builtin / merge.con commit Merge branch 'nd/the-index' (cde5554)
   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#include "commit-reach.h"
  40
  41#define DEFAULT_TWOHEAD (1<<0)
  42#define DEFAULT_OCTOPUS (1<<1)
  43#define NO_FAST_FORWARD (1<<2)
  44#define NO_TRIVIAL      (1<<3)
  45
  46struct strategy {
  47        const char *name;
  48        unsigned attr;
  49};
  50
  51static const char * const builtin_merge_usage[] = {
  52        N_("git merge [<options>] [<commit>...]"),
  53        N_("git merge --abort"),
  54        N_("git merge --continue"),
  55        NULL
  56};
  57
  58static int show_diffstat = 1, shortlog_len = -1, squash;
  59static int option_commit = 1;
  60static int option_edit = -1;
  61static int allow_trivial = 1, have_message, verify_signatures;
  62static int overwrite_ignore = 1;
  63static struct strbuf merge_msg = STRBUF_INIT;
  64static struct strategy **use_strategies;
  65static size_t use_strategies_nr, use_strategies_alloc;
  66static const char **xopts;
  67static size_t xopts_nr, xopts_alloc;
  68static const char *branch;
  69static char *branch_mergeoptions;
  70static int option_renormalize;
  71static int verbosity;
  72static int allow_rerere_auto;
  73static int abort_current_merge;
  74static int continue_current_merge;
  75static int allow_unrelated_histories;
  76static int show_progress = -1;
  77static int default_to_upstream = 1;
  78static int signoff;
  79static const char *sign_commit;
  80static int verify_msg = 1;
  81
  82static struct strategy all_strategy[] = {
  83        { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  84        { "octopus",    DEFAULT_OCTOPUS },
  85        { "resolve",    0 },
  86        { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  87        { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  88};
  89
  90static const char *pull_twohead, *pull_octopus;
  91
  92enum ff_type {
  93        FF_NO,
  94        FF_ALLOW,
  95        FF_ONLY
  96};
  97
  98static enum ff_type fast_forward = FF_ALLOW;
  99
 100static int option_parse_message(const struct option *opt,
 101                                const char *arg, int unset)
 102{
 103        struct strbuf *buf = opt->value;
 104
 105        if (unset)
 106                strbuf_setlen(buf, 0);
 107        else if (arg) {
 108                strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
 109                have_message = 1;
 110        } else
 111                return error(_("switch `m' requires a value"));
 112        return 0;
 113}
 114
 115static int option_read_message(struct parse_opt_ctx_t *ctx,
 116                               const struct option *opt, int unset)
 117{
 118        struct strbuf *buf = opt->value;
 119        const char *arg;
 120
 121        if (unset)
 122                BUG("-F cannot be negated");
 123
 124        if (ctx->opt) {
 125                arg = ctx->opt;
 126                ctx->opt = NULL;
 127        } else if (ctx->argc > 1) {
 128                ctx->argc--;
 129                arg = *++ctx->argv;
 130        } else
 131                return error(_("option `%s' requires a value"), opt->long_name);
 132
 133        if (buf->len)
 134                strbuf_addch(buf, '\n');
 135        if (ctx->prefix && !is_absolute_path(arg))
 136                arg = prefix_filename(ctx->prefix, arg);
 137        if (strbuf_read_file(buf, arg, 0) < 0)
 138                return error(_("could not read file '%s'"), arg);
 139        have_message = 1;
 140
 141        return 0;
 142}
 143
 144static struct strategy *get_strategy(const char *name)
 145{
 146        int i;
 147        struct strategy *ret;
 148        static struct cmdnames main_cmds, other_cmds;
 149        static int loaded;
 150
 151        if (!name)
 152                return NULL;
 153
 154        for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 155                if (!strcmp(name, all_strategy[i].name))
 156                        return &all_strategy[i];
 157
 158        if (!loaded) {
 159                struct cmdnames not_strategies;
 160                loaded = 1;
 161
 162                memset(&not_strategies, 0, sizeof(struct cmdnames));
 163                load_command_list("git-merge-", &main_cmds, &other_cmds);
 164                for (i = 0; i < main_cmds.cnt; i++) {
 165                        int j, found = 0;
 166                        struct cmdname *ent = main_cmds.names[i];
 167                        for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 168                                if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 169                                                && !all_strategy[j].name[ent->len])
 170                                        found = 1;
 171                        if (!found)
 172                                add_cmdname(&not_strategies, ent->name, ent->len);
 173                }
 174                exclude_cmds(&main_cmds, &not_strategies);
 175        }
 176        if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 177                fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 178                fprintf(stderr, _("Available strategies are:"));
 179                for (i = 0; i < main_cmds.cnt; i++)
 180                        fprintf(stderr, " %s", main_cmds.names[i]->name);
 181                fprintf(stderr, ".\n");
 182                if (other_cmds.cnt) {
 183                        fprintf(stderr, _("Available custom strategies are:"));
 184                        for (i = 0; i < other_cmds.cnt; i++)
 185                                fprintf(stderr, " %s", other_cmds.names[i]->name);
 186                        fprintf(stderr, ".\n");
 187                }
 188                exit(1);
 189        }
 190
 191        ret = xcalloc(1, sizeof(struct strategy));
 192        ret->name = xstrdup(name);
 193        ret->attr = NO_TRIVIAL;
 194        return ret;
 195}
 196
 197static void append_strategy(struct strategy *s)
 198{
 199        ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 200        use_strategies[use_strategies_nr++] = s;
 201}
 202
 203static int option_parse_strategy(const struct option *opt,
 204                                 const char *name, int unset)
 205{
 206        if (unset)
 207                return 0;
 208
 209        append_strategy(get_strategy(name));
 210        return 0;
 211}
 212
 213static int option_parse_x(const struct option *opt,
 214                          const char *arg, int unset)
 215{
 216        if (unset)
 217                return 0;
 218
 219        ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 220        xopts[xopts_nr++] = xstrdup(arg);
 221        return 0;
 222}
 223
 224static int option_parse_n(const struct option *opt,
 225                          const char *arg, int unset)
 226{
 227        BUG_ON_OPT_ARG(arg);
 228        show_diffstat = unset;
 229        return 0;
 230}
 231
 232static struct option builtin_merge_options[] = {
 233        { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 234                N_("do not show a diffstat at the end of the merge"),
 235                PARSE_OPT_NOARG, option_parse_n },
 236        OPT_BOOL(0, "stat", &show_diffstat,
 237                N_("show a diffstat at the end of the merge")),
 238        OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
 239        { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
 240          N_("add (at most <n>) entries from shortlog to merge commit message"),
 241          PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 242        OPT_BOOL(0, "squash", &squash,
 243                N_("create a single commit instead of doing a merge")),
 244        OPT_BOOL(0, "commit", &option_commit,
 245                N_("perform a commit if the merge succeeds (default)")),
 246        OPT_BOOL('e', "edit", &option_edit,
 247                N_("edit message before committing")),
