builtin / merge.con commit checkout,merge: disallow overwriting ignored files with --no-overwrite-ignore (c1d7036)
   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, option_edit;
  50static int allow_trivial = 1, have_message;
  51static int overwrite_ignore = 1;
  52static struct strbuf merge_msg;
  53static struct commit_list *remoteheads;
  54static struct strategy **use_strategies;
  55static size_t use_strategies_nr, use_strategies_alloc;
  56static const char **xopts;
  57static size_t xopts_nr, xopts_alloc;
  58static const char *branch;
  59static char *branch_mergeoptions;
  60static int option_renormalize;
  61static int verbosity;
  62static int allow_rerere_auto;
  63static int abort_current_merge;
  64static int show_progress = -1;
  65static int default_to_upstream;
  66
  67static struct strategy all_strategy[] = {
  68        { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  69        { "octopus",    DEFAULT_OCTOPUS },
  70        { "resolve",    0 },
  71        { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  72        { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  73};
  74
  75static const char *pull_twohead, *pull_octopus;
  76
  77static int option_parse_message(const struct option *opt,
  78                                const char *arg, int unset)
  79{
  80        struct strbuf *buf = opt->value;
  81
  82        if (unset)
  83                strbuf_setlen(buf, 0);
  84        else if (arg) {
  85                strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  86                have_message = 1;
  87        } else
  88                return error(_("switch `m' requires a value"));
  89        return 0;
  90}
  91
  92static struct strategy *get_strategy(const char *name)
  93{
  94        int i;
  95        struct strategy *ret;
  96        static struct cmdnames main_cmds, other_cmds;
  97        static int loaded;
  98
  99        if (!name)
 100                return NULL;
 101
 102        for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 103                if (!strcmp(name, all_strategy[i].name))
 104                        return &all_strategy[i];
 105
 106        if (!loaded) {
 107                struct cmdnames not_strategies;
 108                loaded = 1;
 109
 110                memset(&not_strategies, 0, sizeof(struct cmdnames));
 111                load_command_list("git-merge-", &main_cmds, &other_cmds);
 112                for (i = 0; i < main_cmds.cnt; i++) {
 113                        int j, found = 0;
 114                        struct cmdname *ent = main_cmds.names[i];
 115                        for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 116                                if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 117                                                && !all_strategy[j].name[ent->len])
 118                                        found = 1;
 119                        if (!found)
 120                                add_cmdname(&not_strategies, ent->name, ent->len);
 121                }
 122                exclude_cmds(&main_cmds, &not_strategies);
 123        }
 124        if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 125                fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 126                fprintf(stderr, _("Available strategies are:"));
 127                for (i = 0; i < main_cmds.cnt; i++)
 128                        fprintf(stderr, " %s", main_cmds.names[i]->name);
 129                fprintf(stderr, ".\n");
 130                if (other_cmds.cnt) {
 131                        fprintf(stderr, _("Available custom strategies are:"));
 132                        for (i = 0; i < other_cmds.cnt; i++)
 133                                fprintf(stderr, " %s", other_cmds.names[i]->name);
 134                        fprintf(stderr, ".\n");
 135                }
 136                exit(1);
 137        }
 138
 139        ret = xcalloc(1, sizeof(struct strategy));
 140        ret->name = xstrdup(name);
 141        ret->attr = NO_TRIVIAL;
 142        return ret;
 143}
 144
 145static void append_strategy(struct strategy *s)
 146{
 147        ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 148        use_strategies[use_strategies_nr++] = s;
 149}
 150
 151static int option_parse_strategy(const struct option *opt,
 152                                 const char *name, int unset)
 153{
 154        if (unset)
 155                return 0;
 156
 157        append_strategy(get_strategy(name));
 158        return 0;
 159}
 160
 161static int option_parse_x(const struct option *opt,
 162                          const char *arg, int unset)
 163{
 164        if (unset)
 165                return 0;
 166
 167        ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 168        xopts[xopts_nr++] = xstrdup(arg);
 169        return 0;
 170}
 171
 172static int option_parse_n(const struct option *opt,
 173                          const char *arg, int unset)
 174{
 175        show_diffstat = unset;
 176        return 0;
 177}
 178
 179static struct option builtin_merge_options[] = {
 180        { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 181                "do not show a diffstat at the end of the merge",
 182                PARSE_OPT_NOARG, option_parse_n },
 183        OPT_BOOLEAN(0, "stat", &show_diffstat,
 184                "show a diffstat at the end of the merge"),
 185        OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 186        { OPTION_INTEGER, 0, "log", &shortlog_len, "n",
 187          "add (at most <n>) entries from shortlog to merge commit message",
 188          PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 189        OPT_BOOLEAN(0, "squash", &squash,
 190                "create a single commit instead of doing a merge"),
 191        OPT_BOOLEAN(0, "commit", &option_commit,
 192                "perform a commit if the merge succeeds (default)"),
 193        OPT_BOOLEAN('e', "edit", &option_edit,
 194                "edit message before committing"),
 195        OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 196                "allow fast-forward (default)"),
 197        OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
 198                "abort if fast-forward is not possible"),
 199        OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 200        OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
 201                "merge strategy to use", option_parse_strategy),
 202        OPT_CALLBACK('X', "strategy-option", &xopts, "option=value",
 203                "option for selected merge strategy", option_parse_x),
 204        OPT_CALLBACK('m', "message", &merge_msg, "message",
