy),
 260         OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
 261                 N_("option for selected merge strategy"), option_parse_x),
 262         OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
 263                 N_("merge commit message (for a non-fast-forward merge)"),
 264                 option_parse_message),
 265         { OPTION_LOWLEVEL_CALLBACK, 'F', "file", &merge_msg, N_("path"),
 266                 N_("read message from file"), PARSE_OPT_NONEG,
 267                 (parse_opt_cb *) option_read_message },
 268         OPT__VERBOSITY(&verbosity),
 269         OPT_BOOL(0, "abort", &abort_current_merge,
 270                 N_("abort the current in-progress merge")),
 271         OPT_BOOL(0, "quit", &quit_current_merge,
 272                 N_("--abort but leave index and working tree alone")),
 273         OPT_BOOL(0, "continue", &continue_current_merge,
 274                 N_("continue the current in-progress merge")),
 275         OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
 276                  N_("allow merging unrelated histories")),
 277         OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
 278         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
 279           N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 280         OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
 281         OPT_BOOL(0, "signoff", &signoff, N_("add Signed-off-by:")),
 282         OPT_BOOL(0, "verify", &verify_msg, N_("verify commit-msg hook")),
 283         OPT_END()
 284 };
 285
 286 static int save_state(struct object_id *stash)
 287 {
 288         int len;
 289         struct child_process cp = CHILD_PROCESS_INIT;
 290         struct strbuf buffer = STRBUF_INIT;
 291         const char *argv[] = {"stash", "create", NULL};
 292         int rc = -1;
 293
 294         cp.argv = argv;
 295         cp.out = -1;
 296         cp.git_cmd = 1;
 297
 298         if (start_command(&cp))
 299                 die(_("could not run stash."));
 300         len = strbuf_read(&buffer, cp.out, 1024);
 301         close(cp.out);
 302
 303         if (finish_command(&cp) || len < 0)
 304                 die(_("stash failed"));
 305         else if (!len)          /* no changes */
 306                 goto out;
 307         strbuf_setlen(&buffer, buffer.len-1);
 308         if (get_oid(buffer.buf, stash))
 309                 die(_("not a valid object: %s"), buffer.buf);
 310         rc = 0;
 311 out:
 312         strbuf_release(&buffer);
 313         return rc;
 314 }
 315
 316 static void read_empty(const struct object_id *oid, int verbose)
 317 {
 318         int i = 0;
 319         const char *args[7];
 320
 321         args[i++] = "read-tree";
 322         if (verbose)
 323                 args[i++] = "-v";
 324         args[i++] = "-m";
 325         args[i++] = "-u";
 326         args[i++] = empty_tree_oid_hex();
 327         args[i++] = oid_to_hex(oid);
 328         args[i] = NULL;
 329
 330         if (run_command_v_opt(args, RUN_GIT_CMD))
 331                 die(_("read-tree failed"));
 332 }
 333
 334 static void reset_hard(const struct object_id *oid, int verbose)
 335 {
 336         int i = 0;
 337         const char *args[6];
 338
 339         args[i++] = "read-tree";
 340         if (verbose)
 341                 args[i++] = "-v";
 342         args[i++] = "--reset";
 343         args[i++] = "-u";
 344         args[i++] = oid_to_hex(oid);
 345         args[i] = NULL;
 346
 347         if (run_command_v_opt(args, RUN_GIT_CMD))
 348                 die(_("read-tree failed"));
 349 }
 350
 351 static void restore_state(const struct object_id *head,
 352                           const struct object_id *stash)
 353 {
 354         struct strbuf sb = STRBUF_INIT;
 355         const char *args[] = { "stash", "apply", NULL, NULL };
 356
 357         if (is_null_oid(stash))
 358                 return;
 359
 360         reset_hard(head, 1);
 361
 362         args[2] = oid_to_hex(stash);
 363
 364         /*
 365          * It is OK to ignore error here, for example when there was
 366          * nothing to restore.
 367          */
 368         run_command_v_opt(args, RUN_GIT_CMD);
 369
 370         strbuf_release(&sb);
 371         refresh_cache(REFRESH_QUIET);
 372 }
 373
 374 /* This is called when no merge was necessary. */
 375 static void finish_up_to_date(const char *msg)
 376 {
 377         if (verbosity >= 0)
 378                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 379         remove_merge_branch_state(the_repository);
 380 }
 381
 382 static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 383 {
 384         struct rev_info rev;
 385         struct strbuf out = STRBUF_INIT;
 386         struct commit_list *j;
 387         struct pretty_print_context ctx = {0};
 388
 389         printf(_("Squash commit -- not updating HEAD\n"));
 390
 391         repo_init_revisions(the_repository, &rev, NULL);
 392         rev.ignore_merges = 1;
 393         rev.commit_format = CMIT_FMT_MEDIUM;
 394
 395         commit->object.flags |= UNINTERESTING;
 396         add_pending_object(&rev, &commit->object, NULL);
 397
 398         for (j = remoteheads; j; j = j->next)
 399                 add_pending_object(&rev, &j->item->object, NULL);
 400
 401         setup_revisions(0, NULL, &rev, NULL);
 402         if (prepare_revision_walk(&rev))
 403                 die(_("revision walk setup failed"));
 404
 405         ctx.abbrev = rev.abbrev;
 406         ctx.date_mode = rev.date_mode;
 407         ctx.fmt = rev.commit_format;
 408
 409         strbuf_addstr(&out, "Squashed commit of the following:\n");
 410         while ((commit = get_revision(&rev)) != NULL) {
 411                 strbuf_addch(&out, '\n');
 412                 strbuf_addf(&out, "commit %s\n",
 413                         oid_to_hex(&commit->object.oid));
 414                 pretty_print_commit(&ctx, commit, &out);
 415         }
 416         write_file_buf(git_path_squash_msg(the_repository), out.buf, out.len);
 417         strbuf_release(&out);
 418 }
 419
 420 static void finish(struct commit *head_commit,
 421                    struct commit_list *remoteheads,
 422                    const struct object_id *new_head, const char *msg)
 423 {
 424         struct strbuf reflog_message = STRBUF_INIT;
 425         const struct object_id *head = &head_commit->object.oid;
 426
 427         if (!msg)
 428                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 429         else {
 430                 if (verbosity >= 0)
 431                         printf("%s\n", msg);
 432                 strbuf_addf(&reflog_message, "%s: %s",
 433                         getenv("GIT_REFLOG_ACTION"), msg);
 434         }
 435         if (squash) {
 436                 squash_message(head_commit, remoteheads);
 437         } else {
 438                 if (verbosity >= 0 && !merge_msg.len)
 439                         printf(_("No merge message -- not updating HEAD\n"));
 440                 else {
 441                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 442                         update_ref(reflog_message.buf, "HEAD", new_head, head,
 443                                    0, UPDATE_REFS_DIE_ON_ERR);
 444                         /*
 445                          * We ignore errors in 'gc --auto', since the
 446                          * user should see them.