 248        OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
 249        OPT_SET_INT_F(0, "ff-only", &fast_forward,
 250                      N_("abort if fast-forward is not possible"),
 251                      FF_ONLY, PARSE_OPT_NONEG),
 252        OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 253        OPT_BOOL(0, "verify-signatures", &verify_signatures,
 254                N_("verify that the named commit has a valid GPG signature")),
 255        OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
 256                N_("merge strategy to use"), option_parse_strategy),
 257        OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
 258                N_("option for selected merge strategy"), option_parse_x),
 259        OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
 260                N_("merge commit message (for a non-fast-forward merge)"),
 261                option_parse_message),
 262        { OPTION_LOWLEVEL_CALLBACK, 'F', "file", &merge_msg, N_("path"),
 263                N_("read message from file"), PARSE_OPT_NONEG,
 264                (parse_opt_cb *) option_read_message },
 265        OPT__VERBOSITY(&verbosity),
 266        OPT_BOOL(0, "abort", &abort_current_merge,
 267                N_("abort the current in-progress merge")),
 268        OPT_BOOL(0, "continue", &continue_current_merge,
 269                N_("continue the current in-progress merge")),
 270        OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
 271                 N_("allow merging unrelated histories")),
 272        OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
 273        { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
 274          N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 275        OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
 276        OPT_BOOL(0, "signoff", &signoff, N_("add Signed-off-by:")),
 277        OPT_BOOL(0, "verify", &verify_msg, N_("verify commit-msg hook")),
 278        OPT_END()
 279};
 280
 281/* Cleans up metadata that is uninteresting after a succeeded merge. */
 282static void drop_save(void)
 283{
 284        unlink(git_path_merge_head(the_repository));
 285        unlink(git_path_merge_msg(the_repository));
 286        unlink(git_path_merge_mode(the_repository));
 287}
 288
 289static int save_state(struct object_id *stash)
 290{
 291        int len;
 292        struct child_process cp = CHILD_PROCESS_INIT;
 293        struct strbuf buffer = STRBUF_INIT;
 294        const char *argv[] = {"stash", "create", NULL};
 295        int rc = -1;
 296
 297        cp.argv = argv;
 298        cp.out = -1;
 299        cp.git_cmd = 1;
 300
 301        if (start_command(&cp))
 302                die(_("could not run stash."));
 303        len = strbuf_read(&buffer, cp.out, 1024);
 304        close(cp.out);
 305
 306        if (finish_command(&cp) || len < 0)
 307                die(_("stash failed"));
 308        else if (!len)          /* no changes */
 309                goto out;
 310        strbuf_setlen(&buffer, buffer.len-1);
 311        if (get_oid(buffer.buf, stash))
 312                die(_("not a valid object: %s"), buffer.buf);
 313        rc = 0;
 314out:
 315        strbuf_release(&buffer);
 316        return rc;
 317}
 318
 319static void read_empty(const struct object_id *oid, int verbose)
 320{
 321        int i = 0;
 322        const char *args[7];
 323
 324        args[i++] = "read-tree";
 325        if (verbose)
 326                args[i++] = "-v";
 327        args[i++] = "-m";
 328        args[i++] = "-u";
 329        args[i++] = empty_tree_oid_hex();
 330        args[i++] = oid_to_hex(oid);
 331        args[i] = NULL;
 332
 333        if (run_command_v_opt(args, RUN_GIT_CMD))
 334                die(_("read-tree failed"));
 335}
 336
 337static void reset_hard(const struct object_id *oid, int verbose)
 338{
 339        int i = 0;
 340        const char *args[6];
 341
 342        args[i++] = "read-tree";
 343        if (verbose)
 344                args[i++] = "-v";
 345        args[i++] = "--reset";
 346        args[i++] = "-u";
 347        args[i++] = oid_to_hex(oid);
 348        args[i] = NULL;
 349
 350        if (run_command_v_opt(args, RUN_GIT_CMD))
 351                die(_("read-tree failed"));
 352}
 353
 354static void restore_state(const struct object_id *head,
 355                          const struct object_id *stash)
 356{
 357        struct strbuf sb = STRBUF_INIT;
 358        const char *args[] = { "stash", "apply", NULL, NULL };
 359
 360        if (is_null_oid(stash))
 361                return;
 362
 363        reset_hard(head, 1);
 364
 365        args[2] = oid_to_hex(stash);
 366
 367        /*
 368         * It is OK to ignore error here, for example when there was
 369         * nothing to restore.
 370         */
 371        run_command_v_opt(args, RUN_GIT_CMD);
 372
 373        strbuf_release(&sb);
 374        refresh_cache(REFRESH_QUIET);
 375}
 376
 377/* This is called when no merge was necessary. */
 378static void finish_up_to_date(const char *msg)
 379{
 380        if (verbosity >= 0)
 381                printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 382        drop_save();
 383}
 384
 385static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 386{
 387        struct rev_info rev;
 388        struct strbuf out = STRBUF_INIT;
 389        struct commit_list *j;
 390        struct pretty_print_context ctx = {0};
 391
 392        printf(_("Squash commit -- not updating HEAD\n"));
 393
 394        repo_init_revisions(the_repository, &rev, NULL);
 395        rev.ignore_merges = 1;
 396        rev.commit_format = CMIT_FMT_MEDIUM;
 397
 398        commit->object.flags |= UNINTERESTING;
 399        add_pending_object(&rev, &commit->object, NULL);
 400
 401        for (j = remoteheads; j; j = j->next)
 402                add_pending_object(&rev, &j->item->object, NULL);
 403
 404        setup_revisions(0, NULL, &rev, NULL);
 405        if (prepare_revision_walk(&rev))
 406                die(_("revision walk setup failed"));
 407
 408        ctx.abbrev = rev.abbrev;
 409        ctx.date_mode = rev.date_mode;
 410        ctx.fmt = rev.commit_format;
 411
 412        strbuf_addstr(&out, "Squashed commit of the following:\n");
 413        while ((commit = get_revision(&rev)) != NULL) {
 414                strbuf_addch(&out, '\n');
 415                strbuf_addf(&out, "commit %s\n",
 416                        oid_to_hex(&commit->object.oid));
 417                pretty_print_commit(&ctx, commit, &out);
 418        }
 419        write_file_buf(git_path_squash_msg(the_repository), out.buf, out.len);
 420        strbuf_release(&out);
 421}
 422
 423static void finish(struct commit *head_commit,
 424                   struct commit_list *remoteheads,
 425                   const struct object_id *new_head, const char *msg)
 426{
 427        struct strbuf reflog_message = STRBUF_INIT;
 428        const struct object_id *head = &head_commit->object.oid;
 429
 430        if (!msg)
 431                strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 432        else {
 433                if (verbosity >= 0)
 434                        printf("%s\n", msg);
 435                strbuf_addf(&reflog_message, "%s: %s",
 436                        getenv("GIT_REFLOG_ACTION"), msg);
 437        }
 438        if (squash) {
 439                squash_message(head_commit, remoteheads);
 440        } else {
 441                if (verbosity >= 0 && !merge_msg.len)
 442                        printf(_("No merge message -- not updating HEAD\n"));
 443                else {
 444                        const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 445                        update_ref(reflog_message.buf, "HEAD", new_head, head,
 446                                   0, UPDATE_REFS_DIE_ON_ERR);
 447                        /*
 448                         * We ignore errors in 'gc --auto', since the
 449                         * user should see them.