 205                "merge commit message (for a non-fast-forward merge)",
 206                option_parse_message),
 207        OPT__VERBOSITY(&verbosity),
 208        OPT_BOOLEAN(0, "abort", &abort_current_merge,
 209                "abort the current in-progress merge"),
 210        OPT_SET_INT(0, "progress", &show_progress, "force progress reporting", 1),
 211        OPT_BOOLEAN(0, "overwrite-ignore", &overwrite_ignore, "update ignored files (default)"),
 212        OPT_END()
 213};
 214
 215/* Cleans up metadata that is uninteresting after a succeeded merge. */
 216static void drop_save(void)
 217{
 218        unlink(git_path("MERGE_HEAD"));
 219        unlink(git_path("MERGE_MSG"));
 220        unlink(git_path("MERGE_MODE"));
 221}
 222
 223static int save_state(unsigned char *stash)
 224{
 225        int len;
 226        struct child_process cp;
 227        struct strbuf buffer = STRBUF_INIT;
 228        const char *argv[] = {"stash", "create", NULL};
 229
 230        memset(&cp, 0, sizeof(cp));
 231        cp.argv = argv;
 232        cp.out = -1;
 233        cp.git_cmd = 1;
 234
 235        if (start_command(&cp))
 236                die(_("could not run stash."));
 237        len = strbuf_read(&buffer, cp.out, 1024);
 238        close(cp.out);
 239
 240        if (finish_command(&cp) || len < 0)
 241                die(_("stash failed"));
 242        else if (!len)          /* no changes */
 243                return -1;
 244        strbuf_setlen(&buffer, buffer.len-1);
 245        if (get_sha1(buffer.buf, stash))
 246                die(_("not a valid object: %s"), buffer.buf);
 247        return 0;
 248}
 249
 250static void read_empty(unsigned const char *sha1, int verbose)
 251{
 252        int i = 0;
 253        const char *args[7];
 254
 255        args[i++] = "read-tree";
 256        if (verbose)
 257                args[i++] = "-v";
 258        args[i++] = "-m";
 259        args[i++] = "-u";
 260        args[i++] = EMPTY_TREE_SHA1_HEX;
 261        args[i++] = sha1_to_hex(sha1);
 262        args[i] = NULL;
 263
 264        if (run_command_v_opt(args, RUN_GIT_CMD))
 265                die(_("read-tree failed"));
 266}
 267
 268static void reset_hard(unsigned const char *sha1, int verbose)
 269{
 270        int i = 0;
 271        const char *args[6];
 272
 273        args[i++] = "read-tree";
 274        if (verbose)
 275                args[i++] = "-v";
 276        args[i++] = "--reset";
 277        args[i++] = "-u";
 278        args[i++] = sha1_to_hex(sha1);
 279        args[i] = NULL;
 280
 281        if (run_command_v_opt(args, RUN_GIT_CMD))
 282                die(_("read-tree failed"));
 283}
 284
 285static void restore_state(const unsigned char *head,
 286                          const unsigned char *stash)
 287{
 288        struct strbuf sb = STRBUF_INIT;
 289        const char *args[] = { "stash", "apply", NULL, NULL };
 290
 291        if (is_null_sha1(stash))
 292                return;
 293
 294        reset_hard(head, 1);
 295
 296        args[2] = sha1_to_hex(stash);
 297
 298        /*
 299         * It is OK to ignore error here, for example when there was
 300         * nothing to restore.
 301         */
 302        run_command_v_opt(args, RUN_GIT_CMD);
 303
 304        strbuf_release(&sb);
 305        refresh_cache(REFRESH_QUIET);
 306}
 307
 308/* This is called when no merge was necessary. */
 309static void finish_up_to_date(const char *msg)
 310{
 311        if (verbosity >= 0)
 312                printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 313        drop_save();
 314}
 315
 316static void squash_message(struct commit *commit)
 317{
 318        struct rev_info rev;
 319        struct strbuf out = STRBUF_INIT;
 320        struct commit_list *j;
 321        const char *filename;
 322        int fd;
 323        struct pretty_print_context ctx = {0};
 324
 325        printf(_("Squash commit -- not updating HEAD\n"));
 326        filename = git_path("SQUASH_MSG");
 327        fd = open(filename, O_WRONLY | O_CREAT, 0666);
 328        if (fd < 0)
 329                die_errno(_("Could not write to '%s'"), filename);
 330
 331        init_revisions(&rev, NULL);
 332        rev.ignore_merges = 1;
 333        rev.commit_format = CMIT_FMT_MEDIUM;
 334
 335        commit->object.flags |= UNINTERESTING;
 336        add_pending_object(&rev, &commit->object, NULL);
 337
 338        for (j = remoteheads; j; j = j->next)
 339                add_pending_object(&rev, &j->item->object, NULL);
 340
 341        setup_revisions(0, NULL, &rev, NULL);
 342        if (prepare_revision_walk(&rev))
 343                die(_("revision walk setup failed"));
 344
 345        ctx.abbrev = rev.abbrev;
 346        ctx.date_mode = rev.date_mode;
 347        ctx.fmt = rev.commit_format;
 348
 349        strbuf_addstr(&out, "Squashed commit of the following:\n");
 350        while ((commit = get_revision(&rev)) != NULL) {
 351                strbuf_addch(&out, '\n');
 352                strbuf_addf(&out, "commit %s\n",
 353                        sha1_to_hex(commit->object.sha1));
 354                pretty_print_commit(&ctx, commit, &out);
 355        }
 356        if (write(fd, out.buf, out.len) < 0)
 357                die_errno(_("Writing SQUASH_MSG"));
 358        if (close(fd))
 359                die_errno(_("Finishing SQUASH_MSG"));
 360        strbuf_release(&out);
 361}
 362
 363static void finish(struct commit *head_commit,
 364                   const unsigned char *new_head, const char *msg)
 365{
 366        struct strbuf reflog_message = STRBUF_INIT;
 367        const unsigned char *head = head_commit->object.sha1;
 368
 369        if (!msg)
 370                strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 371        else {
 372                if (verbosity >= 0)
 373                        printf("%s\n", msg);
 374                strbuf_addf(&reflog_message, "%s: %s",
 375                        getenv("GIT_REFLOG_ACTION"), msg);
 376        }
 377        if (squash) {
 378                squash_message(head_commit);
 379        } else {
 380                if (verbosity >= 0 && !merge_msg.len)
 381                        printf(_("No merge message -- not updating HEAD\n"));
 382                else {
 383                        const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 384                        update_ref(reflog_message.buf, "HEAD",
 385                                new_head, head, 0,
 386                                DIE_ON_ERR);
 387                        /*
 388                         * We ignore errors in 'gc --auto', since the
 389                         * user should see them.