 447                          */
 448                         close_all_packs(the_repository->objects);
 449                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 450                 }
 451         }
 452         if (new_head && show_diffstat) {
 453                 struct diff_options opts;
 454                 repo_diff_setup(the_repository, &opts);
 455                 opts.stat_width = -1; /* use full terminal width */
 456                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
 457                 opts.output_format |=
 458                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 459                 opts.detect_rename = DIFF_DETECT_RENAME;
 460                 diff_setup_done(&opts);
 461                 diff_tree_oid(head, new_head, "", &opts);
 462                 diffcore_std(&opts);
 463                 diff_flush(&opts);
 464         }
 465
 466         /* Run a post-merge hook */
 467         run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
 468
 469         strbuf_release(&reflog_message);
 470 }
 471
 472 /* Get the name for the merge commit's message. */
 473 static void merge_name(const char *remote, struct strbuf *msg)
 474 {
 475         struct commit *remote_head;
 476         struct object_id branch_head;
 477         struct strbuf buf = STRBUF_INIT;
 478         struct strbuf bname = STRBUF_INIT;
 479         struct merge_remote_desc *desc;
 480         const char *ptr;
 481         char *found_ref;
 482         int len, early;
 483
 484         strbuf_branchname(&bname, remote, 0);
 485         remote = bname.buf;
 486
 487         oidclr(&branch_head);
 488         remote_head = get_merge_parent(remote);
 489         if (!remote_head)
 490                 die(_("'%s' does not point to a commit"), remote);
 491
 492         if (dwim_ref(remote, strlen(remote), &branch_head, &found_ref) > 0) {
 493                 if (starts_with(found_ref, "refs/heads/")) {
 494                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 495                                     oid_to_hex(&branch_head), remote);
 496                         goto cleanup;
 497                 }
 498                 if (starts_with(found_ref, "refs/tags/")) {
 499                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 500                                     oid_to_hex(&branch_head), remote);
 501                         goto cleanup;
 502                 }
 503                 if (starts_with(found_ref, "refs/remotes/")) {
 504                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 505                                     oid_to_hex(&branch_head), remote);
 506                         goto cleanup;
 507                 }
 508         }
 509
 510         /* See if remote matches <name>^^^.. or <name>~<number> */
 511         for (len = 0, ptr = remote + strlen(remote);
 512              remote < ptr && ptr[-1] == '^';
 513              ptr--)
 514                 len++;
 515         if (len)
 516                 early = 1;
 517         else {
 518                 early = 0;
 519                 ptr = strrchr(remote, '~');
 520                 if (ptr) {
 521                         int seen_nonzero = 0;
 522
 523                         len++; /* count ~ */
 524                         while (*++ptr && isdigit(*ptr)) {
 525                                 seen_nonzero |= (*ptr != '0');
 526                                 len++;
 527                         }
 528                         if (*ptr)
 529                                 len = 0; /* not ...~<number> */
 530                         else if (seen_nonzero)
 531                                 early = 1;
 532                         else if (len == 1)
 533                                 early = 1; /* "name~" is "name~1"! */
 534                 }
 535         }
 536         if (len) {
 537                 struct strbuf truname = STRBUF_INIT;
 538                 strbuf_addf(&truname, "refs/heads/%s", remote);
 539                 strbuf_setlen(&truname, truname.len - len);
 540                 if (ref_exists(truname.buf)) {
 541                         strbuf_addf(msg,
 542                                     "%s\t\tbranch '%s'%s of .\n",
 543                                     oid_to_hex(&remote_head->object.oid),
 544                                     truname.buf + 11,
 545                                     (early ? " (early part)" : ""));
 546                         strbuf_release(&truname);
 547                         goto cleanup;
 548                 }
 549                 strbuf_release(&truname);
 550         }
 551
 552         desc = merge_remote_util(remote_head);
 553         if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 554                 strbuf_addf(msg, "%s\t\t%s '%s'\n",
 555                             oid_to_hex(&desc->obj->oid),
 556                             type_name(desc->obj->type),
 557                             remote);
 558                 goto cleanup;
 559         }
 560
 561         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 562                 oid_to_hex(&remote_head->object.oid), remote);
 563 cleanup:
 564         strbuf_release(&buf);
 565         strbuf_release(&bname);
 566 }
 567
 568 static void parse_branch_merge_options(char *bmo)
 569 {
 570         const char **argv;
 571         int argc;
 572
 573         if (!bmo)
 574                 return;
 575         argc = split_cmdline(bmo, &argv);
 576         if (argc < 0)
 577                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 578                     _(split_cmdline_strerror(argc)));
 579         REALLOC_ARRAY(argv, argc + 2);
 580         MOVE_ARRAY(argv + 1, argv, argc + 1);
 581         argc++;
 582         argv[0] = "branch.*.mergeoptions";
 583         parse_options(argc, argv, NULL, builtin_merge_options,
 584                       builtin_merge_usage, 0);
 585         free(argv);
 586 }
 587
 588 static int git_merge_config(const char *k, const char *v, void *cb)
 589 {
 590         int status;
 591
 592         if (branch && starts_with(k, "branch.") &&
 593                 starts_with(k + 7, branch) &&
 594                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 595                 free(branch_mergeoptions);
 596                 branch_mergeoptions = xstrdup(v);
 597                 return 0;
 598         }
 599
 600         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 601                 show_diffstat = git_config_bool(k, v);
 602         else if (!strcmp(k, "merge.verifysignatures"))
 603                 verify_signatures = git_config_bool(k, v);
