builtin / merge.con commit Documentation: add missing article in rev-list-options.txt (8297643)
   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 "parse-options.h"
  11#include "builtin.h"
  12#include "lockfile.h"
  13#include "run-command.h"
  14#include "diff.h"
  15#include "refs.h"
  16#include "commit.h"
  17#include "diffcore.h"
  18#include "revision.h"
  19#include "unpack-trees.h"
  20#include "cache-tree.h"
  21#include "dir.h"
  22#include "utf8.h"
  23#include "log-tree.h"
  24#include "color.h"
  25#include "rerere.h"
  26#include "help.h"
  27#include "merge-recursive.h"
  28#include "resolve-undo.h"
  29#include "remote.h"
  30#include "fmt-merge-msg.h"
  31#include "gpg-interface.h"
  32
  33#define DEFAULT_TWOHEAD (1<<0)
  34#define DEFAULT_OCTOPUS (1<<1)
  35#define NO_FAST_FORWARD (1<<2)
  36#define NO_TRIVIAL      (1<<3)
  37
  38struct strategy {
  39        const char *name;
  40        unsigned attr;
  41};
  42
  43static const char * const builtin_merge_usage[] = {
  44        N_("git merge [options] [<commit>...]"),
  45        N_("git merge [options] <msg> HEAD <commit>"),
  46        N_("git merge --abort"),
  47        NULL
  48};
  49
  50static int show_diffstat = 1, shortlog_len = -1, squash;
  51static int option_commit = 1;
  52static int option_edit = -1;
  53static int allow_trivial = 1, have_message, verify_signatures;
  54static int overwrite_ignore = 1;
  55static struct strbuf merge_msg = STRBUF_INIT;
  56static struct strategy **use_strategies;
  57static size_t use_strategies_nr, use_strategies_alloc;
  58static const char **xopts;
  59static size_t xopts_nr, xopts_alloc;
  60static const char *branch;
  61static char *branch_mergeoptions;
  62static int option_renormalize;
  63static int verbosity;
  64static int allow_rerere_auto;
  65static int abort_current_merge;
  66static int show_progress = -1;
  67static int default_to_upstream = 1;
  68static const char *sign_commit;
  69
  70static struct strategy all_strategy[] = {
  71        { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  72        { "octopus",    DEFAULT_OCTOPUS },
  73        { "resolve",    0 },
  74        { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  75        { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  76};
  77
  78static const char *pull_twohead, *pull_octopus;
  79
  80enum ff_type {
  81        FF_NO,
  82        FF_ALLOW,
  83        FF_ONLY
  84};
  85
  86static enum ff_type fast_forward = FF_ALLOW;
  87
  88static int option_parse_message(const struct option *opt,
  89                                const char *arg, int unset)
  90{
  91        struct strbuf *buf = opt->value;
  92
  93        if (unset)
  94                strbuf_setlen(buf, 0);
  95        else if (arg) {
  96                strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  97                have_message = 1;
  98        } else
  99                return error(_("switch `m' requires a value"));
 100        return 0;
 101}
 102
 103static struct strategy *get_strategy(const char *name)
 104{
 105        int i;
 106        struct strategy *ret;
 107        static struct cmdnames main_cmds, other_cmds;
 108        static int loaded;
 109
 110        if (!name)
 111                return NULL;
 112
 113        for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 114                if (!strcmp(name, all_strategy[i].name))
 115                        return &all_strategy[i];
 116
 117        if (!loaded) {
 118                struct cmdnames not_strategies;
 119                loaded = 1;
 120
 121                memset(&not_strategies, 0, sizeof(struct cmdnames));
 122                load_command_list("git-merge-", &main_cmds, &other_cmds);
 123                for (i = 0; i < main_cmds.cnt; i++) {
 124                        int j, found = 0;
 125                        struct cmdname *ent = main_cmds.names[i];
 126                        for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 127                                if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 128                                                && !all_strategy[j].name[ent->len])
 129                                        found = 1;
 130                        if (!found)
 131                                add_cmdname(&not_strategies, ent->name, ent->len);
 132                }
 133                exclude_cmds(&main_cmds, &not_strategies);
 134        }
 135        if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 136                fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 137                fprintf(stderr, _("Available strategies are:"));
 138                for (i = 0; i < main_cmds.cnt; i++)
 139                        fprintf(stderr, " %s", main_cmds.names[i]->name);
 140                fprintf(stderr, ".\n");
 141                if (other_cmds.cnt) {
 142                        fprintf(stderr, _("Available custom strategies are:"));
 143                        for (i = 0; i < other_cmds.cnt; i++)
 144                                fprintf(stderr, " %s", other_cmds.names[i]->name);
 145                        fprintf(stderr, ".\n");
 146                }
 147                exit(1);
 148        }
 149
 150        ret = xcalloc(1, sizeof(struct strategy));
 151        ret->name = xstrdup(name);
 152        ret->attr = NO_TRIVIAL;
 153        return ret;
 154}
 155
 156static void append_strategy(struct strategy *s)
 157{
 158        ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 159        use_strategies[use_strategies_nr++] = s;
 160}
 161
 162static int option_parse_strategy(const struct option *opt,
 163                                 const char *name, int unset)
 164{
 165        if (unset)
 166                return 0;
 167
 168        append_strategy(get_strategy(name));
 169        return 0;
 170}
 171
 172static int option_parse_x(const struct option *opt,
 173                          const char *arg, int unset)
 174{
 175        if (unset)
 176                return 0;
 177
 178        ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 179        xopts[xopts_nr++] = xstrdup(arg);
 180        return 0;
 181}
 182
 183static int option_parse_n(const struct option *opt,
 184                          const char *arg, int unset)
 185{
 186        show_diffstat = unset;
 187        return 0;
 188}
 189
 190static struct option builtin_merge_options[] = {
 191        { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 192                N_("do not show a diffstat at the end of the merge"),
 193                PARSE_OPT_NOARG, option_parse_n },
 194        OPT_BOOL(0, "stat", &show_diffstat,
 195                N_("show a diffstat at the end of the merge")),
 196        OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
 197        { OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
 198          N_("add (at most <n>) entries from shortlog to merge commit message"),
 199          PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 200        OPT_BOOL(0, "squash", &squash,
 201                N_("create a single commit instead of doing a merge")),
 202        OPT_BOOL(0, "commit", &option_commit,
 203                N_("perform a commit if the merge succeeds (default)")),
 204        OPT_BOOL('e', "edit", &option_edit,
 205                N_("edit message before committing")),
 206        OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
 207        { OPTION_SET_INT, 0, "ff-only", &fast_forward, NULL,