 450                         */
 451                        close_all_packs(the_repository->objects);
 452                        run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 453                }
 454        }
 455        if (new_head && show_diffstat) {
 456                struct diff_options opts;
 457                repo_diff_setup(the_repository, &opts);
 458                opts.stat_width = -1; /* use full terminal width */
 459                opts.stat_graph_width = -1; /* respect statGraphWidth config */
 460                opts.output_format |=
 461                        DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 462                opts.detect_rename = DIFF_DETECT_RENAME;
 463                diff_setup_done(&opts);
 464                diff_tree_oid(head, new_head, "", &opts);
 465                diffcore_std(&opts);
 466                diff_flush(&opts);
 467        }
 468
 469        /* Run a post-merge hook */
 470        run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
 471
 472        strbuf_release(&reflog_message);
 473}
 474
 475/* Get the name for the merge commit's message. */
 476static void merge_name(const char *remote, struct strbuf *msg)
 477{
 478        struct commit *remote_head;
 479        struct object_id branch_head;
 480        struct strbuf buf = STRBUF_INIT;
 481        struct strbuf bname = STRBUF_INIT;
 482        struct merge_remote_desc *desc;
 483        const char *ptr;
 484        char *found_ref;
 485        int len, early;
 486
 487        strbuf_branchname(&bname, remote, 0);
 488        remote = bname.buf;
 489
 490        oidclr(&branch_head);
 491        remote_head = get_merge_parent(remote);
 492        if (!remote_head)
 493                die(_("'%s' does not point to a commit"), remote);
 494
 495        if (dwim_ref(remote, strlen(remote), &branch_head, &found_ref) > 0) {
 496                if (starts_with(found_ref, "refs/heads/")) {
 497                        strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 498                                    oid_to_hex(&branch_head), remote);
 499                        goto cleanup;
 500                }
 501                if (starts_with(found_ref, "refs/tags/")) {
 502                        strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 503                                    oid_to_hex(&branch_head), remote);
 504                        goto cleanup;
 505                }
 506                if (starts_with(found_ref, "refs/remotes/")) {
 507                        strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 508                                    oid_to_hex(&branch_head), remote);
 509                        goto cleanup;
 510                }
 511        }
 512
 513        /* See if remote matches <name>^^^.. or <name>~<number> */
 514        for (len = 0, ptr = remote + strlen(remote);
 515             remote < ptr && ptr[-1] == '^';
 516             ptr--)
 517                len++;
 518        if (len)
 519                early = 1;
 520        else {
 521                early = 0;
 522                ptr = strrchr(remote, '~');
 523                if (ptr) {
 524                        int seen_nonzero = 0;
 525
 526                        len++; /* count ~ */
 527                        while (*++ptr && isdigit(*ptr)) {
 528                                seen_nonzero |= (*ptr != '0');
 529                                len++;
 530                        }
 531                        if (*ptr)
 532                                len = 0; /* not ...~<number> */
 533                        else if (seen_nonzero)
 534                                early = 1;
 535                        else if (len == 1)
 536                                early = 1; /* "name~" is "name~1"! */
 537                }
 538        }
 539        if (len) {
 540                struct strbuf truname = STRBUF_INIT;
 541                strbuf_addf(&truname, "refs/heads/%s", remote);
 542                strbuf_setlen(&truname, truname.len - len);
 543                if (ref_exists(truname.buf)) {
 544                        strbuf_addf(msg,
 545                                    "%s\t\tbranch '%s'%s of .\n",
 546                                    oid_to_hex(&remote_head->object.oid),
 547                                    truname.buf + 11,
 548                                    (early ? " (early part)" : ""));
 549                        strbuf_release(&truname);
 550                        goto cleanup;
 551                }
 552                strbuf_release(&truname);
 553        }
 554
 555        desc = merge_remote_util(remote_head);
 556        if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 557                strbuf_addf(msg, "%s\t\t%s '%s'\n",
 558                            oid_to_hex(&desc->obj->oid),
 559                            type_name(desc->obj->type),
 560                            remote);
 561                goto cleanup;
 562        }
 563
 564        strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 565                oid_to_hex(&remote_head->object.oid), remote);
 566cleanup:
 567        strbuf_release(&buf);
 568        strbuf_release(&bname);
 569}
 570
 571static void parse_branch_merge_options(char *bmo)
 572{
 573        const char **argv;
 574        int argc;
 575
 576        if (!bmo)
 577                return;
 578        argc = split_cmdline(bmo, &argv);
 579        if (argc < 0)
 580                die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 581                    _(split_cmdline_strerror(argc)));
 582        REALLOC_ARRAY(argv, argc + 2);
 583        MOVE_ARRAY(argv + 1, argv, argc + 1);
 584        argc++;
 585        argv[0] = "branch.*.mergeoptions";
 586        parse_options(argc, argv, NULL, builtin_merge_options,
 587                      builtin_merge_usage, 0);
 588        free(argv);
 589}
 590
 591static int git_merge_config(const char *k, const char *v, void *cb)
 592{
 593        int status;
 594
 595        if (branch && starts_with(k, "branch.") &&
 596                starts_with(k + 7, branch) &&
 597                !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 598                free(branch_mergeoptions);
 599                branch_mergeoptions = xstrdup(v);
 600                return 0;
 601        }
 602
 603        if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 604                show_diffstat = git_config_bool(k, v);
 605        else if (!strcmp(k, "merge.verifysignatures"))
 606                verify_signatures = git_config_bool(k, v);
 607        else if (!strcmp(k, "pull.twohead"))
 608                return git_config_string(&pull_twohead, k, v);
 609        else if (!strcmp(k, "pull.octopus"))
 610                return git_config_string(&pull_octopus, k, v);
 611        else if (!strcmp(k, "merge.renormalize"))
 612                option_renormalize = git_config_bool(k, v);
 613        else if (!strcmp(k, "merge.ff")) {
 614                int boolval = git_parse_maybe_bool(v);
 615                if (0 <= boolval) {
 616                        fast_forward = boolval ? FF_ALLOW : FF_NO;
 617                } else if (v && !strcmp(v, "only")) {
 618                        fast_forward = FF_ONLY;
 619                } /* do not barf on values from future versions of git */
 620                return 0;
 621        } else if (!strcmp(k, "merge.defaulttoupstream")) {
 622                default_to_upstream = git_config_bool(k, v);
 623                return 0;
 624        } else if (!strcmp(k, "commit.gpgsign")) {
 625                sign_commit = git_config_bool(k, v) ? "" : NULL;
 626                return 0;
 627        }
 628
 629        status = fmt_merge_msg_config(k, v, cb);
 630        if (status)
 631                return status;
 632        status = git_gpg_config(k, v, NULL);
 633        if (status)
 634                return status;
