f5eb3f549b3732c894016a83e3108df3b3f46d81
   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 "run-command.h"
  13#include "diff.h"
  14#include "refs.h"
  15#include "commit.h"
  16#include "diffcore.h"
  17#include "revision.h"
  18#include "unpack-trees.h"
  19#include "cache-tree.h"
  20#include "dir.h"
  21#include "utf8.h"
  22#include "log-tree.h"
  23#include "color.h"
  24#include "rerere.h"
  25#include "help.h"
  26#include "merge-recursive.h"
  27#include "resolve-undo.h"
  28#include "remote.h"
  29
  30#define DEFAULT_TWOHEAD (1<<0)
  31#define DEFAULT_OCTOPUS (1<<1)
  32#define NO_FAST_FORWARD (1<<2)
  33#define NO_TRIVIAL      (1<<3)
  34
  35struct strategy {
  36        const char *name;
  37        unsigned attr;
  38};
  39
  40static const char * const builtin_merge_usage[] = {
  41        "git merge [options] [<commit>...]",
  42        "git merge [options] <msg> HEAD <commit>",
  43        "git merge --abort",
  44        NULL
  45};
  46
  47static int show_diffstat = 1, shortlog_len, squash;
  48static int option_commit = 1, allow_fast_forward = 1;
  49static int fast_forward_only;
  50static int allow_trivial = 1, have_message;
  51static struct strbuf merge_msg;
  52static struct commit_list *remoteheads;
  53static struct strategy **use_strategies;
  54static size_t use_strategies_nr, use_strategies_alloc;
  55static const char **xopts;
  56static size_t xopts_nr, xopts_alloc;
  57static const char *branch;
  58static char *branch_mergeoptions;
  59static int option_renormalize;
  60static int verbosity;
  61static int allow_rerere_auto;
  62static int abort_current_merge;
  63static int show_progress = -1;
  64static int default_to_upstream;
  65
  66static struct strategy all_strategy[] = {
  67        { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  68        { "octopus",    DEFAULT_OCTOPUS },
  69        { "resolve",    0 },
  70        { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  71        { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  72};
  73
  74static const char *pull_twohead, *pull_octopus;
  75
  76static int option_parse_message(const struct option *opt,
  77                                const char *arg, int unset)
  78{
  79        struct strbuf *buf = opt->value;
  80
  81        if (unset)
  82                strbuf_setlen(buf, 0);
  83        else if (arg) {
  84                strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  85                have_message = 1;
  86        } else
  87                return error(_("switch `m' requires a value"));
  88        return 0;
  89}
  90
  91static struct strategy *get_strategy(const char *name)
  92{
  93        int i;
  94        struct strategy *ret;
  95        static struct cmdnames main_cmds, other_cmds;
  96        static int loaded;
  97
  98        if (!name)
  99                return NULL;
 100
 101        for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 102                if (!strcmp(name, all_strategy[i].name))
 103                        return &all_strategy[i];
 104
 105        if (!loaded) {
 106                struct cmdnames not_strategies;
 107                loaded = 1;
 108
 109                memset(&not_strategies, 0, sizeof(struct cmdnames));
 110                load_command_list("git-merge-", &main_cmds, &other_cmds);
 111                for (i = 0; i < main_cmds.cnt; i++) {
 112                        int j, found = 0;
 113                        struct cmdname *ent = main_cmds.names[i];
 114                        for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 115                                if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 116                                                && !all_strategy[j].name[ent->len])
 117                                        found = 1;
 118                        if (!found)
 119                                add_cmdname(&not_strategies, ent->name, ent->len);
 120                }
 121                exclude_cmds(&main_cmds, &not_strategies);
 122        }
 123        if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 124                fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 125                fprintf(stderr, _("Available strategies are:"));
 126                for (i = 0; i < main_cmds.cnt; i++)
 127                        fprintf(stderr, " %s", main_cmds.names[i]->name);
 128                fprintf(stderr, ".\n");
 129                if (other_cmds.cnt) {
 130                        fprintf(stderr, _("Available custom strategies are:"));
 131                        for (i = 0; i < other_cmds.cnt; i++)
 132                                fprintf(stderr, " %s", other_cmds.names[i]->name);
 133                        fprintf(stderr, ".\n");
 134                }
 135                exit(1);
 136        }
 137
 138        ret = xcalloc(1, sizeof(struct strategy));
 139        ret->name = xstrdup(name);
 140        ret->attr = NO_TRIVIAL;
 141        return ret;
 142}
 143
 144static void append_strategy(struct strategy *s)
 145{
 146        ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 147        use_strategies[use_strategies_nr++] = s;
 148}
 149
 150static int option_parse_strategy(const struct option *opt,
 151                                 const char *name, int unset)
 152{
 153        if (unset)
 154                return 0;
 155
 156        append_strategy(get_strategy(name));
 157        return 0;
 158}
 159
 160static int option_parse_x(const struct option *opt,
 161                          const char *arg, int unset)
 162{
 163        if (unset)
 164                return 0;
 165
 166        ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 167        xopts[xopts_nr++] = xstrdup(arg);
 168        return 0;
 169}
 170
 171static int option_parse_n(const struct option *opt,
 172                          const char *arg, int unset)
 173{
 174        show_diffstat = unset;
 175        return 0;
 176}
 177
 178static struct option builtin_merge_options[] = {
 179        { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 180                "do not show a diffstat at the end of the merge",
 181                PARSE_OPT_NOARG, option_parse_n },
 182        OPT_BOOLEAN(0, "stat", &show_diffstat,
 183                "show a diffstat at the end of the merge"),
 184        OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 185        { OPTION_INTEGER, 0, "log", &shortlog_len, "n",
 186          "add (at most <n>) entries from shortlog to merge commit message",
 187          PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 188        OPT_BOOLEAN(0, "squash", &squash,
 189                "create a single commit instead of doing a merge"),
 190        OPT_BOOLEAN(0, "commit", &option_commit,
 191                "perform a commit if the merge succeeds (default)"),
 192        OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 193                "allow fast-forward (default)"),
 194        OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
