builtin / merge.con commit convert "hashcmp() != 0" to "!hasheq()" (67947c3)
   1/*
   2 * Builtin "git merge"
   3 *
   4 * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
   5 *
   6 * Based on git-merge.sh by Junio C Hamano.
   7 */
   8
   9#include "cache.h"
  10#include "config.h"
  11#include "parse-options.h"
  12#include "builtin.h"
  13#include "lockfile.h"
  14#include "run-command.h"
  15#include "diff.h"
  16#include "refs.h"
  17#include "refspec.h"
  18#include "commit.h"
  19#include "diffcore.h"
  20#include "revision.h"
  21#include "unpack-trees.h"
  22#include "cache-tree.h"
  23#include "dir.h"
  24#include "utf8.h"
  25#include "log-tree.h"
  26#include "color.h"
  27#include "rerere.h"
  28#include "help.h"
  29#include "merge-recursive.h"
  30#include "resolve-undo.h"
  31#include "remote.h"
  32#include "fmt-merge-msg.h"
  33#include "gpg-interface.h"
  34#include "sequencer.h"
  35#include "string-list.h"
  36#include "packfile.h"
  37#include "tag.h"
  38#include "alias.h"
  39
  40#define DEFAULT_TWOHEAD (1<<0)
  41#define DEFAULT_OCTOPUS (1<<1)
  42#define NO_FAST_FORWARD (1<<2)
  43#define NO_TRIVIAL      (1<<3)
  44
  45struct strategy {
  46        const char *name;
  47        unsigned attr;
  48};
  49
  50static const char * const builtin_merge_usage[] = {
  51        N_("git merge [<options>] [<commit>...]"),
  52        N_("git merge --abort"),
  53        N_("git merge --continue"),
  54        NULL
  55};
  56
  57static int show_diffstat = 1, shortlog_len = -1, squash;
  58static int option_commit = 1;
  59static int option_edit = -1;
  60static int allow_trivial = 1, have_message, verify_signatures;
  61static int overwrite_ignore = 1;
  62static struct strbuf merge_msg = STRBUF_INIT;
  63static struct strategy **use_strategies;
  64static size_t use_strategies_nr, use_strategies_alloc;
  65static const char **xopts;
  66static size_t xopts_nr, xopts_alloc;
  67static const char *branch;
  68static char *branch_mergeoptions;
  69static int option_renormalize;
  70static int verbosity;
  71static int allow_rerere_auto;
  72static int abort_current_merge;
  73static int continue_current_merge;
  74static int allow_unrelated_histories;
  75static int show_progress = -1;
  76static int default_to_upstream = 1;
  77static int signoff;
  78static const char *sign_commit;
  79static int verify_msg = 1;
  80
  81static struct strategy all_strategy[] = {
  82        { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  83        { "octopus",    DEFAULT_OCTOPUS },
  84        { "resolve",    0 },
  85        { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  86        { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  87};
  88
  89static const char *pull_twohead, *pull_octopus;
  90
  91enum ff_type {
  92        FF_NO,
  93        FF_ALLOW,
  94        FF_ONLY
  95};
  96
  97static enum ff_type fast_forward = FF_ALLOW;
  98
  99static int option_parse_message(const struct option *opt,
 100                                const char *arg, int unset)
 101{
 102        struct strbuf *buf = opt->value;
 103
 104        if (unset)
 105                strbuf_setlen(buf, 0);
 106        else if (arg) {
 107                strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
 108                have_message = 1;
 109        } else
 110                return error(_("switch `m' requires a value"));
 111        return 0;
 112}
 113
 114static int option_read_message(struct parse_opt_ctx_t *ctx,
 115                               const struct option *opt, int unset)
 116{
 117        struct strbuf *buf = opt->value;
 118        const char *arg;
 119
 120        if (unset)
 121                BUG("-F cannot be negated");
 122
 123        if (ctx->opt) {
 124                arg = ctx->opt;
 125                ctx->opt = NULL;
 126        } else if (ctx->argc > 1) {
 127                ctx->argc--;
 128                arg = *++ctx->argv;
 129        } else
 130                return opterror(opt, "requires a value", 0);
 131
 132        if (buf->len)
 133                strbuf_addch(buf, '\n');
 134        if (ctx->prefix && !is_absolute_path(arg))
 135                arg = prefix_filename(ctx->prefix, arg);
 136        if (strbuf_read_file(buf, arg, 0) < 0)
 137                return error(_("could not read file '%s'"), arg);
 138        have_message = 1;
 139
 140        return 0;
 141}
 142
 143static struct strategy *get_strategy(const char *name)
 144{
 145        int i;
 146        struct strategy *ret;
 147        static struct cmdnames main_cmds, other_cmds;
 148        static int loaded;
 149
 150        if (!name)
 151                return NULL;
 152
 153        for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 154                if (!strcmp(name, all_strategy[i].name))
 155                        return &all_strategy[i];
 156
 157        if (!loaded) {
 158                struct cmdnames not_strategies;
 159                loaded = 1;
 160
 161                memset(&not_strategies, 0, sizeof(struct cmdnames));
 162                load_command_list("git-merge-", &main_cmds, &other_cmds);
 163                for (i = 0; i < main_cmds.cnt; i++) {
 164                        int j, found = 0;
 165                        struct cmdname *ent = main_cmds.names[i];
 166                        for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 167                                if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 168                                                && !all_strategy[j].name[ent->len])