 390                         */
 391                        run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 392                }
 393        }
 394        if (new_head && show_diffstat) {
 395                struct diff_options opts;
 396                diff_setup(&opts);
 397                opts.output_format |=
 398                        DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 399                opts.detect_rename = DIFF_DETECT_RENAME;
 400                if (diff_setup_done(&opts) < 0)
 401                        die(_("diff_setup_done failed"));
 402                diff_tree_sha1(head, new_head, "", &opts);
 403                diffcore_std(&opts);
 404                diff_flush(&opts);
 405        }
 406
 407        /* Run a post-merge hook */
 408        run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
 409
 410        strbuf_release(&reflog_message);
 411}
 412
 413static struct object *want_commit(const char *name)
 414{
 415        struct object *obj;
 416        unsigned char sha1[20];
 417        if (get_sha1(name, sha1))
 418                return NULL;
 419        obj = parse_object(sha1);
 420        return peel_to_type(name, 0, obj, OBJ_COMMIT);
 421}
 422
 423/* Get the name for the merge commit's message. */
 424static void merge_name(const char *remote, struct strbuf *msg)
 425{
 426        struct object *remote_head;
 427        unsigned char branch_head[20], buf_sha[20];
 428        struct strbuf buf = STRBUF_INIT;
 429        struct strbuf bname = STRBUF_INIT;
 430        const char *ptr;
 431        char *found_ref;
 432        int len, early;
 433
 434        strbuf_branchname(&bname, remote);
 435        remote = bname.buf;
 436
 437        memset(branch_head, 0, sizeof(branch_head));
 438        remote_head = want_commit(remote);
 439        if (!remote_head)
 440                die(_("'%s' does not point to a commit"), remote);
 441
 442        if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 443                if (!prefixcmp(found_ref, "refs/heads/")) {
 444                        strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 445                                    sha1_to_hex(branch_head), remote);
 446                        goto cleanup;
 447                }
 448                if (!prefixcmp(found_ref, "refs/remotes/")) {
 449                        strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 450                                    sha1_to_hex(branch_head), remote);
 451                        goto cleanup;
 452                }
 453        }
 454
 455        /* See if remote matches <name>^^^.. or <name>~<number> */
 456        for (len = 0, ptr = remote + strlen(remote);
 457             remote < ptr && ptr[-1] == '^';
 458             ptr--)
 459                len++;
 460        if (len)
 461                early = 1;
 462        else {
 463                early = 0;
 464                ptr = strrchr(remote, '~');
 465                if (ptr) {
 466                        int seen_nonzero = 0;
 467
 468                        len++; /* count ~ */
 469                        while (*++ptr && isdigit(*ptr)) {
 470                                seen_nonzero |= (*ptr != '0');
 471                                len++;
 472                        }
 473                        if (*ptr)
 474                                len = 0; /* not ...~<number> */
 475                        else if (seen_nonzero)
 476                                early = 1;
 477                        else if (len == 1)
 478                                early = 1; /* "name~" is "name~1"! */
 479                }
 480        }
 481        if (len) {
 482                struct strbuf truname = STRBUF_INIT;
 483                strbuf_addstr(&truname, "refs/heads/");
 484                strbuf_addstr(&truname, remote);
 485                strbuf_setlen(&truname, truname.len - len);
 486                if (resolve_ref(truname.buf, buf_sha, 1, NULL)) {
 487                        strbuf_addf(msg,
 488                                    "%s\t\tbranch '%s'%s of .\n",
 489                                    sha1_to_hex(remote_head->sha1),
 490                                    truname.buf + 11,
 491                                    (early ? " (early part)" : ""));
 492                        strbuf_release(&truname);
 493                        goto cleanup;
 494                }
 495        }
 496
 497        if (!strcmp(remote, "FETCH_HEAD") &&
 498                        !access(git_path("FETCH_HEAD"), R_OK)) {
 499                const char *filename;
 500                FILE *fp;
 501                struct strbuf line = STRBUF_INIT;
 502                char *ptr;
 503
 504                filename = git_path("FETCH_HEAD");
 505                fp = fopen(filename, "r");
 506                if (!fp)
 507                        die_errno(_("could not open '%s' for reading"),
 508                                  filename);
 509                strbuf_getline(&line, fp, '\n');
 510                fclose(fp);
 511                ptr = strstr(line.buf, "\tnot-for-merge\t");
 512                if (ptr)
 513                        strbuf_remove(&line, ptr-line.buf+1, 13);
 514                strbuf_addbuf(msg, &line);
 515                strbuf_release(&line);
 516                goto cleanup;
 517        }
 518        strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 519                sha1_to_hex(remote_head->sha1), remote);
 520cleanup:
 521        strbuf_release(&buf);
 522        strbuf_release(&bname);
 523}
 524
 525static void parse_branch_merge_options(char *bmo)
 526{
 527        const char **argv;
 528        int argc;
 529
 530        if (!bmo)
 531                return;
 532        argc = split_cmdline(bmo, &argv);
 533        if (argc < 0)
 534                die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 535                    split_cmdline_strerror(argc));
 536        argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 537        memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 538        argc++;
 539        argv[0] = "branch.*.mergeoptions";
 540        parse_options(argc, argv, NULL, builtin_merge_options,
 541                      builtin_merge_usage, 0);
 542        free(argv);
 543}
 544
 545static int git_merge_config(const char *k, const char *v, void *cb)
 546{
 547        if (branch && !prefixcmp(k, "branch.") &&
 548                !prefixcmp(k + 7, branch) &&
 549                !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 550                free(branch_mergeoptions);
 551                branch_mergeoptions = xstrdup(v);
 552                return 0;
 553        }
 554
 555        if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 556                show_diffstat = git_config_bool(k, v);
 557        else if (!strcmp(k, "pull.twohead"))
 558                return git_config_string(&pull_twohead, k, v);
 559        else if (!strcmp(k, "pull.octopus"))
 560                return git_config_string(&pull_octopus, k, v);
 561        else if (!strcmp(k, "merge.renormalize"))
 562                option_renormalize = git_config_bool(k, v);
 563        else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary")) {
 564                int is_bool;
 565                shortlog_len = git_config_bool_or_int(k, v, &is_bool);
 566                if (!is_bool && shortlog_len < 0)