 195                "abort if fast-forward is not possible"),
 196        OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 197        OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
 198                "merge strategy to use", option_parse_strategy),
 199        OPT_CALLBACK('X', "strategy-option", &xopts, "option=value",
 200                "option for selected merge strategy", option_parse_x),
 201        OPT_CALLBACK('m', "message", &merge_msg, "message",
 202                "merge commit message (for a non-fast-forward merge)",
 203                option_parse_message),
 204        OPT__VERBOSITY(&verbosity),
 205        OPT_BOOLEAN(0, "abort", &abort_current_merge,
 206                "abort the current in-progress merge"),
 207        OPT_SET_INT(0, "progress", &show_progress, "force progress reporting", 1),
 208        OPT_END()
 209};
 210
 211/* Cleans up metadata that is uninteresting after a succeeded merge. */
 212static void drop_save(void)
 213{
 214        unlink(git_path("MERGE_HEAD"));
 215        unlink(git_path("MERGE_MSG"));
 216        unlink(git_path("MERGE_MODE"));
 217}
 218
 219static int save_state(unsigned char *stash)
 220{
 221        int len;
 222        struct child_process cp;
 223        struct strbuf buffer = STRBUF_INIT;
 224        const char *argv[] = {"stash", "create", NULL};
 225
 226        memset(&cp, 0, sizeof(cp));
 227        cp.argv = argv;
 228        cp.out = -1;
 229        cp.git_cmd = 1;
 230
 231        if (start_command(&cp))
 232                die(_("could not run stash."));
 233        len = strbuf_read(&buffer, cp.out, 1024);
 234        close(cp.out);
 235
 236        if (finish_command(&cp) || len < 0)
 237                die(_("stash failed"));
 238        else if (!len)          /* no changes */
 239                return -1;
 240        strbuf_setlen(&buffer, buffer.len-1);
 241        if (get_sha1(buffer.buf, stash))
 242                die(_("not a valid object: %s"), buffer.buf);
 243        return 0;
 244}
 245
 246static void read_empty(unsigned const char *sha1, int verbose)
 247{
 248        int i = 0;
 249        const char *args[7];
 250
 251        args[i++] = "read-tree";
 252        if (verbose)
 253                args[i++] = "-v";
 254        args[i++] = "-m";
 255        args[i++] = "-u";
 256        args[i++] = EMPTY_TREE_SHA1_HEX;
 257        args[i++] = sha1_to_hex(sha1);
 258        args[i] = NULL;
 259
 260        if (run_command_v_opt(args, RUN_GIT_CMD))
 261                die(_("read-tree failed"));
 262}
 263
 264static void reset_hard(unsigned const char *sha1, int verbose)
 265{
 266        int i = 0;
 267        const char *args[6];
 268
 269        args[i++] = "read-tree";
 270        if (verbose)
 271                args[i++] = "-v";
 272        args[i++] = "--reset";
 273        args[i++] = "-u";
 274        args[i++] = sha1_to_hex(sha1);
 275        args[i] = NULL;
 276
 277        if (run_command_v_opt(args, RUN_GIT_CMD))
 278                die(_("read-tree failed"));
 279}
 280
 281static void restore_state(const unsigned char *head,
 282                          const unsigned char *stash)
 283{
 284        struct strbuf sb = STRBUF_INIT;
 285        const char *args[] = { "stash", "apply", NULL, NULL };
 286
 287        if (is_null_sha1(stash))
 288                return;
 289
 290        reset_hard(head, 1);
 291
 292        args[2] = sha1_to_hex(stash);
 293
 294        /*
 295         * It is OK to ignore error here, for example when there was
 296         * nothing to restore.
 297         */
 298        run_command_v_opt(args, RUN_GIT_CMD);
 299
 300        strbuf_release(&sb);
 301        refresh_cache(REFRESH_QUIET);
 302}
 303
 304/* This is called when no merge was necessary. */
 305static void finish_up_to_date(const char *msg)
 306{
 307        if (verbosity >= 0)
 308                printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 309        drop_save();
 310}
 311
 312static void squash_message(struct commit *commit)
 313{
 314        struct rev_info rev;
 315        struct strbuf out = STRBUF_INIT;
 316        struct commit_list *j;
 317        int fd;
 318        struct pretty_print_context ctx = {0};
 319
 320        printf(_("Squash commit -- not updating HEAD\n"));
 321        fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
 322        if (fd < 0)
 323                die_errno(_("Could not write to '%s'"), git_path("SQUASH_MSG"));
 324
 325        init_revisions(&rev, NULL);
 326        rev.ignore_merges = 1;
 327        rev.commit_format = CMIT_FMT_MEDIUM;
 328
 329        commit->object.flags |= UNINTERESTING;
 330        add_pending_object(&rev, &commit->object, NULL);
 331
 332        for (j = remoteheads; j; j = j->next)
 333                add_pending_object(&rev, &j->item->object, NULL);
 334
 335        setup_revisions(0, NULL, &rev, NULL);
 336        if (prepare_revision_walk(&rev))
 337                die(_("revision walk setup failed"));
 338
 339        ctx.abbrev = rev.abbrev;
 340        ctx.date_mode = rev.date_mode;
 341        ctx.fmt = rev.commit_format;
 342
 343        strbuf_addstr(&out, "Squashed commit of the following:\n");
 344        while ((commit = get_revision(&rev)) != NULL) {
 345                strbuf_addch(&out, '\n');
 346                strbuf_addf(&out, "commit %s\n",
 347                        sha1_to_hex(commit->object.sha1));
 348                pretty_print_commit(&ctx, commit, &out);
 349        }
 350        if (write(fd, out.buf, out.len) < 0)
 351                die_errno(_("Writing SQUASH_MSG"));
 352        if (close(fd))
 353                die_errno(_("Finishing SQUASH_MSG"));
 354        strbuf_release(&out);
 355}
 356
 357static void finish(struct commit *head_commit,
 358                   const unsigned char *new_head, const char *msg)
 359{
 360        struct strbuf reflog_message = STRBUF_INIT;
 361        const unsigned char *head = head_commit->object.sha1;
 362
 363        if (!msg)
 364                strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 365        else {
 366                if (verbosity >= 0)
 367                        printf("%s\n", msg);
 368                strbuf_addf(&reflog_message, "%s: %s",
 369                        getenv("GIT_REFLOG_ACTION"), msg);
 370        }
 371        if (squash) {
 372                squash_message(head_commit);
 373        } else {
 374                if (verbosity >= 0 && !merge_msg.len)
 375                        printf(_("No merge message -- not updating HEAD\n"));
 376                else {
 377                        const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 378                        update_ref(reflog_message.buf, "HEAD",
 379                                new_head, head, 0,
 380                                DIE_ON_ERR);
 381                        /*
 382                         * We ignore errors in 'gc --auto', since the
 383                         * user should see them.