 169                                        found = 1;
 170                        if (!found)
 171                                add_cmdname(&not_strategies, ent->name, ent->len);
 172                }
 173                exclude_cmds(&main_cmds, &not_strategies);
 174        }
 175        if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 176                fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 177                fprintf(stderr, _("Available strategies are:"));
 178                for (i = 0; i < main_cmds.cnt; i++)
 179                        fprintf(stderr, " %s", main_cmds.names[i]->name);
 180                fprintf(stderr, ".\n");
 181                if (other_cmds.cnt) {
 182                        fprintf(stderr, _("Available custom strategies are:"));
 183                        for (i = 0; i < other_cmds.cnt; i++)
 184                                fprintf(stderr, " %s", other_cmds.names[i]->name);
 185                        fprintf(stderr, ".\n");
 186                }
 187                exit(1);
 188        }
 189
 190        ret = xcalloc(1, sizeof(struct strategy));
 191        ret->name = xstrdup(name);
 192        ret->attr = NO_TRIVIAL;
 193        return ret;
 194}
 195
 196static void append_strategy(struct strategy *s)
 197{
 198        ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 199        use_strategies[use_strategies_nr++] = s;
 200}
 201
 202static int option_parse_strategy(const struct option *opt,
 203                                 const char *name, int unset)
 204{
 205        if (unset)
 206                return 0;
 207
 208        append_strategy(get_strategy(name));
 209        return 0;
 210}
 211
 212static int option_parse_x(const struct option *opt,
 213                          const char *arg, int unset)
 214{
 215        if (unset)
 216                return 0;
 217
 218        ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 219        xopts[xopts_nr++] = xstrdup(arg);
 220        return 0;
 221}
 222
 223static int option_parse_n(const struct option *opt,
 224                          const char *arg, int unset)
 225{
 226        show_diffstat = unset;
 227        return 0;
 228}
 229
 230static struct option builtin_merge_options[] = {
 231        { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 232                N_("do not show a diffstat at the end of the merge"),
 233                PARSE_OPT_NOARG, option_parse_n },
 234        OPT_BOOL(0, "stat", &show_diffstat,
 235                N_("show a diffstat at the end of the merge")),
 236        OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
 237        { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
 238          N_("add (at most <n>) entries from shortlog to merge commit message"),
 239          PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 240        OPT_BOOL(0, "squash", &squash,
 241                N_("create a single commit instead of doing a merge")),
 242        OPT_BOOL(0, "commit", &option_commit,
 243                N_("perform a commit if the merge succeeds (default)")),
 244        OPT_BOOL('e', "edit", &option_edit,
 245                N_("edit message before committing")),
 246        OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
 247        OPT_SET_INT_F(0, "ff-only", &fast_forward,
 248                      N_("abort if fast-forward is not possible"),
 249                      FF_ONLY, PARSE_OPT_NONEG),
 250        OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 251        OPT_BOOL(0, "verify-signatures", &verify_signatures,
 252                N_("verify that the named commit has a valid GPG signature")),
 253        OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
 254                N_("merge strategy to use"), option_parse_strategy),
 255        OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
 256                N_("option for selected merge strategy"), option_parse_x),
 257        OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
 258                N_("merge commit message (for a non-fast-forward merge)"),
 259                option_parse_message),
 260        { OPTION_LOWLEVEL_CALLBACK, 'F', "file", &merge_msg, N_("path"),
 261                N_("read message from file"), PARSE_OPT_NONEG,
 262                (parse_opt_cb *) option_read_message },
 263        OPT__VERBOSITY(&verbosity),
 264        OPT_BOOL(0, "abort", &abort_current_merge,
 265                N_("abort the current in-progress merge")),
 266        OPT_BOOL(0, "continue", &continue_current_merge,
 267                N_("continue the current in-progress merge")),
 268        OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
 269                 N_("allow merging unrelated histories")),
 270        OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
 271        { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
 272          N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 273        OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
 274        OPT_BOOL(0, "signoff", &signoff, N_("add Signed-off-by:")),
 275        OPT_BOOL(0, "verify", &verify_msg, N_("verify commit-msg hook")),
 276        OPT_END()
 277};
 278
 279/* Cleans up metadata that is uninteresting after a succeeded merge. */
 280static void drop_save(void)
 281{
 282        unlink(git_path_merge_head(the_repository));
 283        unlink(git_path_merge_msg(the_repository));
 284        unlink(git_path_merge_mode(the_repository));
 285}
 286
 287static int save_state(struct object_id *stash)
 288{
 289        int len;
