builtin/pull.c

   1 /*
   2  * Builtin "git pull"
   3  *
   4  * Based on git-pull.sh by Junio C Hamano
   5  *
   6  * Fetch one or more remote refs and merge it/them into the current HEAD.
   7  */
   8 #include "cache.h"
   9 #include "builtin.h"
  10 #include "parse-options.h"
  11 #include "exec_cmd.h"
  12 #include "run-command.h"
  13 #include "sha1-array.h"
  14 #include "remote.h"
  15 #include "dir.h"
  16 #include "refs.h"
  17 #include "revision.h"
  18 #include "tempfile.h"
  19 #include "lockfile.h"
  20
  21 enum rebase_type {
  22         REBASE_INVALID = -1,
  23         REBASE_FALSE = 0,
  24         REBASE_TRUE,
  25         REBASE_PRESERVE,
  26         REBASE_INTERACTIVE
  27 };
  28
  29 /**
  30  * Parses the value of --rebase. If value is a false value, returns
  31  * REBASE_FALSE. If value is a true value, returns REBASE_TRUE. If value is
  32  * "preserve", returns REBASE_PRESERVE. If value is a invalid value, dies with
  33  * a fatal error if fatal is true, otherwise returns REBASE_INVALID.
  34  */
  35 static enum rebase_type parse_config_rebase(const char *key, const char *value,
  36                 int fatal)
  37 {
  38         int v = git_config_maybe_bool("pull.rebase", value);
  39
  40         if (!v)
  41                 return REBASE_FALSE;
  42         else if (v > 0)
  43                 return REBASE_TRUE;
  44         else if (!strcmp(value, "preserve"))
  45                 return REBASE_PRESERVE;
  46         else if (!strcmp(value, "interactive"))
  47                 return REBASE_INTERACTIVE;
  48
  49         if (fatal)
  50                 die(_("Invalid value for %s: %s"), key, value);
  51         else
  52                 error(_("Invalid value for %s: %s"), key, value);
  53
  54         return REBASE_INVALID;
  55 }
  56
  57 /**
  58  * Callback for --rebase, which parses arg with parse_config_rebase().
  59  */
  60 static int parse_opt_rebase(const struct option *opt, const char *arg, int unset)
  61 {
  62         enum rebase_type *value = opt->value;
  63
  64         if (arg)
  65                 *value = parse_config_rebase("--rebase", arg, 0);
  66         else
  67                 *value = unset ? REBASE_FALSE : REBASE_TRUE;
  68         return *value == REBASE_INVALID ? -1 : 0;
  69 }
  70
  71 static const char * const pull_usage[] = {
  72         N_("git pull [<options>] [<repository> [<refspec>...]]"),
  73         NULL
  74 };
  75
  76 /* Shared options */
  77 static int opt_verbosity;
  78 static char *opt_progress;
  79
  80 /* Options passed to git-merge or git-rebase */
  81 static enum rebase_type opt_rebase = -1;
  82 static char *opt_diffstat;
  83 static char *opt_log;
  84 static char *opt_squash;
  85 static char *opt_commit;
  86 static char *opt_edit;
  87 static char *opt_ff;
  88 static char *opt_verify_signatures;
  89 static struct argv_array opt_strategies = ARGV_ARRAY_INIT;
  90 static struct argv_array opt_strategy_opts = ARGV_ARRAY_INIT;
  91 static char *opt_gpg_sign;
  92
  93 /* Options passed to git-fetch */
  94 static char *opt_all;
  95 static char *opt_append;
  96 static char *opt_upload_pack;
  97 static int opt_force;
  98 static char *opt_tags;
  99 static char *opt_prune;
 100 static char *opt_recurse_submodules;
 101 static char *max_children;
 102 static int opt_dry_run;
 103 static char *opt_keep;
 104 static char *opt_depth;
 105 static char *opt_unshallow;
 106 static char *opt_update_shallow;
 107 static char *opt_refmap;
 108
 109 static struct option pull_options[] = {
 110         /* Shared options */
 111         OPT__VERBOSITY(&opt_verbosity),
 112         OPT_PASSTHRU(0, "progress", &opt_progress, NULL,
 113                 N_("force progress reporting"),
 114                 PARSE_OPT_NOARG),
 115
 116         /* Options passed to git-merge or git-rebase */
 117         OPT_GROUP(N_("Options related to merging")),
 118         { OPTION_CALLBACK, 'r', "rebase", &opt_rebase,
 119           "false|true|preserve|interactive",
 120           N_("incorporate changes by rebasing rather than merging"),
 121           PARSE_OPT_OPTARG, parse_opt_rebase },
 122         OPT_PASSTHRU('n', NULL, &opt_diffstat, NULL,
 123                 N_("do not show a diffstat at the end of the merge"),
 124                 PARSE_OPT_NOARG | PARSE_OPT_NONEG),
 125         OPT_PASSTHRU(0, "stat", &opt_diffstat, NULL,