 384                         */
 385                        run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 386                }
 387        }
 388        if (new_head && show_diffstat) {
 389                struct diff_options opts;
 390                diff_setup(&opts);
 391                opts.output_format |=
 392                        DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 393                opts.detect_rename = DIFF_DETECT_RENAME;
 394                if (diff_use_color_default > 0)
 395                        DIFF_OPT_SET(&opts, COLOR_DIFF);
 396                if (diff_setup_done(&opts) < 0)
 397                        die(_("diff_setup_done failed"));
 398                diff_tree_sha1(head, new_head, "", &opts);
 399                diffcore_std(&opts);
 400                diff_flush(&opts);
 401        }
 402
 403        /* Run a post-merge hook */
 404        run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
 405
 406        strbuf_release(&reflog_message);
 407}
 408
 409/* Get the name for the merge commit's message. */
 410static void merge_name(const char *remote, struct strbuf *msg)
 411{
 412        struct object *remote_head;
 413        unsigned char branch_head[20], buf_sha[20];
 414        struct strbuf buf = STRBUF_INIT;
 415        struct strbuf bname = STRBUF_INIT;
 416        const char *ptr;
 417        char *found_ref;
 418        int len, early;
 419
 420        strbuf_branchname(&bname, remote);
 421        remote = bname.buf;
 422
 423        memset(branch_head, 0, sizeof(branch_head));
 424        remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
 425        if (!remote_head)
 426                die(_("'%s' does not point to a commit"), remote);
 427
 428        if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 429                if (!prefixcmp(found_ref, "refs/heads/")) {
 430                        strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 431                                    sha1_to_hex(branch_head), remote);
 432                        goto cleanup;
 433                }
 434                if (!prefixcmp(found_ref, "refs/remotes/")) {
 435                        strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 436                                    sha1_to_hex(branch_head), remote);
 437                        goto cleanup;
 438                }
 439        }
 440
 441        /* See if remote matches <name>^^^.. or <name>~<number> */
 442        for (len = 0, ptr = remote + strlen(remote);
 443             remote < ptr && ptr[-1] == '^';
 444             ptr--)
 445                len++;
 446        if (len)
 447                early = 1;
 448        else {
 449                early = 0;
 450                ptr = strrchr(remote, '~');
 451                if (ptr) {
 452                        int seen_nonzero = 0;
 453
 454                        len++; /* count ~ */
 455                        while (*++ptr && isdigit(*ptr)) {
 456                                seen_nonzero |= (*ptr != '0');
 457                                len++;
 458                        }
 459                        if (*ptr)
 460                                len = 0; /* not ...~<number> */
 461                        else if (seen_nonzero)
 462                                early = 1;
 463                        else if (len == 1)
 464                                early = 1; /* "name~" is "name~1"! */
 465                }
 466        }
 467        if (len) {
 468                struct strbuf truname = STRBUF_INIT;
 469                strbuf_addstr(&truname, "refs/heads/");
 470                strbuf_addstr(&truname, remote);
 471                strbuf_setlen(&truname, truname.len - len);
 472                if (resolve_ref(truname.buf, buf_sha, 1, NULL)) {
 473                        strbuf_addf(msg,
 474                                    "%s\t\tbranch '%s'%s of .\n",
 475                                    sha1_to_hex(remote_head->sha1),
 476                                    truname.buf + 11,
 477                                    (early ? " (early part)" : ""));
 478                        strbuf_release(&truname);
 479                        goto cleanup;
 480                }
 481        }
 482
 483        if (!strcmp(remote, "FETCH_HEAD") &&
 484                        !access(git_path("FETCH_HEAD"), R_OK)) {
 485                FILE *fp;
 486                struct strbuf line = STRBUF_INIT;
 487                char *ptr;
 488
 489                fp = fopen(git_path("FETCH_HEAD"), "r");
 490                if (!fp)
 491                        die_errno(_("could not open '%s' for reading"),
 492                                  git_path("FETCH_HEAD"));
 493                strbuf_getline(&line, fp, '\n');
 494                fclose(fp);
 495                ptr = strstr(line.buf, "\tnot-for-merge\t");
 496                if (ptr)
 497                        strbuf_remove(&line, ptr-line.buf+1, 13);
 498                strbuf_addbuf(msg, &line);
 499                strbuf_release(&line);
 500                goto cleanup;
 501        }
 502        strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 503                sha1_to_hex(remote_head->sha1), remote);
 504cleanup:
 505        strbuf_release(&buf);
 506        strbuf_release(&bname);
 507}
 508
 509static void parse_branch_merge_options(char *bmo)
 510{
 511        const char **argv;
 512        int argc;
 513
 514        if (!bmo)
 515                return;
 516        argc = split_cmdline(bmo, &argv);
 517        if (argc < 0)
 518                die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 519                    split_cmdline_strerror(argc));
 520        argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 521        memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 522        argc++;
 523        argv[0] = "branch.*.mergeoptions";
 524        parse_options(argc, argv, NULL, builtin_merge_options,
 525                      builtin_merge_usage, 0);
 526        free(argv);
 527}
 528
 529static int git_merge_config(const char *k, const char *v, void *cb)
 530{
 531        if (branch && !prefixcmp(k, "branch.") &&
 532                !prefixcmp(k + 7, branch) &&
 533                !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 534                free(branch_mergeoptions);
 535                branch_mergeoptions = xstrdup(v);
 536                return 0;
 537        }
 538
 539        if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 540                show_diffstat = git_config_bool(k, v);
 541        else if (!strcmp(k, "pull.twohead"))
 542                return git_config_string(&pull_twohead, k, v);
 543        else if (!strcmp(k, "pull.octopus"))
 544                return git_config_string(&pull_octopus, k, v);
 545        else if (!strcmp(k, "merge.renormalize"))
 546                option_renormalize = git_config_bool(k, v);
 547        else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary")) {
 548                int is_bool;
 549                shortlog_len = git_config_bool_or_int(k, v, &is_bool);
 550                if (!is_bool && shortlog_len < 0)
 551                        return error(_("%s: negative length %s"), k, v);
 552                if (is_bool && shortlog_len)