 290        struct child_process cp = CHILD_PROCESS_INIT;
 291        struct strbuf buffer = STRBUF_INIT;
 292        const char *argv[] = {"stash", "create", NULL};
 293        int rc = -1;
 294
 295        cp.argv = argv;
 296        cp.out = -1;
 297        cp.git_cmd = 1;
 298
 299        if (start_command(&cp))
 300                die(_("could not run stash."));
 301        len = strbuf_read(&buffer, cp.out, 1024);
 302        close(cp.out);
 303
 304        if (finish_command(&cp) || len < 0)
 305                die(_("stash failed"));
 306        else if (!len)          /* no changes */
 307                goto out;
 308        strbuf_setlen(&buffer, buffer.len-1);
 309        if (get_oid(buffer.buf, stash))
 310                die(_("not a valid object: %s"), buffer.buf);
 311        rc = 0;
 312out:
 313        strbuf_release(&buffer);
 314        return rc;
 315}
 316
 317static void read_empty(const struct object_id *oid, int verbose)
 318{
 319        int i = 0;
 320        const char *args[7];
 321
 322        args[i++] = "read-tree";
 323        if (verbose)
 324                args[i++] = "-v";
 325        args[i++] = "-m";
 326        args[i++] = "-u";
 327        args[i++] = empty_tree_oid_hex();
 328        args[i++] = oid_to_hex(oid);
 329        args[i] = NULL;
 330
 331        if (run_command_v_opt(args, RUN_GIT_CMD))
 332                die(_("read-tree failed"));
 333}
 334
 335static void reset_hard(const struct object_id *oid, int verbose)
 336{
 337        int i = 0;
 338        const char *args[6];
 339
 340        args[i++] = "read-tree";
 341        if (verbose)
 342                args[i++] = "-v";
 343        args[i++] = "--reset";
 344        args[i++] = "-u";
 345        args[i++] = oid_to_hex(oid);
 346        args[i] = NULL;
 347
 348        if (run_command_v_opt(args, RUN_GIT_CMD))
 349                die(_("read-tree failed"));
 350}
 351
 352static void restore_state(const struct object_id *head,
 353                          const struct object_id *stash)
 354{
 355        struct strbuf sb = STRBUF_INIT;
 356        const char *args[] = { "stash", "apply", NULL, NULL };
 357
 358        if (is_null_oid(stash))
 359                return;
 360
 361        reset_hard(head, 1);
 362
 363        args[2] = oid_to_hex(stash);
 364
 365        /*
 366         * It is OK to ignore error here, for example when there was
 367         * nothing to restore.
 368         */
 369        run_command_v_opt(args, RUN_GIT_CMD);
 370
 371        strbuf_release(&sb);
 372        refresh_cache(REFRESH_QUIET);
 373}
 374
 375/* This is called when no merge was necessary. */
 376static void finish_up_to_date(const char *msg)
 377{
 378        if (verbosity >= 0)
 379                printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 380        drop_save();
 381}
 382
 383static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 384{
 385        struct rev_info rev;
 386        struct strbuf out = STRBUF_INIT;
 387        struct commit_list *j;
 388        struct pretty_print_context ctx = {0};
 389
 390        printf(_("Squash commit -- not updating HEAD\n"));
 391
 392        init_revisions(&rev, NULL);
 393        rev.ignore_merges = 1;
 394        rev.commit_format = CMIT_FMT_MEDIUM;
 395
 396        commit->object.flags |= UNINTERESTING;
 397        add_pending_object(&rev, &commit->object, NULL);
 398
 399        for (j = remoteheads; j; j = j->next)
 400                add_pending_object(&rev, &j->item->object, NULL);
 401
 402        setup_revisions(0, NULL, &rev, NULL);
 403        if (prepare_revision_walk(&rev))
 404                die(_("revision walk setup failed"));
 405
 406        ctx.abbrev = rev.abbrev;
 407        ctx.date_mode = rev.date_mode;
 408        ctx.fmt = rev.commit_format;
 409
 410        strbuf_addstr(&out, "Squashed commit of the following:\n");
 411        while ((commit = get_revision(&rev)) != NULL) {
 412                strbuf_addch(&out, '\n');
 413                strbuf_addf(&out, "commit %s\n",
 414                        oid_to_hex(&commit->object.oid));
 415                pretty_print_commit(&ctx, commit, &out);
 416        }
 417        write_file_buf(git_path_squash_msg(the_repository), out.buf, out.len);
 418        strbuf_release(&out);
 419}
 420
 421static void finish(struct commit *head_commit,
 422                   struct commit_list *remoteheads,
 423                   const struct object_id *new_head, const char *msg)
 424{
 425        struct strbuf reflog_message = STRBUF_INIT;
 426        const struct object_id *head = &head_commit->object.oid;
 427
 428        if (!msg)
 429                strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 430        else {
 431                if (verbosity >= 0)
 432                        printf("%s\n", msg);
 433                strbuf_addf(&reflog_message, "%s: %s",
 434                        getenv("GIT_REFLOG_ACTION"), msg);
 435        }
 436        if (squash) {
 437                squash_message(head_commit, remoteheads);
 438        } else {
 439                if (verbosity >= 0 && !merge_msg.len)
 440                        printf(_("No merge message -- not updating HEAD\n"));
 441                else {
 442                        const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 443                        update_ref(reflog_message.buf, "HEAD", new_head, head,
 444                                   0, UPDATE_REFS_DIE_ON_ERR);
 445                        /*
 446                         * We ignore errors in 'gc --auto', since the
 447                         * user should see them.