 567                        return error(_("%s: negative length %s"), k, v);
 568                if (is_bool && shortlog_len)
 569                        shortlog_len = DEFAULT_MERGE_LOG_LEN;
 570                return 0;
 571        } else if (!strcmp(k, "merge.ff")) {
 572                int boolval = git_config_maybe_bool(k, v);
 573                if (0 <= boolval) {
 574                        allow_fast_forward = boolval;
 575                } else if (v && !strcmp(v, "only")) {
 576                        allow_fast_forward = 1;
 577                        fast_forward_only = 1;
 578                } /* do not barf on values from future versions of git */
 579                return 0;
 580        } else if (!strcmp(k, "merge.defaulttoupstream")) {
 581                default_to_upstream = git_config_bool(k, v);
 582                return 0;
 583        }
 584        return git_diff_ui_config(k, v, cb);
 585}
 586
 587static int read_tree_trivial(unsigned char *common, unsigned char *head,
 588                             unsigned char *one)
 589{
 590        int i, nr_trees = 0;
 591        struct tree *trees[MAX_UNPACK_TREES];
 592        struct tree_desc t[MAX_UNPACK_TREES];
 593        struct unpack_trees_options opts;
 594
 595        memset(&opts, 0, sizeof(opts));
 596        opts.head_idx = 2;
 597        opts.src_index = &the_index;
 598        opts.dst_index = &the_index;
 599        opts.update = 1;
 600        opts.verbose_update = 1;
 601        opts.trivial_merges_only = 1;
 602        opts.merge = 1;
 603        trees[nr_trees] = parse_tree_indirect(common);
 604        if (!trees[nr_trees++])
 605                return -1;
 606        trees[nr_trees] = parse_tree_indirect(head);
 607        if (!trees[nr_trees++])
 608                return -1;
 609        trees[nr_trees] = parse_tree_indirect(one);
 610        if (!trees[nr_trees++])
 611                return -1;
 612        opts.fn = threeway_merge;
 613        cache_tree_free(&active_cache_tree);
 614        for (i = 0; i < nr_trees; i++) {
 615                parse_tree(trees[i]);
 616                init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 617        }
 618        if (unpack_trees(nr_trees, t, &opts))
 619                return -1;
 620        return 0;
 621}
 622
 623static void write_tree_trivial(unsigned char *sha1)
 624{
 625        if (write_cache_as_tree(sha1, 0, NULL))
 626                die(_("git write-tree failed to write a tree"));
 627}
 628
 629static const char *merge_argument(struct commit *commit)
 630{
 631        if (commit)
 632                return sha1_to_hex(commit->object.sha1);
 633        else
 634                return EMPTY_TREE_SHA1_HEX;
 635}
 636
 637int try_merge_command(const char *strategy, size_t xopts_nr,
 638                      const char **xopts, struct commit_list *common,
 639                      const char *head_arg, struct commit_list *remotes)
 640{
 641        const char **args;
 642        int i = 0, x = 0, ret;
 643        struct commit_list *j;
 644        struct strbuf buf = STRBUF_INIT;
 645
 646        args = xmalloc((4 + xopts_nr + commit_list_count(common) +
 647                        commit_list_count(remotes)) * sizeof(char *));
 648        strbuf_addf(&buf, "merge-%s", strategy);
 649        args[i++] = buf.buf;
 650        for (x = 0; x < xopts_nr; x++) {
 651                char *s = xmalloc(strlen(xopts[x])+2+1);
 652                strcpy(s, "--");
 653                strcpy(s+2, xopts[x]);
 654                args[i++] = s;
 655        }
 656        for (j = common; j; j = j->next)
 657                args[i++] = xstrdup(merge_argument(j->item));
 658        args[i++] = "--";
 659        args[i++] = head_arg;
 660        for (j = remotes; j; j = j->next)
 661                args[i++] = xstrdup(merge_argument(j->item));
 662        args[i] = NULL;
 663        ret = run_command_v_opt(args, RUN_GIT_CMD);
 664        strbuf_release(&buf);
 665        i = 1;
 666        for (x = 0; x < xopts_nr; x++)
 667                free((void *)args[i++]);
 668        for (j = common; j; j = j->next)
 669                free((void *)args[i++]);
 670        i += 2;
 671        for (j = remotes; j; j = j->next)
 672                free((void *)args[i++]);
 673        free(args);
 674        discard_cache();
 675        if (read_cache() < 0)
 676                die(_("failed to read the cache"));
 677        resolve_undo_clear();
 678
 679        return ret;
 680}
 681
 682static int try_merge_strategy(const char *strategy, struct commit_list *common,
 683                              struct commit *head, const char *head_arg)
 684{
 685        int index_fd;
 686        struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 687
 688        index_fd = hold_locked_index(lock, 1);
 689        refresh_cache(REFRESH_QUIET);
 690        if (active_cache_changed &&
 691                        (write_cache(index_fd, active_cache, active_nr) ||
 692                         commit_locked_index(lock)))
 693                return error(_("Unable to write index."));
 694        rollback_lock_file(lock);
 695
 696        if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 697                int clean, x;
 698                struct commit *result;
 699                struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 700                int index_fd;
 701                struct commit_list *reversed = NULL;
 702                struct merge_options o;
 703                struct commit_list *j;
 704
 705                if (remoteheads->next) {
 706                        error(_("Not handling anything other than two heads merge."));
 707                        return 2;
 708                }
 709
 710                init_merge_options(&o);
 711                if (!strcmp(strategy, "subtree"))
 712                        o.subtree_shift = "";
 713
 714                o.renormalize = option_renormalize;
 715                o.show_rename_progress =
 716                        show_progress == -1 ? isatty(2) : show_progress;
 717
 718                for (x = 0; x < xopts_nr; x++)
 719                        if (parse_merge_opt(&o, xopts[x]))
 720                                die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 721
 722                o.branch1 = head_arg;
 723                o.branch2 = remoteheads->item->util;
 724
 725                for (j = common; j; j = j->next)
 726                        commit_list_insert(j->item, &reversed);
 727
 728                index_fd = hold_locked_index(lock, 1);
 729                clean = merge_recursive(&o, head,
 730                                remoteheads->item, reversed, &result);
 731                if (active_cache_changed &&
 732                                (write_cache(index_fd, active_cache, active_nr) ||
 733                                 commit_locked_index(lock)))
 734                        die (_("unable to write %s"), get_index_file());
 735                rollback_lock_file(lock);
 736                return clean ? 0 : 1;
 737        } else {
 738                return try_merge_command(strategy, xopts_nr, xopts,
 739                                                common, head_arg, remoteheads);
 740        }
 741}
 742
 743static void count_diff_files(struct diff_queue_struct *q,
 744                             struct diff_options *opt, void *data)
 745{
 746        int *count = data;
 747