 553                        shortlog_len = DEFAULT_MERGE_LOG_LEN;
 554                return 0;
 555        } else if (!strcmp(k, "merge.ff")) {
 556                int boolval = git_config_maybe_bool(k, v);
 557                if (0 <= boolval) {
 558                        allow_fast_forward = boolval;
 559                } else if (v && !strcmp(v, "only")) {
 560                        allow_fast_forward = 1;
 561                        fast_forward_only = 1;
 562                } /* do not barf on values from future versions of git */
 563                return 0;
 564        } else if (!strcmp(k, "merge.defaulttoupstream")) {
 565                default_to_upstream = git_config_bool(k, v);
 566                return 0;
 567        }
 568        return git_diff_ui_config(k, v, cb);
 569}
 570
 571static int read_tree_trivial(unsigned char *common, unsigned char *head,
 572                             unsigned char *one)
 573{
 574        int i, nr_trees = 0;
 575        struct tree *trees[MAX_UNPACK_TREES];
 576        struct tree_desc t[MAX_UNPACK_TREES];
 577        struct unpack_trees_options opts;
 578
 579        memset(&opts, 0, sizeof(opts));
 580        opts.head_idx = 2;
 581        opts.src_index = &the_index;
 582        opts.dst_index = &the_index;
 583        opts.update = 1;
 584        opts.verbose_update = 1;
 585        opts.trivial_merges_only = 1;
 586        opts.merge = 1;
 587        trees[nr_trees] = parse_tree_indirect(common);
 588        if (!trees[nr_trees++])
 589                return -1;
 590        trees[nr_trees] = parse_tree_indirect(head);
 591        if (!trees[nr_trees++])
 592                return -1;
 593        trees[nr_trees] = parse_tree_indirect(one);
 594        if (!trees[nr_trees++])
 595                return -1;
 596        opts.fn = threeway_merge;
 597        cache_tree_free(&active_cache_tree);
 598        for (i = 0; i < nr_trees; i++) {
 599                parse_tree(trees[i]);
 600                init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 601        }
 602        if (unpack_trees(nr_trees, t, &opts))
 603                return -1;
 604        return 0;
 605}
 606
 607static void write_tree_trivial(unsigned char *sha1)
 608{
 609        if (write_cache_as_tree(sha1, 0, NULL))
 610                die(_("git write-tree failed to write a tree"));
 611}
 612
 613static const char *merge_argument(struct commit *commit)
 614{
 615        if (commit)
 616                return sha1_to_hex(commit->object.sha1);
 617        else
 618                return EMPTY_TREE_SHA1_HEX;
 619}
 620
 621int try_merge_command(const char *strategy, size_t xopts_nr,
 622                      const char **xopts, struct commit_list *common,
 623                      const char *head_arg, struct commit_list *remotes)
 624{
 625        const char **args;
 626        int i = 0, x = 0, ret;
 627        struct commit_list *j;
 628        struct strbuf buf = STRBUF_INIT;
 629
 630        args = xmalloc((4 + xopts_nr + commit_list_count(common) +
 631                        commit_list_count(remotes)) * sizeof(char *));
 632        strbuf_addf(&buf, "merge-%s", strategy);
 633        args[i++] = buf.buf;
 634        for (x = 0; x < xopts_nr; x++) {
 635                char *s = xmalloc(strlen(xopts[x])+2+1);
 636                strcpy(s, "--");
 637                strcpy(s+2, xopts[x]);
 638                args[i++] = s;
 639        }
 640        for (j = common; j; j = j->next)
 641                args[i++] = xstrdup(merge_argument(j->item));
 642        args[i++] = "--";
 643        args[i++] = head_arg;
 644        for (j = remotes; j; j = j->next)
 645                args[i++] = xstrdup(merge_argument(j->item));
 646        args[i] = NULL;
 647        ret = run_command_v_opt(args, RUN_GIT_CMD);
 648        strbuf_release(&buf);
 649        i = 1;
 650        for (x = 0; x < xopts_nr; x++)
 651                free((void *)args[i++]);
 652        for (j = common; j; j = j->next)
 653                free((void *)args[i++]);
 654        i += 2;
 655        for (j = remotes; j; j = j->next)
 656                free((void *)args[i++]);
 657        free(args);
 658        discard_cache();
 659        if (read_cache() < 0)
 660                die(_("failed to read the cache"));
 661        resolve_undo_clear();
 662
 663        return ret;
 664}
 665
 666static int try_merge_strategy(const char *strategy, struct commit_list *common,
 667                              struct commit *head, const char *head_arg)
 668{
 669        int index_fd;
 670        struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 671
 672        index_fd = hold_locked_index(lock, 1);
 673        refresh_cache(REFRESH_QUIET);
 674        if (active_cache_changed &&
 675                        (write_cache(index_fd, active_cache, active_nr) ||
 676                         commit_locked_index(lock)))
 677                return error(_("Unable to write index."));
 678        rollback_lock_file(lock);
 679
 680        if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 681                int clean, x;
 682                struct commit *result;
 683                struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 684                int index_fd;
 685                struct commit_list *reversed = NULL;
 686                struct merge_options o;
 687                struct commit_list *j;
 688
 689                if (remoteheads->next) {
 690                        error(_("Not handling anything other than two heads merge."));
 691                        return 2;
 692                }
 693
 694                init_merge_options(&o);
 695                if (!strcmp(strategy, "subtree"))
 696                        o.subtree_shift = "";
 697
 698                o.renormalize = option_renormalize;
 699                o.show_rename_progress =
 700                        show_progress == -1 ? isatty(2) : show_progress;
 701
 702                for (x = 0; x < xopts_nr; x++)
 703                        if (parse_merge_opt(&o, xopts[x]))
 704                                die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 705
 706                o.branch1 = head_arg;
 707                o.branch2 = remoteheads->item->util;
 708
 709                for (j = common; j; j = j->next)
 710                        commit_list_insert(j->item, &reversed);
 711
 712                index_fd = hold_locked_index(lock, 1);
 713                clean = merge_recursive(&o, head,
 714                                remoteheads->item, reversed, &result);
 715                if (active_cache_changed &&
 716                                (write_cache(index_fd, active_cache, active_nr) ||
 717                                 commit_locked_index(lock)))
 718                        die (_("unable to write %s"), get_index_file());
 719                rollback_lock_file(lock);
 720                return clean ? 0 : 1;
 721        } else {
 722                return try_merge_command(strategy, xopts_nr, xopts,
 723                                                common, head_arg, remoteheads);
 724        }
 725}
 726
 727static void count_diff_files(struct diff_queue_struct *q,
 728                             struct diff_options *opt, void *data)
 729{
 730        int *count = data;
 731
 732        (*count) += q->nr;
 733}
 734
 735static int count_unmerged_entries(void)
