builtin/merge.c

   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 #include "fmt-merge-msg.h"
  30 #include "gpg-interface.h"
  31
  32 #define DEFAULT_TWOHEAD (1<<0)
  33 #define DEFAULT_OCTOPUS (1<<1)
  34 #define NO_FAST_FORWARD (1<<2)
  35 #define NO_TRIVIAL      (1<<3)
  36
  37 struct strategy {
  38         const char *name;
  39         unsigned attr;
  40 };
  41
  42 static const char * const builtin_merge_usage[] = {
  43         "git merge [options] [<commit>...]",
  44         "git merge [options] <msg> HEAD <commit>",
  45         "git merge --abort",
  46         NULL
  47 };
  48
  49 static int show_diffstat = 1, shortlog_len = -1, squash;
  50 static int option_commit = 1, allow_fast_forward = 1;
  51 static int fast_forward_only, option_edit = -1;
  52 static int allow_trivial = 1, have_message;
  53 static int overwrite_ignore = 1;
  54 static struct strbuf merge_msg = STRBUF_INIT;
  55 static struct commit_list *remoteheads;
  56 static struct strategy **use_strategies;
  57 static size_t use_strategies_nr, use_strategies_alloc;
  58 static const char **xopts;
  59 static size_t xopts_nr, xopts_alloc;
  60 static const char *branch;
  61 static char *branch_mergeoptions;
  62 static int option_renormalize;
  63 static int verbosity;
  64 static int allow_rerere_auto;
  65 static int abort_current_merge;
  66 static int show_progress = -1;
  67 static int default_to_upstream;
  68 static const char *sign_commit;
  69
  70 static struct strategy all_strategy[] = {
  71         { "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
  72         { "octopus",    DEFAULT_OCTOPUS },
  73         { "resolve",    0 },
  74         { "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
  75         { "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
  76 };
  77
  78 static const char *pull_twohead, *pull_octopus;
  79
  80 static int option_parse_message(const struct option *opt,
  81                                 const char *arg, int unset)
  82 {
  83         struct strbuf *buf = opt->value;
  84
  85         if (unset)
  86                 strbuf_setlen(buf, 0);
  87         else if (arg) {
  88                 strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
  89                 have_message = 1;
  90         } else
  91                 return error(_("switch `m' requires a value"));
  92         return 0;
  93 }
  94
  95 static struct strategy *get_strategy(const char *name)
  96 {
  97         int i;
  98         struct strategy *ret;
  99         static struct cmdnames main_cmds, other_cmds;
 100         static int loaded;
 101
 102         if (!name)
 103                 return NULL;
 104
 105         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 106                 if (!strcmp(name, all_strategy[i].name))
 107                         return &all_strategy[i];
 108
 109         if (!loaded) {
 110                 struct cmdnames not_strategies;
 111                 loaded = 1;
 112
 113                 memset(&not_strategies, 0, sizeof(struct cmdnames));
 114                 load_command_list("git-merge-", &main_cmds, &other_cmds);
 115                 for (i = 0; i < main_cmds.cnt; i++) {
 116                         int j, found = 0;
 117                         struct cmdname *ent = main_cmds.names[i];
 118                         for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
 119                                 if (!strncmp(ent->name, all_strategy[j].name, ent->len)
 120                                                 && !all_strategy[j].name[ent->len])
 121                                         found = 1;
 122                         if (!found)
 123                                 add_cmdname(&not_strategies, ent->name, ent->len);
 124                 }
 125                 exclude_cmds(&main_cmds, &not_strategies);
 126         }
 127         if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
 128                 fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
 129                 fprintf(stderr, _("Available strategies are:"));
 130                 for (i = 0; i < main_cmds.cnt; i++)
 131                         fprintf(stderr, " %s", main_cmds.names[i]->name);
 132                 fprintf(stderr, ".\n");
 133                 if (other_cmds.cnt) {
 134                         fprintf(stderr, _("Available custom strategies are:"));
 135                         for (i = 0; i < other_cmds.cnt; i++)
 136                                 fprintf(stderr, " %s", other_cmds.names[i]->name);
 137                         fprintf(stderr, ".\n");
 138                 }
 139                 exit(1);
 140         }
 141
 142         ret = xcalloc(1, sizeof(struct strategy));
 143         ret->name = xstrdup(name);
 144         ret->attr = NO_TRIVIAL;
 145         return ret;
 146 }
 147
 148 static void append_strategy(struct strategy *s)
 149 {
 150         ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
 151         use_strategies[use_strategies_nr++] = s;
 152 }
 153
 154 static int option_parse_strategy(const struct option *opt,
 155                                  const char *name, int unset)
 156 {
 157         if (unset)
 158                 return 0;
 159
 160         append_strategy(get_strategy(name));
 161         return 0;
 162 }
 163
 164 static int option_parse_x(const struct option *opt,
 165                           const char *arg, int unset)
 166 {
 167         if (unset)
 168                 return 0;
 169
 170         ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
 171         xopts[xopts_nr++] = xstrdup(arg);
 172         return 0;
 173 }
 174
 175 static int option_parse_n(const struct option *opt,
 176                           const char *arg, int unset)
 177 {
 178         show_diffstat = unset;
 179         return 0;
 180 }
 181
 182 static struct option builtin_merge_options[] = {
 183         { OPTION_CALLBACK, 'n', NULL, NULL, NULL,
 184                 "do not show a diffstat at the end of the merge",
 185                 PARSE_OPT_NOARG, option_parse_n },
 186         OPT_BOOLEAN(0, "stat", &show_diffstat,
 187                 "show a diffstat at the end of the merge"),
 188         OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
 189         { OPTION_INTEGER, 0, "log", &shortlog_len, "n",
 190           "add (at most <n>) entries from shortlog to merge commit message",
 191           PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
 192         OPT_BOOLEAN(0, "squash", &squash,
 193                 "create a single commit instead of doing a merge"),
 194         OPT_BOOLEAN(0, "commit", &option_commit,
 195                 "perform a commit if the merge succeeds (default)"),
 196         OPT_BOOL('e', "edit", &option_edit,
 197                 "edit message before committing"),
 198         OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 199                 "allow fast-forward (default)"),
 200         OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
 201                 "abort if fast-forward is not possible"),
 202         OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 203         OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