 748        (*count) += q->nr;
 749}
 750
 751static int count_unmerged_entries(void)
 752{
 753        int i, ret = 0;
 754
 755        for (i = 0; i < active_nr; i++)
 756                if (ce_stage(active_cache[i]))
 757                        ret++;
 758
 759        return ret;
 760}
 761
 762int checkout_fast_forward(const unsigned char *head, const unsigned char *remote)
 763{
 764        struct tree *trees[MAX_UNPACK_TREES];
 765        struct unpack_trees_options opts;
 766        struct tree_desc t[MAX_UNPACK_TREES];
 767        int i, fd, nr_trees = 0;
 768        struct dir_struct dir;
 769        struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 770
 771        refresh_cache(REFRESH_QUIET);
 772
 773        fd = hold_locked_index(lock_file, 1);
 774
 775        memset(&trees, 0, sizeof(trees));
 776        memset(&opts, 0, sizeof(opts));
 777        memset(&t, 0, sizeof(t));
 778        if (overwrite_ignore) {
 779                memset(&dir, 0, sizeof(dir));
 780                dir.flags |= DIR_SHOW_IGNORED;
 781                setup_standard_excludes(&dir);
 782                opts.dir = &dir;
 783        }
 784
 785        opts.head_idx = 1;
 786        opts.src_index = &the_index;
 787        opts.dst_index = &the_index;
 788        opts.update = 1;
 789        opts.verbose_update = 1;
 790        opts.merge = 1;
 791        opts.fn = twoway_merge;
 792        setup_unpack_trees_porcelain(&opts, "merge");
 793
 794        trees[nr_trees] = parse_tree_indirect(head);
 795        if (!trees[nr_trees++])
 796                return -1;
 797        trees[nr_trees] = parse_tree_indirect(remote);
 798        if (!trees[nr_trees++])
 799                return -1;
 800        for (i = 0; i < nr_trees; i++) {
 801                parse_tree(trees[i]);
 802                init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 803        }
 804        if (unpack_trees(nr_trees, t, &opts))
 805                return -1;
 806        if (write_cache(fd, active_cache, active_nr) ||
 807                commit_locked_index(lock_file))
 808                die(_("unable to write new index file"));
 809        return 0;
 810}
 811
 812static void split_merge_strategies(const char *string, struct strategy **list,
 813                                   int *nr, int *alloc)
 814{
 815        char *p, *q, *buf;
 816
 817        if (!string)
 818                return;
 819
 820        buf = xstrdup(string);
 821        q = buf;
 822        for (;;) {
 823                p = strchr(q, ' ');
 824                if (!p) {
 825                        ALLOC_GROW(*list, *nr + 1, *alloc);
 826                        (*list)[(*nr)++].name = xstrdup(q);
 827                        free(buf);
 828                        return;
 829                } else {
 830                        *p = '\0';
 831                        ALLOC_GROW(*list, *nr + 1, *alloc);
 832                        (*list)[(*nr)++].name = xstrdup(q);
 833                        q = ++p;
 834                }
 835        }
 836}
 837
 838static void add_strategies(const char *string, unsigned attr)
 839{
 840        struct strategy *list = NULL;
 841        int list_alloc = 0, list_nr = 0, i;
 842
 843        memset(&list, 0, sizeof(list));
 844        split_merge_strategies(string, &list, &list_nr, &list_alloc);
 845        if (list) {
 846                for (i = 0; i < list_nr; i++)
 847                        append_strategy(get_strategy(list[i].name));
 848                return;
 849        }
 850        for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 851                if (all_strategy[i].attr & attr)
 852                        append_strategy(&all_strategy[i]);
 853
 854}
 855
 856static void write_merge_msg(struct strbuf *msg)
 857{
 858        const char *filename = git_path("MERGE_MSG");
 859        int fd = open(filename, O_WRONLY | O_CREAT, 0666);
 860        if (fd < 0)
 861                die_errno(_("Could not open '%s' for writing"),
 862                          filename);
 863        if (write_in_full(fd, msg->buf, msg->len) != msg->len)
 864                die_errno(_("Could not write to '%s'"), filename);
 865        close(fd);
 866}
 867
 868static void read_merge_msg(struct strbuf *msg)
 869{
 870        const char *filename = git_path("MERGE_MSG");
 871        strbuf_reset(msg);
 872        if (strbuf_read_file(msg, filename, 0) < 0)
 873                die_errno(_("Could not read from '%s'"), filename);
 874}
 875
 876static void write_merge_state(void);
 877static void abort_commit(const char *err_msg)
 878{
 879        if (err_msg)
 880                error("%s", err_msg);
 881        fprintf(stderr,
 882                _("Not committing merge; use 'git commit' to complete the merge.\n"));
 883        write_merge_state();
 884        exit(1);
 885}
 886
 887static void prepare_to_commit(void)
 888{
 889        struct strbuf msg = STRBUF_INIT;
 890        strbuf_addbuf(&msg, &merge_msg);
 891        strbuf_addch(&msg, '\n');
 892        write_merge_msg(&msg);
 893        run_hook(get_index_file(), "prepare-commit-msg",
 894                 git_path("MERGE_MSG"), "merge", NULL, NULL);
 895        if (option_edit) {
 896                if (launch_editor(git_path("MERGE_MSG"), NULL, NULL))
 897                        abort_commit(NULL);
 898        }
 899        read_merge_msg(&msg);
 900        stripspace(&msg, option_edit);
 901        if (!msg.len)
 902                abort_commit(_("Empty commit message."));
 903        strbuf_release(&merge_msg);
 904        strbuf_addbuf(&merge_msg, &msg);
 905        strbuf_release(&msg);
 906}
 907
 908static int merge_trivial(struct commit *head)
 909{
 910        unsigned char result_tree[20], result_commit[20];
 911        struct commit_list *parent = xmalloc(sizeof(*parent));
 912
 913        write_tree_trivial(result_tree);
 914        printf(_("Wonderful.\n"));
 915        parent->item = head;
 916        parent->next = xmalloc(sizeof(*parent->next));
 917        parent->next->item = remoteheads->item;
 918        parent->next->next = NULL;
 919        prepare_to_commit();
 920        commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
 921        finish(head, result_commit, "In-index merge");
 922        drop_save();
 923        return 0;
 924}
 925
 926static int finish_automerge(struct commit *head,
 927                            struct commit_list *common,
 928                            unsigned char *result_tree,
 929                            const char *wt_strategy)
 930{
 931        struct commit_list *parents = NULL, *j;
 932        struct strbuf buf = STRBUF_INIT;
 933        unsigned char result_commit[20];
 934
 935        free_commit_list(common);
 936        if (allow_fast_forward) {
 937                parents = remoteheads;
 938                commit_list_insert(head, &parents);
 939                parents = reduce_heads(parents);
 940        } else {
 941                struct commit_list **pptr = &parents;
 942
 943                pptr = &commit_list_insert(head,
 944                                pptr)->next;
 945                for (j = remoteheads; j; j = j->next)
 946                        pptr = &commit_list_insert(j->item, pptr)->next;
 947        }
 948        strbuf_addch(&merge_msg, '\n');
 949        prepare_to_commit();
 950        free_commit_list(remoteheads);
 951        commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