 736{
 737        int i, ret = 0;
 738
 739        for (i = 0; i < active_nr; i++)
 740                if (ce_stage(active_cache[i]))
 741                        ret++;
 742
 743        return ret;
 744}
 745
 746int checkout_fast_forward(const unsigned char *head, const unsigned char *remote)
 747{
 748        struct tree *trees[MAX_UNPACK_TREES];
 749        struct unpack_trees_options opts;
 750        struct tree_desc t[MAX_UNPACK_TREES];
 751        int i, fd, nr_trees = 0;
 752        struct dir_struct dir;
 753        struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 754
 755        refresh_cache(REFRESH_QUIET);
 756
 757        fd = hold_locked_index(lock_file, 1);
 758
 759        memset(&trees, 0, sizeof(trees));
 760        memset(&opts, 0, sizeof(opts));
 761        memset(&t, 0, sizeof(t));
 762        memset(&dir, 0, sizeof(dir));
 763        dir.flags |= DIR_SHOW_IGNORED;
 764        dir.exclude_per_dir = ".gitignore";
 765        opts.dir = &dir;
 766
 767        opts.head_idx = 1;
 768        opts.src_index = &the_index;
 769        opts.dst_index = &the_index;
 770        opts.update = 1;
 771        opts.verbose_update = 1;
 772        opts.merge = 1;
 773        opts.fn = twoway_merge;
 774        setup_unpack_trees_porcelain(&opts, "merge");
 775
 776        trees[nr_trees] = parse_tree_indirect(head);
 777        if (!trees[nr_trees++])
 778                return -1;
 779        trees[nr_trees] = parse_tree_indirect(remote);
 780        if (!trees[nr_trees++])
 781                return -1;
 782        for (i = 0; i < nr_trees; i++) {
 783                parse_tree(trees[i]);
 784                init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 785        }
 786        if (unpack_trees(nr_trees, t, &opts))
 787                return -1;
 788        if (write_cache(fd, active_cache, active_nr) ||
 789                commit_locked_index(lock_file))
 790                die(_("unable to write new index file"));
 791        return 0;
 792}
 793
 794static void split_merge_strategies(const char *string, struct strategy **list,
 795                                   int *nr, int *alloc)
 796{
 797        char *p, *q, *buf;
 798
 799        if (!string)
 800                return;
 801
 802        buf = xstrdup(string);
 803        q = buf;
 804        for (;;) {
 805                p = strchr(q, ' ');
 806                if (!p) {
 807                        ALLOC_GROW(*list, *nr + 1, *alloc);
 808                        (*list)[(*nr)++].name = xstrdup(q);
 809                        free(buf);
 810                        return;
 811                } else {
 812                        *p = '\0';
 813                        ALLOC_GROW(*list, *nr + 1, *alloc);
 814                        (*list)[(*nr)++].name = xstrdup(q);
 815                        q = ++p;
 816                }
 817        }
 818}
 819
 820static void add_strategies(const char *string, unsigned attr)
 821{
 822        struct strategy *list = NULL;
 823        int list_alloc = 0, list_nr = 0, i;
 824
 825        memset(&list, 0, sizeof(list));
 826        split_merge_strategies(string, &list, &list_nr, &list_alloc);
 827        if (list) {
 828                for (i = 0; i < list_nr; i++)
 829                        append_strategy(get_strategy(list[i].name));
 830                return;
 831        }
 832        for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 833                if (all_strategy[i].attr & attr)
 834                        append_strategy(&all_strategy[i]);
 835
 836}
 837
 838static void write_merge_msg(void)
 839{
 840        int fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
 841        if (fd < 0)
 842                die_errno(_("Could not open '%s' for writing"),
 843                          git_path("MERGE_MSG"));
 844        if (write_in_full(fd, merge_msg.buf, merge_msg.len) != merge_msg.len)
 845                die_errno(_("Could not write to '%s'"), git_path("MERGE_MSG"));
 846        close(fd);
 847}
 848
 849static void read_merge_msg(void)
 850{
 851        strbuf_reset(&merge_msg);
 852        if (strbuf_read_file(&merge_msg, git_path("MERGE_MSG"), 0) < 0)
 853                die_errno(_("Could not read from '%s'"), git_path("MERGE_MSG"));
 854}
 855
 856static void run_prepare_commit_msg(void)
 857{
 858        write_merge_msg();
 859        run_hook(get_index_file(), "prepare-commit-msg",
 860                 git_path("MERGE_MSG"), "merge", NULL, NULL);
 861        read_merge_msg();
 862}
 863
 864static int merge_trivial(struct commit *head)
 865{
 866        unsigned char result_tree[20], result_commit[20];
 867        struct commit_list *parent = xmalloc(sizeof(*parent));
 868
 869        write_tree_trivial(result_tree);
 870        printf(_("Wonderful.\n"));
 871        parent->item = head;
 872        parent->next = xmalloc(sizeof(*parent->next));
 873        parent->next->item = remoteheads->item;
 874        parent->next->next = NULL;
 875        run_prepare_commit_msg();
 876        commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 877        finish(head, result_commit, "In-index merge");
 878        drop_save();
 879        return 0;
 880}
 881
 882static int finish_automerge(struct commit *head,
 883                            struct commit_list *common,
 884                            unsigned char *result_tree,
 885                            const char *wt_strategy)
 886{
 887        struct commit_list *parents = NULL, *j;
 888        struct strbuf buf = STRBUF_INIT;
 889        unsigned char result_commit[20];
 890
 891        free_commit_list(common);
 892        if (allow_fast_forward) {
 893                parents = remoteheads;
 894                commit_list_insert(head, &parents);
 895                parents = reduce_heads(parents);
 896        } else {
 897                struct commit_list **pptr = &parents;
 898
 899                pptr = &commit_list_insert(head,
 900                                pptr)->next;
 901                for (j = remoteheads; j; j = j->next)
 902                        pptr = &commit_list_insert(j->item, pptr)->next;
 903        }
 904        free_commit_list(remoteheads);
 905        strbuf_addch(&merge_msg, '\n');
 906        run_prepare_commit_msg();
 907        commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 908        strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
 909        finish(head, result_commit, buf.buf);
 910        strbuf_release(&buf);
 911        drop_save();
 912        return 0;
 913}
 914
 915static int suggest_conflicts(int renormalizing)
 916{
 917        FILE *fp;
 918        int pos;
 919
 920        fp = fopen(git_path("MERGE_MSG"), "a");
 921        if (!fp)
 922                die_errno(_("Could not open '%s' for writing"),
 923                          git_path("MERGE_MSG"));
 924        fprintf(fp, "\nConflicts:\n");
 925        for (pos = 0; pos < active_nr; pos++) {
 926                struct cache_entry *ce = active_cache[pos];
 927
 928                if (ce_stage(ce)) {
 929                        fprintf(fp, "\t%s\n", ce->name);
 930                        while (pos + 1 < active_nr &&
 931                                        !strcmp(ce->name,
 932                                                active_cache[pos + 1]->name))