 208                N_("abort if fast-forward is not possible"),
 209                PARSE_OPT_NOARG | PARSE_OPT_NONEG, NULL, FF_ONLY },
 210        OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 211        OPT_BOOL(0, "verify-signatures", &verify_signatures,
 212                N_("Verify that the named commit has a valid GPG signature")),
 213        OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
 214                N_("merge strategy to use"), option_parse_strategy),
 215        OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
 216                N_("option for selected merge strategy"), option_parse_x),
 217        OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
 218                N_("merge commit message (for a non-fast-forward merge)"),
 219                option_parse_message),
 220        OPT__VERBOSITY(&verbosity),
 221        OPT_BOOL(0, "abort", &abort_current_merge,
 222                N_("abort the current in-progress merge")),
 223        OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
 224        { OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
 225          N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 226        OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
 227        OPT_END()
 228};
 229
 230/* Cleans up metadata that is uninteresting after a succeeded merge. */
 231static void drop_save(void)
 232{
 233        unlink(git_path("MERGE_HEAD"));
 234        unlink(git_path("MERGE_MSG"));
 235        unlink(git_path("MERGE_MODE"));
 236}
 237
 238static int save_state(unsigned char *stash)
 239{
 240        int len;
 241        struct child_process cp = CHILD_PROCESS_INIT;
 242        struct strbuf buffer = STRBUF_INIT;
 243        const char *argv[] = {"stash", "create", NULL};
 244
 245        cp.argv = argv;
 246        cp.out = -1;
 247        cp.git_cmd = 1;
 248
 249        if (start_command(&cp))
 250                die(_("could not run stash."));
 251        len = strbuf_read(&buffer, cp.out, 1024);
 252        close(cp.out);
 253
 254        if (finish_command(&cp) || len < 0)
 255                die(_("stash failed"));
 256        else if (!len)          /* no changes */
 257                return -1;
 258        strbuf_setlen(&buffer, buffer.len-1);
 259        if (get_sha1(buffer.buf, stash))
 260                die(_("not a valid object: %s"), buffer.buf);
 261        return 0;
 262}
 263
 264static void read_empty(unsigned const char *sha1, int verbose)
 265{
 266        int i = 0;
 267        const char *args[7];
 268
 269        args[i++] = "read-tree";
 270        if (verbose)
 271                args[i++] = "-v";
 272        args[i++] = "-m";
 273        args[i++] = "-u";
 274        args[i++] = EMPTY_TREE_SHA1_HEX;
 275        args[i++] = sha1_to_hex(sha1);
 276        args[i] = NULL;
 277
 278        if (run_command_v_opt(args, RUN_GIT_CMD))
 279                die(_("read-tree failed"));
 280}
 281
 282static void reset_hard(unsigned const char *sha1, int verbose)
 283{
 284        int i = 0;
 285        const char *args[6];
 286
 287        args[i++] = "read-tree";
 288        if (verbose)
 289                args[i++] = "-v";
 290        args[i++] = "--reset";
 291        args[i++] = "-u";
 292        args[i++] = sha1_to_hex(sha1);
 293        args[i] = NULL;
 294
 295        if (run_command_v_opt(args, RUN_GIT_CMD))
 296                die(_("read-tree failed"));
 297}
 298
 299static void restore_state(const unsigned char *head,
 300                          const unsigned char *stash)
 301{
 302        struct strbuf sb = STRBUF_INIT;
 303        const char *args[] = { "stash", "apply", NULL, NULL };
 304
 305        if (is_null_sha1(stash))
 306                return;
 307
 308        reset_hard(head, 1);
 309
 310        args[2] = sha1_to_hex(stash);
 311
 312        /*
 313         * It is OK to ignore error here, for example when there was
 314         * nothing to restore.
 315         */
 316        run_command_v_opt(args, RUN_GIT_CMD);
 317
 318        strbuf_release(&sb);
 319        refresh_cache(REFRESH_QUIET);
 320}
 321
 322/* This is called when no merge was necessary. */
 323static void finish_up_to_date(const char *msg)
 324{
 325        if (verbosity >= 0)
 326                printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 327        drop_save();
 328}
 329
 330static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 331{
 332        struct rev_info rev;
 333        struct strbuf out = STRBUF_INIT;
 334        struct commit_list *j;
 335        const char *filename;
 336        int fd;
 337        struct pretty_print_context ctx = {0};
 338
 339        printf(_("Squash commit -- not updating HEAD\n"));
 340        filename = git_path("SQUASH_MSG");
 341        fd = open(filename, O_WRONLY | O_CREAT, 0666);
 342        if (fd < 0)
 343                die_errno(_("Could not write to '%s'"), filename);
 344
 345        init_revisions(&rev, NULL);
 346        rev.ignore_merges = 1;
 347        rev.commit_format = CMIT_FMT_MEDIUM;
 348
 349        commit->object.flags |= UNINTERESTING;
 350        add_pending_object(&rev, &commit->object, NULL);
 351
 352        for (j = remoteheads; j; j = j->next)
 353                add_pending_object(&rev, &j->item->object, NULL);
 354
 355        setup_revisions(0, NULL, &rev, NULL);
 356        if (prepare_revision_walk(&rev))
 357                die(_("revision walk setup failed"));
 358
 359        ctx.abbrev = rev.abbrev;
 360        ctx.date_mode = rev.date_mode;
 361        ctx.fmt = rev.commit_format;
 362
 363        strbuf_addstr(&out, "Squashed commit of the following:\n");
 364        while ((commit = get_revision(&rev)) != NULL) {
 365                strbuf_addch(&out, '\n');
 366                strbuf_addf(&out, "commit %s\n",
 367                        sha1_to_hex(commit->object.sha1));
 368                pretty_print_commit(&ctx, commit, &out);
 369        }
 370        if (write_in_full(fd, out.buf, out.len) != out.len)
 371                die_errno(_("Writing SQUASH_MSG"));
 372        if (close(fd))
 373                die_errno(_("Finishing SQUASH_MSG"));
 374        strbuf_release(&out);
 375}
 376
 377static void finish(struct commit *head_commit,
 378                   struct commit_list *remoteheads,
 379                   const unsigned char *new_head, const char *msg)
 380{
 381        struct strbuf reflog_message = STRBUF_INIT;
 382        const unsigned char *head = head_commit->object.sha1;
 383
 384        if (!msg)
 385                strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 386        else {
 387                if (verbosity >= 0)
 388                        printf("%s\n", msg);
 389                strbuf_addf(&reflog_message, "%s: %s",
 390                        getenv("GIT_REFLOG_ACTION"), msg);
 391        }
 392        if (squash) {
 393                squash_message(head_commit, remoteheads);
 394        } else {
 395                if (verbosity >= 0 && !merge_msg.len)
 396                        printf(_("No merge message -- not updating HEAD\n"));
 397                else {
 398                        const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 399                        update_ref(reflog_message.buf, "HEAD",
 400                                new_head, head, 0,
 401                                UPDATE_REFS_DIE_ON_ERR);
 402                        /*
 403                         * We ignore errors in 'gc --auto', since the
 404                         * user should see them.