 952        strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 953        finish(head, result_commit, buf.buf);
 954        strbuf_release(&buf);
 955        drop_save();
 956        return 0;
 957}
 958
 959static int suggest_conflicts(int renormalizing)
 960{
 961        const char *filename;
 962        FILE *fp;
 963        int pos;
 964
 965        filename = git_path("MERGE_MSG");
 966        fp = fopen(filename, "a");
 967        if (!fp)
 968                die_errno(_("Could not open '%s' for writing"), filename);
 969        fprintf(fp, "\nConflicts:\n");
 970        for (pos = 0; pos < active_nr; pos++) {
 971                struct cache_entry *ce = active_cache[pos];
 972
 973                if (ce_stage(ce)) {
 974                        fprintf(fp, "\t%s\n", ce->name);
 975                        while (pos + 1 < active_nr &&
 976                                        !strcmp(ce->name,
 977                                                active_cache[pos + 1]->name))
 978                                pos++;
 979                }
 980        }
 981        fclose(fp);
 982        rerere(allow_rerere_auto);
 983        printf(_("Automatic merge failed; "
 984                        "fix conflicts and then commit the result.\n"));
 985        return 1;
 986}
 987
 988static struct commit *is_old_style_invocation(int argc, const char **argv,
 989                                              const unsigned char *head)
 990{
 991        struct commit *second_token = NULL;
 992        if (argc > 2) {
 993                unsigned char second_sha1[20];
 994
 995                if (get_sha1(argv[1], second_sha1))
 996                        return NULL;
 997                second_token = lookup_commit_reference_gently(second_sha1, 0);
 998                if (!second_token)
 999                        die(_("'%s' is not a commit"), argv[1]);
1000                if (hashcmp(second_token->object.sha1, head))
1001                        return NULL;
1002        }
1003        return second_token;
1004}
1005
1006static int evaluate_result(void)
1007{
1008        int cnt = 0;
1009        struct rev_info rev;
1010
1011        /* Check how many files differ. */
1012        init_revisions(&rev, "");
1013        setup_revisions(0, NULL, &rev, NULL);
1014        rev.diffopt.output_format |=
1015                DIFF_FORMAT_CALLBACK;
1016        rev.diffopt.format_callback = count_diff_files;
1017        rev.diffopt.format_callback_data = &cnt;
1018        run_diff_files(&rev, 0);
1019
1020        /*
1021         * Check how many unmerged entries are
1022         * there.
1023         */
1024        cnt += count_unmerged_entries();
1025
1026        return cnt;
1027}
1028
1029/*
1030 * Pretend as if the user told us to merge with the tracking
1031 * branch we have for the upstream of the current branch
1032 */
1033static int setup_with_upstream(const char ***argv)
1034{
1035        struct branch *branch = branch_get(NULL);
1036        int i;
1037        const char **args;
1038
1039        if (!branch)
1040                die(_("No current branch."));
1041        if (!branch->remote)
1042                die(_("No remote for the current branch."));
1043        if (!branch->merge_nr)
1044                die(_("No default upstream defined for the current branch."));
1045
1046        args = xcalloc(branch->merge_nr + 1, sizeof(char *));
1047        for (i = 0; i < branch->merge_nr; i++) {
1048                if (!branch->merge[i]->dst)
1049                        die(_("No remote tracking branch for %s from %s"),
1050                            branch->merge[i]->src, branch->remote_name);
1051                args[i] = branch->merge[i]->dst;
1052        }
1053        args[i] = NULL;
1054        *argv = args;
1055        return i;
1056}
1057
1058static void write_merge_state(void)
1059{
1060        const char *filename;
1061        int fd;
1062        struct commit_list *j;
1063        struct strbuf buf = STRBUF_INIT;
1064
1065        for (j = remoteheads; j; j = j->next)
1066                strbuf_addf(&buf, "%s\n",
1067                        sha1_to_hex(j->item->object.sha1));
1068        filename = git_path("MERGE_HEAD");
1069        fd = open(filename, O_WRONLY | O_CREAT, 0666);
1070        if (fd < 0)
1071                die_errno(_("Could not open '%s' for writing"), filename);
1072        if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1073                die_errno(_("Could not write to '%s'"), filename);
1074        close(fd);
1075        strbuf_addch(&merge_msg, '\n');
1076        write_merge_msg(&merge_msg);
1077
1078        filename = git_path("MERGE_MODE");
1079        fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
1080        if (fd < 0)
1081                die_errno(_("Could not open '%s' for writing"), filename);
1082        strbuf_reset(&buf);
1083        if (!allow_fast_forward)
1084                strbuf_addf(&buf, "no-ff");
1085        if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1086                die_errno(_("Could not write to '%s'"), filename);
1087        close(fd);
1088}
1089
1090int cmd_merge(int argc, const char **argv, const char *prefix)
1091{
1092        unsigned char result_tree[20];
1093        unsigned char stash[20];
1094        unsigned char head_sha1[20];
1095        struct commit *head_commit;
1096        struct strbuf buf = STRBUF_INIT;
1097        const char *head_arg;
1098        int flag, i;
1099        int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1100        struct commit_list *common = NULL;
1101        const char *best_strategy = NULL, *wt_strategy = NULL;
1102        struct commit_list **remotes = &remoteheads;
1103
1104        if (argc == 2 && !strcmp(argv[1], "-h"))
1105                usage_with_options(builtin_merge_usage, builtin_merge_options);
1106
1107        /*
1108         * Check if we are _not_ on a detached HEAD, i.e. if there is a
1109         * current branch.
1110         */
1111        branch = resolve_ref("HEAD", head_sha1, 0, &flag);
1112        if (branch && !prefixcmp(branch, "refs/heads/"))
1113                branch += 11;
1114        if (!branch || is_null_sha1(head_sha1))
1115                head_commit = NULL;
1116        else
1117                head_commit = lookup_commit_or_die(head_sha1, "HEAD");
1118
1119        git_config(git_merge_config, NULL);
1120
1121        if (branch_mergeoptions)
1122                parse_branch_merge_options(branch_mergeoptions);
1123        argc = parse_options(argc, argv, prefix, builtin_merge_options,
1124                        builtin_merge_usage, 0);
1125
1126        if (verbosity < 0 && show_progress == -1)
1127                show_progress = 0;
1128
1129        if (abort_current_merge) {
1130                int nargc = 2;
1131                const char *nargv[] = {"reset", "--merge", NULL};
1132
1133                if (!file_exists(git_path("MERGE_HEAD")))
1134                        die(_("There is no merge to abort (MERGE_HEAD missing)."));
1135
1136                /* Invoke 'git reset --merge' */
1137                return cmd_reset(nargc, nargv, prefix);
1138        }
1139
1140        if (read_cache_unmerged())
1141                die_resolve_conflict("merge");
1142
1143        if (file_exists(git_path("MERGE_HEAD"))) {
1144                /*
1145                 * There is no unmerged entry, don't advise 'git
1146                 * add/rm <file>', just 'git commit'.