 126                 N_("show a diffstat at the end of the merge"),
 127                 PARSE_OPT_NOARG),
 128         OPT_PASSTHRU(0, "summary", &opt_diffstat, NULL,
 129                 N_("(synonym to --stat)"),
 130                 PARSE_OPT_NOARG | PARSE_OPT_HIDDEN),
 131         OPT_PASSTHRU(0, "log", &opt_log, N_("n"),
 132                 N_("add (at most <n>) entries from shortlog to merge commit message"),
 133                 PARSE_OPT_OPTARG),
 134         OPT_PASSTHRU(0, "squash", &opt_squash, NULL,
 135                 N_("create a single commit instead of doing a merge"),
 136                 PARSE_OPT_NOARG),
 137         OPT_PASSTHRU(0, "commit", &opt_commit, NULL,
 138                 N_("perform a commit if the merge succeeds (default)"),
 139                 PARSE_OPT_NOARG),
 140         OPT_PASSTHRU(0, "edit", &opt_edit, NULL,
 141                 N_("edit message before committing"),
 142                 PARSE_OPT_NOARG),
 143         OPT_PASSTHRU(0, "ff", &opt_ff, NULL,
 144                 N_("allow fast-forward"),
 145                 PARSE_OPT_NOARG),
 146         OPT_PASSTHRU(0, "ff-only", &opt_ff, NULL,
 147                 N_("abort if fast-forward is not possible"),
 148                 PARSE_OPT_NOARG | PARSE_OPT_NONEG),
 149         OPT_PASSTHRU(0, "verify-signatures", &opt_verify_signatures, NULL,
 150                 N_("verify that the named commit has a valid GPG signature"),
 151                 PARSE_OPT_NOARG),
 152         OPT_PASSTHRU_ARGV('s', "strategy", &opt_strategies, N_("strategy"),
 153                 N_("merge strategy to use"),
 154                 0),
 155         OPT_PASSTHRU_ARGV('X', "strategy-option", &opt_strategy_opts,
 156                 N_("option=value"),
 157                 N_("option for selected merge strategy"),
 158                 0),
 159         OPT_PASSTHRU('S', "gpg-sign", &opt_gpg_sign, N_("key-id"),
 160                 N_("GPG sign commit"),
 161                 PARSE_OPT_OPTARG),
 162
 163         /* Options passed to git-fetch */
 164         OPT_GROUP(N_("Options related to fetching")),
 165         OPT_PASSTHRU(0, "all", &opt_all, NULL,
 166                 N_("fetch from all remotes"),
 167                 PARSE_OPT_NOARG),
 168         OPT_PASSTHRU('a', "append", &opt_append, NULL,
 169                 N_("append to .git/FETCH_HEAD instead of overwriting"),
 170                 PARSE_OPT_NOARG),
 171         OPT_PASSTHRU(0, "upload-pack", &opt_upload_pack, N_("path"),
 172                 N_("path to upload pack on remote end"),
 173                 0),
 174         OPT__FORCE(&opt_force, N_("force overwrite of local branch")),
 175         OPT_PASSTHRU('t', "tags", &opt_tags, NULL,
 176                 N_("fetch all tags and associated objects"),
 177                 PARSE_OPT_NOARG),
 178         OPT_PASSTHRU('p', "prune", &opt_prune, NULL,
 179                 N_("prune remote-tracking branches no longer on remote"),
 180                 PARSE_OPT_NOARG),
 181         OPT_PASSTHRU(0, "recurse-submodules", &opt_recurse_submodules,
 182                 N_("on-demand"),
 183                 N_("control recursive fetching of submodules"),
 184                 PARSE_OPT_OPTARG),
 185         OPT_PASSTHRU('j', "jobs", &max_children, N_("n"),
 186                 N_("number of submodules pulled in parallel"),
 187                 PARSE_OPT_OPTARG),
 188         OPT_BOOL(0, "dry-run", &opt_dry_run,
 189                 N_("dry run")),
 190         OPT_PASSTHRU('k', "keep", &opt_keep, NULL,
 191                 N_("keep downloaded pack"),
 192                 PARSE_OPT_NOARG),
 193         OPT_PASSTHRU(0, "depth", &opt_depth, N_("depth"),
 194                 N_("deepen history of shallow clone"),
 195                 0),
 196         OPT_PASSTHRU(0, "unshallow", &opt_unshallow, NULL,
 197                 N_("convert to a complete repository"),
 198                 PARSE_OPT_NONEG | PARSE_OPT_NOARG),
 199         OPT_PASSTHRU(0, "update-shallow", &opt_update_shallow, NULL,
 200                 N_("accept refs that update .git/shallow"),
 201                 PARSE_OPT_NOARG),
 202         OPT_PASSTHRU(0, "refmap", &opt_refmap, N_("refmap"),
 203                 N_("specify fetch refmap"),
 204                 PARSE_OPT_NONEG),
 205
 206         OPT_END()
 207 };
 208
 209 /**
 210  * Pushes "-q" or "-v" switches into arr to match the opt_verbosity level.