 204                 "merge strategy to use", option_parse_strategy),
 205         OPT_CALLBACK('X', "strategy-option", &xopts, "option=value",
 206                 "option for selected merge strategy", option_parse_x),
 207         OPT_CALLBACK('m', "message", &merge_msg, "message",
 208                 "merge commit message (for a non-fast-forward merge)",
 209                 option_parse_message),
 210         OPT__VERBOSITY(&verbosity),
 211         OPT_BOOLEAN(0, "abort", &abort_current_merge,
 212                 "abort the current in-progress merge"),
 213         OPT_SET_INT(0, "progress", &show_progress, "force progress reporting", 1),
 214         { OPTION_STRING, 'S', "gpg-sign", &sign_commit, "key id",
 215           "GPG sign commit", PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 216         OPT_BOOLEAN(0, "overwrite-ignore", &overwrite_ignore, "update ignored files (default)"),
 217         OPT_END()
 218 };
 219
 220 /* Cleans up metadata that is uninteresting after a succeeded merge. */
 221 static void drop_save(void)
 222 {
 223         unlink(git_path("MERGE_HEAD"));
 224         unlink(git_path("MERGE_MSG"));
 225         unlink(git_path("MERGE_MODE"));
 226 }
 227
 228 static int save_state(unsigned char *stash)
 229 {
 230         int len;
 231         struct child_process cp;
 232         struct strbuf buffer = STRBUF_INIT;
 233         const char *argv[] = {"stash", "create", NULL};
 234
 235         memset(&cp, 0, sizeof(cp));
 236         cp.argv = argv;
 237         cp.out = -1;
 238         cp.git_cmd = 1;
 239
 240         if (start_command(&cp))
 241                 die(_("could not run stash."));
 242         len = strbuf_read(&buffer, cp.out, 1024);
 243         close(cp.out);
 244
 245         if (finish_command(&cp) || len < 0)
 246                 die(_("stash failed"));
 247         else if (!len)          /* no changes */
 248                 return -1;
 249         strbuf_setlen(&buffer, buffer.len-1);
 250         if (get_sha1(buffer.buf, stash))
 251                 die(_("not a valid object: %s"), buffer.buf);
 252         return 0;
 253 }
 254
 255 static void read_empty(unsigned const char *sha1, int verbose)
 256 {
 257         int i = 0;
 258         const char *args[7];
 259
 260         args[i++] = "read-tree";
 261         if (verbose)
 262                 args[i++] = "-v";
 263         args[i++] = "-m";
 264         args[i++] = "-u";
 265         args[i++] = EMPTY_TREE_SHA1_HEX;
 266         args[i++] = sha1_to_hex(sha1);
 267         args[i] = NULL;
 268
 269         if (run_command_v_opt(args, RUN_GIT_CMD))
 270                 die(_("read-tree failed"));
 271 }
 272
 273 static void reset_hard(unsigned const char *sha1, int verbose)
 274 {
 275         int i = 0;
 276         const char *args[6];
 277
 278         args[i++] = "read-tree";
 279         if (verbose)
 280                 args[i++] = "-v";
 281         args[i++] = "--reset";
 282         args[i++] = "-u";
 283         args[i++] = sha1_to_hex(sha1);
 284         args[i] = NULL;
 285
 286         if (run_command_v_opt(args, RUN_GIT_CMD))
 287                 die(_("read-tree failed"));
 288 }
 289
 290 static void restore_state(const unsigned char *head,
 291                           const unsigned char *stash)
 292 {
 293         struct strbuf sb = STRBUF_INIT;
 294         const char *args[] = { "stash", "apply", NULL, NULL };
 295
 296         if (is_null_sha1(stash))
 297                 return;
 298
 299         reset_hard(head, 1);
 300
 301         args[2] = sha1_to_hex(stash);
 302
 303         /*
 304          * It is OK to ignore error here, for example when there was
 305          * nothing to restore.
 306          */
 307         run_command_v_opt(args, RUN_GIT_CMD);
 308
 309         strbuf_release(&sb);
 310         refresh_cache(REFRESH_QUIET);
 311 }
 312
 313 /* This is called when no merge was necessary. */
 314 static void finish_up_to_date(const char *msg)
 315 {
 316         if (verbosity >= 0)
 317                 printf("%s%s\n", squash ? _(" (nothing to squash)") : "", msg);
 318         drop_save();
 319 }
 320
 321 static void squash_message(struct commit *commit)
 322 {
 323         struct rev_info rev;
 324         struct strbuf out = STRBUF_INIT;
 325         struct commit_list *j;
 326         const char *filename;
 327         int fd;
 328         struct pretty_print_context ctx = {0};
 329
 330         printf(_("Squash commit -- not updating HEAD\n"));
 331         filename = git_path("SQUASH_MSG");
 332         fd = open(filename, O_WRONLY | O_CREAT, 0666);
 333         if (fd < 0)
 334                 die_errno(_("Could not write to '%s'"), filename);
 335
 336         init_revisions(&rev, NULL);
 337         rev.ignore_merges = 1;
 338         rev.commit_format = CMIT_FMT_MEDIUM;
 339
 340         commit->object.flags |= UNINTERESTING;
 341         add_pending_object(&rev, &commit->object, NULL);
 342
 343         for (j = remoteheads; j; j = j->next)
 344                 add_pending_object(&rev, &j->item->object, NULL);
 345
 346         setup_revisions(0, NULL, &rev, NULL);
 347         if (prepare_revision_walk(&rev))
 348                 die(_("revision walk setup failed"));
 349
 350         ctx.abbrev = rev.abbrev;
 351         ctx.date_mode = rev.date_mode;
 352         ctx.fmt = rev.commit_format;
 353
 354         strbuf_addstr(&out, "Squashed commit of the following:\n");
 355         while ((commit = get_revision(&rev)) != NULL) {
 356                 strbuf_addch(&out, '\n');
 357                 strbuf_addf(&out, "commit %s\n",
 358                         sha1_to_hex(commit->object.sha1));
 359                 pretty_print_commit(&ctx, commit, &out);
 360         }
 361         if (write(fd, out.buf, out.len) < 0)
 362                 die_errno(_("Writing SQUASH_MSG"));
 363         if (close(fd))
 364                 die_errno(_("Finishing SQUASH_MSG"));
 365         strbuf_release(&out);
 366 }
 367
 368 static void finish(struct commit *head_commit,
 369                    const unsigned char *new_head, const char *msg)
 370 {
 371         struct strbuf reflog_message = STRBUF_INIT;
 372         const unsigned char *head = head_commit->object.sha1;
 373
 374         if (!msg)
 375                 strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
 376         else {
 377                 if (verbosity >= 0)
 378                         printf("%s\n", msg);
 379                 strbuf_addf(&reflog_message, "%s: %s",
 380                         getenv("GIT_REFLOG_ACTION"), msg);
 381         }
 382         if (squash) {
 383                 squash_message(head_commit);
 384         } else {
 385                 if (verbosity >= 0 && !merge_msg.len)
 386                         printf(_("No merge message -- not updating HEAD\n"));
 387                 else {
 388                         const char *argv_gc_auto[] = { "gc", "--auto", NULL };
 389                         update_ref(reflog_message.buf, "HEAD",
 390                                 new_head, head, 0,
 391                                 DIE_ON_ERR);
 392                         /*
 393                          * We ignore errors in 'gc --auto', since the
 394                          * user should see them.