 448                         */
 449                        close_all_packs(the_repository->objects);
 450                        run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 451                }
 452        }
 453        if (new_head && show_diffstat) {
 454                struct diff_options opts;
 455                diff_setup(&opts);
 456                opts.stat_width = -1; /* use full terminal width */
 457                opts.stat_graph_width = -1; /* respect statGraphWidth config */
 458                opts.output_format |=
 459                        DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 460                opts.detect_rename = DIFF_DETECT_RENAME;
 461                diff_setup_done(&opts);
 462                diff_tree_oid(head, new_head, "", &opts);
 463                diffcore_std(&opts);
 464                diff_flush(&opts);
 465        }
 466
 467        /* Run a post-merge hook */
 468        run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
 469
 470        strbuf_release(&reflog_message);
 471}
 472
 473/* Get the name for the merge commit's message. */
 474static void merge_name(const char *remote, struct strbuf *msg)
 475{
 476        struct commit *remote_head;
 477        struct object_id branch_head;
 478        struct strbuf buf = STRBUF_INIT;
 479        struct strbuf bname = STRBUF_INIT;
 480        struct merge_remote_desc *desc;
 481        const char *ptr;
 482        char *found_ref;
 483        int len, early;
 484
 485        strbuf_branchname(&bname, remote, 0);
 486        remote = bname.buf;
 487
 488        oidclr(&branch_head);
 489        remote_head = get_merge_parent(remote);
 490        if (!remote_head)
 491                die(_("'%s' does not point to a commit"), remote);
 492
 493        if (dwim_ref(remote, strlen(remote), &branch_head, &found_ref) > 0) {
 494                if (starts_with(found_ref, "refs/heads/")) {
 495                        strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 496                                    oid_to_hex(&branch_head), remote);
 497                        goto cleanup;
 498                }
 499                if (starts_with(found_ref, "refs/tags/")) {
 500                        strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 501                                    oid_to_hex(&branch_head), remote);
 502                        goto cleanup;
 503                }
 504                if (starts_with(found_ref, "refs/remotes/")) {
 505                        strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 506                                    oid_to_hex(&branch_head), remote);
 507                        goto cleanup;
 508                }
 509        }
 510
 511        /* See if remote matches <name>^^^.. or <name>~<number> */
 512        for (len = 0, ptr = remote + strlen(remote);
 513             remote < ptr && ptr[-1] == '^';
 514             ptr--)
 515                len++;
 516        if (len)
 517                early = 1;
 518        else {
 519                early = 0;
 520                ptr = strrchr(remote, '~');
 521                if (ptr) {
 522                        int seen_nonzero = 0;
 523
 524                        len++; /* count ~ */
 525                        while (*++ptr && isdigit(*ptr)) {
 526                                seen_nonzero |= (*ptr != '0');
 527                                len++;
 528                        }
 529                        if (*ptr)
 530                                len = 0; /* not ...~<number> */
 531                        else if (seen_nonzero)
 532                                early = 1;
 533                        else if (len == 1)
 534                                early = 1; /* "name~" is "name~1"! */
 535                }
 536        }
 537        if (len) {
 538                struct strbuf truname = STRBUF_INIT;
 539                strbuf_addf(&truname, "refs/heads/%s", remote);
 540                strbuf_setlen(&truname, truname.len - len);
 541                if (ref_exists(truname.buf)) {
 542                        strbuf_addf(msg,
 543                                    "%s\t\tbranch '%s'%s of .\n",
 544                                    oid_to_hex(&remote_head->object.oid),
 545                                    truname.buf + 11,
 546                                    (early ? " (early part)" : ""));
 547                        strbuf_release(&truname);
 548                        goto cleanup;
 549                }
 550                strbuf_release(&truname);
 551        }
 552
 553        desc = merge_remote_util(remote_head);
 554        if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 555                strbuf_addf(msg, "%s\t\t%s '%s'\n",
 556                            oid_to_hex(&desc->obj->oid),
 557                            type_name(desc->obj->type),
 558                            remote);
 559                goto cleanup;
 560        }
 561
 562        strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 563                oid_to_hex(&remote_head->object.oid), remote);
 564cleanup:
 565        strbuf_release(&buf);
 566        strbuf_release(&bname);
 567}
 568
 569static void parse_branch_merge_options(char *bmo)
 570{
 571        const char **argv;
 572        int argc;
 573
 574        if (!bmo)
 575                return;
 576        argc = split_cmdline(bmo, &argv);
 577        if (argc < 0)
 578                die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 579                    split_cmdline_strerror(argc));
 580        REALLOC_ARRAY(argv, argc + 2);
 581        MOVE_ARRAY(argv + 1, argv, argc + 1);
 582        argc++;
 583        argv[0] = "branch.*.mergeoptions";
 584        parse_options(argc, argv, NULL, builtin_merge_options,
 585                      builtin_merge_usage, 0);
 586        free(argv);
 587}
 588
 589static int git_merge_config(const char *k, const char *v, void *cb)
 590{
 591        int status;
 592
 593        if (branch && starts_with(k, "branch.") &&
 594                starts_with(k + 7, branch) &&