 211  */
 212 static void argv_push_verbosity(struct argv_array *arr)
 213 {
 214         int verbosity;
 215
 216         for (verbosity = opt_verbosity; verbosity > 0; verbosity--)
 217                 argv_array_push(arr, "-v");
 218
 219         for (verbosity = opt_verbosity; verbosity < 0; verbosity++)
 220                 argv_array_push(arr, "-q");
 221 }
 222
 223 /**
 224  * Pushes "-f" switches into arr to match the opt_force level.
 225  */
 226 static void argv_push_force(struct argv_array *arr)
 227 {
 228         int force = opt_force;
 229         while (force-- > 0)
 230                 argv_array_push(arr, "-f");
 231 }
 232
 233 /**
 234  * Sets the GIT_REFLOG_ACTION environment variable to the concatenation of argv
 235  */
 236 static void set_reflog_message(int argc, const char **argv)
 237 {
 238         int i;
 239         struct strbuf msg = STRBUF_INIT;
 240
 241         for (i = 0; i < argc; i++) {
 242                 if (i)
 243                         strbuf_addch(&msg, ' ');
 244                 strbuf_addstr(&msg, argv[i]);
 245         }
 246
 247         setenv("GIT_REFLOG_ACTION", msg.buf, 0);
 248
 249         strbuf_release(&msg);
 250 }
 251
 252 /**
 253  * If pull.ff is unset, returns NULL. If pull.ff is "true", returns "--ff". If
 254  * pull.ff is "false", returns "--no-ff". If pull.ff is "only", returns
 255  * "--ff-only". Otherwise, if pull.ff is set to an invalid value, die with an
 256  * error.
 257  */
 258 static const char *config_get_ff(void)
 259 {
 260         const char *value;
 261
 262         if (git_config_get_value("pull.ff", &value))
 263                 return NULL;
 264
 265         switch (git_config_maybe_bool("pull.ff", value)) {
 266         case 0:
 267                 return "--no-ff";
 268         case 1:
 269                 return "--ff";
 270         }
 271
 272         if (!strcmp(value, "only"))
 273                 return "--ff-only";
 274
 275         die(_("Invalid value for pull.ff: %s"), value);
 276 }
 277
 278 /**
 279  * Returns the default configured value for --rebase. It first looks for the
 280  * value of "branch.$curr_branch.rebase", where $curr_branch is the current
 281  * branch, and if HEAD is detached or the configuration key does not exist,
 282  * looks for the value of "pull.rebase". If both configuration keys do not
 283  * exist, returns REBASE_FALSE.
 284  */
 285 static enum rebase_type config_get_rebase(void)
 286 {
 287         struct branch *curr_branch = branch_get("HEAD");
 288         const char *value;
 289
 290         if (curr_branch) {
 291                 char *key = xstrfmt("branch.%s.rebase", curr_branch->name);
 292
 293                 if (!git_config_get_value(key, &value)) {
 294                         enum rebase_type ret = parse_config_rebase(key, value, 1);
 295                         free(key);
 296                         return ret;
 297                 }
 298
 299                 free(key);
 300         }
 301
 302         if (!git_config_get_value("pull.rebase", &value))
 303                 return parse_config_rebase("pull.rebase", value, 1);
 304
 305         return REBASE_FALSE;
 306 }
 307
 308 /**
 309  * Returns 1 if there are unstaged changes, 0 otherwise.