 604         else if (!strcmp(k, "pull.twohead"))
 605                 return git_config_string(&pull_twohead, k, v);
 606         else if (!strcmp(k, "pull.octopus"))
 607                 return git_config_string(&pull_octopus, k, v);
 608         else if (!strcmp(k, "merge.renormalize"))
 609                 option_renormalize = git_config_bool(k, v);
 610         else if (!strcmp(k, "merge.ff")) {
 611                 int boolval = git_parse_maybe_bool(v);
 612                 if (0 <= boolval) {
 613                         fast_forward = boolval ? FF_ALLOW : FF_NO;
 614                 } else if (v && !strcmp(v, "only")) {
 615                         fast_forward = FF_ONLY;
 616                 } /* do not barf on values from future versions of git */
 617                 return 0;
 618         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 619                 default_to_upstream = git_config_bool(k, v);
 620                 return 0;
 621         } else if (!strcmp(k, "commit.gpgsign")) {
 622                 sign_commit = git_config_bool(k, v) ? "" : NULL;
 623                 return 0;
 624         }
 625
 626         status = fmt_merge_msg_config(k, v, cb);
 627         if (status)
 628                 return status;
 629         status = git_gpg_config(k, v, NULL);
 630         if (status)
 631                 return status;
 632         return git_diff_ui_config(k, v, cb);
 633 }
 634
 635 static int read_tree_trivial(struct object_id *common, struct object_id *head,
 636                              struct object_id *one)
 637 {
 638         int i, nr_trees = 0;
 639         struct tree *trees[MAX_UNPACK_TREES];
 640         struct tree_desc t[MAX_UNPACK_TREES];
 641         struct unpack_trees_options opts;
 642
 643         memset(&opts, 0, sizeof(opts));
 644         opts.head_idx = 2;
 645         opts.src_index = &the_index;
 646         opts.dst_index = &the_index;
 647         opts.update = 1;
 648         opts.verbose_update = 1;
 649         opts.trivial_merges_only = 1;
 650         opts.merge = 1;
 651         trees[nr_trees] = parse_tree_indirect(common);
 652         if (!trees[nr_trees++])
 653                 return -1;
 654         trees[nr_trees] = parse_tree_indirect(head);
 655         if (!trees[nr_trees++])
 656                 return -1;
 657         trees[nr_trees] = parse_tree_indirect(one);
 658         if (!trees[nr_trees++])
 659                 return -1;
 660         opts.fn = threeway_merge;
 661         cache_tree_free(&active_cache_tree);
 662         for (i = 0; i < nr_trees; i++) {
 663                 parse_tree(trees[i]);
 664                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 665         }
 666         if (unpack_trees(nr_trees, t, &opts))
 667                 return -1;
 668         return 0;
 669 }
 670
 671 static void write_tree_trivial(struct object_id *oid)
 672 {
 673         if (write_cache_as_tree(oid, 0, NULL))
 674                 die(_("git write-tree failed to write a tree"));
 675 }
 676
 677 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 678                               struct commit_list *remoteheads,
 679                               struct commit *head)
 680 {
 681         struct lock_file lock = LOCK_INIT;
 682         const char *head_arg = "HEAD";
 683
 684         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 685         refresh_cache(REFRESH_QUIET);
 686         if (write_locked_index(&the_index, &lock,
 687                                COMMIT_LOCK | SKIP_IF_UNCHANGED))
 688                 return error(_("Unable to write index."));
 689
 690         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 691                 int clean, x;
 692                 struct commit *result;
 693                 struct commit_list *reversed = NULL;
 694                 struct merge_options o;
 695                 struct commit_list *j;
 696
 697                 if (remoteheads->next) {
 698                         error(_("Not handling anything other than two heads merge."));
 699                         return 2;
 700                 }
 701
 702                 init_merge_options(&o, the_repository);
 703                 if (!strcmp(strategy, "subtree"))
 704                         o.subtree_shift = "";
 705
 706                 o.renormalize = option_renormalize;
 707                 o.show_rename_progress =
 708                         show_progress == -1 ? isatty(2) : show_progress;
 709
 710                 for (x = 0; x < xopts_nr; x++)
 711                         if (parse_merge_opt(&o, xopts[x]))
 712                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 713
 714                 o.branch1 = head_arg;
 715                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 716
 717                 for (j = common; j; j = j->next)
 718                         commit_list_insert(j->item, &reversed);
 719
 720                 hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 721                 clean = merge_recursive(&o, head,
 722                                 remoteheads->item, reversed, &result);
 723                 if (clean < 0)
 724                         exit(128);
 725                 if (write_locked_index(&the_index, &lock,
 726                                        COMMIT_LOCK | SKIP_IF_UNCHANGED))
 727                         die(_("unable to write %s"), get_index_file());
 728                 return clean ? 0 : 1;
 729         } else {
 730                 return try_merge_command(the_repository,
 731                                          strategy, xopts_nr, xopts,
 732                                          common, head_arg, remoteheads);
 733         }
 734 }
 735
 736 static void count_diff_files(struct diff_queue_struct *q,
 737                              struct diff_options *opt, void *data)
 738 {
 739         int *count = data;
 740
 741         (*count) += q->nr;
 742 }
 743
 744 static int count_unmerged_entries(void)
 745 {
 746         int i, ret = 0;
 747
 748         for (i = 0; i < active_nr; i++)
 749                 if (ce_stage(active_cache[i]))
 750                         ret++;
 751
 752         return ret;
 753 }
 754
 755 static void add_strategies(const char *string, unsigned attr)
 756 {
 757         int i;
 758
 759         if (string) {
 760                 struct string_list list = STRING_LIST_INIT_DUP;
 761                 struct string_list_item *item;
 762                 string_list_split(&list, string, ' ', -1);
 763                 for_each_string_list_item(item, &list)
 764                         append_strategy(get_strategy(item->string));
 765                 string_list_clear(&list, 0);