 595                !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 596                free(branch_mergeoptions);
 597                branch_mergeoptions = xstrdup(v);
 598                return 0;
 599        }
 600
 601        if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 602                show_diffstat = git_config_bool(k, v);
 603        else if (!strcmp(k, "merge.verifysignatures"))
 604                verify_signatures = git_config_bool(k, v);
 605        else if (!strcmp(k, "pull.twohead"))
 606                return git_config_string(&pull_twohead, k, v);
 607        else if (!strcmp(k, "pull.octopus"))
 608                return git_config_string(&pull_octopus, k, v);
 609        else if (!strcmp(k, "merge.renormalize"))
 610                option_renormalize = git_config_bool(k, v);
 611        else if (!strcmp(k, "merge.ff")) {
 612                int boolval = git_parse_maybe_bool(v);
 613                if (0 <= boolval) {
 614                        fast_forward = boolval ? FF_ALLOW : FF_NO;
 615                } else if (v && !strcmp(v, "only")) {
 616                        fast_forward = FF_ONLY;
 617                } /* do not barf on values from future versions of git */
 618                return 0;
 619        } else if (!strcmp(k, "merge.defaulttoupstream")) {
 620                default_to_upstream = git_config_bool(k, v);
 621                return 0;
 622        } else if (!strcmp(k, "commit.gpgsign")) {
 623                sign_commit = git_config_bool(k, v) ? "" : NULL;
 624                return 0;
 625        }
 626
 627        status = fmt_merge_msg_config(k, v, cb);
 628        if (status)
 629                return status;
 630        status = git_gpg_config(k, v, NULL);
 631        if (status)
 632                return status;
 633        return git_diff_ui_config(k, v, cb);
 634}
 635
 636static int read_tree_trivial(struct object_id *common, struct object_id *head,
 637                             struct object_id *one)
 638{
 639        int i, nr_trees = 0;
 640        struct tree *trees[MAX_UNPACK_TREES];
 641        struct tree_desc t[MAX_UNPACK_TREES];
 642        struct unpack_trees_options opts;
 643
 644        memset(&opts, 0, sizeof(opts));
 645        opts.head_idx = 2;
 646        opts.src_index = &the_index;
 647        opts.dst_index = &the_index;
 648        opts.update = 1;
 649        opts.verbose_update = 1;
 650        opts.trivial_merges_only = 1;
 651        opts.merge = 1;
 652        trees[nr_trees] = parse_tree_indirect(common);
 653        if (!trees[nr_trees++])
 654                return -1;
 655        trees[nr_trees] = parse_tree_indirect(head);
 656        if (!trees[nr_trees++])
 657                return -1;
 658        trees[nr_trees] = parse_tree_indirect(one);
 659        if (!trees[nr_trees++])
 660                return -1;
 661        opts.fn = threeway_merge;
 662        cache_tree_free(&active_cache_tree);
 663        for (i = 0; i < nr_trees; i++) {
 664                parse_tree(trees[i]);
 665                init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 666        }
 667        if (unpack_trees(nr_trees, t, &opts))
 668                return -1;
 669        return 0;
 670}
 671
 672static void write_tree_trivial(struct object_id *oid)
 673{
 674        if (write_cache_as_tree(oid, 0, NULL))
 675                die(_("git write-tree failed to write a tree"));
 676}
 677
 678static int try_merge_strategy(const char *strategy, struct commit_list *common,
 679                              struct commit_list *remoteheads,
 680                              struct commit *head)
 681{
 682        struct lock_file lock = LOCK_INIT;
 683        const char *head_arg = "HEAD";
 684
 685        hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 686        refresh_cache(REFRESH_QUIET);
 687        if (write_locked_index(&the_index, &lock,
 688                               COMMIT_LOCK | SKIP_IF_UNCHANGED))
 689                return error(_("Unable to write index."));
 690
 691        if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 692                int clean, x;
 693                struct commit *result;
 694                struct commit_list *reversed = NULL;
 695                struct merge_options o;
 696                struct commit_list *j;
 697
 698                if (remoteheads->next) {
 699                        error(_("Not handling anything other than two heads merge."));
 700                        return 2;
 701                }
 702
 703                init_merge_options(&o);
 704                if (!strcmp(strategy, "subtree"))
 705                        o.subtree_shift = "";
 706
 707                o.renormalize = option_renormalize;
 708                o.show_rename_progress =
 709                        show_progress == -1 ? isatty(2) : show_progress;
 710
 711                for (x = 0; x < xopts_nr; x++)
 712                        if (parse_merge_opt(&o, xopts[x]))
 713                                die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 714
 715                o.branch1 = head_arg;
 716                o.branch2 = merge_remote_util(remoteheads->item)->name;
 717
 718                for (j = common; j; j = j->next)
 719                        commit_list_insert(j->item, &reversed);
 720
 721                hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 722                clean = merge_recursive(&o, head,
 723                                remoteheads->item, reversed, &result);
 724                if (clean < 0)
 725                        exit(128);
 726                if (write_locked_index(&the_index, &lock,
 727                                       COMMIT_LOCK | SKIP_IF_UNCHANGED))
 728                        die(_("unable to write %s"), get_index_file());
 729                return clean ? 0 : 1;
 730        } else {
 731                return try_merge_command(strategy, xopts_nr, xopts,
 732                                                common, head_arg, remoteheads);
 733        }
 734}
 735
 736static 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