 933                                pos++;
 934                }
 935        }
 936        fclose(fp);
 937        rerere(allow_rerere_auto);
 938        printf(_("Automatic merge failed; "
 939                        "fix conflicts and then commit the result.\n"));
 940        return 1;
 941}
 942
 943static struct commit *is_old_style_invocation(int argc, const char **argv,
 944                                              const unsigned char *head)
 945{
 946        struct commit *second_token = NULL;
 947        if (argc > 2) {
 948                unsigned char second_sha1[20];
 949
 950                if (get_sha1(argv[1], second_sha1))
 951                        return NULL;
 952                second_token = lookup_commit_reference_gently(second_sha1, 0);
 953                if (!second_token)
 954                        die(_("'%s' is not a commit"), argv[1]);
 955                if (hashcmp(second_token->object.sha1, head))
 956                        return NULL;
 957        }
 958        return second_token;
 959}
 960
 961static int evaluate_result(void)
 962{
 963        int cnt = 0;
 964        struct rev_info rev;
 965
 966        /* Check how many files differ. */
 967        init_revisions(&rev, "");
 968        setup_revisions(0, NULL, &rev, NULL);
 969        rev.diffopt.output_format |=
 970                DIFF_FORMAT_CALLBACK;
 971        rev.diffopt.format_callback = count_diff_files;
 972        rev.diffopt.format_callback_data = &cnt;
 973        run_diff_files(&rev, 0);
 974
 975        /*
 976         * Check how many unmerged entries are
 977         * there.
 978         */
 979        cnt += count_unmerged_entries();
 980
 981        return cnt;
 982}
 983
 984/*
 985 * Pretend as if the user told us to merge with the tracking
 986 * branch we have for the upstream of the current branch
 987 */
 988static int setup_with_upstream(const char ***argv)
 989{
 990        struct branch *branch = branch_get(NULL);
 991        int i;
 992        const char **args;
 993
 994        if (!branch)
 995                die(_("No current branch."));
 996        if (!branch->remote)
 997                die(_("No remote for the current branch."));
 998        if (!branch->merge_nr)
 999                die(_("No default upstream defined for the current branch."));
1000
1001        args = xcalloc(branch->merge_nr + 1, sizeof(char *));
1002        for (i = 0; i < branch->merge_nr; i++) {
1003                if (!branch->merge[i]->dst)
1004                        die(_("No remote tracking branch for %s from %s"),
1005                            branch->merge[i]->src, branch->remote_name);
1006                args[i] = branch->merge[i]->dst;
1007        }
1008        args[i] = NULL;
1009        *argv = args;
1010        return i;
1011}
1012
1013int cmd_merge(int argc, const char **argv, const char *prefix)
1014{
1015        unsigned char result_tree[20];
1016        unsigned char stash[20];
1017        unsigned char head_sha1[20];
1018        struct commit *head_commit;
1019        struct strbuf buf = STRBUF_INIT;
1020        const char *head_arg;
1021        int flag, i;
1022        int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1023        struct commit_list *common = NULL;
1024        const char *best_strategy = NULL, *wt_strategy = NULL;
1025        struct commit_list **remotes = &remoteheads;
1026
1027        if (argc == 2 && !strcmp(argv[1], "-h"))
1028                usage_with_options(builtin_merge_usage, builtin_merge_options);
1029
1030        /*
1031         * Check if we are _not_ on a detached HEAD, i.e. if there is a
1032         * current branch.
1033         */
1034        branch = resolve_ref("HEAD", head_sha1, 0, &flag);
1035        if (branch && !prefixcmp(branch, "refs/heads/"))
1036                branch += 11;
1037        if (!branch || is_null_sha1(head_sha1))
1038                head_commit = NULL;
1039        else {
1040                head_commit = lookup_commit(head_sha1);
1041                if (!head_commit)
1042                        die(_("could not parse HEAD"));
1043        }
1044
1045        git_config(git_merge_config, NULL);
1046
1047        /* for color.ui */
1048        if (diff_use_color_default == -1)
1049                diff_use_color_default = git_use_color_default;
1050
1051        if (branch_mergeoptions)
1052                parse_branch_merge_options(branch_mergeoptions);
1053        argc = parse_options(argc, argv, prefix, builtin_merge_options,
1054                        builtin_merge_usage, 0);
1055
1056        if (verbosity < 0 && show_progress == -1)
1057                show_progress = 0;
1058
1059        if (abort_current_merge) {
1060                int nargc = 2;
1061                const char *nargv[] = {"reset", "--merge", NULL};
1062
1063                if (!file_exists(git_path("MERGE_HEAD")))
1064                        die(_("There is no merge to abort (MERGE_HEAD missing)."));
1065
1066                /* Invoke 'git reset --merge' */
1067                return cmd_reset(nargc, nargv, prefix);
1068        }
1069
1070        if (read_cache_unmerged())
1071                die_resolve_conflict("merge");
1072
1073        if (file_exists(git_path("MERGE_HEAD"))) {
1074                /*
1075                 * There is no unmerged entry, don't advise 'git
1076                 * add/rm <file>', just 'git commit'.
1077                 */
1078                if (advice_resolve_conflict)
1079                        die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1080                                  "Please, commit your changes before you can merge."));
1081                else
1082                        die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1083        }
1084        if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1085                if (advice_resolve_conflict)
1086                        die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1087                            "Please, commit your changes before you can merge."));
1088                else
1089                        die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1090        }
1091        resolve_undo_clear();
1092
1093        if (verbosity < 0)
1094                show_diffstat = 0;
1095
1096        if (squash) {
1097                if (!allow_fast_forward)
1098                        die(_("You cannot combine --squash with --no-ff."));
1099                option_commit = 0;
1100        }
1101
1102        if (!allow_fast_forward && fast_forward_only)
1103                die(_("You cannot combine --no-ff with --ff-only."));
1104
1105        if (!abort_current_merge) {
1106                if (!argc && default_to_upstream)
1107                        argc = setup_with_upstream(&argv);
1108                else if (argc == 1 && !strcmp(argv[0], "-"))
1109                        argv[0] = "@{-1}";
1110        }
1111        if (!argc)
1112                usage_with_options(builtin_merge_usage,
1113                        builtin_merge_options);
1114
1115        /*
1116         * This could be traditional "merge <msg> HEAD <commit>..."  and
1117         * the way we can tell it is to see if the second token is HEAD,
1118         * but some people might have misused the interface and used a
1119         * committish that is the same as HEAD there instead.