 405                         */
 406                        run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 407                }
 408        }
 409        if (new_head && show_diffstat) {
 410                struct diff_options opts;
 411                diff_setup(&opts);
 412                opts.stat_width = -1; /* use full terminal width */
 413                opts.stat_graph_width = -1; /* respect statGraphWidth config */
 414                opts.output_format |=
 415                        DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 416                opts.detect_rename = DIFF_DETECT_RENAME;
 417                diff_setup_done(&opts);
 418                diff_tree_sha1(head, new_head, "", &opts);
 419                diffcore_std(&opts);
 420                diff_flush(&opts);
 421        }
 422
 423        /* Run a post-merge hook */
 424        run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
 425
 426        strbuf_release(&reflog_message);
 427}
 428
 429/* Get the name for the merge commit's message. */
 430static void merge_name(const char *remote, struct strbuf *msg)
 431{
 432        struct commit *remote_head;
 433        unsigned char branch_head[20];
 434        struct strbuf buf = STRBUF_INIT;
 435        struct strbuf bname = STRBUF_INIT;
 436        const char *ptr;
 437        char *found_ref;
 438        int len, early;
 439
 440        strbuf_branchname(&bname, remote);
 441        remote = bname.buf;
 442
 443        memset(branch_head, 0, sizeof(branch_head));
 444        remote_head = get_merge_parent(remote);
 445        if (!remote_head)
 446                die(_("'%s' does not point to a commit"), remote);
 447
 448        if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 449                if (starts_with(found_ref, "refs/heads/")) {
 450                        strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 451                                    sha1_to_hex(branch_head), remote);
 452                        goto cleanup;
 453                }
 454                if (starts_with(found_ref, "refs/tags/")) {
 455                        strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 456                                    sha1_to_hex(branch_head), remote);
 457                        goto cleanup;
 458                }
 459                if (starts_with(found_ref, "refs/remotes/")) {
 460                        strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 461                                    sha1_to_hex(branch_head), remote);
 462                        goto cleanup;
 463                }
 464        }
 465
 466        /* See if remote matches <name>^^^.. or <name>~<number> */
 467        for (len = 0, ptr = remote + strlen(remote);
 468             remote < ptr && ptr[-1] == '^';
 469             ptr--)
 470                len++;
 471        if (len)
 472                early = 1;
 473        else {
 474                early = 0;
 475                ptr = strrchr(remote, '~');
 476                if (ptr) {
 477                        int seen_nonzero = 0;
 478
 479                        len++; /* count ~ */
 480                        while (*++ptr && isdigit(*ptr)) {
 481                                seen_nonzero |= (*ptr != '0');
 482                                len++;
 483                        }
 484                        if (*ptr)
 485                                len = 0; /* not ...~<number> */
 486                        else if (seen_nonzero)
 487                                early = 1;
 488                        else if (len == 1)
 489                                early = 1; /* "name~" is "name~1"! */
 490                }
 491        }
 492        if (len) {
 493                struct strbuf truname = STRBUF_INIT;
 494                strbuf_addstr(&truname, "refs/heads/");
 495                strbuf_addstr(&truname, remote);
 496                strbuf_setlen(&truname, truname.len - len);
 497                if (ref_exists(truname.buf)) {
 498                        strbuf_addf(msg,
 499                                    "%s\t\tbranch '%s'%s of .\n",
 500                                    sha1_to_hex(remote_head->object.sha1),
 501                                    truname.buf + 11,
 502                                    (early ? " (early part)" : ""));
 503                        strbuf_release(&truname);
 504                        goto cleanup;
 505                }
 506        }
 507
 508        if (!strcmp(remote, "FETCH_HEAD") &&
 509                        !access(git_path("FETCH_HEAD"), R_OK)) {
 510                const char *filename;
 511                FILE *fp;
 512                struct strbuf line = STRBUF_INIT;
 513                char *ptr;
 514
 515                filename = git_path("FETCH_HEAD");
 516                fp = fopen(filename, "r");
 517                if (!fp)
 518                        die_errno(_("could not open '%s' for reading"),
 519                                  filename);
 520                strbuf_getline(&line, fp, '\n');
 521                fclose(fp);
 522                ptr = strstr(line.buf, "\tnot-for-merge\t");
 523                if (ptr)
 524                        strbuf_remove(&line, ptr-line.buf+1, 13);
 525                strbuf_addbuf(msg, &line);
 526                strbuf_release(&line);
 527                goto cleanup;
 528        }
 529
 530        if (remote_head->util) {
 531                struct merge_remote_desc *desc;
 532                desc = merge_remote_util(remote_head);
 533                if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 534                        strbuf_addf(msg, "%s\t\t%s '%s'\n",
 535                                    sha1_to_hex(desc->obj->sha1),
 536                                    typename(desc->obj->type),
 537                                    remote);
 538                        goto cleanup;
 539                }
 540        }
 541
 542        strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 543                sha1_to_hex(remote_head->object.sha1), remote);
 544cleanup:
 545        strbuf_release(&buf);
 546        strbuf_release(&bname);
 547}
 548
 549static void parse_branch_merge_options(char *bmo)
 550{
 551        const char **argv;
 552        int argc;
 553
 554        if (!bmo)
 555                return;
 556        argc = split_cmdline(bmo, &argv);
 557        if (argc < 0)
 558                die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 559                    split_cmdline_strerror(argc));
 560        REALLOC_ARRAY(argv, argc + 2);
 561        memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 562        argc++;
 563        argv[0] = "branch.*.mergeoptions";
 564        parse_options(argc, argv, NULL, builtin_merge_options,
 565                      builtin_merge_usage, 0);
 566        free(argv);
 567}
 568
 569static int git_merge_config(const char *k, const char *v, void *cb)
 570{
 571        int status;
 572
 573        if (branch && starts_with(k, "branch.") &&
 574                starts_with(k + 7, branch) &&
 575                !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 576                free(branch_mergeoptions);
 577                branch_mergeoptions = xstrdup(v);