 766                 return;
 767         }
 768         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 769                 if (all_strategy[i].attr & attr)
 770                         append_strategy(&all_strategy[i]);
 771
 772 }
 773
 774 static void read_merge_msg(struct strbuf *msg)
 775 {
 776         const char *filename = git_path_merge_msg(the_repository);
 777         strbuf_reset(msg);
 778         if (strbuf_read_file(msg, filename, 0) < 0)
 779                 die_errno(_("Could not read from '%s'"), filename);
 780 }
 781
 782 static void write_merge_state(struct commit_list *);
 783 static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
 784 {
 785         if (err_msg)
 786                 error("%s", err_msg);
 787         fprintf(stderr,
 788                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 789         write_merge_state(remoteheads);
 790         exit(1);
 791 }
 792
 793 static const char merge_editor_comment[] =
 794 N_("Please enter a commit message to explain why this merge is necessary,\n"
 795    "especially if it merges an updated upstream into a topic branch.\n"
 796    "\n"
 797    "Lines starting with '%c' will be ignored, and an empty message aborts\n"
 798    "the commit.\n");
 799
 800 static void write_merge_heads(struct commit_list *);
 801 static void prepare_to_commit(struct commit_list *remoteheads)
 802 {
 803         struct strbuf msg = STRBUF_INIT;
 804         strbuf_addbuf(&msg, &merge_msg);
 805         strbuf_addch(&msg, '\n');
 806         if (squash)
 807                 BUG("the control must not reach here under --squash");
 808         if (0 < option_edit)
 809                 strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
 810         if (signoff)
 811                 append_signoff(&msg, ignore_non_trailer(msg.buf, msg.len), 0);
 812         write_merge_heads(remoteheads);
 813         write_file_buf(git_path_merge_msg(the_repository), msg.buf, msg.len);
 814         if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
 815                             git_path_merge_msg(the_repository), "merge", NULL))
 816                 abort_commit(remoteheads, NULL);
 817         if (0 < option_edit) {
 818                 if (launch_editor(git_path_merge_msg(the_repository), NULL, NULL))
 819                         abort_commit(remoteheads, NULL);
 820         }
 821
 822         if (verify_msg && run_commit_hook(0 < option_edit, get_index_file(),
 823                                           "commit-msg",
 824                                           git_path_merge_msg(the_repository), NULL))
 825                 abort_commit(remoteheads, NULL);
 826
 827         read_merge_msg(&msg);
 828         strbuf_stripspace(&msg, 0 < option_edit);
 829         if (!msg.len)
 830                 abort_commit(remoteheads, _("Empty commit message."));
 831         strbuf_release(&merge_msg);
 832         strbuf_addbuf(&merge_msg, &msg);
 833         strbuf_release(&msg);
 834 }
 835
 836 static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 837 {
 838         struct object_id result_tree, result_commit;
 839         struct commit_list *parents, **pptr = &parents;
 840         struct lock_file lock = LOCK_INIT;
 841
 842         hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 843         refresh_cache(REFRESH_QUIET);
 844         if (write_locked_index(&the_index, &lock,
 845                                COMMIT_LOCK | SKIP_IF_UNCHANGED))
 846                 return error(_("Unable to write index."));
 847
 848         write_tree_trivial(&result_tree);
 849         printf(_("Wonderful.\n"));
 850         pptr = commit_list_append(head, pptr);
 851         pptr = commit_list_append(remoteheads->item, pptr);
 852         prepare_to_commit(remoteheads);
 853         if (commit_tree(merge_msg.buf, merge_msg.len, &result_tree, parents,
 854                         &result_commit, NULL, sign_commit))
 855                 die(_("failed to write commit object"));
 856         finish(head, remoteheads, &result_commit, "In-index merge");
 857         remove_merge_branch_state(the_repository);
 858         return 0;
 859 }
 860
 861 static int finish_automerge(struct commit *head,
 862                             int head_subsumed,
 863                             struct commit_list *common,
 864                             struct commit_list *remoteheads,
 865                             struct object_id *result_tree,
 866                             const char *wt_strategy)
 867 {
 868         struct commit_list *parents = NULL;
 869         struct strbuf buf = STRBUF_INIT;
 870         struct object_id result_commit;
 871
 872         free_commit_list(common);
 873         parents = remoteheads;
 874         if (!head_subsumed || fast_forward == FF_NO)
 875                 commit_list_insert(head, &parents);
 876         strbuf_addch(&merge_msg, '\n');
 877         prepare_to_commit(remoteheads);
 878         if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 879                         &result_commit, NULL, sign_commit))
 880                 die(_("failed to write commit object"));
 881         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 882         finish(head, remoteheads, &result_commit, buf.buf);
 883         strbuf_release(&buf);
 884         remove_merge_branch_state(the_repository);
 885         return 0;
 886 }
 887
 888 static int suggest_conflicts(void)
 889 {
 890         const char *filename;
 891         FILE *fp;
 892         struct strbuf msgbuf = STRBUF_INIT;
 893
 894         filename = git_path_merge_msg(the_repository);
 895         fp = xfopen(filename, "a");
 896
 897         append_conflicts_hint(&the_index, &msgbuf);
 898         fputs(msgbuf.buf, fp);
 899         strbuf_release(&msgbuf);
 900         fclose(fp);
 901         repo_rerere(the_repository, allow_rerere_auto);
 902         printf(_("Automatic merge failed; "
 903                         "fix conflicts and then commit the result.\n"));
 904         return 1;
 905 }
 906
 907 static int evaluate_result(void)
 908 {
 909         int cnt = 0;
 910         struct rev_info rev;
 911
 912         /* Check how many files differ. */
 913         repo_init_revisions(the_repository, &rev, "");
 914         setup_revisions(0, NULL, &rev, NULL);
 915         rev.diffopt.output_format |=
 916                 DIFF_FORMAT_CALLBACK;
 917         rev.diffopt.format_callback = count_diff_files;
 918         rev.diffopt.format_callback_data = &cnt;
 919         run_diff_files(&rev, 0);
 920
 921         /*
 922          * Check how many unmerged entries are
 923          * there.