1120         * Traditional format never would have "-m" so it is an
1121         * additional safety measure to check for it.
1122         */
1123
1124        if (!have_message && head_commit &&
1125            is_old_style_invocation(argc, argv, head_commit->object.sha1)) {
1126                strbuf_addstr(&merge_msg, argv[0]);
1127                head_arg = argv[1];
1128                argv += 2;
1129                argc -= 2;
1130        } else if (!head_commit) {
1131                struct object *remote_head;
1132                /*
1133                 * If the merged head is a valid one there is no reason
1134                 * to forbid "git merge" into a branch yet to be born.
1135                 * We do the same for "git pull".
1136                 */
1137                if (argc != 1)
1138                        die(_("Can merge only exactly one commit into "
1139                                "empty head"));
1140                if (squash)
1141                        die(_("Squash commit into empty head not supported yet"));
1142                if (!allow_fast_forward)
1143                        die(_("Non-fast-forward commit does not make sense into "
1144                            "an empty head"));
1145                remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
1146                if (!remote_head)
1147                        die(_("%s - not something we can merge"), argv[0]);
1148                read_empty(remote_head->sha1, 0);
1149                update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
1150                                DIE_ON_ERR);
1151                return 0;
1152        } else {
1153                struct strbuf merge_names = STRBUF_INIT;
1154
1155                /* We are invoked directly as the first-class UI. */
1156                head_arg = "HEAD";
1157
1158                /*
1159                 * All the rest are the commits being merged;
1160                 * prepare the standard merge summary message to
1161                 * be appended to the given message.  If remote
1162                 * is invalid we will die later in the common
1163                 * codepath so we discard the error in this
1164                 * loop.
1165                 */
1166                for (i = 0; i < argc; i++)
1167                        merge_name(argv[i], &merge_names);
1168
1169                if (!have_message || shortlog_len) {
1170                        fmt_merge_msg(&merge_names, &merge_msg, !have_message,
1171                                      shortlog_len);
1172                        if (merge_msg.len)
1173                                strbuf_setlen(&merge_msg, merge_msg.len - 1);
1174                }
1175        }
1176
1177        if (!head_commit || !argc)
1178                usage_with_options(builtin_merge_usage,
1179                        builtin_merge_options);
1180
1181        strbuf_addstr(&buf, "merge");
1182        for (i = 0; i < argc; i++)
1183                strbuf_addf(&buf, " %s", argv[i]);
1184        setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1185        strbuf_reset(&buf);
1186
1187        for (i = 0; i < argc; i++) {
1188                struct object *o;
1189                struct commit *commit;
1190
1191                o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
1192                if (!o)
1193                        die(_("%s - not something we can merge"), argv[i]);
1194                commit = lookup_commit(o->sha1);
1195                commit->util = (void *)argv[i];
1196                remotes = &commit_list_insert(commit, remotes)->next;
1197
1198                strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
1199                setenv(buf.buf, argv[i], 1);
1200                strbuf_reset(&buf);
1201        }
1202
1203        if (!use_strategies) {
1204                if (!remoteheads->next)
1205                        add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1206                else
1207                        add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1208        }
1209
1210        for (i = 0; i < use_strategies_nr; i++) {
1211                if (use_strategies[i]->attr & NO_FAST_FORWARD)
1212                        allow_fast_forward = 0;
1213                if (use_strategies[i]->attr & NO_TRIVIAL)
1214                        allow_trivial = 0;
1215        }
1216
1217        if (!remoteheads->next)
1218                common = get_merge_bases(head_commit, remoteheads->item, 1);
1219        else {
1220                struct commit_list *list = remoteheads;
1221                commit_list_insert(head_commit, &list);
1222                common = get_octopus_merge_bases(list);
1223                free(list);
1224        }
1225
1226        update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
1227                   NULL, 0, DIE_ON_ERR);
1228
1229        if (!common)
1230                ; /* No common ancestors found. We need a real merge. */
1231        else if (!remoteheads->next && !common->next &&
1232                        common->item == remoteheads->item) {
1233                /*
1234                 * If head can reach all the merge then we are up to date.
1235                 * but first the most common case of merging one remote.
1236                 */
1237                finish_up_to_date("Already up-to-date.");
1238                return 0;
1239        } else if (allow_fast_forward && !remoteheads->next &&
1240                        !common->next &&
1241                        !hashcmp(common->item->object.sha1, head_commit->object.sha1)) {
1242                /* Again the most common case of merging one remote. */
1243                struct strbuf msg = STRBUF_INIT;
1244                struct object *o;
1245                char hex[41];
1246
1247                strcpy(hex, find_unique_abbrev(head_commit->object.sha1, DEFAULT_ABBREV));
1248
1249                if (verbosity >= 0)
1250                        printf(_("Updating %s..%s\n"),
1251                                hex,
1252                                find_unique_abbrev(remoteheads->item->object.sha1,
1253                                DEFAULT_ABBREV));
1254                strbuf_addstr(&msg, "Fast-forward");
1255                if (have_message)
1256                        strbuf_addstr(&msg,
1257                                " (no commit created; -m option ignored)");
1258                o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
1259                        0, NULL, OBJ_COMMIT);
1260                if (!o)
1261                        return 1;
1262
1263                if (checkout_fast_forward(head_commit->object.sha1, remoteheads->item->object.sha1))
1264                        return 1;
1265
1266                finish(head_commit, o->sha1, msg.buf);
1267                drop_save();
1268                return 0;
1269        } else if (!remoteheads->next && common->next)
1270                ;
1271                /*
1272                 * We are not doing octopus and not fast-forward.  Need
1273                 * a real merge.
1274                 */
1275        else if (!remoteheads->next && !common->next && option_commit) {
1276                /*
1277                 * We are not doing octopus, not fast-forward, and have
1278                 * only one common.