 395                          */
 396                         run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
 397                 }
 398         }
 399         if (new_head && show_diffstat) {
 400                 struct diff_options opts;
 401                 diff_setup(&opts);
 402                 opts.stat_width = -1; /* use full terminal width */
 403                 opts.stat_graph_width = -1; /* respect statGraphWidth config */
 404                 opts.output_format |=
 405                         DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 406                 opts.detect_rename = DIFF_DETECT_RENAME;
 407                 if (diff_setup_done(&opts) < 0)
 408                         die(_("diff_setup_done failed"));
 409                 diff_tree_sha1(head, new_head, "", &opts);
 410                 diffcore_std(&opts);
 411                 diff_flush(&opts);
 412         }
 413
 414         /* Run a post-merge hook */
 415         run_hook(NULL, "post-merge", squash ? "1" : "0", NULL);
 416
 417         strbuf_release(&reflog_message);
 418 }
 419
 420 /* Get the name for the merge commit's message. */
 421 static void merge_name(const char *remote, struct strbuf *msg)
 422 {
 423         struct commit *remote_head;
 424         unsigned char branch_head[20];
 425         struct strbuf buf = STRBUF_INIT;
 426         struct strbuf bname = STRBUF_INIT;
 427         const char *ptr;
 428         char *found_ref;
 429         int len, early;
 430
 431         strbuf_branchname(&bname, remote);
 432         remote = bname.buf;
 433
 434         memset(branch_head, 0, sizeof(branch_head));
 435         remote_head = get_merge_parent(remote);
 436         if (!remote_head)
 437                 die(_("'%s' does not point to a commit"), remote);
 438
 439         if (dwim_ref(remote, strlen(remote), branch_head, &found_ref) > 0) {
 440                 if (!prefixcmp(found_ref, "refs/heads/")) {
 441                         strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 442                                     sha1_to_hex(branch_head), remote);
 443                         goto cleanup;
 444                 }
 445                 if (!prefixcmp(found_ref, "refs/tags/")) {
 446                         strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
 447                                     sha1_to_hex(branch_head), remote);
 448                         goto cleanup;
 449                 }
 450                 if (!prefixcmp(found_ref, "refs/remotes/")) {
 451                         strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 452                                     sha1_to_hex(branch_head), remote);
 453                         goto cleanup;
 454                 }
 455         }
 456
 457         /* See if remote matches <name>^^^.. or <name>~<number> */
 458         for (len = 0, ptr = remote + strlen(remote);
 459              remote < ptr && ptr[-1] == '^';
 460              ptr--)
 461                 len++;
 462         if (len)
 463                 early = 1;
 464         else {
 465                 early = 0;
 466                 ptr = strrchr(remote, '~');
 467                 if (ptr) {
 468                         int seen_nonzero = 0;
 469
 470                         len++; /* count ~ */
 471                         while (*++ptr && isdigit(*ptr)) {
 472                                 seen_nonzero |= (*ptr != '0');
 473                                 len++;
 474                         }
 475                         if (*ptr)
 476                                 len = 0; /* not ...~<number> */
 477                         else if (seen_nonzero)
 478                                 early = 1;
 479                         else if (len == 1)
 480                                 early = 1; /* "name~" is "name~1"! */
 481                 }
 482         }
 483         if (len) {
 484                 struct strbuf truname = STRBUF_INIT;
 485                 strbuf_addstr(&truname, "refs/heads/");
 486                 strbuf_addstr(&truname, remote);
 487                 strbuf_setlen(&truname, truname.len - len);
 488                 if (ref_exists(truname.buf)) {
 489                         strbuf_addf(msg,
 490                                     "%s\t\tbranch '%s'%s of .\n",
 491                                     sha1_to_hex(remote_head->object.sha1),
 492                                     truname.buf + 11,
 493                                     (early ? " (early part)" : ""));
 494                         strbuf_release(&truname);
 495                         goto cleanup;
 496                 }
 497         }
 498
 499         if (!strcmp(remote, "FETCH_HEAD") &&
 500                         !access(git_path("FETCH_HEAD"), R_OK)) {
 501                 const char *filename;
 502                 FILE *fp;
 503                 struct strbuf line = STRBUF_INIT;
 504                 char *ptr;
 505
 506                 filename = git_path("FETCH_HEAD");
 507                 fp = fopen(filename, "r");
 508                 if (!fp)
 509                         die_errno(_("could not open '%s' for reading"),
 510                                   filename);
 511                 strbuf_getline(&line, fp, '\n');
 512                 fclose(fp);
 513                 ptr = strstr(line.buf, "\tnot-for-merge\t");
 514                 if (ptr)
 515                         strbuf_remove(&line, ptr-line.buf+1, 13);
 516                 strbuf_addbuf(msg, &line);
 517                 strbuf_release(&line);
 518                 goto cleanup;
 519         }
 520         strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 521                 sha1_to_hex(remote_head->object.sha1), remote);
 522 cleanup:
 523         strbuf_release(&buf);
 524         strbuf_release(&bname);
 525 }
 526
 527 static void parse_branch_merge_options(char *bmo)
 528 {
 529         const char **argv;
 530         int argc;
 531
 532         if (!bmo)
 533                 return;
 534         argc = split_cmdline(bmo, &argv);
 535         if (argc < 0)
 536                 die(_("Bad branch.%s.mergeoptions string: %s"), branch,
 537                     split_cmdline_strerror(argc));
 538         argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
 539         memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
 540         argc++;
 541         argv[0] = "branch.*.mergeoptions";
 542         parse_options(argc, argv, NULL, builtin_merge_options,
 543                       builtin_merge_usage, 0);
 544         free(argv);
 545 }
 546
 547 static int git_merge_config(const char *k, const char *v, void *cb)
 548 {
 549         int status;
 550
 551         if (branch && !prefixcmp(k, "branch.") &&
 552                 !prefixcmp(k + 7, branch) &&
 553                 !strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
 554                 free(branch_mergeoptions);
 555                 branch_mergeoptions = xstrdup(v);
 556                 return 0;
 557         }
 558
 559         if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
 560                 show_diffstat = git_config_bool(k, v);
 561         else if (!strcmp(k, "pull.twohead"))
 562                 return git_config_string(&pull_twohead, k, v);
 563         else if (!strcmp(k, "pull.octopus"))
 564                 return git_config_string(&pull_octopus, k, v);
 565         else if (!strcmp(k, "merge.renormalize"))
 566                 option_renormalize = git_config_bool(k, v);
 567         else if (!strcmp(k, "merge.ff")) {
 568                 int boolval = git_config_maybe_bool(k, v);
 569                 if (0 <= boolval) {
 570                         allow_fast_forward = boolval;
 571                 } else if (v && !strcmp(v, "only")) {
 572                         allow_fast_forward = 1;
 573                         fast_forward_only = 1;
 574                 } /* do not barf on values from future versions of git */
 575                 return 0;
 576         } else if (!strcmp(k, "merge.defaulttoupstream")) {
 577                 default_to_upstream = git_config_bool(k, v);
 578                 return 0;
 579         }
 580
 581         status = fmt_merge_msg_config(k, v, cb);
 582         if (status)
 583                 return status;
 584         status = git_gpg_config(k, v, NULL);
 585         if (status)
 586                 return status;
 587         return git_diff_ui_config(k, v, cb);
 588 }
 589
 590 static int read_tree_trivial(unsigned char *common, unsigned char *head,
 591                              unsigned char *one)
 592 {
 593         int i, nr_trees = 0;
 594         struct tree *trees[MAX_UNPACK_TREES];
 595         struct tree_desc t[MAX_UNPACK_TREES];