 635        return git_diff_ui_config(k, v, cb);
 636}
 637
 638static int read_tree_trivial(struct object_id *common, struct object_id *head,
 639                             struct object_id *one)
 640{
 641        int i, nr_trees = 0;
 642        struct tree *trees[MAX_UNPACK_TREES];
 643        struct tree_desc t[MAX_UNPACK_TREES];
 644        struct unpack_trees_options opts;
 645
 646        memset(&opts, 0, sizeof(opts));
 647        opts.head_idx = 2;
 648        opts.src_index = &the_index;
 649        opts.dst_index = &the_index;
 650        opts.update = 1;
 651        opts.verbose_update = 1;
 652        opts.trivial_merges_only = 1;
 653        opts.merge = 1;
 654        trees[nr_trees] = parse_tree_indirect(common);
 655        if (!trees[nr_trees++])
 656                return -1;
 657        trees[nr_trees] = parse_tree_indirect(head);
 658        if (!trees[nr_trees++])
 659                return -1;
 660        trees[nr_trees] = parse_tree_indirect(one);
 661        if (!trees[nr_trees++])
 662                return -1;
 663        opts.fn = threeway_merge;
 664        cache_tree_free(&active_cache_tree);
 665        for (i = 0; i < nr_trees; i++) {
 666                parse_tree(trees[i]);
 667                init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 668        }
 669        if (unpack_trees(nr_trees, t, &opts))
 670                return -1;
 671        return 0;
 672}
 673
 674static void write_tree_trivial(struct object_id *oid)
 675{
 676        if (write_cache_as_tree(oid, 0, NULL))
 677                die(_("git write-tree failed to write a tree"));
 678}
 679
 680static int try_merge_strategy(const char *strategy, struct commit_list *common,
 681                              struct commit_list *remoteheads,
 682                              struct commit *head)
 683{
 684        struct lock_file lock = LOCK_INIT;
 685        const char *head_arg = "HEAD";
 686
 687        hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 688        refresh_cache(REFRESH_QUIET);
 689        if (write_locked_index(&the_index, &lock,
 690                               COMMIT_LOCK | SKIP_IF_UNCHANGED))
 691                return error(_("Unable to write index."));
 692
 693        if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 694                int clean, x;
 695                struct commit *result;
 696                struct commit_list *reversed = NULL;
 697                struct merge_options o;
 698                struct commit_list *j;
 699
 700                if (remoteheads->next) {
 701                        error(_("Not handling anything other than two heads merge."));
 702                        return 2;
 703                }
 704
 705                init_merge_options(&o);
 706                if (!strcmp(strategy, "subtree"))
 707                        o.subtree_shift = "";
 708
 709                o.renormalize = option_renormalize;
 710                o.show_rename_progress =
 711                        show_progress == -1 ? isatty(2) : show_progress;
 712
 713                for (x = 0; x < xopts_nr; x++)
 714                        if (parse_merge_opt(&o, xopts[x]))
 715                                die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 716
 717                o.branch1 = head_arg;
 718                o.branch2 = merge_remote_util(remoteheads->item)->name;
 719
 720                for (j = common; j; j = j->next)
 721                        commit_list_insert(j->item, &reversed);
 722
 723                hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 724                clean = merge_recursive(&o, head,
 725                                remoteheads->item, reversed, &result);
 726                if (clean < 0)
 727                        exit(128);
 728                if (write_locked_index(&the_index, &lock,
 729                                       COMMIT_LOCK | SKIP_IF_UNCHANGED))
 730                        die(_("unable to write %s"), get_index_file());
 731                return clean ? 0 : 1;
 732        } else {
 733                return try_merge_command(the_repository,
 734                                         strategy, xopts_nr, xopts,
 735                                         common, head_arg, remoteheads);
 736        }
 737}
 738
 739static void count_diff_files(struct diff_queue_struct *q,
 740                             struct diff_options *opt, void *data)
 741{
 742        int *count = data;
 743
 744        (*count) += q->nr;
 745}
 746
 747static int count_unmerged_entries(void)
 748{
 749        int i, ret = 0;
 750
 751        for (i = 0; i < active_nr; i++)
 752                if (ce_stage(active_cache[i]))
 753                        ret++;
 754
 755        return ret;
 756}
 757
 758static void add_strategies(const char *string, unsigned attr)
 759{
 760        int i;
 761
 762        if (string) {
 763                struct string_list list = STRING_LIST_INIT_DUP;
 764                struct string_list_item *item;
 765                string_list_split(&list, string, ' ', -1);
 766                for_each_string_list_item(item, &list)
 767                        append_strategy(get_strategy(item->string));
 768                string_list_clear(&list, 0);
 769                return;
 770        }
 771        for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 772                if (all_strategy[i].attr & attr)
 773                        append_strategy(&all_strategy[i]);
 774
 775}
 776
 777static void read_merge_msg(struct strbuf *msg)
 778{
 779        const char *filename = git_path_merge_msg(the_repository);
 780        strbuf_reset(msg);
 781        if (strbuf_read_file(msg, filename, 0) < 0)
 782                die_errno(_("Could not read from '%s'"), filename);
 783}
 784
 785static void write_merge_state(struct commit_list *);
 786static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
 787{
 788        if (err_msg)
 789                error("%s", err_msg);
 790        fprintf(stderr,
 791                _("Not committing merge; use 'git commit' to complete the merge.\n"));
 792        write_merge_state(remoteheads);
 793        exit(1);
 794}
 795
 796static const char merge_editor_comment[] =
 797N_("Please enter a commit message to explain why this merge is necessary,\n"
 798   "especially if it merges an updated upstream into a topic branch.\n"
 799   "\n"
 800   "Lines starting with '%c' will be ignored, and an empty message aborts\n"
 801   "the commit.\n");
 802
 803static void write_merge_heads(struct commit_list *);
 804static void prepare_to_commit(struct commit_list *remoteheads)
 805{
 806        struct strbuf msg = STRBUF_INIT;
 807        strbuf_addbuf(&msg, &merge_msg);
 808        strbuf_addch(&msg, '\n');
 809        if (squash)
 810                BUG("the control must not reach here under --squash");
 811        if (0 < option_edit)
 812                strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
 813        if (signoff)
 814                append_signoff(&msg, ignore_non_trailer(msg.buf, msg.len), 0);
 815        write_merge_heads(remoteheads);
 816        write_file_buf(git_path_merge_msg(the_repository), msg.buf, msg.len);
 817        if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
 818                            git_path_merge_msg(the_repository), "merge", NULL))
 819                abort_commit(remoteheads, NULL);
 820        if (0 < option_edit) {
 821                if (launch_editor(git_path_merge_msg(the_repository), NULL, NULL))
 822                        abort_commit(remoteheads, NULL);
 823        }
 824
 825        if (verify_msg && run_commit_hook(0 < option_edit, get_index_file(),
 826                                          "commit-msg",
 827                                          git_path_merge_msg(the_repository), NULL))
 828                abort_commit(remoteheads, NULL);
 829
 830        read_merge_msg(&msg);