 310  */
 311 static int has_unstaged_changes(const char *prefix)
 312 {
 313         struct rev_info rev_info;
 314         int result;
 315
 316         init_revisions(&rev_info, prefix);
 317         DIFF_OPT_SET(&rev_info.diffopt, IGNORE_SUBMODULES);
 318         DIFF_OPT_SET(&rev_info.diffopt, QUICK);
 319         diff_setup_done(&rev_info.diffopt);
 320         result = run_diff_files(&rev_info, 0);
 321         return diff_result_code(&rev_info.diffopt, result);
 322 }
 323
 324 /**
 325  * Returns 1 if there are uncommitted changes, 0 otherwise.
 326  */
 327 static int has_uncommitted_changes(const char *prefix)
 328 {
 329         struct rev_info rev_info;
 330         int result;
 331
 332         if (is_cache_unborn())
 333                 return 0;
 334
 335         init_revisions(&rev_info, prefix);
 336         DIFF_OPT_SET(&rev_info.diffopt, IGNORE_SUBMODULES);
 337         DIFF_OPT_SET(&rev_info.diffopt, QUICK);
 338         add_head_to_pending(&rev_info);
 339         diff_setup_done(&rev_info.diffopt);
 340         result = run_diff_index(&rev_info, 1);
 341         return diff_result_code(&rev_info.diffopt, result);
 342 }
 343
 344 /**
 345  * If the work tree has unstaged or uncommitted changes, dies with the
 346  * appropriate message.
 347  */
 348 static void die_on_unclean_work_tree(const char *prefix)
 349 {
 350         struct lock_file *lock_file = xcalloc(1, sizeof(*lock_file));
 351         int do_die = 0;
 352
 353         hold_locked_index(lock_file, 0);
 354         refresh_cache(REFRESH_QUIET);
 355         update_index_if_able(&the_index, lock_file);
 356         rollback_lock_file(lock_file);
 357
 358         if (has_unstaged_changes(prefix)) {
 359                 error(_("Cannot pull with rebase: You have unstaged changes."));
 360                 do_die = 1;
 361         }
 362
 363         if (has_uncommitted_changes(prefix)) {
 364                 if (do_die)
 365                         error(_("Additionally, your index contains uncommitted changes."));
 366                 else
 367                         error(_("Cannot pull with rebase: Your index contains uncommitted changes."));
 368                 do_die = 1;
 369         }
 370
 371         if (do_die)
 372                 exit(1);
 373 }
 374
 375 /**
 376  * Appends merge candidates from FETCH_HEAD that are not marked not-for-merge
 377  * into merge_heads.
 378  */
 379 static void get_merge_heads(struct sha1_array *merge_heads)
 380 {
 381         const char *filename = git_path("FETCH_HEAD");
 382         FILE *fp;
 383         struct strbuf sb = STRBUF_INIT;
 384         unsigned char sha1[GIT_SHA1_RAWSZ];
 385
 386         if (!(fp = fopen(filename, "r")))
 387                 die_errno(_("could not open '%s' for reading"), filename);
 388         while (strbuf_getline_lf(&sb, fp) != EOF) {
 389                 if (get_sha1_hex(sb.buf, sha1))
 390                         continue;  /* invalid line: does not start with SHA1 */
 391                 if (starts_with(sb.buf + GIT_SHA1_HEXSZ, "\tnot-for-merge\t"))
 392                         continue;  /* ref is not-for-merge */
 393                 sha1_array_append(merge_heads, sha1);
 394         }
 395         fclose(fp);
 396         strbuf_release(&sb);
 397 }
 398
 399 /**
 400  * Used by die_no_merge_candidates() as a for_each_remote() callback to
 401  * retrieve the name of the remote if the repository only has one remote.
 402  */
 403 static int get_only_remote(struct remote *remote, void *cb_data)
 404 {
 405         const char **remote_name = cb_data;
 406
 407         if (*remote_name)
 408                 return -1;
 409
 410         *remote_name = remote->name;
 411         return 0;
 412 }
 413
 414 /**
 415  * Dies with the appropriate reason for why there are no merge candidates:
 416  *
 417  * 1. We fetched from a specific remote, and a refspec was given, but it ended
 418  *    up not fetching anything. This is usually because the user provided a
 419  *    wildcard refspec which had no matches on the remote end.
 420  *
 421  * 2. We fetched from a non-default remote, but didn't specify a branch to
 422  *    merge. We can't use the configured one because it applies to the default
 423  *    remote, thus the user must specify the branches to merge.