 578                return 0;
 579        }
 580
 581        if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 582                show_diffstat = git_config_bool(k, v);
 583        else if (!strcmp(k, "pull.twohead"))
 584                return git_config_string(&pull_twohead, k, v);
 585        else if (!strcmp(k, "pull.octopus"))
 586                return git_config_string(&pull_octopus, k, v);
 587        else if (!strcmp(k, "merge.renormalize"))
 588                option_renormalize = git_config_bool(k, v);
 589        else if (!strcmp(k, "merge.ff")) {
 590                int boolval = git_config_maybe_bool(k, v);
 591                if (0 <= boolval) {
 592                        fast_forward = boolval ? FF_ALLOW : FF_NO;
 593                } else if (v && !strcmp(v, "only")) {
 594                        fast_forward = FF_ONLY;
 595                } /* do not barf on values from future versions of git */
 596                return 0;
 597        } else if (!strcmp(k, "merge.defaulttoupstream")) {
 598                default_to_upstream = git_config_bool(k, v);
 599                return 0;
 600        } else if (!strcmp(k, "commit.gpgsign")) {
 601                sign_commit = git_config_bool(k, v) ? "" : NULL;
 602                return 0;
 603        }
 604
 605        status = fmt_merge_msg_config(k, v, cb);
 606        if (status)
 607                return status;
 608        status = git_gpg_config(k, v, NULL);
 609        if (status)
 610                return status;
 611        return git_diff_ui_config(k, v, cb);
 612}
 613
 614static int read_tree_trivial(unsigned char *common, unsigned char *head,
 615                             unsigned char *one)
 616{
 617        int i, nr_trees = 0;
 618        struct tree *trees[MAX_UNPACK_TREES];
 619        struct tree_desc t[MAX_UNPACK_TREES];
 620        struct unpack_trees_options opts;
 621
 622        memset(&opts, 0, sizeof(opts));
 623        opts.head_idx = 2;
 624        opts.src_index = &the_index;
 625        opts.dst_index = &the_index;
 626        opts.update = 1;
 627        opts.verbose_update = 1;
 628        opts.trivial_merges_only = 1;
 629        opts.merge = 1;
 630        trees[nr_trees] = parse_tree_indirect(common);
 631        if (!trees[nr_trees++])
 632                return -1;
 633        trees[nr_trees] = parse_tree_indirect(head);
 634        if (!trees[nr_trees++])
 635                return -1;
 636        trees[nr_trees] = parse_tree_indirect(one);
 637        if (!trees[nr_trees++])
 638                return -1;
 639        opts.fn = threeway_merge;
 640        cache_tree_free(&active_cache_tree);
 641        for (i = 0; i < nr_trees; i++) {
 642                parse_tree(trees[i]);
 643                init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 644        }
 645        if (unpack_trees(nr_trees, t, &opts))
 646                return -1;
 647        return 0;
 648}
 649
 650static void write_tree_trivial(unsigned char *sha1)
 651{
 652        if (write_cache_as_tree(sha1, 0, NULL))
 653                die(_("git write-tree failed to write a tree"));
 654}
 655
 656static int try_merge_strategy(const char *strategy, struct commit_list *common,
 657                              struct commit_list *remoteheads,
 658                              struct commit *head, const char *head_arg)
 659{
 660        static struct lock_file lock;
 661
 662        hold_locked_index(&lock, 1);
 663        refresh_cache(REFRESH_QUIET);
 664        if (active_cache_changed &&
 665            write_locked_index(&the_index, &lock, COMMIT_LOCK))
 666                return error(_("Unable to write index."));
 667        rollback_lock_file(&lock);
 668
 669        if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 670                int clean, x;
 671                struct commit *result;
 672                struct commit_list *reversed = NULL;
 673                struct merge_options o;
 674                struct commit_list *j;
 675
 676                if (remoteheads->next) {
 677                        error(_("Not handling anything other than two heads merge."));
 678                        return 2;
 679                }
 680
 681                init_merge_options(&o);
 682                if (!strcmp(strategy, "subtree"))
 683                        o.subtree_shift = "";
 684
 685                o.renormalize = option_renormalize;
 686                o.show_rename_progress =
 687                        show_progress == -1 ? isatty(2) : show_progress;
 688
 689                for (x = 0; x < xopts_nr; x++)
 690                        if (parse_merge_opt(&o, xopts[x]))
 691                                die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 692
 693                o.branch1 = head_arg;
 694                o.branch2 = merge_remote_util(remoteheads->item)->name;
 695
 696                for (j = common; j; j = j->next)
 697                        commit_list_insert(j->item, &reversed);
 698
 699                hold_locked_index(&lock, 1);
 700                clean = merge_recursive(&o, head,
 701                                remoteheads->item, reversed, &result);
 702                if (active_cache_changed &&
 703                    write_locked_index(&the_index, &lock, COMMIT_LOCK))
 704                        die (_("unable to write %s"), get_index_file());
 705                rollback_lock_file(&lock);
 706                return clean ? 0 : 1;
 707        } else {
 708                return try_merge_command(strategy, xopts_nr, xopts,
 709                                                common, head_arg, remoteheads);
 710        }
 711}
 712
 713static void count_diff_files(struct diff_queue_struct *q,
 714                             struct diff_options *opt, void *data)
 715{
 716        int *count = data;
 717
 718        (*count) += q->nr;
 719}
 720
 721static int count_unmerged_entries(void)
 722{
 723        int i, ret = 0;
 724
 725        for (i = 0; i < active_nr; i++)
 726                if (ce_stage(active_cache[i]))
 727                        ret++;
 728
 729        return ret;
 730}
 731
 732static void split_merge_strategies(const char *string, struct strategy **list,
 733                                   int *nr, int *alloc)
 734{
 735        char *p, *q, *buf;
 736
 737        if (!string)
 738                return;
 739
 740        buf = xstrdup(string);
 741        q = buf;
 742        for (;;) {
 743                p = strchr(q, ' ');
 744                if (!p) {
 745                        ALLOC_GROW(*list, *nr + 1, *alloc);
 746                        (*list)[(*nr)++].name = xstrdup(q);
 747                        free(buf);
 748                        return;
 749                } else {
 750                        *p = '\0';
 751                        ALLOC_GROW(*list, *nr + 1, *alloc);
 752                        (*list)[(*nr)++].name = xstrdup(q);
 753                        q = ++p;
 754                }
 755        }
 756}
 757
 758static void add_strategies(const char *string, unsigned attr)
 759{
 760        struct strategy *list = NULL;
 761        int list_alloc = 0, list_nr = 0, i;
 762
 763        memset(&list, 0, sizeof(list));
 764        split_merge_strategies(string, &list, &list_nr, &list_alloc);