1279                 */
1280                refresh_cache(REFRESH_QUIET);
1281                if (allow_trivial && !fast_forward_only) {
1282                        /* See if it is really trivial. */
1283                        git_committer_info(IDENT_ERROR_ON_NO_NAME);
1284                        printf(_("Trying really trivial in-index merge...\n"));
1285                        if (!read_tree_trivial(common->item->object.sha1,
1286                                        head_commit->object.sha1, remoteheads->item->object.sha1))
1287                                return merge_trivial(head_commit);
1288                        printf(_("Nope.\n"));
1289                }
1290        } else {
1291                /*
1292                 * An octopus.  If we can reach all the remote we are up
1293                 * to date.
1294                 */
1295                int up_to_date = 1;
1296                struct commit_list *j;
1297
1298                for (j = remoteheads; j; j = j->next) {
1299                        struct commit_list *common_one;
1300
1301                        /*
1302                         * Here we *have* to calculate the individual
1303                         * merge_bases again, otherwise "git merge HEAD^
1304                         * HEAD^^" would be missed.
1305                         */
1306                        common_one = get_merge_bases(head_commit, j->item, 1);
1307                        if (hashcmp(common_one->item->object.sha1,
1308                                j->item->object.sha1)) {
1309                                up_to_date = 0;
1310                                break;
1311                        }
1312                }
1313                if (up_to_date) {
1314                        finish_up_to_date("Already up-to-date. Yeeah!");
1315                        return 0;
1316                }
1317        }
1318
1319        if (fast_forward_only)
1320                die(_("Not possible to fast-forward, aborting."));
1321
1322        /* We are going to make a new commit. */
1323        git_committer_info(IDENT_ERROR_ON_NO_NAME);
1324
1325        /*
1326         * At this point, we need a real merge.  No matter what strategy
1327         * we use, it would operate on the index, possibly affecting the
1328         * working tree, and when resolved cleanly, have the desired
1329         * tree in the index -- this means that the index must be in
1330         * sync with the head commit.  The strategies are responsible
1331         * to ensure this.
1332         */
1333        if (use_strategies_nr == 1 ||
1334            /*
1335             * Stash away the local changes so that we can try more than one.
1336             */
1337            save_state(stash))
1338                hashcpy(stash, null_sha1);
1339
1340        for (i = 0; i < use_strategies_nr; i++) {
1341                int ret;
1342                if (i) {
1343                        printf(_("Rewinding the tree to pristine...\n"));
1344                        restore_state(head_commit->object.sha1, stash);
1345                }
1346                if (use_strategies_nr != 1)
1347                        printf(_("Trying merge strategy %s...\n"),
1348                                use_strategies[i]->name);
1349                /*
1350                 * Remember which strategy left the state in the working
1351                 * tree.
1352                 */
1353                wt_strategy = use_strategies[i]->name;
1354
1355                ret = try_merge_strategy(use_strategies[i]->name,
1356                                         common, head_commit, head_arg);
1357                if (!option_commit && !ret) {
1358                        merge_was_ok = 1;
1359                        /*
1360                         * This is necessary here just to avoid writing
1361                         * the tree, but later we will *not* exit with
1362                         * status code 1 because merge_was_ok is set.
1363                         */
1364                        ret = 1;
1365                }
1366
1367                if (ret) {
1368                        /*
1369                         * The backend exits with 1 when conflicts are
1370                         * left to be resolved, with 2 when it does not
1371                         * handle the given merge at all.
1372                         */
1373                        if (ret == 1) {
1374                                int cnt = evaluate_result();
1375
1376                                if (best_cnt <= 0 || cnt <= best_cnt) {
1377                                        best_strategy = use_strategies[i]->name;
1378                                        best_cnt = cnt;
1379                                }
1380                        }
1381                        if (merge_was_ok)
1382                                break;
1383                        else
1384                                continue;
1385                }
1386
1387                /* Automerge succeeded. */
1388                write_tree_trivial(result_tree);
1389                automerge_was_ok = 1;
1390                break;
1391        }
1392
1393        /*
1394         * If we have a resulting tree, that means the strategy module
1395         * auto resolved the merge cleanly.
1396         */
1397        if (automerge_was_ok)
1398                return finish_automerge(head_commit, common, result_tree,
1399                                        wt_strategy);
1400
1401        /*
1402         * Pick the result from the best strategy and have the user fix
1403         * it up.
1404         */
1405        if (!best_strategy) {
1406                restore_state(head_commit->object.sha1, stash);
1407                if (use_strategies_nr > 1)
1408                        fprintf(stderr,
1409                                _("No merge strategy handled the merge.\n"));
1410                else
1411                        fprintf(stderr, _("Merge with strategy %s failed.\n"),
1412                                use_strategies[0]->name);
1413                return 2;
1414        } else if (best_strategy == wt_strategy)
1415                ; /* We already have its result in the working tree. */
1416        else {
1417                printf(_("Rewinding the tree to pristine...\n"));
1418                restore_state(head_commit->object.sha1, stash);
1419                printf(_("Using the %s to prepare resolving by hand.\n"),
1420                        best_strategy);
1421                try_merge_strategy(best_strategy, common, head_commit, head_arg);
1422        }
1423
1424        if (squash)
1425                finish(head_commit, NULL, NULL);
1426        else {
1427                int fd;
1428                struct commit_list *j;
1429
1430                for (j = remoteheads; j; j = j->next)
1431                        strbuf_addf(&buf, "%s\n",
1432                                sha1_to_hex(j->item->object.sha1));
1433                fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
1434                if (fd < 0)
1435                        die_errno(_("Could not open '%s' for writing"),
1436                                  git_path("MERGE_HEAD"));
1437                if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1438                        die_errno(_("Could not write to '%s'"), git_path("MERGE_HEAD"));
1439                close(fd);
1440                strbuf_addch(&merge_msg, '\n');
1441                write_merge_msg();
1442                fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
1443                if (fd < 0)
1444                        die_errno(_("Could not open '%s' for writing"),
1445                                  git_path("MERGE_MODE"));
1446                strbuf_reset(&buf);
1447                if (!allow_fast_forward)
1448                        strbuf_addf(&buf, "no-ff");
1449                if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1450                        die_errno(_("Could not write to '%s'"), git_path("MERGE_MODE"));
1451                close(fd);
1452        }
1453
1454        if (merge_was_ok) {
1455                fprintf(stderr, _("Automatic merge went well; "
1456                        "stopped before committing as requested\n"));
1457                return 0;
1458        } else
1459                return suggest_conflicts(option_renormalize);
1460}