 924          */
 925         cnt += count_unmerged_entries();
 926
 927         return cnt;
 928 }
 929
 930 /*
 931  * Pretend as if the user told us to merge with the remote-tracking
 932  * branch we have for the upstream of the current branch
 933  */
 934 static int setup_with_upstream(const char ***argv)
 935 {
 936         struct branch *branch = branch_get(NULL);
 937         int i;
 938         const char **args;
 939
 940         if (!branch)
 941                 die(_("No current branch."));
 942         if (!branch->remote_name)
 943                 die(_("No remote for the current branch."));
 944         if (!branch->merge_nr)
 945                 die(_("No default upstream defined for the current branch."));
 946
 947         args = xcalloc(st_add(branch->merge_nr, 1), sizeof(char *));
 948         for (i = 0; i < branch->merge_nr; i++) {
 949                 if (!branch->merge[i]->dst)
 950                         die(_("No remote-tracking branch for %s from %s"),
 951                             branch->merge[i]->src, branch->remote_name);
 952                 args[i] = branch->merge[i]->dst;
 953         }
 954         args[i] = NULL;
 955         *argv = args;
 956         return i;
 957 }
 958
 959 static void write_merge_heads(struct commit_list *remoteheads)
 960 {
 961         struct commit_list *j;
 962         struct strbuf buf = STRBUF_INIT;
 963
 964         for (j = remoteheads; j; j = j->next) {
 965                 struct object_id *oid;
 966                 struct commit *c = j->item;
 967                 struct merge_remote_desc *desc;
 968
 969                 desc = merge_remote_util(c);
 970                 if (desc && desc->obj) {
 971                         oid = &desc->obj->oid;
 972                 } else {
 973                         oid = &c->object.oid;
 974                 }
 975                 strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
 976         }
 977         write_file_buf(git_path_merge_head(the_repository), buf.buf, buf.len);
 978
 979         strbuf_reset(&buf);
 980         if (fast_forward == FF_NO)
 981                 strbuf_addstr(&buf, "no-ff");
 982         write_file_buf(git_path_merge_mode(the_repository), buf.buf, buf.len);
 983         strbuf_release(&buf);
 984 }
 985
 986 static void write_merge_state(struct commit_list *remoteheads)
 987 {
 988         write_merge_heads(remoteheads);
 989         strbuf_addch(&merge_msg, '\n');
 990         write_file_buf(git_path_merge_msg(the_repository), merge_msg.buf,
 991                        merge_msg.len);
 992 }
 993
 994 static int default_edit_option(void)
 995 {
 996         static const char name[] = "GIT_MERGE_AUTOEDIT";
 997         const char *e = getenv(name);
 998         struct stat st_stdin, st_stdout;
 999
1000         if (have_message)
1001                 /* an explicit -m msg without --[no-]edit */
1002                 return 0;
1003
1004         if (e) {
1005                 int v = git_parse_maybe_bool(e);
1006                 if (v < 0)
1007                         die(_("Bad value '%s' in environment '%s'"), e, name);
1008                 return v;
1009         }
1010
1011         /* Use editor if stdin and stdout are the same and is a tty */
1012         return (!fstat(0, &st_stdin) &&
1013                 !fstat(1, &st_stdout) &&
1014                 isatty(0) && isatty(1) &&
1015                 st_stdin.st_dev == st_stdout.st_dev &&
1016                 st_stdin.st_ino == st_stdout.st_ino &&
1017                 st_stdin.st_mode == st_stdout.st_mode);
1018 }
1019
1020 static struct commit_list *reduce_parents(struct commit *head_commit,
1021                                           int *head_subsumed,
1022                                           struct commit_list *remoteheads)
1023 {
1024         struct commit_list *parents, **remotes;
1025
1026         /*
1027          * Is the current HEAD reachable from another commit being
1028          * merged?  If so we do not want to record it as a parent of
1029          * the resulting merge, unless --no-ff is given.  We will flip
1030          * this variable to 0 when we find HEAD among the independent
1031          * tips being merged.
1032          */
1033         *head_subsumed = 1;
1034
1035         /* Find what parents to record by checking independent ones. */
1036         parents = reduce_heads(remoteheads);
1037         free_commit_list(remoteheads);
1038
1039         remoteheads = NULL;
1040         remotes = &remoteheads;
1041         while (parents) {
1042                 struct commit *commit = pop_commit(&parents);
1043                 if (commit == head_commit)
1044                         *head_subsumed = 0;
1045                 else
1046                         remotes = &commit_list_insert(commit, remotes)->next;
1047         }
1048         return remoteheads;
1049 }
1050
1051 static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
1052 {
1053         struct fmt_merge_msg_opts opts;
1054
1055         memset(&opts, 0, sizeof(opts));
1056         opts.add_title = !have_message;
1057         opts.shortlog_len = shortlog_len;
1058         opts.credit_people = (0 < option_edit);
1059
1060         fmt_merge_msg(merge_names, merge_msg, &opts);
1061         if (merge_msg->len)
1062                 strbuf_setlen(merge_msg, merge_msg->len - 1);
1063 }
1064
1065 static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1066 {
1067         const char *filename;
1068         int fd, pos, npos;
1069         struct strbuf fetch_head_file = STRBUF_INIT;
1070         const unsigned hexsz = the_hash_algo->hexsz;
1071
1072         if (!merge_names)
1073                 merge_names = &fetch_head_file;
1074
1075         filename = git_path_fetch_head(the_repository);
1076         fd = open(filename, O_RDONLY);
1077         if (fd < 0)
1078                 die_errno(_("could not open '%s' for reading"), filename);
1079
1080         if (strbuf_read(merge_names, fd, 0) < 0)
1081                 die_errno(_("could not read '%s'"), filename);
1082         if (close(fd) < 0)
1083                 die_errno(_("could not close '%s'"), filename);
1084
1085         for (pos = 0; pos < merge_names->len; pos = npos) {
1086                 struct object_id oid;
1087                 char *ptr;
1088                 struct commit *commit;
1089
1090                 ptr = strchr(merge_names->buf + pos, '\n');
1091                 if (ptr)
1092                         npos = ptr - merge_names->buf + 1;
1093                 else
1094                         npos = merge_names->len;
1095
1096                 if (npos - pos < hexsz + 2 ||
1097                     get_oid_hex(merge_names->buf + pos, &oid))
1098                         commit = NULL; /* bad */
1099                 else if (memcmp(merge_names->buf + pos + hexsz, "\t\t", 2))
1100                         continue; /* not-for-merge */
1101                 else {
1102                         char saved = merge_names->buf[pos + hexsz];
1103                         merge_names->buf[pos + hexsz] = '\0';
1104                         commit = get_merge_parent(merge_names->buf + pos);
1105                         merge_names->buf[pos + hexsz] = saved;
1106                 }
1107                 if (!commit) {
1108                         if (ptr)
1109                                 *ptr = '\0';
1110                         die(_("not something we can merge in %s: %s"),
1111                             filename, merge_names->buf + pos);
1112                 }
1113                 remotes = &commit_list_insert(commit, remotes)->next;