 744static 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
 755static 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
 774static 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
 782static void write_merge_state(struct commit_list *);
 783static 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
 793static const char merge_editor_comment[] =
 794N_("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
 800static void write_merge_heads(struct commit_list *);
 801static 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
 836static 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        drop_save();
 858        return 0;
 859}
 860
 861static 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        drop_save();
 885        return 0;
 886}
 887
 888static 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(&msgbuf);
 898        fputs(msgbuf.buf, fp);
 899        strbuf_release(&msgbuf);
 900        fclose(fp);
 901        rerere(allow_rerere_auto);
 902        printf(_("Automatic merge failed; "
 903                        "fix conflicts and then commit the result.\n"));
 904        return 1;
 905}
 906
 907static int evaluate_result(void)
 908{
 909        int cnt = 0;
 910        struct rev_info rev;
 911
 912        /* Check how many files differ. */
 913        init_revisions(&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 */
 934static 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
 959static 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
 986static 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
 994static 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
1020static 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
1051static 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
1065static 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
1120static 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
1163static 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
1200int 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 (continue_current_merge) {
1259                int nargc = 1;
1260                const char *nargv[] = {"commit", NULL};
1261
1262                if (orig_argc != 2)
1263                        usage_msg_opt(_("--continue expects no arguments"),
1264                              builtin_merge_usage, builtin_merge_options);
1265
1266                if (!file_exists(git_path_merge_head(the_repository)))
1267                        die(_("There is no merge in progress (MERGE_HEAD missing)."));
1268
1269                /* Invoke 'git commit' */
1270                ret = cmd_commit(nargc, nargv, prefix);
1271                goto done;
1272        }
1273
1274        if (read_cache_unmerged())
1275                die_resolve_conflict("merge");
1276
1277        if (file_exists(git_path_merge_head(the_repository))) {
1278                /*
1279                 * There is no unmerged entry, don't advise 'git
1280                 * add/rm <file>', just 'git commit'.
1281                 */
1282                if (advice_resolve_conflict)
1283                        die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1284                                  "Please, commit your changes before you merge."));
1285                else
1286                        die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1287        }
1288        if (file_exists(git_path_cherry_pick_head(the_repository))) {
1289                if (advice_resolve_conflict)
1290                        die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1291                            "Please, commit your changes before you merge."));
1292                else
1293                        die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1294        }
1295        resolve_undo_clear();
1296
1297        if (verbosity < 0)
1298                show_diffstat = 0;
1299
1300        if (squash) {
1301                if (fast_forward == FF_NO)
1302                        die(_("You cannot combine --squash with --no-ff."));
1303                option_commit = 0;
1304        }
1305
1306        if (!argc) {
1307                if (default_to_upstream)
1308                        argc = setup_with_upstream(&argv);
1309                else
1310                        die(_("No commit specified and merge.defaultToUpstream not set."));
1311        } else if (argc == 1 && !strcmp(argv[0], "-")) {
1312                argv[0] = "@{-1}";
1313        }
1314
1315        if (!argc)
1316                usage_with_options(builtin_merge_usage,
1317                        builtin_merge_options);
1318
1319        if (!head_commit) {
1320                /*
1321                 * If the merged head is a valid one there is no reason
1322                 * to forbid "git merge" into a branch yet to be born.
1323                 * We do the same for "git pull".
1324                 */
1325                struct object_id *remote_head_oid;
1326                if (squash)
1327                        die(_("Squash commit into empty head not supported yet"));
1328                if (fast_forward == FF_NO)
1329                        die(_("Non-fast-forward commit does not make sense into "
1330                            "an empty head"));
1331                remoteheads = collect_parents(head_commit, &head_subsumed,
1332                                              argc, argv, NULL);
1333                if (!remoteheads)
1334                        die(_("%s - not something we can merge"), argv[0]);
1335                if (remoteheads->next)
1336                        die(_("Can merge only exactly one commit into empty head"));
1337                remote_head_oid = &remoteheads->item->object.oid;
1338                read_empty(remote_head_oid, 0);
1339                update_ref("initial pull", "HEAD", remote_head_oid, NULL, 0,
1340                           UPDATE_REFS_DIE_ON_ERR);
1341                goto done;
1342        }
1343
1344        /*
1345         * All the rest are the commits being merged; prepare
1346         * the standard merge summary message to be appended
1347         * to the given message.