 765        if (list) {
 766                for (i = 0; i < list_nr; i++)
 767                        append_strategy(get_strategy(list[i].name));
 768                return;
 769        }
 770        for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 771                if (all_strategy[i].attr & attr)
 772                        append_strategy(&all_strategy[i]);
 773
 774}
 775
 776static void write_merge_msg(struct strbuf *msg)
 777{
 778        const char *filename = git_path("MERGE_MSG");
 779        int fd = open(filename, O_WRONLY | O_CREAT, 0666);
 780        if (fd < 0)
 781                die_errno(_("Could not open '%s' for writing"),
 782                          filename);
 783        if (write_in_full(fd, msg->buf, msg->len) != msg->len)
 784                die_errno(_("Could not write to '%s'"), filename);
 785        close(fd);
 786}
 787
 788static void read_merge_msg(struct strbuf *msg)
 789{
 790        const char *filename = git_path("MERGE_MSG");
 791        strbuf_reset(msg);
 792        if (strbuf_read_file(msg, filename, 0) < 0)
 793                die_errno(_("Could not read from '%s'"), filename);
 794}
 795
 796static void write_merge_state(struct commit_list *);
 797static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
 798{
 799        if (err_msg)
 800                error("%s", err_msg);
 801        fprintf(stderr,
 802                _("Not committing merge; use 'git commit' to complete the merge.\n"));
 803        write_merge_state(remoteheads);
 804        exit(1);
 805}
 806
 807static const char merge_editor_comment[] =
 808N_("Please enter a commit message to explain why this merge is necessary,\n"
 809   "especially if it merges an updated upstream into a topic branch.\n"
 810   "\n"
 811   "Lines starting with '%c' will be ignored, and an empty message aborts\n"
 812   "the commit.\n");
 813
 814static void prepare_to_commit(struct commit_list *remoteheads)
 815{
 816        struct strbuf msg = STRBUF_INIT;
 817        strbuf_addbuf(&msg, &merge_msg);
 818        strbuf_addch(&msg, '\n');
 819        if (0 < option_edit)
 820                strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
 821        write_merge_msg(&msg);
 822        if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
 823                            git_path("MERGE_MSG"), "merge", NULL))
 824                abort_commit(remoteheads, NULL);
 825        if (0 < option_edit) {
 826                if (launch_editor(git_path("MERGE_MSG"), NULL, NULL))
 827                        abort_commit(remoteheads, NULL);
 828        }
 829        read_merge_msg(&msg);
 830        stripspace(&msg, 0 < option_edit);
 831        if (!msg.len)
 832                abort_commit(remoteheads, _("Empty commit message."));
 833        strbuf_release(&merge_msg);
 834        strbuf_addbuf(&merge_msg, &msg);
 835        strbuf_release(&msg);
 836}
 837
 838static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 839{
 840        unsigned char result_tree[20], result_commit[20];
 841        struct commit_list *parents, **pptr = &parents;
 842
 843        write_tree_trivial(result_tree);
 844        printf(_("Wonderful.\n"));
 845        pptr = commit_list_append(head, pptr);
 846        pptr = commit_list_append(remoteheads->item, pptr);
 847        prepare_to_commit(remoteheads);
 848        if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 849                        result_commit, NULL, sign_commit))
 850                die(_("failed to write commit object"));
 851        finish(head, remoteheads, result_commit, "In-index merge");
 852        drop_save();
 853        return 0;
 854}
 855
 856static int finish_automerge(struct commit *head,
 857                            int head_subsumed,
 858                            struct commit_list *common,
 859                            struct commit_list *remoteheads,
 860                            unsigned char *result_tree,
 861                            const char *wt_strategy)
 862{
 863        struct commit_list *parents = NULL;
 864        struct strbuf buf = STRBUF_INIT;
 865        unsigned char result_commit[20];
 866
 867        free_commit_list(common);
 868        parents = remoteheads;
 869        if (!head_subsumed || fast_forward == FF_NO)
 870                commit_list_insert(head, &parents);
 871        strbuf_addch(&merge_msg, '\n');
 872        prepare_to_commit(remoteheads);
 873        if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
 874                        result_commit, NULL, sign_commit))
 875                die(_("failed to write commit object"));
 876        strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 877        finish(head, remoteheads, result_commit, buf.buf);
 878        strbuf_release(&buf);
 879        drop_save();
 880        return 0;
 881}
 882
 883static int suggest_conflicts(int renormalizing)
 884{
 885        const char *filename;
 886        FILE *fp;
 887        int pos;
 888
 889        filename = git_path("MERGE_MSG");
 890        fp = fopen(filename, "a");
 891        if (!fp)
 892                die_errno(_("Could not open '%s' for writing"), filename);
 893        fprintf(fp, "\nConflicts:\n");
 894        for (pos = 0; pos < active_nr; pos++) {
 895                const struct cache_entry *ce = active_cache[pos];
 896
 897                if (ce_stage(ce)) {
 898                        fprintf(fp, "\t%s\n", ce->name);
 899                        while (pos + 1 < active_nr &&
 900                                        !strcmp(ce->name,
 901                                                active_cache[pos + 1]->name))
 902                                pos++;
 903                }
 904        }
 905        fclose(fp);
 906        rerere(allow_rerere_auto);
 907        printf(_("Automatic merge failed; "
 908                        "fix conflicts and then commit the result.\n"));
 909        return 1;
 910}
 911
 912static struct commit *is_old_style_invocation(int argc, const char **argv,
 913                                              const unsigned char *head)
 914{
 915        struct commit *second_token = NULL;
 916        if (argc > 2) {
 917                unsigned char second_sha1[20];
 918
 919                if (get_sha1(argv[1], second_sha1))
 920                        return NULL;
 921                second_token = lookup_commit_reference_gently(second_sha1, 0);
 922                if (!second_token)
 923                        die(_("'%s' is not a commit"), argv[1]);
 924                if (hashcmp(second_token->object.sha1, head))
 925                        return NULL;
 926        }
 927        return second_token;
 928}
 929
 930static int evaluate_result(void)
 931{
 932        int cnt = 0;
 933        struct rev_info rev;
 934
 935        /* Check how many files differ. */
 936        init_revisions(&rev, "");
 937        setup_revisions(0, NULL, &rev, NULL);
 938        rev.diffopt.output_format |=
 939                DIFF_FORMAT_CALLBACK;
 940        rev.diffopt.format_callback = count_diff_files;
 941        rev.diffopt.format_callback_data = &cnt;
 942        run_diff_files(&rev, 0);
 943
 944        /*
 945         * Check how many unmerged entries are
 946         * there.