1114         }
1115
1116         if (merge_names == &fetch_head_file)
1117                 strbuf_release(&fetch_head_file);
1118 }
1119
1120 static struct commit_list *collect_parents(struct commit *head_commit,
1121                                            int *head_subsumed,
1122                                            int argc, const char **argv,
1123                                            struct strbuf *merge_msg)
1124 {
1125         int i;
1126         struct commit_list *remoteheads = NULL;
1127         struct commit_list **remotes = &remoteheads;
1128         struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1129
1130         if (merge_msg && (!have_message || shortlog_len))
1131                 autogen = &merge_names;
1132
1133         if (head_commit)
1134                 remotes = &commit_list_insert(head_commit, remotes)->next;
1135
1136         if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1137                 handle_fetch_head(remotes, autogen);
1138                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1139         } else {
1140                 for (i = 0; i < argc; i++) {
1141                         struct commit *commit = get_merge_parent(argv[i]);
1142                         if (!commit)
1143                                 help_unknown_ref(argv[i], "merge",
1144                                                  _("not something we can merge"));
1145                         remotes = &commit_list_insert(commit, remotes)->next;
1146                 }
1147                 remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1148                 if (autogen) {
1149                         struct commit_list *p;
1150                         for (p = remoteheads; p; p = p->next)
1151                                 merge_name(merge_remote_util(p->item)->name, autogen);
1152                 }
1153         }
1154
1155         if (autogen) {
1156                 prepare_merge_message(autogen, merge_msg);
1157                 strbuf_release(autogen);
1158         }
1159
1160         return remoteheads;
1161 }
1162
1163 static int merging_a_throwaway_tag(struct commit *commit)
1164 {
1165         char *tag_ref;
1166         struct object_id oid;
1167         int is_throwaway_tag = 0;
1168
1169         /* Are we merging a tag? */
1170         if (!merge_remote_util(commit) ||
1171             !merge_remote_util(commit)->obj ||
1172             merge_remote_util(commit)->obj->type != OBJ_TAG)
1173                 return is_throwaway_tag;
1174
1175         /*
1176          * Now we know we are merging a tag object.  Are we downstream
1177          * and following the tags from upstream?  If so, we must have
1178          * the tag object pointed at by "refs/tags/$T" where $T is the
1179          * tagname recorded in the tag object.  We want to allow such
1180          * a "just to catch up" merge to fast-forward.
1181          *
1182          * Otherwise, we are playing an integrator's role, making a
1183          * merge with a throw-away tag from a contributor with
1184          * something like "git pull $contributor $signed_tag".
1185          * We want to forbid such a merge from fast-forwarding
1186          * by default; otherwise we would not keep the signature
1187          * anywhere.
1188          */
1189         tag_ref = xstrfmt("refs/tags/%s",
1190                           ((struct tag *)merge_remote_util(commit)->obj)->tag);
1191         if (!read_ref(tag_ref, &oid) &&
1192             oideq(&oid, &merge_remote_util(commit)->obj->oid))
1193                 is_throwaway_tag = 0;
1194         else
1195                 is_throwaway_tag = 1;
1196         free(tag_ref);
1197         return is_throwaway_tag;
1198 }
1199
1200 int cmd_merge(int argc, const char **argv, const char *prefix)
1201 {
1202         struct object_id result_tree, stash, head_oid;
1203         struct commit *head_commit;
1204         struct strbuf buf = STRBUF_INIT;
1205         int i, ret = 0, head_subsumed;
1206         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1207         struct commit_list *common = NULL;
1208         const char *best_strategy = NULL, *wt_strategy = NULL;
1209         struct commit_list *remoteheads, *p;
1210         void *branch_to_free;
1211         int orig_argc = argc;
1212
1213         if (argc == 2 && !strcmp(argv[1], "-h"))
1214                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1215
1216         /*
1217          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1218          * current branch.
1219          */
1220         branch = branch_to_free = resolve_refdup("HEAD", 0, &head_oid, NULL);
1221         if (branch)
1222                 skip_prefix(branch, "refs/heads/", &branch);
1223
1224         init_diff_ui_defaults();
1225         git_config(git_merge_config, NULL);
1226
1227         if (!branch || is_null_oid(&head_oid))
1228                 head_commit = NULL;
1229         else
1230                 head_commit = lookup_commit_or_die(&head_oid, "HEAD");
1231
1232         if (branch_mergeoptions)
1233                 parse_branch_merge_options(branch_mergeoptions);
1234         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1235                         builtin_merge_usage, 0);
1236         if (shortlog_len < 0)
1237                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1238
1239         if (verbosity < 0 && show_progress == -1)
1240                 show_progress = 0;
1241
1242         if (abort_current_merge) {
1243                 int nargc = 2;
1244                 const char *nargv[] = {"reset", "--merge", NULL};
1245
1246                 if (orig_argc != 2)
1247                         usage_msg_opt(_("--abort expects no arguments"),
1248                               builtin_merge_usage, builtin_merge_options);
1249
1250                 if (!file_exists(git_path_merge_head(the_repository)))
1251                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1252
1253                 /* Invoke 'git reset --merge' */
1254                 ret = cmd_reset(nargc, nargv, prefix);
1255                 goto done;
1256         }
1257
1258         if (quit_current_merge) {
1259                 if (orig_argc != 2)
1260                         usage_msg_opt(_("--quit expects no arguments"),
1261                                       builtin_merge_usage,
1262                                       builtin_merge_options);
1263
1264                 remove_merge_branch_state(the_repository);
1265                 goto done;
1266         }
1267
1268         if (continue_current_merge) {
1269                 int nargc = 1;
1270                 const char *nargv[] = {"commit", NULL};
1271
1272                 if (orig_argc != 2)
1273                         usage_msg_opt(_("--continue expects no arguments"),
1274                               builtin_merge_usage, builtin_merge_options);
1275
1276                 if (!file_exists(git_path_merge_head(the_repository)))
1277                         die(_("There is no merge in progress (MERGE_HEAD missing)."));
1278
1279                 /* Invoke 'git commit' */
1280                 ret = cmd_commit(nargc, nargv, prefix);
1281                 goto done;
1282         }
1283
1284         if (read_cache_unmerged())
1285                 die_resolve_conflict("merge");
1286
1287         if (file_exists(git_path_merge_head(the_repository))) {
1288                 /*
1289                  * There is no unmerged entry, don't advise 'git
1290                  * add/rm <file>', just 'git commit'.