 424  *
 425  * 3. We fetched from the branch's or repo's default remote, but:
 426  *
 427  *    a. We are not on a branch, so there will never be a configured branch to
 428  *       merge with.
 429  *
 430  *    b. We are on a branch, but there is no configured branch to merge with.
 431  *
 432  * 4. We fetched from the branch's or repo's default remote, but the configured
 433  *    branch to merge didn't get fetched. (Either it doesn't exist, or wasn't
 434  *    part of the configured fetch refspec.)
 435  */
 436 static void NORETURN die_no_merge_candidates(const char *repo, const char **refspecs)
 437 {
 438         struct branch *curr_branch = branch_get("HEAD");
 439         const char *remote = curr_branch ? curr_branch->remote_name : NULL;
 440
 441         if (*refspecs) {
 442                 if (opt_rebase)
 443                         fprintf_ln(stderr, _("There is no candidate for rebasing against among the refs that you just fetched."));
 444                 else
 445                         fprintf_ln(stderr, _("There are no candidates for merging among the refs that you just fetched."));
 446                 fprintf_ln(stderr, _("Generally this means that you provided a wildcard refspec which had no\n"
 447                                         "matches on the remote end."));
 448         } else if (repo && curr_branch && (!remote || strcmp(repo, remote))) {
 449                 fprintf_ln(stderr, _("You asked to pull from the remote '%s', but did not specify\n"
 450                         "a branch. Because this is not the default configured remote\n"
 451                         "for your current branch, you must specify a branch on the command line."),
 452                         repo);
 453         } else if (!curr_branch) {
 454                 fprintf_ln(stderr, _("You are not currently on a branch."));
 455                 if (opt_rebase)
 456                         fprintf_ln(stderr, _("Please specify which branch you want to rebase against."));
 457                 else
 458                         fprintf_ln(stderr, _("Please specify which branch you want to merge with."));
 459                 fprintf_ln(stderr, _("See git-pull(1) for details."));
 460                 fprintf(stderr, "\n");
 461                 fprintf_ln(stderr, "    git pull %s %s", _("<remote>"), _("<branch>"));
 462                 fprintf(stderr, "\n");
 463         } else if (!curr_branch->merge_nr) {
 464                 const char *remote_name = NULL;
 465
 466                 if (for_each_remote(get_only_remote, &remote_name) || !remote_name)
 467                         remote_name = _("<remote>");
 468
 469                 fprintf_ln(stderr, _("There is no tracking information for the current branch."));
 470                 if (opt_rebase)
 471                         fprintf_ln(stderr, _("Please specify which branch you want to rebase against."));
 472                 else
 473                         fprintf_ln(stderr, _("Please specify which branch you want to merge with."));
 474                 fprintf_ln(stderr, _("See git-pull(1) for details."));
 475                 fprintf(stderr, "\n");
 476                 fprintf_ln(stderr, "    git pull %s %s", _("<remote>"), _("<branch>"));
 477                 fprintf(stderr, "\n");
 478                 fprintf_ln(stderr, _("If you wish to set tracking information for this branch you can do so with:"));
 479                 fprintf(stderr, "\n");
 480                 fprintf_ln(stderr, "    git branch --set-upstream-to=%s/%s %s\n",
 481                                 remote_name, _("<branch>"), curr_branch->name);
 482         } else
 483                 fprintf_ln(stderr, _("Your configuration specifies to merge with the ref '%s'\n"
 484                         "from the remote, but no such ref was fetched."),
 485                         *curr_branch->merge_name);
 486         exit(1);
 487 }
 488
 489 /**
 490  * Parses argv into [<repo> [<refspecs>...]], returning their values in `repo`
 491  * as a string and `refspecs` as a null-terminated array of strings. If `repo`
 492  * is not provided in argv, it is set to NULL.
 493  */
 494 static void parse_repo_refspecs(int argc, const char **argv, const char **repo,
 495                 const char ***refspecs)
 496 {
 497         if (argc > 0) {
 498                 *repo = *argv++;
 499                 argc--;
 500         } else
 501                 *repo = NULL;
 502         *refspecs = argv;
 503 }
 504
 505 /**
 506  * Runs git-fetch, returning its exit status. `repo` and `refspecs` are the
 507  * repository and refspecs to fetch, or NULL if they are not provided.