 831        strbuf_stripspace(&msg, 0 < option_edit);
 832        if (!msg.len)
 833                abort_commit(remoteheads, _("Empty commit message."));
 834        strbuf_release(&merge_msg);
 835        strbuf_addbuf(&merge_msg, &msg);
 836        strbuf_release(&msg);
 837}
 838
 839static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 840{
 841        struct object_id result_tree, result_commit;
 842        struct commit_list *parents, **pptr = &parents;
 843        struct lock_file lock = LOCK_INIT;
 844
 845        hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
 846        refresh_cache(REFRESH_QUIET);
 847        if (write_locked_index(&the_index, &lock,
 848                               COMMIT_LOCK | SKIP_IF_UNCHANGED))
 849                return error(_("Unable to write index."));
 850
 851        write_tree_trivial(&result_tree);
 852        printf(_("Wonderful.\n"));
 853        pptr = commit_list_append(head, pptr);
 854        pptr = commit_list_append(remoteheads->item, pptr);
 855        prepare_to_commit(remoteheads);
 856        if (commit_tree(merge_msg.buf, merge_msg.len, &result_tree, parents,
 857                        &result_commit, NULL, sign_commit))
 858                die(_("failed to write commit object"));
 859        finish(head, remoteheads, &result_commit, "In-index merge");
 860        drop_save();
 861        return 0;
 862}
 863
 864static int finish_automerge(struct commit *head,
 865                            int head_subsumed,
 866                            struct commit_list *common,
 867                            struct commit_list *remoteheads,
 868                            struct object_id *result_tree,
 869                            const char *wt_strategy)
 870{
 871        struct commit_list *parents = NULL;
 872        struct strbuf buf = STRBUF_INIT;
 873        struct object_id result_commit;
 874
 875        free_commit_list(common);
 876        parents = remoteheads;
 877        if (!head_subsumed || fast_forward == FF_NO)
 878                commit_list_insert(head, &parents);
 879        strbuf_addch(&merge_msg, '\n');
 880        prepare_to_commit(remoteheads);
 881        if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 882                        &result_commit, NULL, sign_commit))
 883                die(_("failed to write commit object"));
 884        strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 885        finish(head, remoteheads, &result_commit, buf.buf);
 886        strbuf_release(&buf);
 887        drop_save();
 888        return 0;
 889}
 890
 891static int suggest_conflicts(void)
 892{
 893        const char *filename;
 894        FILE *fp;
 895        struct strbuf msgbuf = STRBUF_INIT;
 896
 897        filename = git_path_merge_msg(the_repository);
 898        fp = xfopen(filename, "a");
 899
 900        append_conflicts_hint(&the_index, &msgbuf);
 901        fputs(msgbuf.buf, fp);
 902        strbuf_release(&msgbuf);
 903        fclose(fp);
 904        repo_rerere(the_repository, allow_rerere_auto);
 905        printf(_("Automatic merge failed; "
 906                        "fix conflicts and then commit the result.\n"));
 907        return 1;
 908}
 909
 910static int evaluate_result(void)
 911{
 912        int cnt = 0;
 913        struct rev_info rev;
 914
 915        /* Check how many files differ. */
 916        repo_init_revisions(the_repository, &rev, "");
 917        setup_revisions(0, NULL, &rev, NULL);
 918        rev.diffopt.output_format |=
 919                DIFF_FORMAT_CALLBACK;
 920        rev.diffopt.format_callback = count_diff_files;
 921        rev.diffopt.format_callback_data = &cnt;
 922        run_diff_files(&rev, 0);
 923
 924        /*
 925         * Check how many unmerged entries are
 926         * there.
 927         */
 928        cnt += count_unmerged_entries();
 929
 930        return cnt;
 931}
 932
 933/*
 934 * Pretend as if the user told us to merge with the remote-tracking
 935 * branch we have for the upstream of the current branch
 936 */
 937static int setup_with_upstream(const char ***argv)
 938{
 939        struct branch *branch = branch_get(NULL);
 940        int i;
 941        const char **args;
 942
 943        if (!branch)
 944                die(_("No current branch."));
 945        if (!branch->remote_name)
 946                die(_("No remote for the current branch."));
 947        if (!branch->merge_nr)
 948                die(_("No default upstream defined for the current branch."));
 949
 950        args = xcalloc(st_add(branch->merge_nr, 1), sizeof(char *));
 951        for (i = 0; i < branch->merge_nr; i++) {
 952                if (!branch->merge[i]->dst)
 953                        die(_("No remote-tracking branch for %s from %s"),
 954                            branch->merge[i]->src, branch->remote_name);
 955                args[i] = branch->merge[i]->dst;
 956        }
 957        args[i] = NULL;
 958        *argv = args;
 959        return i;
 960}
 961
 962static void write_merge_heads(struct commit_list *remoteheads)
 963{
 964        struct commit_list *j;
 965        struct strbuf buf = STRBUF_INIT;
 966
 967        for (j = remoteheads; j; j = j->next) {
 968                struct object_id *oid;
 969                struct commit *c = j->item;
 970                struct merge_remote_desc *desc;
 971
 972                desc = merge_remote_util(c);
 973                if (desc && desc->obj) {
 974                        oid = &desc->obj->oid;
 975                } else {
 976                        oid = &c->object.oid;
 977                }
 978                strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
 979        }
 980        write_file_buf(git_path_merge_head(the_repository), buf.buf, buf.len);
 981
 982        strbuf_reset(&buf);
 983        if (fast_forward == FF_NO)
 984                strbuf_addstr(&buf, "no-ff");
 985        write_file_buf(git_path_merge_mode(the_repository), buf.buf, buf.len);
 986        strbuf_release(&buf);
 987}
 988
 989static void write_merge_state(struct commit_list *remoteheads)
 990{
 991        write_merge_heads(remoteheads);
 992        strbuf_addch(&merge_msg, '\n');
 993        write_file_buf(git_path_merge_msg(the_repository), merge_msg.buf,
 994                       merge_msg.len);
 995}
 996
 997static int default_edit_option(void)
 998{
 999        static const char name[] = "GIT_MERGE_AUTOEDIT";
1000        const char *e = getenv(name);
1001        struct stat st_stdin, st_stdout;
1002
1003        if (have_message)
1004                /* an explicit -m msg without --[no-]edit */
1005                return 0;
1006
1007        if (e) {
1008                int v = git_parse_maybe_bool(e);
1009                if (v < 0)
1010                        die(_("Bad value '%s' in environment '%s'"), e, name);
1011                return v;
1012        }
1013
1014        /* Use editor if stdin and stdout are the same and is a tty */
1015        return (!fstat(0, &st_stdin) &&
1016                !fstat(1, &st_stdout) &&
1017                isatty(0) && isatty(1) &&
1018                st_stdin.st_dev == st_stdout.st_dev &&
1019                st_stdin.st_ino == st_stdout.st_ino &&
1020                st_stdin.st_mode == st_stdout.st_mode);
1021}
1022
1023static struct commit_list *reduce_parents(struct commit *head_commit,
1024                                          int *head_subsumed,
1025                                          struct commit_list *remoteheads)
1026{
1027        struct commit_list *parents, **remotes;
1028
1029        /*
1030         * Is the current HEAD reachable from another commit being
1031         * merged?  If so we do not want to record it as a parent of
1032         * the resulting merge, unless --no-ff is given.  We will flip
1033         * this variable to 0 when we find HEAD among the independent
1034         * tips being merged.