1291                  */
1292                 if (advice_resolve_conflict)
1293                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1294                                   "Please, commit your changes before you merge."));
1295                 else
1296                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1297         }
1298         if (file_exists(git_path_cherry_pick_head(the_repository))) {
1299                 if (advice_resolve_conflict)
1300                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1301                             "Please, commit your changes before you merge."));
1302                 else
1303                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1304         }
1305         resolve_undo_clear();
1306
1307         if (verbosity < 0)
1308                 show_diffstat = 0;
1309
1310         if (squash) {
1311                 if (fast_forward == FF_NO)
1312                         die(_("You cannot combine --squash with --no-ff."));
1313                 option_commit = 0;
1314         }
1315
1316         if (!argc) {
1317                 if (default_to_upstream)
1318                         argc = setup_with_upstream(&argv);
1319                 else
1320                         die(_("No commit specified and merge.defaultToUpstream not set."));
1321         } else if (argc == 1 && !strcmp(argv[0], "-")) {
1322                 argv[0] = "@{-1}";
1323         }
1324
1325         if (!argc)
1326                 usage_with_options(builtin_merge_usage,
1327                         builtin_merge_options);
1328
1329         if (!head_commit) {
1330                 /*
1331                  * If the merged head is a valid one there is no reason
1332                  * to forbid "git merge" into a branch yet to be born.
1333                  * We do the same for "git pull".
1334                  */
1335                 struct object_id *remote_head_oid;
1336                 if (squash)
1337                         die(_("Squash commit into empty head not supported yet"));
1338                 if (fast_forward == FF_NO)
1339                         die(_("Non-fast-forward commit does not make sense into "
1340                             "an empty head"));
1341                 remoteheads = collect_parents(head_commit, &head_subsumed,
1342                                               argc, argv, NULL);
1343                 if (!remoteheads)
1344                         die(_("%s - not something we can merge"), argv[0]);
1345                 if (remoteheads->next)
1346                         die(_("Can merge only exactly one commit into empty head"));
1347
1348                 if (verify_signatures)
1349                         verify_merge_signature(remoteheads->item, verbosity);
1350
1351                 remote_head_oid = &remoteheads->item->object.oid;
1352                 read_empty(remote_head_oid, 0);
1353                 update_ref("initial pull", "HEAD", remote_head_oid, NULL, 0,
1354                            UPDATE_REFS_DIE_ON_ERR);
1355                 goto done;
1356         }
1357
1358         /*
1359          * All the rest are the commits being merged; prepare
1360          * the standard merge summary message to be appended
1361          * to the given message.
1362          */
1363         remoteheads = collect_parents(head_commit, &head_subsumed,
1364                                       argc, argv, &merge_msg);
1365
1366         if (!head_commit || !argc)
1367                 usage_with_options(builtin_merge_usage,
1368                         builtin_merge_options);
1369
1370         if (verify_signatures) {
1371                 for (p = remoteheads; p; p = p->next) {
1372                         verify_merge_signature(p->item, verbosity);
1373                 }
1374         }
1375
1376         strbuf_addstr(&buf, "merge");
1377         for (p = remoteheads; p; p = p->next)
1378                 strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1379         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1380         strbuf_reset(&buf);
1381
1382         for (p = remoteheads; p; p = p->next) {
1383                 struct commit *commit = p->item;
1384                 strbuf_addf(&buf, "GITHEAD_%s",
1385                             oid_to_hex(&commit->object.oid));
1386                 setenv(buf.buf, merge_remote_util(commit)->name, 1);
1387                 strbuf_reset(&buf);
1388                 if (fast_forward != FF_ONLY && merging_a_throwaway_tag(commit))
1389                         fast_forward = FF_NO;
1390         }
1391
1392         if (option_edit < 0)
1393                 option_edit = default_edit_option();
1394
1395         if (!use_strategies) {
1396                 if (!remoteheads)
1397                         ; /* already up-to-date */
1398                 else if (!remoteheads->next)
1399                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1400                 else
1401                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1402         }
1403
1404         for (i = 0; i < use_strategies_nr; i++) {
1405                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1406                         fast_forward = FF_NO;
1407                 if (use_strategies[i]->attr & NO_TRIVIAL)
1408                         allow_trivial = 0;
1409         }
1410
1411         if (!remoteheads)
1412                 ; /* already up-to-date */
1413         else if (!remoteheads->next)
1414                 common = get_merge_bases(head_commit, remoteheads->item);
1415         else {
1416                 struct commit_list *list = remoteheads;
1417                 commit_list_insert(head_commit, &list);
1418                 common = get_octopus_merge_bases(list);
1419                 free(list);
1420         }
1421
1422         update_ref("updating ORIG_HEAD", "ORIG_HEAD",
1423                    &head_commit->object.oid, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1424
1425         if (remoteheads && !common) {
1426                 /* No common ancestors found. */
1427                 if (!allow_unrelated_histories)
1428                         die(_("refusing to merge unrelated histories"));
1429                 /* otherwise, we need a real merge. */
1430         } else if (!remoteheads ||
1431                  (!remoteheads->next && !common->next &&
1432                   common->item == remoteheads->item)) {
1433                 /*
1434                  * If head can reach all the merge then we are up to date.
1435                  * but first the most common case of merging one remote.
1436                  */
1437                 finish_up_to_date(_("Already up to date."));
1438                 goto done;
1439         } else if (fast_forward != FF_NO && !remoteheads->next &&
1440                         !common->next &&
1441                         oideq(&common->item->object.oid, &head_commit->object.oid)) {
1442                 /* Again the most common case of merging one remote. */
1443                 struct strbuf msg = STRBUF_INIT;
1444                 struct commit *commit;
1445
1446                 if (verbosity >= 0) {
1447                         printf(_("Updating %s..%s\n"),
1448                                find_unique_abbrev(&head_commit->object.oid,
1449                                                   DEFAULT_ABBREV),
1450                                find_unique_abbrev(&remoteheads->item->object.oid,
1451                                                   DEFAULT_ABBREV));
1452                 }
1453                 strbuf_addstr(&msg, "Fast-forward");
1454                 if (have_message)
1455                         strbuf_addstr(&msg,
1456                                 " (no commit created; -m option ignored)");
1457                 commit = remoteheads->item;
1458                 if (!commit) {
1459                         ret = 1;
1460                         goto done;
1461                 }
1462
1463                 if (checkout_fast_forward(the_repository,
1464                                           &head_commit->object.oid,
1465                                           &commit->object.oid,
1466                                           overwrite_ignore)) {
1467                         ret = 1;
1468                         goto done;
1469                 }
1470
1471                 finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
1472                 remove_merge_branch_state(the_repository);
1473                 goto done;
1474         } else if (!remoteheads->next && common->next)
1475                 ;
1476                 /*
1477                  * We are not doing octopus and not fast-forward.  Need
1478                  * a real merge.