1147                 */
1148                if (advice_resolve_conflict)
1149                        die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1150                                  "Please, commit your changes before you can merge."));
1151                else
1152                        die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1153        }
1154        if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1155                if (advice_resolve_conflict)
1156                        die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1157                            "Please, commit your changes before you can merge."));
1158                else
1159                        die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1160        }
1161        resolve_undo_clear();
1162
1163        if (verbosity < 0)
1164                show_diffstat = 0;
1165
1166        if (squash) {
1167                if (!allow_fast_forward)
1168                        die(_("You cannot combine --squash with --no-ff."));
1169                option_commit = 0;
1170        }
1171
1172        if (!allow_fast_forward && fast_forward_only)
1173                die(_("You cannot combine --no-ff with --ff-only."));
1174
1175        if (!abort_current_merge) {
1176                if (!argc && default_to_upstream)
1177                        argc = setup_with_upstream(&argv);
1178                else if (argc == 1 && !strcmp(argv[0], "-"))
1179                        argv[0] = "@{-1}";
1180        }
1181        if (!argc)
1182                usage_with_options(builtin_merge_usage,
1183                        builtin_merge_options);
1184
1185        /*
1186         * This could be traditional "merge <msg> HEAD <commit>..."  and
1187         * the way we can tell it is to see if the second token is HEAD,
1188         * but some people might have misused the interface and used a
1189         * committish that is the same as HEAD there instead.
1190         * Traditional format never would have "-m" so it is an
1191         * additional safety measure to check for it.
1192         */
1193
1194        if (!have_message && head_commit &&
1195            is_old_style_invocation(argc, argv, head_commit->object.sha1)) {
1196                strbuf_addstr(&merge_msg, argv[0]);
1197                head_arg = argv[1];
1198                argv += 2;
1199                argc -= 2;
1200        } else if (!head_commit) {
1201                struct object *remote_head;
1202                /*
1203                 * If the merged head is a valid one there is no reason
1204                 * to forbid "git merge" into a branch yet to be born.
1205                 * We do the same for "git pull".
1206                 */
1207                if (argc != 1)
1208                        die(_("Can merge only exactly one commit into "
1209                                "empty head"));
1210                if (squash)
1211                        die(_("Squash commit into empty head not supported yet"));
1212                if (!allow_fast_forward)
1213                        die(_("Non-fast-forward commit does not make sense into "
1214                            "an empty head"));
1215                remote_head = want_commit(argv[0]);
1216                if (!remote_head)
1217                        die(_("%s - not something we can merge"), argv[0]);
1218                read_empty(remote_head->sha1, 0);
1219                update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
1220                                DIE_ON_ERR);
1221                return 0;
1222        } else {
1223                struct strbuf merge_names = STRBUF_INIT;
1224
1225                /* We are invoked directly as the first-class UI. */
1226                head_arg = "HEAD";
1227
1228                /*
1229                 * All the rest are the commits being merged;
1230                 * prepare the standard merge summary message to
1231                 * be appended to the given message.  If remote
1232                 * is invalid we will die later in the common
1233                 * codepath so we discard the error in this
1234                 * loop.
1235                 */
1236                for (i = 0; i < argc; i++)
1237                        merge_name(argv[i], &merge_names);
1238
1239                if (!have_message || shortlog_len) {
1240                        fmt_merge_msg(&merge_names, &merge_msg, !have_message,
1241                                      shortlog_len);
1242                        if (merge_msg.len)
1243                                strbuf_setlen(&merge_msg, merge_msg.len - 1);
1244                }
1245        }
1246
1247        if (!head_commit || !argc)
1248                usage_with_options(builtin_merge_usage,
1249                        builtin_merge_options);
1250
1251        strbuf_addstr(&buf, "merge");
1252        for (i = 0; i < argc; i++)
1253                strbuf_addf(&buf, " %s", argv[i]);
1254        setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1255        strbuf_reset(&buf);
1256
1257        for (i = 0; i < argc; i++) {
1258                struct object *o;
1259                struct commit *commit;
1260
1261                o = want_commit(argv[i]);
1262                if (!o)
1263                        die(_("%s - not something we can merge"), argv[i]);
1264                commit = lookup_commit(o->sha1);
1265                commit->util = (void *)argv[i];
1266                remotes = &commit_list_insert(commit, remotes)->next;
1267
1268                strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
1269                setenv(buf.buf, argv[i], 1);
1270                strbuf_reset(&buf);
1271        }
1272
1273        if (!use_strategies) {
1274                if (!remoteheads->next)
1275                        add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1276                else
1277                        add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1278        }
1279
1280        for (i = 0; i < use_strategies_nr; i++) {
1281                if (use_strategies[i]->attr & NO_FAST_FORWARD)
1282                        allow_fast_forward = 0;
1283                if (use_strategies[i]->attr & NO_TRIVIAL)
1284                        allow_trivial = 0;
1285        }
1286
1287        if (!remoteheads->next)
1288                common = get_merge_bases(head_commit, remoteheads->item, 1);
1289        else {
1290                struct commit_list *list = remoteheads;
1291                commit_list_insert(head_commit, &list);
1292                common = get_octopus_merge_bases(list);
1293                free(list);
1294        }
1295
1296        update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
1297                   NULL, 0, DIE_ON_ERR);
1298
1299        if (!common)
1300                ; /* No common ancestors found. We need a real merge. */
1301        else if (!remoteheads->next && !common->next &&
1302                        common->item == remoteheads->item) {
1303                /*
1304                 * If head can reach all the merge then we are up to date.
1305                 * but first the most common case of merging one remote.