1035         */
1036        *head_subsumed = 1;
1037
1038        /* Find what parents to record by checking independent ones. */
1039        parents = reduce_heads(remoteheads);
1040        free_commit_list(remoteheads);
1041
1042        remoteheads = NULL;
1043        remotes = &remoteheads;
1044        while (parents) {
1045                struct commit *commit = pop_commit(&parents);
1046                if (commit == head_commit)
1047                        *head_subsumed = 0;
1048                else
1049                        remotes = &commit_list_insert(commit, remotes)->next;
1050        }
1051        return remoteheads;
1052}
1053
1054static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *merge_msg)
1055{
1056        struct fmt_merge_msg_opts opts;
1057
1058        memset(&opts, 0, sizeof(opts));
1059        opts.add_title = !have_message;
1060        opts.shortlog_len = shortlog_len;
1061        opts.credit_people = (0 < option_edit);
1062
1063        fmt_merge_msg(merge_names, merge_msg, &opts);
1064        if (merge_msg->len)
1065                strbuf_setlen(merge_msg, merge_msg->len - 1);
1066}
1067
1068static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge_names)
1069{
1070        const char *filename;
1071        int fd, pos, npos;
1072        struct strbuf fetch_head_file = STRBUF_INIT;
1073        const unsigned hexsz = the_hash_algo->hexsz;
1074
1075        if (!merge_names)
1076                merge_names = &fetch_head_file;
1077
1078        filename = git_path_fetch_head(the_repository);
1079        fd = open(filename, O_RDONLY);
1080        if (fd < 0)
1081                die_errno(_("could not open '%s' for reading"), filename);
1082
1083        if (strbuf_read(merge_names, fd, 0) < 0)
1084                die_errno(_("could not read '%s'"), filename);
1085        if (close(fd) < 0)
1086                die_errno(_("could not close '%s'"), filename);
1087
1088        for (pos = 0; pos < merge_names->len; pos = npos) {
1089                struct object_id oid;
1090                char *ptr;
1091                struct commit *commit;
1092
1093                ptr = strchr(merge_names->buf + pos, '\n');
1094                if (ptr)
1095                        npos = ptr - merge_names->buf + 1;
1096                else
1097                        npos = merge_names->len;
1098
1099                if (npos - pos < hexsz + 2 ||
1100                    get_oid_hex(merge_names->buf + pos, &oid))
1101                        commit = NULL; /* bad */
1102                else if (memcmp(merge_names->buf + pos + hexsz, "\t\t", 2))
1103                        continue; /* not-for-merge */
1104                else {
1105                        char saved = merge_names->buf[pos + hexsz];
1106                        merge_names->buf[pos + hexsz] = '\0';
1107                        commit = get_merge_parent(merge_names->buf + pos);
1108                        merge_names->buf[pos + hexsz] = saved;
1109                }
1110                if (!commit) {
1111                        if (ptr)
1112                                *ptr = '\0';
1113                        die(_("not something we can merge in %s: %s"),
1114                            filename, merge_names->buf + pos);
1115                }
1116                remotes = &commit_list_insert(commit, remotes)->next;
1117        }
1118
1119        if (merge_names == &fetch_head_file)
1120                strbuf_release(&fetch_head_file);
1121}
1122
1123static struct commit_list *collect_parents(struct commit *head_commit,
1124                                           int *head_subsumed,
1125                                           int argc, const char **argv,
1126                                           struct strbuf *merge_msg)
1127{
1128        int i;
1129        struct commit_list *remoteheads = NULL;
1130        struct commit_list **remotes = &remoteheads;
1131        struct strbuf merge_names = STRBUF_INIT, *autogen = NULL;
1132
1133        if (merge_msg && (!have_message || shortlog_len))
1134                autogen = &merge_names;
1135
1136        if (head_commit)
1137                remotes = &commit_list_insert(head_commit, remotes)->next;
1138
1139        if (argc == 1 && !strcmp(argv[0], "FETCH_HEAD")) {
1140                handle_fetch_head(remotes, autogen);
1141                remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1142        } else {
1143                for (i = 0; i < argc; i++) {
1144                        struct commit *commit = get_merge_parent(argv[i]);
1145                        if (!commit)
1146                                help_unknown_ref(argv[i], "merge",
1147                                                 _("not something we can merge"));
1148                        remotes = &commit_list_insert(commit, remotes)->next;
1149                }
1150                remoteheads = reduce_parents(head_commit, head_subsumed, remoteheads);
1151                if (autogen) {
1152                        struct commit_list *p;
1153                        for (p = remoteheads; p; p = p->next)
1154                                merge_name(merge_remote_util(p->item)->name, autogen);
1155                }
1156        }
1157
1158        if (autogen) {
1159                prepare_merge_message(autogen, merge_msg);
1160                strbuf_release(autogen);
1161        }
1162
1163        return remoteheads;
1164}
1165
1166static int merging_a_throwaway_tag(struct commit *commit)
1167{
1168        char *tag_ref;
1169        struct object_id oid;
1170        int is_throwaway_tag = 0;
1171
1172        /* Are we merging a tag? */
1173        if (!merge_remote_util(commit) ||
1174            !merge_remote_util(commit)->obj ||
1175            merge_remote_util(commit)->obj->type != OBJ_TAG)
1176                return is_throwaway_tag;
1177
1178        /*
1179         * Now we know we are merging a tag object.  Are we downstream
1180         * and following the tags from upstream?  If so, we must have
1181         * the tag object pointed at by "refs/tags/$T" where $T is the
1182         * tagname recorded in the tag object.  We want to allow such
1183         * a "just to catch up" merge to fast-forward.
1184         *
1185         * Otherwise, we are playing an integrator's role, making a
1186         * merge with a throw-away tag from a contributor with
1187         * something like "git pull $contributor $signed_tag".
1188         * We want to forbid such a merge from fast-forwarding
1189         * by default; otherwise we would not keep the signature
1190         * anywhere.
1191         */
1192        tag_ref = xstrfmt("refs/tags/%s",
1193                          ((struct tag *)merge_remote_util(commit)->obj)->tag);
1194        if (!read_ref(tag_ref, &oid) &&
1195            oideq(&oid, &merge_remote_util(commit)->obj->oid))
1196                is_throwaway_tag = 0;
1197        else
1198                is_throwaway_tag = 1;
1199        free(tag_ref);
1200        return is_throwaway_tag;
1201}
1202
1203int cmd_merge(int argc, const char **argv, const char *prefix)
1204{
1205        struct object_id result_tree, stash, head_oid;
1206        struct commit *head_commit;
1207        struct strbuf buf = STRBUF_INIT;
1208        int i, ret = 0, head_subsumed;
1209        int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1210        struct commit_list *common = NULL;
1211        const char *best_strategy = NULL, *wt_strategy = NULL;
1212        struct commit_list *remoteheads, *p;
1213        void *branch_to_free;
1214        int orig_argc = argc;
1215
1216        if (argc == 2 && !strcmp(argv[1], "-h"))
1217                usage_with_options(builtin_merge_usage, builtin_merge_options);
1218
1219        /*
1220         * Check if we are _not_ on a detached HEAD, i.e. if there is a
1221         * current branch.