1479                  */
1480         else if (!remoteheads->next && !common->next && option_commit) {
1481                 /*
1482                  * We are not doing octopus, not fast-forward, and have
1483                  * only one common.
1484                  */
1485                 refresh_cache(REFRESH_QUIET);
1486                 if (allow_trivial && fast_forward != FF_ONLY) {
1487                         /* See if it is really trivial. */
1488                         git_committer_info(IDENT_STRICT);
1489                         printf(_("Trying really trivial in-index merge...\n"));
1490                         if (!read_tree_trivial(&common->item->object.oid,
1491                                                &head_commit->object.oid,
1492                                                &remoteheads->item->object.oid)) {
1493                                 ret = merge_trivial(head_commit, remoteheads);
1494                                 goto done;
1495                         }
1496                         printf(_("Nope.\n"));
1497                 }
1498         } else {
1499                 /*
1500                  * An octopus.  If we can reach all the remote we are up
1501                  * to date.
1502                  */
1503                 int up_to_date = 1;
1504                 struct commit_list *j;
1505
1506                 for (j = remoteheads; j; j = j->next) {
1507                         struct commit_list *common_one;
1508
1509                         /*
1510                          * Here we *have* to calculate the individual
1511                          * merge_bases again, otherwise "git merge HEAD^
1512                          * HEAD^^" would be missed.
1513                          */
1514                         common_one = get_merge_bases(head_commit, j->item);
1515                         if (!oideq(&common_one->item->object.oid, &j->item->object.oid)) {
1516                                 up_to_date = 0;
1517                                 break;
1518                         }
1519                 }
1520                 if (up_to_date) {
1521                         finish_up_to_date(_("Already up to date. Yeeah!"));
1522                         goto done;
1523                 }
1524         }
1525
1526         if (fast_forward == FF_ONLY)
1527                 die(_("Not possible to fast-forward, aborting."));
1528
1529         /* We are going to make a new commit. */
1530         git_committer_info(IDENT_STRICT);
1531
1532         /*
1533          * At this point, we need a real merge.  No matter what strategy
1534          * we use, it would operate on the index, possibly affecting the
1535          * working tree, and when resolved cleanly, have the desired
1536          * tree in the index -- this means that the index must be in
1537          * sync with the head commit.  The strategies are responsible
1538          * to ensure this.
1539          */
1540         if (use_strategies_nr == 1 ||
1541             /*
1542              * Stash away the local changes so that we can try more than one.
1543              */
1544             save_state(&stash))
1545                 oidclr(&stash);
1546
1547         for (i = 0; i < use_strategies_nr; i++) {
1548                 int ret;
1549                 if (i) {
1550                         printf(_("Rewinding the tree to pristine...\n"));
1551                         restore_state(&head_commit->object.oid, &stash);
1552                 }
1553                 if (use_strategies_nr != 1)
1554                         printf(_("Trying merge strategy %s...\n"),
1555                                 use_strategies[i]->name);
1556                 /*
1557                  * Remember which strategy left the state in the working
1558                  * tree.
1559                  */
1560                 wt_strategy = use_strategies[i]->name;
1561
1562                 ret = try_merge_strategy(use_strategies[i]->name,
1563                                          common, remoteheads,
1564                                          head_commit);
1565                 if (!option_commit && !ret) {
1566                         merge_was_ok = 1;
1567                         /*
1568                          * This is necessary here just to avoid writing
1569                          * the tree, but later we will *not* exit with
1570                          * status code 1 because merge_was_ok is set.
1571                          */
1572                         ret = 1;
1573                 }
1574
1575                 if (ret) {
1576                         /*
1577                          * The backend exits with 1 when conflicts are
1578                          * left to be resolved, with 2 when it does not
1579                          * handle the given merge at all.
1580                          */
1581                         if (ret == 1) {
1582                                 int cnt = evaluate_result();
1583
1584                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1585                                         best_strategy = use_strategies[i]->name;
1586                                         best_cnt = cnt;
1587                                 }
1588                         }
1589                         if (merge_was_ok)
1590                                 break;
1591                         else
1592                                 continue;
1593                 }
1594
1595                 /* Automerge succeeded. */
1596                 write_tree_trivial(&result_tree);
1597                 automerge_was_ok = 1;
1598                 break;
1599         }
1600
1601         /*
1602          * If we have a resulting tree, that means the strategy module
1603          * auto resolved the merge cleanly.
1604          */
1605         if (automerge_was_ok) {
1606                 ret = finish_automerge(head_commit, head_subsumed,
1607                                        common, remoteheads,
1608                                        &result_tree, wt_strategy);
1609                 goto done;
1610         }
1611
1612         /*
1613          * Pick the result from the best strategy and have the user fix
1614          * it up.
1615          */
1616         if (!best_strategy) {
1617                 restore_state(&head_commit->object.oid, &stash);
1618                 if (use_strategies_nr > 1)
1619                         fprintf(stderr,
1620                                 _("No merge strategy handled the merge.\n"));
1621                 else
1622                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1623                                 use_strategies[0]->name);
1624                 ret = 2;
1625                 goto done;
1626         } else if (best_strategy == wt_strategy)
1627                 ; /* We already have its result in the working tree. */
1628         else {
1629                 printf(_("Rewinding the tree to pristine...\n"));
1630                 restore_state(&head_commit->object.oid, &stash);
1631                 printf(_("Using the %s to prepare resolving by hand.\n"),
1632                         best_strategy);
1633                 try_merge_strategy(best_strategy, common, remoteheads,
1634                                    head_commit);
1635         }
1636
1637         if (squash)
1638                 finish(head_commit, remoteheads, NULL, NULL);
1639         else
1640                 write_merge_state(remoteheads);
1641
1642         if (merge_was_ok)
1643                 fprintf(stderr, _("Automatic merge went well; "
1644                         "stopped before committing as requested\n"));
1645         else
1646                 ret = suggest_conflicts();
1647
1648 done:
1649         free(branch_to_free);
1650         return ret;
1651 }