 596         struct unpack_trees_options opts;
 597
 598         memset(&opts, 0, sizeof(opts));
 599         opts.head_idx = 2;
 600         opts.src_index = &the_index;
 601         opts.dst_index = &the_index;
 602         opts.update = 1;
 603         opts.verbose_update = 1;
 604         opts.trivial_merges_only = 1;
 605         opts.merge = 1;
 606         trees[nr_trees] = parse_tree_indirect(common);
 607         if (!trees[nr_trees++])
 608                 return -1;
 609         trees[nr_trees] = parse_tree_indirect(head);
 610         if (!trees[nr_trees++])
 611                 return -1;
 612         trees[nr_trees] = parse_tree_indirect(one);
 613         if (!trees[nr_trees++])
 614                 return -1;
 615         opts.fn = threeway_merge;
 616         cache_tree_free(&active_cache_tree);
 617         for (i = 0; i < nr_trees; i++) {
 618                 parse_tree(trees[i]);
 619                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 620         }
 621         if (unpack_trees(nr_trees, t, &opts))
 622                 return -1;
 623         return 0;
 624 }
 625
 626 static void write_tree_trivial(unsigned char *sha1)
 627 {
 628         if (write_cache_as_tree(sha1, 0, NULL))
 629                 die(_("git write-tree failed to write a tree"));
 630 }
 631
 632 static const char *merge_argument(struct commit *commit)
 633 {
 634         if (commit)
 635                 return sha1_to_hex(commit->object.sha1);
 636         else
 637                 return EMPTY_TREE_SHA1_HEX;
 638 }
 639
 640 int try_merge_command(const char *strategy, size_t xopts_nr,
 641                       const char **xopts, struct commit_list *common,
 642                       const char *head_arg, struct commit_list *remotes)
 643 {
 644         const char **args;
 645         int i = 0, x = 0, ret;
 646         struct commit_list *j;
 647         struct strbuf buf = STRBUF_INIT;
 648
 649         args = xmalloc((4 + xopts_nr + commit_list_count(common) +
 650                         commit_list_count(remotes)) * sizeof(char *));
 651         strbuf_addf(&buf, "merge-%s", strategy);
 652         args[i++] = buf.buf;
 653         for (x = 0; x < xopts_nr; x++) {
 654                 char *s = xmalloc(strlen(xopts[x])+2+1);
 655                 strcpy(s, "--");
 656                 strcpy(s+2, xopts[x]);
 657                 args[i++] = s;
 658         }
 659         for (j = common; j; j = j->next)
 660                 args[i++] = xstrdup(merge_argument(j->item));
 661         args[i++] = "--";
 662         args[i++] = head_arg;
 663         for (j = remotes; j; j = j->next)
 664                 args[i++] = xstrdup(merge_argument(j->item));
 665         args[i] = NULL;
 666         ret = run_command_v_opt(args, RUN_GIT_CMD);
 667         strbuf_release(&buf);
 668         i = 1;
 669         for (x = 0; x < xopts_nr; x++)
 670                 free((void *)args[i++]);
 671         for (j = common; j; j = j->next)
 672                 free((void *)args[i++]);
 673         i += 2;
 674         for (j = remotes; j; j = j->next)
 675                 free((void *)args[i++]);
 676         free(args);
 677         discard_cache();
 678         if (read_cache() < 0)
 679                 die(_("failed to read the cache"));
 680         resolve_undo_clear();
 681
 682         return ret;
 683 }
 684
 685 static int try_merge_strategy(const char *strategy, struct commit_list *common,
 686                               struct commit *head, const char *head_arg)
 687 {
 688         int index_fd;
 689         struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 690
 691         index_fd = hold_locked_index(lock, 1);
 692         refresh_cache(REFRESH_QUIET);
 693         if (active_cache_changed &&
 694                         (write_cache(index_fd, active_cache, active_nr) ||
 695                          commit_locked_index(lock)))
 696                 return error(_("Unable to write index."));
 697         rollback_lock_file(lock);
 698
 699         if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
 700                 int clean, x;
 701                 struct commit *result;
 702                 struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 703                 int index_fd;
 704                 struct commit_list *reversed = NULL;
 705                 struct merge_options o;
 706                 struct commit_list *j;
 707
 708                 if (remoteheads->next) {
 709                         error(_("Not handling anything other than two heads merge."));
 710                         return 2;
 711                 }
 712
 713                 init_merge_options(&o);
 714                 if (!strcmp(strategy, "subtree"))
 715                         o.subtree_shift = "";
 716
 717                 o.renormalize = option_renormalize;
 718                 o.show_rename_progress =
 719                         show_progress == -1 ? isatty(2) : show_progress;
 720
 721                 for (x = 0; x < xopts_nr; x++)
 722                         if (parse_merge_opt(&o, xopts[x]))
 723                                 die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 724
 725                 o.branch1 = head_arg;
 726                 o.branch2 = merge_remote_util(remoteheads->item)->name;
 727
 728                 for (j = common; j; j = j->next)
 729                         commit_list_insert(j->item, &reversed);
 730
 731                 index_fd = hold_locked_index(lock, 1);
 732                 clean = merge_recursive(&o, head,
 733                                 remoteheads->item, reversed, &result);
 734                 if (active_cache_changed &&
 735                                 (write_cache(index_fd, active_cache, active_nr) ||
 736                                  commit_locked_index(lock)))
 737                         die (_("unable to write %s"), get_index_file());
 738                 rollback_lock_file(lock);
 739                 return clean ? 0 : 1;
 740         } else {
 741                 return try_merge_command(strategy, xopts_nr, xopts,
 742                                                 common, head_arg, remoteheads);
 743         }
 744 }
 745
 746 static void count_diff_files(struct diff_queue_struct *q,
 747                              struct diff_options *opt, void *data)
 748 {
 749         int *count = data;
 750
 751         (*count) += q->nr;
 752 }
 753
 754 static int count_unmerged_entries(void)
 755 {
 756         int i, ret = 0;
 757
 758         for (i = 0; i < active_nr; i++)
 759                 if (ce_stage(active_cache[i]))
 760                         ret++;
 761
 762         return ret;
 763 }
 764
 765 int checkout_fast_forward(const unsigned char *head, const unsigned char *remote)
 766 {
 767         struct tree *trees[MAX_UNPACK_TREES];
 768         struct unpack_trees_options opts;
 769         struct tree_desc t[MAX_UNPACK_TREES];
 770         int i, fd, nr_trees = 0;
 771         struct dir_struct dir;
 772         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 773
 774         refresh_cache(REFRESH_QUIET);
 775
 776         fd = hold_locked_index(lock_file, 1);
 777
 778         memset(&trees, 0, sizeof(trees));
 779         memset(&opts, 0, sizeof(opts));
 780         memset(&t, 0, sizeof(t));
 781         if (overwrite_ignore) {
 782                 memset(&dir, 0, sizeof(dir));
 783                 dir.flags |= DIR_SHOW_IGNORED;
 784                 setup_standard_excludes(&dir);
 785                 opts.dir = &dir;
 786         }
 787
 788         opts.head_idx = 1;
 789         opts.src_index = &the_index;
 790         opts.dst_index = &the_index;
 791         opts.update = 1;
 792         opts.verbose_update = 1;
 793         opts.merge = 1;
 794         opts.fn = twoway_merge;
 795         setup_unpack_trees_porcelain(&opts, "merge");
 796
 797         trees[nr_trees] = parse_tree_indirect(head);
 798         if (!trees[nr_trees++])
 799                 return -1;
 800         trees[nr_trees] = parse_tree_indirect(remote);
 801         if (!trees[nr_trees++])
 802                 return -1;
 803         for (i = 0; i < nr_trees; i++) {
 804                 parse_tree(trees[i]);
 805                 init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
 806         }
 807         if (unpack_trees(nr_trees, t, &opts))
 808                 return -1;
 809         if (write_cache(fd, active_cache, active_nr) ||
 810                 commit_locked_index(lock_file))
 811                 die(_("unable to write new index file"));
 812         return 0;
 813 }
 814
 815 static void split_merge_strategies(const char *string, struct strategy **list,