1222         */
1223        branch = branch_to_free = resolve_refdup("HEAD", 0, &head_oid, NULL);
1224        if (branch)
1225                skip_prefix(branch, "refs/heads/", &branch);
1226
1227        init_diff_ui_defaults();
1228        git_config(git_merge_config, NULL);
1229
1230        if (!branch || is_null_oid(&head_oid))
1231                head_commit = NULL;
1232        else
1233                head_commit = lookup_commit_or_die(&head_oid, "HEAD");
1234
1235        if (branch_mergeoptions)
1236                parse_branch_merge_options(branch_mergeoptions);
1237        argc = parse_options(argc, argv, prefix, builtin_merge_options,
1238                        builtin_merge_usage, 0);
1239        if (shortlog_len < 0)
1240                shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1241
1242        if (verbosity < 0 && show_progress == -1)
1243                show_progress = 0;
1244
1245        if (abort_current_merge) {
1246                int nargc = 2;
1247                const char *nargv[] = {"reset", "--merge", NULL};
1248
1249                if (orig_argc != 2)
1250                        usage_msg_opt(_("--abort expects no arguments"),
1251                              builtin_merge_usage, builtin_merge_options);
1252
1253                if (!file_exists(git_path_merge_head(the_repository)))
1254                        die(_("There is no merge to abort (MERGE_HEAD missing)."));
1255
1256                /* Invoke 'git reset --merge' */
1257                ret = cmd_reset(nargc, nargv, prefix);
1258                goto done;
1259        }
1260
1261        if (continue_current_merge) {
1262                int nargc = 1;
1263                const char *nargv[] = {"commit", NULL};
1264
1265                if (orig_argc != 2)
1266                        usage_msg_opt(_("--continue expects no arguments"),
1267                              builtin_merge_usage, builtin_merge_options);
1268
1269                if (!file_exists(git_path_merge_head(the_repository)))
1270                        die(_("There is no merge in progress (MERGE_HEAD missing)."));
1271
1272                /* Invoke 'git commit' */
1273                ret = cmd_commit(nargc, nargv, prefix);
1274                goto done;
1275        }
1276
1277        if (read_cache_unmerged())
1278                die_resolve_conflict("merge");
1279
1280        if (file_exists(git_path_merge_head(the_repository))) {
1281                /*
1282                 * There is no unmerged entry, don't advise 'git
1283                 * add/rm <file>', just 'git commit'.
1284                 */
1285                if (advice_resolve_conflict)
1286                        die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1287                                  "Please, commit your changes before you merge."));
1288                else
1289                        die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1290        }
1291        if (file_exists(git_path_cherry_pick_head(the_repository))) {
1292                if (advice_resolve_conflict)
1293                        die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1294                            "Please, commit your changes before you merge."));
1295                else
1296                        die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1297        }
1298        resolve_undo_clear();
1299
1300        if (verbosity < 0)
1301                show_diffstat = 0;
1302
1303        if (squash) {
1304                if (fast_forward == FF_NO)
1305                        die(_("You cannot combine --squash with --no-ff."));
1306                option_commit = 0;
1307        }
1308
1309        if (!argc) {
1310                if (default_to_upstream)
1311                        argc = setup_with_upstream(&argv);
1312                else
1313                        die(_("No commit specified and merge.defaultToUpstream not set."));
1314        } else if (argc == 1 && !strcmp(argv[0], "-")) {
1315                argv[0] = "@{-1}";
1316        }
1317
1318        if (!argc)
1319                usage_with_options(builtin_merge_usage,
1320                        builtin_merge_options);
1321
1322        if (!head_commit) {
1323                /*
1324                 * If the merged head is a valid one there is no reason
1325                 * to forbid "git merge" into a branch yet to be born.
1326                 * We do the same for "git pull".
1327                 */
1328                struct object_id *remote_head_oid;
1329                if (squash)
1330                        die(_("Squash commit into empty head not supported yet"));
1331                if (fast_forward == FF_NO)
1332                        die(_("Non-fast-forward commit does not make sense into "
1333                            "an empty head"));
1334                remoteheads = collect_parents(head_commit, &head_subsumed,
1335                                              argc, argv, NULL);
1336                if (!remoteheads)
1337                        die(_("%s - not something we can merge"), argv[0]);
1338                if (remoteheads->next)
1339                        die(_("Can merge only exactly one commit into empty head"));
1340
1341                if (verify_signatures)
1342                        verify_merge_signature(remoteheads->item, verbosity);
1343
1344                remote_head_oid = &remoteheads->item->object.oid;
1345                read_empty(remote_head_oid, 0);
1346                update_ref("initial pull", "HEAD", remote_head_oid, NULL, 0,
1347                           UPDATE_REFS_DIE_ON_ERR);
1348                goto done;
1349        }
1350
1351        /*
1352         * All the rest are the commits being merged; prepare
1353         * the standard merge summary message to be appended
1354         * to the given message.
1355         */
1356        remoteheads = collect_parents(head_commit, &head_subsumed,
1357                                      argc, argv, &merge_msg);
1358
1359        if (!head_commit || !argc)
1360                usage_with_options(builtin_merge_usage,
1361                        builtin_merge_options);
1362
1363        if (verify_signatures) {
1364                for (p = remoteheads; p; p = p->next) {
1365                        verify_merge_signature(p->item, verbosity);
1366                }
1367        }
1368
1369        strbuf_addstr(&buf, "merge");
1370        for (p = remoteheads; p; p = p->next)
1371                strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1372        setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1373        strbuf_reset(&buf);
1374
1375        for (p = remoteheads; p; p = p->next) {
1376                struct commit *commit = p->item;
1377                strbuf_addf(&buf, "GITHEAD_%s",
1378                            oid_to_hex(&commit->object.oid));
1379                setenv(buf.buf, merge_remote_util(commit)->name, 1);
1380                strbuf_reset(&buf);
1381                if (fast_forward != FF_ONLY && merging_a_throwaway_tag(commit))
1382                        fast_forward = FF_NO;
1383        }
1384
1385        if (option_edit < 0)
1386                option_edit = default_edit_option();
1387
1388        if (!use_strategies) {
1389                if (!remoteheads)
1390                        ; /* already up-to-date */
1391                else if (!remoteheads->next)
1392                        add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1393                else
1394                        add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1395        }
1396
1397        for (i = 0; i < use_strategies_nr; i++) {
1398                if (use_strategies[i]->attr & NO_FAST_FORWARD)
1399                        fast_forward = FF_NO;
1400                if (use_strategies[i]->attr & NO_TRIVIAL)
1401                        allow_trivial = 0;
1402        }
1403
1404        if (!remoteheads)
1405                ; /* already up-to-date */
1406        else if (!remoteheads->next)
1407                common = get_merge_bases(head_commit, remoteheads->item);
1408        else {
1409                struct commit_list *list = remoteheads;
1410                commit_list_insert(head_commit, &list);
1411                common = get_octopus_merge_bases(list);
1412                free(list);
1413        }
1414
1415        update_ref("updating ORIG_HEAD", "ORIG_HEAD",
1416                   &head_commit->object.oid, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1417
1418        if (remoteheads && !common) {
1419                /* No common ancestors found. */
1420                if (!allow_unrelated_histories)
1421                        die(_("refusing to merge unrelated histories"));
1422                /* otherwise, we need a real merge. */
1423        } else if (!remoteheads ||
1424                 (!remoteheads->next && !common->next &&
1425                  common->item == remoteheads->item)) {
1426                /*
1427                 * If head can reach all the merge then we are up to date.
1428                 * but first the most common case of merging one remote.