1306                 */
1307                finish_up_to_date("Already up-to-date.");
1308                return 0;
1309        } else if (allow_fast_forward && !remoteheads->next &&
1310                        !common->next &&
1311                        !hashcmp(common->item->object.sha1, head_commit->object.sha1)) {
1312                /* Again the most common case of merging one remote. */
1313                struct strbuf msg = STRBUF_INIT;
1314                struct object *o;
1315                char hex[41];
1316
1317                strcpy(hex, find_unique_abbrev(head_commit->object.sha1, DEFAULT_ABBREV));
1318
1319                if (verbosity >= 0)
1320                        printf(_("Updating %s..%s\n"),
1321                                hex,
1322                                find_unique_abbrev(remoteheads->item->object.sha1,
1323                                DEFAULT_ABBREV));
1324                strbuf_addstr(&msg, "Fast-forward");
1325                if (have_message)
1326                        strbuf_addstr(&msg,
1327                                " (no commit created; -m option ignored)");
1328                o = want_commit(sha1_to_hex(remoteheads->item->object.sha1));
1329                if (!o)
1330                        return 1;
1331
1332                if (checkout_fast_forward(head_commit->object.sha1, remoteheads->item->object.sha1))
1333                        return 1;
1334
1335                finish(head_commit, o->sha1, msg.buf);
1336                drop_save();
1337                return 0;
1338        } else if (!remoteheads->next && common->next)
1339                ;
1340                /*
1341                 * We are not doing octopus and not fast-forward.  Need
1342                 * a real merge.
1343                 */
1344        else if (!remoteheads->next && !common->next && option_commit) {
1345                /*
1346                 * We are not doing octopus, not fast-forward, and have
1347                 * only one common.
1348                 */
1349                refresh_cache(REFRESH_QUIET);
1350                if (allow_trivial && !fast_forward_only) {
1351                        /* See if it is really trivial. */
1352                        git_committer_info(IDENT_ERROR_ON_NO_NAME);
1353                        printf(_("Trying really trivial in-index merge...\n"));
1354                        if (!read_tree_trivial(common->item->object.sha1,
1355                                        head_commit->object.sha1, remoteheads->item->object.sha1))
1356                                return merge_trivial(head_commit);
1357                        printf(_("Nope.\n"));
1358                }
1359        } else {
1360                /*
1361                 * An octopus.  If we can reach all the remote we are up
1362                 * to date.
1363                 */
1364                int up_to_date = 1;
1365                struct commit_list *j;
1366
1367                for (j = remoteheads; j; j = j->next) {
1368                        struct commit_list *common_one;
1369
1370                        /*
1371                         * Here we *have* to calculate the individual
1372                         * merge_bases again, otherwise "git merge HEAD^
1373                         * HEAD^^" would be missed.
1374                         */
1375                        common_one = get_merge_bases(head_commit, j->item, 1);
1376                        if (hashcmp(common_one->item->object.sha1,
1377                                j->item->object.sha1)) {
1378                                up_to_date = 0;
1379                                break;
1380                        }
1381                }
1382                if (up_to_date) {
1383                        finish_up_to_date("Already up-to-date. Yeeah!");
1384                        return 0;
1385                }
1386        }
1387
1388        if (fast_forward_only)
1389                die(_("Not possible to fast-forward, aborting."));
1390
1391        /* We are going to make a new commit. */
1392        git_committer_info(IDENT_ERROR_ON_NO_NAME);
1393
1394        /*
1395         * At this point, we need a real merge.  No matter what strategy
1396         * we use, it would operate on the index, possibly affecting the
1397         * working tree, and when resolved cleanly, have the desired
1398         * tree in the index -- this means that the index must be in
1399         * sync with the head commit.  The strategies are responsible
1400         * to ensure this.
1401         */
1402        if (use_strategies_nr == 1 ||
1403            /*
1404             * Stash away the local changes so that we can try more than one.
1405             */
1406            save_state(stash))
1407                hashcpy(stash, null_sha1);
1408
1409        for (i = 0; i < use_strategies_nr; i++) {
1410                int ret;
1411                if (i) {
1412                        printf(_("Rewinding the tree to pristine...\n"));
1413                        restore_state(head_commit->object.sha1, stash);
1414                }
1415                if (use_strategies_nr != 1)
1416                        printf(_("Trying merge strategy %s...\n"),
1417                                use_strategies[i]->name);
1418                /*
1419                 * Remember which strategy left the state in the working
1420                 * tree.
1421                 */
1422                wt_strategy = use_strategies[i]->name;
1423
1424                ret = try_merge_strategy(use_strategies[i]->name,
1425                                         common, head_commit, head_arg);
1426                if (!option_commit && !ret) {
1427                        merge_was_ok = 1;
1428                        /*
1429                         * This is necessary here just to avoid writing
1430                         * the tree, but later we will *not* exit with
1431                         * status code 1 because merge_was_ok is set.
1432                         */
1433                        ret = 1;
1434                }
1435
1436                if (ret) {
1437                        /*
1438                         * The backend exits with 1 when conflicts are
1439                         * left to be resolved, with 2 when it does not
1440                         * handle the given merge at all.
1441                         */
1442                        if (ret == 1) {
1443                                int cnt = evaluate_result();
1444
1445                                if (best_cnt <= 0 || cnt <= best_cnt) {
1446                                        best_strategy = use_strategies[i]->name;
1447                                        best_cnt = cnt;
1448                                }
1449                        }
1450                        if (merge_was_ok)
1451                                break;
1452                        else
1453                                continue;
1454                }
1455
1456                /* Automerge succeeded. */
1457                write_tree_trivial(result_tree);
1458                automerge_was_ok = 1;
1459                break;
1460        }
1461
1462        /*
1463         * If we have a resulting tree, that means the strategy module
1464         * auto resolved the merge cleanly.
1465         */
1466        if (automerge_was_ok)
1467                return finish_automerge(head_commit, common, result_tree,
1468                                        wt_strategy);
1469
1470        /*
1471         * Pick the result from the best strategy and have the user fix
1472         * it up.
1473         */
1474        if (!best_strategy) {
1475                restore_state(head_commit->object.sha1, stash);
1476                if (use_strategies_nr > 1)
1477                        fprintf(stderr,
1478                                _("No merge strategy handled the merge.\n"));
1479                else
1480                        fprintf(stderr, _("Merge with strategy %s failed.\n"),
1481                                use_strategies[0]->name);
1482                return 2;
1483        } else if (best_strategy == wt_strategy)
1484                ; /* We already have its result in the working tree. */
1485        else {
1486                printf(_("Rewinding the tree to pristine...\n"));
1487                restore_state(head_commit->object.sha1, stash);
1488                printf(_("Using the %s to prepare resolving by hand.\n"),
1489                        best_strategy);
1490                try_merge_strategy(best_strategy, common, head_commit, head_arg);
1491        }
1492
1493        if (squash)
1494                finish(head_commit, NULL, NULL);
1495        else
1496                write_merge_state();
1497
1498        if (merge_was_ok) {
1499                fprintf(stderr, _("Automatic merge went well; "
1500                        "stopped before committing as requested\n"));
1501                return 0;
1502        } else
1503                return suggest_conflicts(option_renormalize);
1504}