 816                                    int *nr, int *alloc)
 817 {
 818         char *p, *q, *buf;
 819
 820         if (!string)
 821                 return;
 822
 823         buf = xstrdup(string);
 824         q = buf;
 825         for (;;) {
 826                 p = strchr(q, ' ');
 827                 if (!p) {
 828                         ALLOC_GROW(*list, *nr + 1, *alloc);
 829                         (*list)[(*nr)++].name = xstrdup(q);
 830                         free(buf);
 831                         return;
 832                 } else {
 833                         *p = '\0';
 834                         ALLOC_GROW(*list, *nr + 1, *alloc);
 835                         (*list)[(*nr)++].name = xstrdup(q);
 836                         q = ++p;
 837                 }
 838         }
 839 }
 840
 841 static void add_strategies(const char *string, unsigned attr)
 842 {
 843         struct strategy *list = NULL;
 844         int list_alloc = 0, list_nr = 0, i;
 845
 846         memset(&list, 0, sizeof(list));
 847         split_merge_strategies(string, &list, &list_nr, &list_alloc);
 848         if (list) {
 849                 for (i = 0; i < list_nr; i++)
 850                         append_strategy(get_strategy(list[i].name));
 851                 return;
 852         }
 853         for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 854                 if (all_strategy[i].attr & attr)
 855                         append_strategy(&all_strategy[i]);
 856
 857 }
 858
 859 static void write_merge_msg(struct strbuf *msg)
 860 {
 861         const char *filename = git_path("MERGE_MSG");
 862         int fd = open(filename, O_WRONLY | O_CREAT, 0666);
 863         if (fd < 0)
 864                 die_errno(_("Could not open '%s' for writing"),
 865                           filename);
 866         if (write_in_full(fd, msg->buf, msg->len) != msg->len)
 867                 die_errno(_("Could not write to '%s'"), filename);
 868         close(fd);
 869 }
 870
 871 static void read_merge_msg(struct strbuf *msg)
 872 {
 873         const char *filename = git_path("MERGE_MSG");
 874         strbuf_reset(msg);
 875         if (strbuf_read_file(msg, filename, 0) < 0)
 876                 die_errno(_("Could not read from '%s'"), filename);
 877 }
 878
 879 static void write_merge_state(void);
 880 static void abort_commit(const char *err_msg)
 881 {
 882         if (err_msg)
 883                 error("%s", err_msg);
 884         fprintf(stderr,
 885                 _("Not committing merge; use 'git commit' to complete the merge.\n"));
 886         write_merge_state();
 887         exit(1);
 888 }
 889
 890 static const char merge_editor_comment[] =
 891 N_("Please enter a commit message to explain why this merge is necessary,\n"
 892    "especially if it merges an updated upstream into a topic branch.\n"
 893    "\n"
 894    "Lines starting with '#' will be ignored, and an empty message aborts\n"
 895    "the commit.\n");
 896
 897 static void prepare_to_commit(void)
 898 {
 899         struct strbuf msg = STRBUF_INIT;
 900         const char *comment = _(merge_editor_comment);
 901         strbuf_addbuf(&msg, &merge_msg);
 902         strbuf_addch(&msg, '\n');
 903         if (0 < option_edit)
 904                 strbuf_add_lines(&msg, "# ", comment, strlen(comment));
 905         write_merge_msg(&msg);
 906         run_hook(get_index_file(), "prepare-commit-msg",
 907                  git_path("MERGE_MSG"), "merge", NULL, NULL);
 908         if (0 < option_edit) {
 909                 if (launch_editor(git_path("MERGE_MSG"), NULL, NULL))
 910                         abort_commit(NULL);
 911         }
 912         read_merge_msg(&msg);
 913         stripspace(&msg, 0 < option_edit);
 914         if (!msg.len)
 915                 abort_commit(_("Empty commit message."));
 916         strbuf_release(&merge_msg);
 917         strbuf_addbuf(&merge_msg, &msg);
 918         strbuf_release(&msg);
 919 }
 920
 921 static int merge_trivial(struct commit *head)
 922 {
 923         unsigned char result_tree[20], result_commit[20];
 924         struct commit_list *parent = xmalloc(sizeof(*parent));
 925
 926         write_tree_trivial(result_tree);
 927         printf(_("Wonderful.\n"));
 928         parent->item = head;
 929         parent->next = xmalloc(sizeof(*parent->next));
 930         parent->next->item = remoteheads->item;
 931         parent->next->next = NULL;
 932         prepare_to_commit();
 933         if (commit_tree(&merge_msg, result_tree, parent, result_commit, NULL,
 934                         sign_commit))
 935                 die(_("failed to write commit object"));
 936         finish(head, result_commit, "In-index merge");
 937         drop_save();
 938         return 0;
 939 }
 940
 941 static int finish_automerge(struct commit *head,
 942                             struct commit_list *common,
 943                             unsigned char *result_tree,
 944                             const char *wt_strategy)
 945 {
 946         struct commit_list *parents = NULL, *j;
 947         struct strbuf buf = STRBUF_INIT;
 948         unsigned char result_commit[20];
 949
 950         free_commit_list(common);
 951         if (allow_fast_forward) {
 952                 parents = remoteheads;
 953                 commit_list_insert(head, &parents);
 954                 parents = reduce_heads(parents);
 955         } else {
 956                 struct commit_list **pptr = &parents;
 957
 958                 pptr = &commit_list_insert(head,
 959                                 pptr)->next;
 960                 for (j = remoteheads; j; j = j->next)
 961                         pptr = &commit_list_insert(j->item, pptr)->next;
 962         }
 963         strbuf_addch(&merge_msg, '\n');
 964         prepare_to_commit();
 965         free_commit_list(remoteheads);
 966         if (commit_tree(&merge_msg, result_tree, parents, result_commit,
 967                         NULL, sign_commit))
 968                 die(_("failed to write commit object"));
 969         strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
 970         finish(head, result_commit, buf.buf);
 971         strbuf_release(&buf);
 972         drop_save();
 973         return 0;
 974 }
 975
 976 static int suggest_conflicts(int renormalizing)
 977 {
 978         const char *filename;
 979         FILE *fp;
 980         int pos;
 981
 982         filename = git_path("MERGE_MSG");
 983         fp = fopen(filename, "a");
 984         if (!fp)
 985                 die_errno(_("Could not open '%s' for writing"), filename);
 986         fprintf(fp, "\nConflicts:\n");
 987         for (pos = 0; pos < active_nr; pos++) {
 988                 struct cache_entry *ce = active_cache[pos];
 989
 990                 if (ce_stage(ce)) {
 991                         fprintf(fp, "\t%s\n", ce->name);
 992                         while (pos + 1 < active_nr &&
 993                                         !strcmp(ce->name,
 994                                                 active_cache[pos + 1]->name))
 995                                 pos++;
 996                 }
 997         }
 998         fclose(fp);
 999         rerere(allow_rerere_auto);
1000         printf(_("Automatic merge failed; "
1001                         "fix conflicts and then commit the result.\n"));
1002         return 1;
1003 }
1004
1005 static struct commit *is_old_style_invocation(int argc, const char **argv,
1006                                               const unsigned char *head)
1007 {
1008         struct commit *second_token = NULL;
1009         if (argc > 2) {
1010                 unsigned char second_sha1[20];
1011
1012                 if (get_sha1(argv[1], second_sha1))
1013                         return NULL;
1014                 second_token = lookup_commit_reference_gently(second_sha1, 0);
1015                 if (!second_token)
1016                         die(_("'%s' is not a commit"), argv[1]);
1017                 if (hashcmp(second_token->object.sha1, head))
1018                         return NULL;
1019         }
1020         return second_token;
1021 }
1022
1023 static int evaluate_result(void)
1024 {
1025         int cnt = 0;
1026         struct rev_info rev;
1027
1028         /* Check how many files differ. */
1029         init_revisions(&rev, "");
1030         setup_revisions(0, NULL, &rev, NULL);
1031         rev.diffopt.output_format |=
1032                 DIFF_FORMAT_CALLBACK;
1033         rev.diffopt.format_callback = count_diff_files;
1034         rev.diffopt.format_callback_data = &cnt;
1035         run_diff_files(&rev, 0);
1036
1037         /*
1038          * Check how many unmerged entries are
1039          * there.