1429                 */
1430                finish_up_to_date(_("Already up to date."));
1431                goto done;
1432        } else if (fast_forward != FF_NO && !remoteheads->next &&
1433                        !common->next &&
1434                        oideq(&common->item->object.oid, &head_commit->object.oid)) {
1435                /* Again the most common case of merging one remote. */
1436                struct strbuf msg = STRBUF_INIT;
1437                struct commit *commit;
1438
1439                if (verbosity >= 0) {
1440                        printf(_("Updating %s..%s\n"),
1441                               find_unique_abbrev(&head_commit->object.oid,
1442                                                  DEFAULT_ABBREV),
1443                               find_unique_abbrev(&remoteheads->item->object.oid,
1444                                                  DEFAULT_ABBREV));
1445                }
1446                strbuf_addstr(&msg, "Fast-forward");
1447                if (have_message)
1448                        strbuf_addstr(&msg,
1449                                " (no commit created; -m option ignored)");
1450                commit = remoteheads->item;
1451                if (!commit) {
1452                        ret = 1;
1453                        goto done;
1454                }
1455
1456                if (checkout_fast_forward(the_repository,
1457                                          &head_commit->object.oid,
1458                                          &commit->object.oid,
1459                                          overwrite_ignore)) {
1460                        ret = 1;
1461                        goto done;
1462                }
1463
1464                finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
1465                drop_save();
1466                goto done;
1467        } else if (!remoteheads->next && common->next)
1468                ;
1469                /*
1470                 * We are not doing octopus and not fast-forward.  Need
1471                 * a real merge.
1472                 */
1473        else if (!remoteheads->next && !common->next && option_commit) {
1474                /*
1475                 * We are not doing octopus, not fast-forward, and have
1476                 * only one common.
1477                 */
1478                refresh_cache(REFRESH_QUIET);
1479                if (allow_trivial && fast_forward != FF_ONLY) {
1480                        /* See if it is really trivial. */
1481                        git_committer_info(IDENT_STRICT);
1482                        printf(_("Trying really trivial in-index merge...\n"));
1483                        if (!read_tree_trivial(&common->item->object.oid,
1484                                               &head_commit->object.oid,
1485                                               &remoteheads->item->object.oid)) {
1486                                ret = merge_trivial(head_commit, remoteheads);
1487                                goto done;
1488                        }
1489                        printf(_("Nope.\n"));
1490                }
1491        } else {
1492                /*
1493                 * An octopus.  If we can reach all the remote we are up
1494                 * to date.
1495                 */
1496                int up_to_date = 1;
1497                struct commit_list *j;
1498
1499                for (j = remoteheads; j; j = j->next) {
1500                        struct commit_list *common_one;
1501
1502                        /*
1503                         * Here we *have* to calculate the individual
1504                         * merge_bases again, otherwise "git merge HEAD^
1505                         * HEAD^^" would be missed.
1506                         */
1507                        common_one = get_merge_bases(head_commit, j->item);
1508                        if (!oideq(&common_one->item->object.oid, &j->item->object.oid)) {
1509                                up_to_date = 0;
1510                                break;
1511                        }
1512                }
1513                if (up_to_date) {
1514                        finish_up_to_date(_("Already up to date. Yeeah!"));
1515                        goto done;
1516                }
1517        }
1518
1519        if (fast_forward == FF_ONLY)
1520                die(_("Not possible to fast-forward, aborting."));
1521
1522        /* We are going to make a new commit. */
1523        git_committer_info(IDENT_STRICT);
1524
1525        /*
1526         * At this point, we need a real merge.  No matter what strategy
1527         * we use, it would operate on the index, possibly affecting the
1528         * working tree, and when resolved cleanly, have the desired
1529         * tree in the index -- this means that the index must be in
1530         * sync with the head commit.  The strategies are responsible
1531         * to ensure this.
1532         */
1533        if (use_strategies_nr == 1 ||
1534            /*
1535             * Stash away the local changes so that we can try more than one.
1536             */
1537            save_state(&stash))
1538                oidclr(&stash);
1539
1540        for (i = 0; i < use_strategies_nr; i++) {
1541                int ret;
1542                if (i) {
1543                        printf(_("Rewinding the tree to pristine...\n"));
1544                        restore_state(&head_commit->object.oid, &stash);
1545                }
1546                if (use_strategies_nr != 1)
1547                        printf(_("Trying merge strategy %s...\n"),
1548                                use_strategies[i]->name);
1549                /*
1550                 * Remember which strategy left the state in the working
1551                 * tree.
1552                 */
1553                wt_strategy = use_strategies[i]->name;
1554
1555                ret = try_merge_strategy(use_strategies[i]->name,
1556                                         common, remoteheads,
1557                                         head_commit);
1558                if (!option_commit && !ret) {
1559                        merge_was_ok = 1;
1560                        /*
1561                         * This is necessary here just to avoid writing
1562                         * the tree, but later we will *not* exit with
1563                         * status code 1 because merge_was_ok is set.
1564                         */
1565                        ret = 1;
1566                }
1567
1568                if (ret) {
1569                        /*
1570                         * The backend exits with 1 when conflicts are
1571                         * left to be resolved, with 2 when it does not
1572                         * handle the given merge at all.
1573                         */
1574                        if (ret == 1) {
1575                                int cnt = evaluate_result();
1576
1577                                if (best_cnt <= 0 || cnt <= best_cnt) {
1578                                        best_strategy = use_strategies[i]->name;
1579                                        best_cnt = cnt;
1580                                }
1581                        }
1582                        if (merge_was_ok)
1583                                break;
1584                        else
1585                                continue;
1586                }
1587
1588                /* Automerge succeeded. */
1589                write_tree_trivial(&result_tree);
1590                automerge_was_ok = 1;
1591                break;
1592        }
1593
1594        /*
1595         * If we have a resulting tree, that means the strategy module
1596         * auto resolved the merge cleanly.
1597         */
1598        if (automerge_was_ok) {
1599                ret = finish_automerge(head_commit, head_subsumed,
1600                                       common, remoteheads,
1601                                       &result_tree, wt_strategy);
1602                goto done;
1603        }
1604
1605        /*
1606         * Pick the result from the best strategy and have the user fix
1607         * it up.
1608         */
1609        if (!best_strategy) {
1610                restore_state(&head_commit->object.oid, &stash);
1611                if (use_strategies_nr > 1)
1612                        fprintf(stderr,
1613                                _("No merge strategy handled the merge.\n"));
1614                else
1615                        fprintf(stderr, _("Merge with strategy %s failed.\n"),
1616                                use_strategies[0]->name);
1617                ret = 2;
1618                goto done;
1619        } else if (best_strategy == wt_strategy)
1620                ; /* We already have its result in the working tree. */
1621        else {
1622                printf(_("Rewinding the tree to pristine...\n"));
1623                restore_state(&head_commit->object.oid, &stash);
1624                printf(_("Using the %s to prepare resolving by hand.\n"),
1625                        best_strategy);
1626                try_merge_strategy(best_strategy, common, remoteheads,
1627                                   head_commit);
1628        }
1629
1630        if (squash)
1631                finish(head_commit, remoteheads, NULL, NULL);
1632        else
1633                write_merge_state(remoteheads);
1634
1635        if (merge_was_ok)
1636                fprintf(stderr, _("Automatic merge went well; "
1637                        "stopped before committing as requested\n"));
1638        else
1639                ret = suggest_conflicts();
1640
1641done:
1642        free(branch_to_free);
1643        return ret;
1644}