1348         */
1349        remoteheads = collect_parents(head_commit, &head_subsumed,
1350                                      argc, argv, &merge_msg);
1351
1352        if (!head_commit || !argc)
1353                usage_with_options(builtin_merge_usage,
1354                        builtin_merge_options);
1355
1356        if (verify_signatures) {
1357                for (p = remoteheads; p; p = p->next) {
1358                        struct commit *commit = p->item;
1359                        char hex[GIT_MAX_HEXSZ + 1];
1360                        struct signature_check signature_check;
1361                        memset(&signature_check, 0, sizeof(signature_check));
1362
1363                        check_commit_signature(commit, &signature_check);
1364
1365                        find_unique_abbrev_r(hex, &commit->object.oid, DEFAULT_ABBREV);
1366                        switch (signature_check.result) {
1367                        case 'G':
1368                                break;
1369                        case 'U':
1370                                die(_("Commit %s has an untrusted GPG signature, "
1371                                      "allegedly by %s."), hex, signature_check.signer);
1372                        case 'B':
1373                                die(_("Commit %s has a bad GPG signature "
1374                                      "allegedly by %s."), hex, signature_check.signer);
1375                        default: /* 'N' */
1376                                die(_("Commit %s does not have a GPG signature."), hex);
1377                        }
1378                        if (verbosity >= 0 && signature_check.result == 'G')
1379                                printf(_("Commit %s has a good GPG signature by %s\n"),
1380                                       hex, signature_check.signer);
1381
1382                        signature_check_clear(&signature_check);
1383                }
1384        }
1385
1386        strbuf_addstr(&buf, "merge");
1387        for (p = remoteheads; p; p = p->next)
1388                strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1389        setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1390        strbuf_reset(&buf);
1391
1392        for (p = remoteheads; p; p = p->next) {
1393                struct commit *commit = p->item;
1394                strbuf_addf(&buf, "GITHEAD_%s",
1395                            oid_to_hex(&commit->object.oid));
1396                setenv(buf.buf, merge_remote_util(commit)->name, 1);
1397                strbuf_reset(&buf);
1398                if (fast_forward != FF_ONLY && merging_a_throwaway_tag(commit))
1399                        fast_forward = FF_NO;
1400        }
1401
1402        if (option_edit < 0)
1403                option_edit = default_edit_option();
1404
1405        if (!use_strategies) {
1406                if (!remoteheads)
1407                        ; /* already up-to-date */
1408                else if (!remoteheads->next)
1409                        add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1410                else
1411                        add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1412        }
1413
1414        for (i = 0; i < use_strategies_nr; i++) {
1415                if (use_strategies[i]->attr & NO_FAST_FORWARD)
1416                        fast_forward = FF_NO;
1417                if (use_strategies[i]->attr & NO_TRIVIAL)
1418                        allow_trivial = 0;
1419        }
1420
1421        if (!remoteheads)
1422                ; /* already up-to-date */
1423        else if (!remoteheads->next)
1424                common = get_merge_bases(head_commit, remoteheads->item);
1425        else {
1426                struct commit_list *list = remoteheads;
1427                commit_list_insert(head_commit, &list);
1428                common = get_octopus_merge_bases(list);
1429                free(list);
1430        }
1431
1432        update_ref("updating ORIG_HEAD", "ORIG_HEAD",
1433                   &head_commit->object.oid, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1434
1435        if (remoteheads && !common) {
1436                /* No common ancestors found. */
1437                if (!allow_unrelated_histories)
1438                        die(_("refusing to merge unrelated histories"));
1439                /* otherwise, we need a real merge. */
1440        } else if (!remoteheads ||
1441                 (!remoteheads->next && !common->next &&
1442                  common->item == remoteheads->item)) {
1443                /*
1444                 * If head can reach all the merge then we are up to date.
1445                 * but first the most common case of merging one remote.
1446                 */
1447                finish_up_to_date(_("Already up to date."));
1448                goto done;
1449        } else if (fast_forward != FF_NO && !remoteheads->next &&
1450                        !common->next &&
1451                        oideq(&common->item->object.oid, &head_commit->object.oid)) {
1452                /* Again the most common case of merging one remote. */
1453                struct strbuf msg = STRBUF_INIT;
1454                struct commit *commit;
1455
1456                if (verbosity >= 0) {
1457                        printf(_("Updating %s..%s\n"),
1458                               find_unique_abbrev(&head_commit->object.oid,
1459                                                  DEFAULT_ABBREV),
1460                               find_unique_abbrev(&remoteheads->item->object.oid,
1461                                                  DEFAULT_ABBREV));
1462                }
1463                strbuf_addstr(&msg, "Fast-forward");
1464                if (have_message)
1465                        strbuf_addstr(&msg,
1466                                " (no commit created; -m option ignored)");
1467                commit = remoteheads->item;
1468                if (!commit) {
1469                        ret = 1;
1470                        goto done;
1471                }
1472
1473                if (checkout_fast_forward(&head_commit->object.oid,
1474                                          &commit->object.oid,
1475                                          overwrite_ignore)) {
1476                        ret = 1;
1477                        goto done;
1478                }
1479
1480                finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
1481                drop_save();
1482                goto done;
1483        } else if (!remoteheads->next && common->next)
1484                ;
1485                /*
1486                 * We are not doing octopus and not fast-forward.  Need
1487                 * a real merge.
1488                 */
1489        else if (!remoteheads->next && !common->next && option_commit) {
1490                /*
1491                 * We are not doing octopus, not fast-forward, and have
1492                 * only one common.
1493                 */
1494                refresh_cache(REFRESH_QUIET);
1495                if (allow_trivial && fast_forward != FF_ONLY) {
1496                        /* See if it is really trivial. */
1497                        git_committer_info(IDENT_STRICT);
1498                        printf(_("Trying really trivial in-index merge...\n"));
1499                        if (!read_tree_trivial(&common->item->object.oid,
1500                                               &head_commit->object.oid,
1501                                               &remoteheads->item->object.oid)) {
1502                                ret = merge_trivial(head_commit, remoteheads);
1503                                goto done;
1504                        }
1505                        printf(_("Nope.\n"));
1506                }
1507        } else {
1508                /*
1509                 * An octopus.  If we can reach all the remote we are up
1510                 * to date.