1040          */
1041         cnt += count_unmerged_entries();
1042
1043         return cnt;
1044 }
1045
1046 /*
1047  * Pretend as if the user told us to merge with the tracking
1048  * branch we have for the upstream of the current branch
1049  */
1050 static int setup_with_upstream(const char ***argv)
1051 {
1052         struct branch *branch = branch_get(NULL);
1053         int i;
1054         const char **args;
1055
1056         if (!branch)
1057                 die(_("No current branch."));
1058         if (!branch->remote)
1059                 die(_("No remote for the current branch."));
1060         if (!branch->merge_nr)
1061                 die(_("No default upstream defined for the current branch."));
1062
1063         args = xcalloc(branch->merge_nr + 1, sizeof(char *));
1064         for (i = 0; i < branch->merge_nr; i++) {
1065                 if (!branch->merge[i]->dst)
1066                         die(_("No remote tracking branch for %s from %s"),
1067                             branch->merge[i]->src, branch->remote_name);
1068                 args[i] = branch->merge[i]->dst;
1069         }
1070         args[i] = NULL;
1071         *argv = args;
1072         return i;
1073 }
1074
1075 static void write_merge_state(void)
1076 {
1077         const char *filename;
1078         int fd;
1079         struct commit_list *j;
1080         struct strbuf buf = STRBUF_INIT;
1081
1082         for (j = remoteheads; j; j = j->next) {
1083                 unsigned const char *sha1;
1084                 struct commit *c = j->item;
1085                 if (c->util && merge_remote_util(c)->obj) {
1086                         sha1 = merge_remote_util(c)->obj->sha1;
1087                 } else {
1088                         sha1 = c->object.sha1;
1089                 }
1090                 strbuf_addf(&buf, "%s\n", sha1_to_hex(sha1));
1091         }
1092         filename = git_path("MERGE_HEAD");
1093         fd = open(filename, O_WRONLY | O_CREAT, 0666);
1094         if (fd < 0)
1095                 die_errno(_("Could not open '%s' for writing"), filename);
1096         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1097                 die_errno(_("Could not write to '%s'"), filename);
1098         close(fd);
1099         strbuf_addch(&merge_msg, '\n');
1100         write_merge_msg(&merge_msg);
1101
1102         filename = git_path("MERGE_MODE");
1103         fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
1104         if (fd < 0)
1105                 die_errno(_("Could not open '%s' for writing"), filename);
1106         strbuf_reset(&buf);
1107         if (!allow_fast_forward)
1108                 strbuf_addf(&buf, "no-ff");
1109         if (write_in_full(fd, buf.buf, buf.len) != buf.len)
1110                 die_errno(_("Could not write to '%s'"), filename);
1111         close(fd);
1112 }
1113
1114 static int default_edit_option(void)
1115 {
1116         static const char name[] = "GIT_MERGE_AUTOEDIT";
1117         const char *e = getenv(name);
1118         struct stat st_stdin, st_stdout;
1119
1120         if (have_message)
1121                 /* an explicit -m msg without --[no-]edit */
1122                 return 0;
1123
1124         if (e) {
1125                 int v = git_config_maybe_bool(name, e);
1126                 if (v < 0)
1127                         die("Bad value '%s' in environment '%s'", e, name);
1128                 return v;
1129         }
1130
1131         /* Use editor if stdin and stdout are the same and is a tty */
1132         return (!fstat(0, &st_stdin) &&
1133                 !fstat(1, &st_stdout) &&
1134                 isatty(0) && isatty(1) &&
1135                 st_stdin.st_dev == st_stdout.st_dev &&
1136                 st_stdin.st_ino == st_stdout.st_ino &&
1137                 st_stdin.st_mode == st_stdout.st_mode);
1138 }
1139
1140
1141 int cmd_merge(int argc, const char **argv, const char *prefix)
1142 {
1143         unsigned char result_tree[20];
1144         unsigned char stash[20];
1145         unsigned char head_sha1[20];
1146         struct commit *head_commit;
1147         struct strbuf buf = STRBUF_INIT;
1148         const char *head_arg;
1149         int flag, i, ret = 0;
1150         int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
1151         struct commit_list *common = NULL;
1152         const char *best_strategy = NULL, *wt_strategy = NULL;
1153         struct commit_list **remotes = &remoteheads;
1154         void *branch_to_free;
1155
1156         if (argc == 2 && !strcmp(argv[1], "-h"))
1157                 usage_with_options(builtin_merge_usage, builtin_merge_options);
1158
1159         /*
1160          * Check if we are _not_ on a detached HEAD, i.e. if there is a
1161          * current branch.
1162          */
1163         branch = branch_to_free = resolve_refdup("HEAD", head_sha1, 0, &flag);
1164         if (branch && !prefixcmp(branch, "refs/heads/"))
1165                 branch += 11;
1166         if (!branch || is_null_sha1(head_sha1))
1167                 head_commit = NULL;
1168         else
1169                 head_commit = lookup_commit_or_die(head_sha1, "HEAD");
1170
1171         git_config(git_merge_config, NULL);
1172
1173         if (branch_mergeoptions)
1174                 parse_branch_merge_options(branch_mergeoptions);
1175         argc = parse_options(argc, argv, prefix, builtin_merge_options,
1176                         builtin_merge_usage, 0);
1177         if (shortlog_len < 0)
1178                 shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
1179
1180         if (verbosity < 0 && show_progress == -1)
1181                 show_progress = 0;
1182
1183         if (abort_current_merge) {
1184                 int nargc = 2;
1185                 const char *nargv[] = {"reset", "--merge", NULL};
1186
1187                 if (!file_exists(git_path("MERGE_HEAD")))
1188                         die(_("There is no merge to abort (MERGE_HEAD missing)."));
1189
1190                 /* Invoke 'git reset --merge' */
1191                 ret = cmd_reset(nargc, nargv, prefix);
1192                 goto done;
1193         }
1194
1195         if (read_cache_unmerged())
1196                 die_resolve_conflict("merge");
1197
1198         if (file_exists(git_path("MERGE_HEAD"))) {
1199                 /*
1200                  * There is no unmerged entry, don't advise 'git
1201                  * add/rm <file>', just 'git commit'.