 947         */
 948        cnt += count_unmerged_entries();
 949
 950        return cnt;
 951}
 952
 953/*
 954 * Pretend as if the user told us to merge with the remote-tracking
 955 * branch we have for the upstream of the current branch
 956 */
 957static int setup_with_upstream(const char ***argv)
 958{
 959        struct branch *branch = branch_get(NULL);
 960        int i;
 961        const char **args;
 962
 963        if (!branch)
 964                die(_("No current branch."));
 965        if (!branch->remote)
 966                die(_("No remote for the current branch."));
 967        if (!branch->merge_nr)
 968                die(_("No default upstream defined for the current branch."));
 969
 970        args = xcalloc(branch->merge_nr + 1, sizeof(char *));
 971        for (i = 0; i < branch->merge_nr; i++) {
 972                if (!branch->merge[i]->dst)
 973                        die(_("No remote-tracking branch for %s from %s"),
 974                            branch->merge[i]->src, branch->remote_name);
 975                args[i] = branch->merge[i]->dst;
 976        }
 977        args[i] = NULL;
 978        *argv = args;
 979        return i;
 980}
 981
 982static void write_merge_state(struct commit_list *remoteheads)
 983{
 984        const char *filename;
 985        int fd;
 986        struct commit_list *j;
 987        struct strbuf buf = STRBUF_INIT;
 988
 989        for (j = remoteheads; j; j = j->next) {
 990                unsigned const char *sha1;
 991                struct commit *c = j->item;
 992                if (c->util && merge_remote_util(c)->obj) {
 993                        sha1 = merge_remote_util(c)->obj->sha1;
 994                } else {
 995                        sha1 = c->object.sha1;
 996                }
 997                strbuf_addf(&buf, "%s\n", sha1_to_hex(sha1));
 998        }
 999        filename = git_path("MERGE_HEAD");
1000        fd = open(filename, O_WRONLY | O_CREAT, 0666);
1001        if (fd < 0)
1002                die_errno(_("Could not open '%s' for writing"), filename);
1003        if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1004                die_errno(_("Could not write to '%s'"), filename);
1005        close(fd);
1006        strbuf_addch(&merge_msg, '\n');
1007        write_merge_msg(&merge_msg);
1008
1009        filename = git_path("MERGE_MODE");
1010        fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
1011        if (fd < 0)
1012                die_errno(_("Could not open '%s' for writing"), filename);
1013        strbuf_reset(&buf);
1014        if (fast_forward == FF_NO)
1015                strbuf_addf(&buf, "no-ff");
1016        if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1017                die_errno(_("Could not write to '%s'"), filename);
1018        close(fd);
1019}
1020
1021static int default_edit_option(void)
1022{
1023        static const char name[] = "GIT_MERGE_AUTOEDIT";
1024        const char *e = getenv(name);
1025        struct stat st_stdin, st_stdout;
1026
1027        if (have_message)
1028                /* an explicit -m msg without --[no-]edit */
1029                return 0;
1030
1031        if (e) {
1032                int v = git_config_maybe_bool(name, e);
1033                if (v < 0)
1034                        die("Bad value '%s' in environment '%s'", e, name);
1035                return v;
1036        }
1037
1038        /* Use editor if stdin and stdout are the same and is a tty */
1039        return (!fstat(0, &st_stdin) &&
1040                !fstat(1, &st_stdout) &&
1041                isatty(0) && isatty(1) &&
1042                st_stdin.st_dev == st_stdout.st_dev &&
1043                st_stdin.st_ino == st_stdout.st_ino &&
1044                st_stdin.st_mode == st_stdout.st_mode);
1045}
1046
1047static struct commit_list *collect_parents(struct commit *head_commit,
1048                                           int *head_subsumed,
1049                                           int argc, const char **argv)
1050{
1051        int i;
1052        struct commit_list *remoteheads = NULL, *parents, *next;
1053        struct commit_list **remotes = &remoteheads;
1054
1055        if (head_commit)
1056                remotes = &commit_list_insert(head_commit, remotes)->next;
1057        for (i = 0; i < argc; i++) {
1058                struct commit *commit = get_merge_parent(argv[i]);
1059                if (!commit)
1060                        help_unknown_ref(argv[i], "merge",
1061                                         "not something we can merge");
1062                remotes = &commit_list_insert(commit, remotes)->next;
1063        }
1064        *remotes = NULL;
1065
1066        parents = reduce_heads(remoteheads);
1067
1068        *head_subsumed = 1; /* we will flip this to 0 when we find it */
1069        for (remoteheads = NULL, remotes = &remoteheads;
1070             parents;
1071             parents = next) {
1072                struct commit *commit = parents->item;
1073                next = parents->next;
1074                if (commit == head_commit)
1075                        *head_subsumed = 0;
1076                else
1077                        remotes = &commit_list_insert(commit, remotes)->next;
1078        }
1079        return remoteheads;
1080}
1081
1082int cmd_merge(int argc, const char **argv, const char *prefix)
1083{
1084        unsigned char result_tree[20];
1085        unsigned char stash[20];
1086        unsigned char head_sha1[20];
1087        struct commit *head_commit;
1088        struct strbuf buf = STRBUF_INIT;
1089        const char *head_arg;
1090        int flag, i, ret = 0, head_subsumed;
1091        int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1092        struct commit_list *common = NULL;
1093        const char *best_strategy = NULL, *wt_strategy = NULL;
1094        struct commit_list *remoteheads, *p;
1095        void *branch_to_free;
1096
1097        if (argc == 2 && !strcmp(argv[1], "-h"))
1098                usage_with_options(builtin_merge_usage, builtin_merge_options);
1099
1100        /*
1101         * Check if we are _not_ on a detached HEAD, i.e. if there is a
1102         * current branch.
1103         */
1104        branch = branch_to_free = resolve_refdup("HEAD", 0, head_sha1, &flag);
1105        if (branch && starts_with(branch, "refs/heads/"))
1106                branch += 11;
1107        if (!branch || is_null_sha1(head_sha1))
1108                head_commit = NULL;
1109        else
1110                head_commit = lookup_commit_or_die(head_sha1, "HEAD");
1111
1112        git_config(git_merge_config, NULL);
1113
1114        if (branch_mergeoptions)
1115                parse_branch_merge_options(branch_mergeoptions);
1116        argc = parse_options(argc, argv, prefix, builtin_merge_options,
1117                        builtin_merge_usage, 0);
1118        if (shortlog_len < 0)
1119                shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1120
1121        if (verbosity < 0 && show_progress == -1)
1122                show_progress = 0;
1123
1124        if (abort_current_merge) {
1125                int nargc = 2;
1126                const char *nargv[] = {"reset", "--merge", NULL};
1127
1128                if (!file_exists(git_path("MERGE_HEAD")))
1129                        die(_("There is no merge to abort (MERGE_HEAD missing)."));
1130
1131                /* Invoke 'git reset --merge' */
1132                ret = cmd_reset(nargc, nargv, prefix);
1133                goto done;
1134        }
1135
1136        if (read_cache_unmerged())
1137                die_resolve_conflict("merge");
1138
1139        if (file_exists(git_path("MERGE_HEAD"))) {
1140                /*
1141                 * There is no unmerged entry, don't advise 'git
1142                 * add/rm <file>', just 'git commit'.
1143                 */
1144                if (advice_resolve_conflict)
1145                        die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1146                                  "Please, commit your changes before you merge."));
1147                else
1148                        die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1149        }
1150        if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1151                if (advice_resolve_conflict)
1152                        die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1153                            "Please, commit your changes before you merge."));
1154                else
1155                        die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1156        }
1157        resolve_undo_clear();
1158
1159        if (verbosity < 0)
1160                show_diffstat = 0;
1161
1162        if (squash) {
1163                if (fast_forward == FF_NO)
1164                        die(_("You cannot combine --squash with --no-ff."));
1165                option_commit = 0;
1166        }
1167
1168        if (!abort_current_merge) {
1169                if (!argc) {
1170                        if (default_to_upstream)
1171                                argc = setup_with_upstream(&argv);
1172                        else
1173                                die(_("No commit specified and merge.defaultToUpstream not set."));
1174                } else if (argc == 1 && !strcmp(argv[0], "-"))
1175                        argv[0] = "@{-1}";
1176        }
1177        if (!argc)
1178                usage_with_options(builtin_merge_usage,
1179                        builtin_merge_options);
1180
1181        /*
1182         * This could be traditional "merge <msg> HEAD <commit>..."  and
1183         * the way we can tell it is to see if the second token is HEAD,
1184         * but some people might have misused the interface and used a
1185         * commit-ish that is the same as HEAD there instead.