1511                 */
1512                int up_to_date = 1;
1513                struct commit_list *j;
1514
1515                for (j = remoteheads; j; j = j->next) {
1516                        struct commit_list *common_one;
1517
1518                        /*
1519                         * Here we *have* to calculate the individual
1520                         * merge_bases again, otherwise "git merge HEAD^
1521                         * HEAD^^" would be missed.
1522                         */
1523                        common_one = get_merge_bases(head_commit, j->item);
1524                        if (!oideq(&common_one->item->object.oid, &j->item->object.oid)) {
1525                                up_to_date = 0;
1526                                break;
1527                        }
1528                }
1529                if (up_to_date) {
1530                        finish_up_to_date(_("Already up to date. Yeeah!"));
1531                        goto done;
1532                }
1533        }
1534
1535        if (fast_forward == FF_ONLY)
1536                die(_("Not possible to fast-forward, aborting."));
1537
1538        /* We are going to make a new commit. */
1539        git_committer_info(IDENT_STRICT);
1540
1541        /*
1542         * At this point, we need a real merge.  No matter what strategy
1543         * we use, it would operate on the index, possibly affecting the
1544         * working tree, and when resolved cleanly, have the desired
1545         * tree in the index -- this means that the index must be in
1546         * sync with the head commit.  The strategies are responsible
1547         * to ensure this.
1548         */
1549        if (use_strategies_nr == 1 ||
1550            /*
1551             * Stash away the local changes so that we can try more than one.
1552             */
1553            save_state(&stash))
1554                oidclr(&stash);
1555
1556        for (i = 0; i < use_strategies_nr; i++) {
1557                int ret;
1558                if (i) {
1559                        printf(_("Rewinding the tree to pristine...\n"));
1560                        restore_state(&head_commit->object.oid, &stash);
1561                }
1562                if (use_strategies_nr != 1)
1563                        printf(_("Trying merge strategy %s...\n"),
1564                                use_strategies[i]->name);
1565                /*
1566                 * Remember which strategy left the state in the working
1567                 * tree.
1568                 */
1569                wt_strategy = use_strategies[i]->name;
1570
1571                ret = try_merge_strategy(use_strategies[i]->name,
1572                                         common, remoteheads,
1573                                         head_commit);
1574                if (!option_commit && !ret) {
1575                        merge_was_ok = 1;
1576                        /*
1577                         * This is necessary here just to avoid writing
1578                         * the tree, but later we will *not* exit with
1579                         * status code 1 because merge_was_ok is set.
1580                         */
1581                        ret = 1;
1582                }
1583
1584                if (ret) {
1585                        /*
1586                         * The backend exits with 1 when conflicts are
1587                         * left to be resolved, with 2 when it does not
1588                         * handle the given merge at all.
1589                         */
1590                        if (ret == 1) {
1591                                int cnt = evaluate_result();
1592
1593                                if (best_cnt <= 0 || cnt <= best_cnt) {
1594                                        best_strategy = use_strategies[i]->name;
1595                                        best_cnt = cnt;
1596                                }
1597                        }
1598                        if (merge_was_ok)
1599                                break;
1600                        else
1601                                continue;
1602                }
1603
1604                /* Automerge succeeded. */
1605                write_tree_trivial(&result_tree);
1606                automerge_was_ok = 1;
1607                break;
1608        }
1609
1610        /*
1611         * If we have a resulting tree, that means the strategy module
1612         * auto resolved the merge cleanly.
1613         */
1614        if (automerge_was_ok) {
1615                ret = finish_automerge(head_commit, head_subsumed,
1616                                       common, remoteheads,
1617                                       &result_tree, wt_strategy);
1618                goto done;
1619        }
1620
1621        /*
1622         * Pick the result from the best strategy and have the user fix
1623         * it up.
1624         */
1625        if (!best_strategy) {
1626                restore_state(&head_commit->object.oid, &stash);
1627                if (use_strategies_nr > 1)
1628                        fprintf(stderr,
1629                                _("No merge strategy handled the merge.\n"));
1630                else
1631                        fprintf(stderr, _("Merge with strategy %s failed.\n"),
1632                                use_strategies[0]->name);
1633                ret = 2;
1634                goto done;
1635        } else if (best_strategy == wt_strategy)
1636                ; /* We already have its result in the working tree. */
1637        else {
1638                printf(_("Rewinding the tree to pristine...\n"));
1639                restore_state(&head_commit->object.oid, &stash);
1640                printf(_("Using the %s to prepare resolving by hand.\n"),
1641                        best_strategy);
1642                try_merge_strategy(best_strategy, common, remoteheads,
1643                                   head_commit);
1644        }
1645
1646        if (squash)
1647                finish(head_commit, remoteheads, NULL, NULL);
1648        else
1649                write_merge_state(remoteheads);
1650
1651        if (merge_was_ok)
1652                fprintf(stderr, _("Automatic merge went well; "
1653                        "stopped before committing as requested\n"));
1654        else
1655                ret = suggest_conflicts();
1656
1657done:
1658        free(branch_to_free);
1659        return ret;
1660}