1202                  */
1203                 if (advice_resolve_conflict)
1204                         die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
1205                                   "Please, commit your changes before you can merge."));
1206                 else
1207                         die(_("You have not concluded your merge (MERGE_HEAD exists)."));
1208         }
1209         if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
1210                 if (advice_resolve_conflict)
1211                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
1212                             "Please, commit your changes before you can merge."));
1213                 else
1214                         die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
1215         }
1216         resolve_undo_clear();
1217
1218         if (verbosity < 0)
1219                 show_diffstat = 0;
1220
1221         if (squash) {
1222                 if (!allow_fast_forward)
1223                         die(_("You cannot combine --squash with --no-ff."));
1224                 option_commit = 0;
1225         }
1226
1227         if (!allow_fast_forward && fast_forward_only)
1228                 die(_("You cannot combine --no-ff with --ff-only."));
1229
1230         if (!abort_current_merge) {
1231                 if (!argc) {
1232                         if (default_to_upstream)
1233                                 argc = setup_with_upstream(&argv);
1234                         else
1235                                 die(_("No commit specified and merge.defaultToUpstream not set."));
1236                 } else if (argc == 1 && !strcmp(argv[0], "-"))
1237                         argv[0] = "@{-1}";
1238         }
1239         if (!argc)
1240                 usage_with_options(builtin_merge_usage,
1241                         builtin_merge_options);
1242
1243         /*
1244          * This could be traditional "merge <msg> HEAD <commit>..."  and
1245          * the way we can tell it is to see if the second token is HEAD,
1246          * but some people might have misused the interface and used a
1247          * committish that is the same as HEAD there instead.
1248          * Traditional format never would have "-m" so it is an
1249          * additional safety measure to check for it.
1250          */
1251
1252         if (!have_message && head_commit &&
1253             is_old_style_invocation(argc, argv, head_commit->object.sha1)) {
1254                 strbuf_addstr(&merge_msg, argv[0]);
1255                 head_arg = argv[1];
1256                 argv += 2;
1257                 argc -= 2;
1258         } else if (!head_commit) {
1259                 struct commit *remote_head;
1260                 /*
1261                  * If the merged head is a valid one there is no reason
1262                  * to forbid "git merge" into a branch yet to be born.
1263                  * We do the same for "git pull".
1264                  */
1265                 if (argc != 1)
1266                         die(_("Can merge only exactly one commit into "
1267                                 "empty head"));
1268                 if (squash)
1269                         die(_("Squash commit into empty head not supported yet"));
1270                 if (!allow_fast_forward)
1271                         die(_("Non-fast-forward commit does not make sense into "
1272                             "an empty head"));
1273                 remote_head = get_merge_parent(argv[0]);
1274                 if (!remote_head)
1275                         die(_("%s - not something we can merge"), argv[0]);
1276                 read_empty(remote_head->object.sha1, 0);
1277                 update_ref("initial pull", "HEAD", remote_head->object.sha1,
1278                            NULL, 0, DIE_ON_ERR);
1279                 goto done;
1280         } else {
1281                 struct strbuf merge_names = STRBUF_INIT;
1282
1283                 /* We are invoked directly as the first-class UI. */
1284                 head_arg = "HEAD";
1285
1286                 /*
1287                  * All the rest are the commits being merged; prepare
1288                  * the standard merge summary message to be appended
1289                  * to the given message.
1290                  */
1291                 for (i = 0; i < argc; i++)
1292                         merge_name(argv[i], &merge_names);
1293
1294                 if (!have_message || shortlog_len) {
1295                         struct fmt_merge_msg_opts opts;
1296                         memset(&opts, 0, sizeof(opts));
1297                         opts.add_title = !have_message;
1298                         opts.shortlog_len = shortlog_len;
1299
1300                         fmt_merge_msg(&merge_names, &merge_msg, &opts);
1301                         if (merge_msg.len)
1302                                 strbuf_setlen(&merge_msg, merge_msg.len - 1);
1303                 }
1304         }
1305
1306         if (!head_commit || !argc)
1307                 usage_with_options(builtin_merge_usage,
1308                         builtin_merge_options);
1309
1310         strbuf_addstr(&buf, "merge");
1311         for (i = 0; i < argc; i++)
1312                 strbuf_addf(&buf, " %s", argv[i]);
1313         setenv("GIT_REFLOG_ACTION", buf.buf, 0);
1314         strbuf_reset(&buf);
1315
1316         for (i = 0; i < argc; i++) {
1317                 struct commit *commit = get_merge_parent(argv[i]);
1318                 if (!commit)
1319                         die(_("%s - not something we can merge"), argv[i]);
1320                 remotes = &commit_list_insert(commit, remotes)->next;
1321                 strbuf_addf(&buf, "GITHEAD_%s",
1322                             sha1_to_hex(commit->object.sha1));
1323                 setenv(buf.buf, argv[i], 1);
1324                 strbuf_reset(&buf);
1325                 if (!fast_forward_only &&
1326                     merge_remote_util(commit) &&
1327                     merge_remote_util(commit)->obj &&
1328                     merge_remote_util(commit)->obj->type == OBJ_TAG)
1329                         allow_fast_forward = 0;
1330         }
1331
1332         if (option_edit < 0)
1333                 option_edit = default_edit_option();
1334
1335         if (!use_strategies) {
1336                 if (!remoteheads->next)
1337                         add_strategies(pull_twohead, DEFAULT_TWOHEAD);
1338                 else
1339                         add_strategies(pull_octopus, DEFAULT_OCTOPUS);
1340         }
1341
1342         for (i = 0; i < use_strategies_nr; i++) {
1343                 if (use_strategies[i]->attr & NO_FAST_FORWARD)
1344                         allow_fast_forward = 0;
1345                 if (use_strategies[i]->attr & NO_TRIVIAL)
1346                         allow_trivial = 0;
1347         }
1348
1349         if (!remoteheads->next)
1350                 common = get_merge_bases(head_commit, remoteheads->item, 1);
1351         else {
1352                 struct commit_list *list = remoteheads;
1353                 commit_list_insert(head_commit, &list);
1354                 common = get_octopus_merge_bases(list);
1355                 free(list);
1356         }
1357
1358         update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
1359                    NULL, 0, DIE_ON_ERR);
1360
1361         if (!common)
1362                 ; /* No common ancestors found. We need a real merge. */
1363         else if (!remoteheads->next && !common->next &&
1364                         common->item == remoteheads->item) {
1365                 /*
1366                  * If head can reach all the merge then we are up to date.
1367                  * but first the most common case of merging one remote.