1186         * Traditional format never would have "-m" so it is an
1187         * additional safety measure to check for it.
1188         */
1189
1190        if (!have_message && head_commit &&
1191            is_old_style_invocation(argc, argv, head_commit->object.sha1)) {
1192                strbuf_addstr(&merge_msg, argv[0]);
1193                head_arg = argv[1];
1194                argv += 2;
1195                argc -= 2;
1196                remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
1197        } else if (!head_commit) {
1198                struct commit *remote_head;
1199                /*
1200                 * If the merged head is a valid one there is no reason
1201                 * to forbid "git merge" into a branch yet to be born.
1202                 * We do the same for "git pull".
1203                 */
1204                if (argc != 1)
1205                        die(_("Can merge only exactly one commit into "
1206                                "empty head"));
1207                if (squash)
1208                        die(_("Squash commit into empty head not supported yet"));
1209                if (fast_forward == FF_NO)
1210                        die(_("Non-fast-forward commit does not make sense into "
1211                            "an empty head"));
1212                remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
1213                remote_head = remoteheads->item;
1214                if (!remote_head)
1215                        die(_("%s - not something we can merge"), argv[0]);
1216                read_empty(remote_head->object.sha1, 0);
1217                update_ref("initial pull", "HEAD", remote_head->object.sha1,
1218                           NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1219                goto done;
1220        } else {
1221                struct strbuf merge_names = STRBUF_INIT;
1222
1223                /* We are invoked directly as the first-class UI. */
1224                head_arg = "HEAD";
1225
1226                /*
1227                 * All the rest are the commits being merged; prepare
1228                 * the standard merge summary message to be appended
1229                 * to the given message.
1230                 */
1231                remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
1232                for (p = remoteheads; p; p = p->next)
1233                        merge_name(merge_remote_util(p->item)->name, &merge_names);
1234
1235                if (!have_message || shortlog_len) {
1236                        struct fmt_merge_msg_opts opts;
1237                        memset(&opts, 0, sizeof(opts));
1238                        opts.add_title = !have_message;
1239                        opts.shortlog_len = shortlog_len;
1240                        opts.credit_people = (0 < option_edit);
1241
1242                        fmt_merge_msg(&merge_names, &merge_msg, &opts);
1243                        if (merge_msg.len)
1244                                strbuf_setlen(&merge_msg, merge_msg.len - 1);
1245                }
1246        }
1247
1248        if (!head_commit || !argc)
1249                usage_with_options(builtin_merge_usage,
1250                        builtin_merge_options);
1251
1252        if (verify_signatures) {
1253                for (p = remoteheads; p; p = p->next) {
1254                        struct commit *commit = p->item;
1255                        char hex[41];
1256                        struct signature_check signature_check;
1257                        memset(&signature_check, 0, sizeof(signature_check));
1258
1259                        check_commit_signature(commit, &signature_check);
1260
1261                        strcpy(hex, find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
1262                        switch (signature_check.result) {
1263                        case 'G':
1264                                break;
1265                        case 'U':
1266                                die(_("Commit %s has an untrusted GPG signature, "
1267                                      "allegedly by %s."), hex, signature_check.signer);
1268                        case 'B':
1269                                die(_("Commit %s has a bad GPG signature "
1270                                      "allegedly by %s."), hex, signature_check.signer);
1271                        default: /* 'N' */
1272                                die(_("Commit %s does not have a GPG signature."), hex);
1273                        }
1274                        if (verbosity >= 0 && signature_check.result == 'G')
1275                                printf(_("Commit %s has a good GPG signature by %s\n"),
1276                                       hex, signature_check.signer);
1277
1278                        signature_check_clear(&signature_check);
1279                }
1280        }
1281
1282        strbuf_addstr(&buf, "merge");
1283        for (p = remoteheads; p; p = p->next)
1284                strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
1285        setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1286        strbuf_reset(&buf);
1287
1288        for (p = remoteheads; p; p = p->next) {
1289                struct commit *commit = p->item;
1290                strbuf_addf(&buf, "GITHEAD_%s",
1291                            sha1_to_hex(commit->object.sha1));
1292                setenv(buf.buf, merge_remote_util(commit)->name, 1);
1293                strbuf_reset(&buf);
1294                if (fast_forward != FF_ONLY &&
1295                    merge_remote_util(commit) &&
1296                    merge_remote_util(commit)->obj &&
1297                    merge_remote_util(commit)->obj->type == OBJ_TAG)
1298                        fast_forward = FF_NO;
1299        }
1300
1301        if (option_edit < 0)
1302                option_edit = default_edit_option();
1303
1304        if (!use_strategies) {
1305                if (!remoteheads)
1306                        ; /* already up-to-date */
1307                else if (!remoteheads->next)
1308                        add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1309                else
1310                        add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1311        }
1312
1313        for (i = 0; i < use_strategies_nr; i++) {
1314                if (use_strategies[i]->attr & NO_FAST_FORWARD)
1315                        fast_forward = FF_NO;
1316                if (use_strategies[i]->attr & NO_TRIVIAL)
1317                        allow_trivial = 0;
1318        }
1319
1320        if (!remoteheads)
1321                ; /* already up-to-date */
1322        else if (!remoteheads->next)
1323                common = get_merge_bases(head_commit, remoteheads->item, 1);
1324        else {
1325                struct commit_list *list = remoteheads;
1326                commit_list_insert(head_commit, &list);
1327                common = get_octopus_merge_bases(list);
1328                free(list);
1329        }
1330
1331        update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
1332                   NULL, 0, UPDATE_REFS_DIE_ON_ERR);
1333
1334        if (remoteheads && !common)
1335                ; /* No common ancestors found. We need a real merge. */
1336        else if (!remoteheads ||
1337                 (!remoteheads->next && !common->next &&
1338                  common->item == remoteheads->item)) {
1339                /*
1340                 * If head can reach all the merge then we are up to date.
1341                 * but first the most common case of merging one remote.
1342                 */
1343                finish_up_to_date("Already up-to-date.");
1344                goto done;
1345        } else if (fast_forward != FF_NO && !remoteheads->next &&
1346                        !common->next &&
1347                        !hashcmp(common->item->object.sha1, head_commit->object.sha1)) {
1348                /* Again the most common case of merging one remote. */
1349                struct strbuf msg = STRBUF_INIT;
1350                struct commit *commit;
1351                char hex[41];
1352
1353                strcpy(hex, find_unique_abbrev(head_commit->object.sha1, DEFAULT_ABBREV));
1354
1355                if (verbosity >= 0)
1356                        printf(_("Updating %s..%s\n"),
1357                                hex,
1358                                find_unique_abbrev(remoteheads->item->object.sha1,
1359                                DEFAULT_ABBREV));
1360                strbuf_addstr(&msg, "Fast-forward");
1361                if (have_message)
1362                        strbuf_addstr(&msg,
1363                                " (no commit created; -m option ignored)");
1364                commit = remoteheads->item;
1365                if (!commit) {
1366                        ret = 1;
1367                        goto done;
1368                }
1369
1370                if (checkout_fast_forward(head_commit->object.sha1,
1371                                          commit->object.sha1,
1372                                          overwrite_ignore)) {
1373                        ret = 1;
1374                        goto done;
1375                }
1376
1377                finish(head_commit, remoteheads, commit->object.sha1, msg.buf);
1378                drop_save();
1379                goto done;
1380        } else if (!remoteheads->next && common->next)
1381                ;
1382                /*
1383                 * We are not doing octopus and not fast-forward.  Need
1384                 * a real merge.
1385                 */
1386        else if (!remoteheads->next && !common->next && option_commit) {
1387                /*
1388                 * We are not doing octopus, not fast-forward, and have
1389                 * only one common.
1390                 */
1391                refresh_cache(REFRESH_QUIET);
1392                if (allow_trivial && fast_forward != FF_ONLY) {
1393                        /* See if it is really trivial. */
1394                        git_committer_info(IDENT_STRICT);
1395                        printf(_("Trying really trivial in-index merge...\n"));
1396                        if (!read_tree_trivial(common->item->object.sha1,
1397                                               head_commit->object.sha1,
1398                                               remoteheads->item->object.sha1)) {
1399                                ret = merge_trivial(head_commit, remoteheads);
1400                                goto done;
1401                        }
1402                        printf(_("Nope.\n"));
1403                }
1404        } else {
1405                /*
1406                 * An octopus.  If we can reach all the remote we are up
1407                 * to date.
1408                 */
1409                int up_to_date = 1;
1410                struct commit_list *j;
1411
1412                for (j = remoteheads; j; j = j->next) {
1413                        struct commit_list *common_one;
1414
1415                        /*
1416                         * Here we *have* to calculate the individual
1417                         * merge_bases again, otherwise "git merge HEAD^
1418                         * HEAD^^" would be missed.
1419                         */
1420                        common_one = get_merge_bases(head_commit, j->item, 1);
1421                        if (hashcmp(common_one->item->object.sha1,
1422                                j->item->object.sha1)) {
1423                                up_to_date = 0;
1424                                break;
1425                        }
1426                }
1427                if (up_to_date) {
1428                        finish_up_to_date("Already up-to-date. Yeeah!");
1429                        goto done;
1430                }
1431        }
1432
1433        if (fast_forward == FF_ONLY)
1434                die(_("Not possible to fast-forward, aborting."));
1435
1436        /* We are going to make a new commit. */
1437        git_committer_info(IDENT_STRICT);
1438
1439        /*
1440         * At this point, we need a real merge.  No matter what strategy
1441         * we use, it would operate on the index, possibly affecting the
1442         * working tree, and when resolved cleanly, have the desired
1443         * tree in the index -- this means that the index must be in
1444         * sync with the head commit.  The strategies are responsible
1445         * to ensure this.
1446         */
1447        if (use_strategies_nr == 1 ||
1448            /*
1449             * Stash away the local changes so that we can try more than one.
1450             */
1451            save_state(stash))
1452                hashcpy(stash, null_sha1);
1453
1454        for (i = 0; i < use_strategies_nr; i++) {
1455                int ret;
1456                if (i) {
1457                        printf(_("Rewinding the tree to pristine...\n"));
1458                        restore_state(head_commit->object.sha1, stash);
1459                }
1460                if (use_strategies_nr != 1)
1461                        printf(_("Trying merge strategy %s...\n"),
1462                                use_strategies[i]->name);
1463                /*
1464                 * Remember which strategy left the state in the working
1465                 * tree.
1466                 */
1467                wt_strategy = use_strategies[i]->name;
1468
1469                ret = try_merge_strategy(use_strategies[i]->name,
1470                                         common, remoteheads,
1471                                         head_commit, head_arg);
1472                if (!option_commit && !ret) {
1473                        merge_was_ok = 1;
1474                        /*
1475                         * This is necessary here just to avoid writing
1476                         * the tree, but later we will *not* exit with
1477                         * status code 1 because merge_was_ok is set.
1478                         */
1479                        ret = 1;
1480                }
1481
1482                if (ret) {
1483                        /*
1484                         * The backend exits with 1 when conflicts are
1485                         * left to be resolved, with 2 when it does not
1486                         * handle the given merge at all.
1487                         */
1488                        if (ret == 1) {
1489                                int cnt = evaluate_result();
1490
1491                                if (best_cnt <= 0 || cnt <= best_cnt) {
1492                                        best_strategy = use_strategies[i]->name;
1493                                        best_cnt = cnt;
1494                                }
1495                        }
1496                        if (merge_was_ok)
1497                                break;
1498                        else
1499                                continue;
1500                }
1501
1502                /* Automerge succeeded. */
1503                write_tree_trivial(result_tree);
1504                automerge_was_ok = 1;
1505                break;
1506        }
1507
1508        /*
1509         * If we have a resulting tree, that means the strategy module
1510         * auto resolved the merge cleanly.
1511         */
1512        if (automerge_was_ok) {
1513                ret = finish_automerge(head_commit, head_subsumed,
1514                                       common, remoteheads,
1515                                       result_tree, wt_strategy);
1516                goto done;
1517        }
1518
1519        /*
1520         * Pick the result from the best strategy and have the user fix
1521         * it up.
1522         */
1523        if (!best_strategy) {
1524                restore_state(head_commit->object.sha1, stash);
1525                if (use_strategies_nr > 1)
1526                        fprintf(stderr,
1527                                _("No merge strategy handled the merge.\n"));
1528                else
1529                        fprintf(stderr, _("Merge with strategy %s failed.\n"),
1530                                use_strategies[0]->name);
1531                ret = 2;
1532                goto done;
1533        } else if (best_strategy == wt_strategy)
1534                ; /* We already have its result in the working tree. */
1535        else {
1536                printf(_("Rewinding the tree to pristine...\n"));
1537                restore_state(head_commit->object.sha1, stash);
1538                printf(_("Using the %s to prepare resolving by hand.\n"),
1539                        best_strategy);
1540                try_merge_strategy(best_strategy, common, remoteheads,
1541                                   head_commit, head_arg);
1542        }
1543
1544        if (squash)
1545                finish(head_commit, remoteheads, NULL, NULL);
1546        else
1547                write_merge_state(remoteheads);
1548
1549        if (merge_was_ok)
1550                fprintf(stderr, _("Automatic merge went well; "
1551                        "stopped before committing as requested\n"));
1552        else
1553                ret = suggest_conflicts(option_renormalize);
1554
1555done:
1556        free(branch_to_free);
1557        return ret;
1558}