1368                  */
1369                 finish_up_to_date("Already up-to-date.");
1370                 goto done;
1371         } else if (allow_fast_forward && !remoteheads->next &&
1372                         !common->next &&
1373                         !hashcmp(common->item->object.sha1, head_commit->object.sha1)) {
1374                 /* Again the most common case of merging one remote. */
1375                 struct strbuf msg = STRBUF_INIT;
1376                 struct commit *commit;
1377                 char hex[41];
1378
1379                 strcpy(hex, find_unique_abbrev(head_commit->object.sha1, DEFAULT_ABBREV));
1380
1381                 if (verbosity >= 0)
1382                         printf(_("Updating %s..%s\n"),
1383                                 hex,
1384                                 find_unique_abbrev(remoteheads->item->object.sha1,
1385                                 DEFAULT_ABBREV));
1386                 strbuf_addstr(&msg, "Fast-forward");
1387                 if (have_message)
1388                         strbuf_addstr(&msg,
1389                                 " (no commit created; -m option ignored)");
1390                 commit = remoteheads->item;
1391                 if (!commit) {
1392                         ret = 1;
1393                         goto done;
1394                 }
1395
1396                 if (checkout_fast_forward(head_commit->object.sha1,
1397                                           commit->object.sha1)) {
1398                         ret = 1;
1399                         goto done;
1400                 }
1401
1402                 finish(head_commit, commit->object.sha1, msg.buf);
1403                 drop_save();
1404                 goto done;
1405         } else if (!remoteheads->next && common->next)
1406                 ;
1407                 /*
1408                  * We are not doing octopus and not fast-forward.  Need
1409                  * a real merge.
1410                  */
1411         else if (!remoteheads->next && !common->next && option_commit) {
1412                 /*
1413                  * We are not doing octopus, not fast-forward, and have
1414                  * only one common.
1415                  */
1416                 refresh_cache(REFRESH_QUIET);
1417                 if (allow_trivial && !fast_forward_only) {
1418                         /* See if it is really trivial. */
1419                         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1420                         printf(_("Trying really trivial in-index merge...\n"));
1421                         if (!read_tree_trivial(common->item->object.sha1,
1422                                                head_commit->object.sha1,
1423                                                remoteheads->item->object.sha1)) {
1424                                 ret = merge_trivial(head_commit);
1425                                 goto done;
1426                         }
1427                         printf(_("Nope.\n"));
1428                 }
1429         } else {
1430                 /*
1431                  * An octopus.  If we can reach all the remote we are up
1432                  * to date.
1433                  */
1434                 int up_to_date = 1;
1435                 struct commit_list *j;
1436
1437                 for (j = remoteheads; j; j = j->next) {
1438                         struct commit_list *common_one;
1439
1440                         /*
1441                          * Here we *have* to calculate the individual
1442                          * merge_bases again, otherwise "git merge HEAD^
1443                          * HEAD^^" would be missed.
1444                          */
1445                         common_one = get_merge_bases(head_commit, j->item, 1);
1446                         if (hashcmp(common_one->item->object.sha1,
1447                                 j->item->object.sha1)) {
1448                                 up_to_date = 0;
1449                                 break;
1450                         }
1451                 }
1452                 if (up_to_date) {
1453                         finish_up_to_date("Already up-to-date. Yeeah!");
1454                         goto done;
1455                 }
1456         }
1457
1458         if (fast_forward_only)
1459                 die(_("Not possible to fast-forward, aborting."));
1460
1461         /* We are going to make a new commit. */
1462         git_committer_info(IDENT_ERROR_ON_NO_NAME);
1463
1464         /*
1465          * At this point, we need a real merge.  No matter what strategy
1466          * we use, it would operate on the index, possibly affecting the
1467          * working tree, and when resolved cleanly, have the desired
1468          * tree in the index -- this means that the index must be in
1469          * sync with the head commit.  The strategies are responsible
1470          * to ensure this.
1471          */
1472         if (use_strategies_nr == 1 ||
1473             /*
1474              * Stash away the local changes so that we can try more than one.
1475              */
1476             save_state(stash))
1477                 hashcpy(stash, null_sha1);
1478
1479         for (i = 0; i < use_strategies_nr; i++) {
1480                 int ret;
1481                 if (i) {
1482                         printf(_("Rewinding the tree to pristine...\n"));
1483                         restore_state(head_commit->object.sha1, stash);
1484                 }
1485                 if (use_strategies_nr != 1)
1486                         printf(_("Trying merge strategy %s...\n"),
1487                                 use_strategies[i]->name);
1488                 /*
1489                  * Remember which strategy left the state in the working
1490                  * tree.
1491                  */
1492                 wt_strategy = use_strategies[i]->name;
1493
1494                 ret = try_merge_strategy(use_strategies[i]->name,
1495                                          common, head_commit, head_arg);
1496                 if (!option_commit && !ret) {
1497                         merge_was_ok = 1;
1498                         /*
1499                          * This is necessary here just to avoid writing
1500                          * the tree, but later we will *not* exit with
1501                          * status code 1 because merge_was_ok is set.
1502                          */
1503                         ret = 1;
1504                 }
1505
1506                 if (ret) {
1507                         /*
1508                          * The backend exits with 1 when conflicts are
1509                          * left to be resolved, with 2 when it does not
1510                          * handle the given merge at all.
1511                          */
1512                         if (ret == 1) {
1513                                 int cnt = evaluate_result();
1514
1515                                 if (best_cnt <= 0 || cnt <= best_cnt) {
1516                                         best_strategy = use_strategies[i]->name;
1517                                         best_cnt = cnt;
1518                                 }
1519                         }
1520                         if (merge_was_ok)
1521                                 break;
1522                         else
1523                                 continue;
1524                 }
1525
1526                 /* Automerge succeeded. */
1527                 write_tree_trivial(result_tree);
1528                 automerge_was_ok = 1;
1529                 break;
1530         }
1531
1532         /*
1533          * If we have a resulting tree, that means the strategy module
1534          * auto resolved the merge cleanly.
1535          */
1536         if (automerge_was_ok) {
1537                 ret = finish_automerge(head_commit, common, result_tree,
1538                                        wt_strategy);
1539                 goto done;
1540         }
1541
1542         /*
1543          * Pick the result from the best strategy and have the user fix
1544          * it up.
1545          */
1546         if (!best_strategy) {
1547                 restore_state(head_commit->object.sha1, stash);
1548                 if (use_strategies_nr > 1)
1549                         fprintf(stderr,
1550                                 _("No merge strategy handled the merge.\n"));
1551                 else
1552                         fprintf(stderr, _("Merge with strategy %s failed.\n"),
1553                                 use_strategies[0]->name);
1554                 ret = 2;
1555                 goto done;
1556         } else if (best_strategy == wt_strategy)
1557                 ; /* We already have its result in the working tree. */
1558         else {
1559                 printf(_("Rewinding the tree to pristine...\n"));
1560                 restore_state(head_commit->object.sha1, stash);
1561                 printf(_("Using the %s to prepare resolving by hand.\n"),
1562                         best_strategy);
1563                 try_merge_strategy(best_strategy, common, head_commit, head_arg);
1564         }
1565
1566         if (squash)
1567                 finish(head_commit, NULL, NULL);
1568         else
1569                 write_merge_state();
1570
1571         if (merge_was_ok)
1572                 fprintf(stderr, _("Automatic merge went well; "
1573                         "stopped before committing as requested\n"));
1574         else
1575                 ret = suggest_conflicts(option_renormalize);
1576
1577 done:
1578         free(branch_to_free);
1579         return ret;
1580 }