 508  */
 509 static int run_fetch(const char *repo, const char **refspecs)
 510 {
 511         struct argv_array args = ARGV_ARRAY_INIT;
 512         int ret;
 513
 514         argv_array_pushl(&args, "fetch", "--update-head-ok", NULL);
 515
 516         /* Shared options */
 517         argv_push_verbosity(&args);
 518         if (opt_progress)
 519                 argv_array_push(&args, opt_progress);
 520
 521         /* Options passed to git-fetch */
 522         if (opt_all)
 523                 argv_array_push(&args, opt_all);
 524         if (opt_append)
 525                 argv_array_push(&args, opt_append);
 526         if (opt_upload_pack)
 527                 argv_array_push(&args, opt_upload_pack);
 528         argv_push_force(&args);
 529         if (opt_tags)
 530                 argv_array_push(&args, opt_tags);
 531         if (opt_prune)
 532                 argv_array_push(&args, opt_prune);
 533         if (opt_recurse_submodules)
 534                 argv_array_push(&args, opt_recurse_submodules);
 535         if (max_children)
 536                 argv_array_push(&args, max_children);
 537         if (opt_dry_run)
 538                 argv_array_push(&args, "--dry-run");
 539         if (opt_keep)
 540                 argv_array_push(&args, opt_keep);
 541         if (opt_depth)
 542                 argv_array_push(&args, opt_depth);
 543         if (opt_unshallow)
 544                 argv_array_push(&args, opt_unshallow);
 545         if (opt_update_shallow)
 546                 argv_array_push(&args, opt_update_shallow);
 547         if (opt_refmap)
 548                 argv_array_push(&args, opt_refmap);
 549
 550         if (repo) {
 551                 argv_array_push(&args, repo);
 552                 argv_array_pushv(&args, refspecs);
 553         } else if (*refspecs)
 554                 die("BUG: refspecs without repo?");
 555         ret = run_command_v_opt(args.argv, RUN_GIT_CMD);
 556         argv_array_clear(&args);
 557         return ret;
 558 }
 559
 560 /**
 561  * "Pulls into void" by branching off merge_head.
 562  */
 563 static int pull_into_void(const unsigned char *merge_head,
 564                 const unsigned char *curr_head)
 565 {
 566         /*
 567          * Two-way merge: we treat the index as based on an empty tree,
 568          * and try to fast-forward to HEAD. This ensures we will not lose
 569          * index/worktree changes that the user already made on the unborn
 570          * branch.
 571          */
 572         if (checkout_fast_forward(EMPTY_TREE_SHA1_BIN, merge_head, 0))
 573                 return 1;
 574
 575         if (update_ref("initial pull", "HEAD", merge_head, curr_head, 0, UPDATE_REFS_DIE_ON_ERR))
 576                 return 1;
 577
 578         return 0;
 579 }
 580
 581 /**
 582  * Runs git-merge, returning its exit status.
 583  */
 584 static int run_merge(void)
 585 {
 586         int ret;
 587         struct argv_array args = ARGV_ARRAY_INIT;
 588
 589         argv_array_pushl(&args, "merge", NULL);
 590
 591         /* Shared options */
 592         argv_push_verbosity(&args);
 593         if (opt_progress)
 594                 argv_array_push(&args, opt_progress);
 595
 596         /* Options passed to git-merge */
 597         if (opt_diffstat)
 598                 argv_array_push(&args, opt_diffstat);
 599         if (opt_log)
 600                 argv_array_push(&args, opt_log);
 601         if (opt_squash)
 602                 argv_array_push(&args, opt_squash);
 603         if (opt_commit)
 604                 argv_array_push(&args, opt_commit);
 605         if (opt_edit)
 606                 argv_array_push(&args, opt_edit);
 607         if (opt_ff)
 608                 argv_array_push(&args, opt_ff);
 609         if (opt_verify_signatures)
 610                 argv_array_push(&args, opt_verify_signatures);
 611         argv_array_pushv(&args, opt_strategies.argv);
 612         argv_array_pushv(&args, opt_strategy_opts.argv);
 613         if (opt_gpg_sign)
 614                 argv_array_push(&args, opt_gpg_sign);
 615
 616         argv_array_push(&args, "FETCH_HEAD");
 617         ret = run_command_v_opt(args.argv, RUN_GIT_CMD);
 618         argv_array_clear(&args);
 619         return ret;
 620 }
 621
 622 /**
 623  * Returns remote's upstream branch for the current branch. If remote is NULL,
 624  * the current branch's configured default remote is used. Returns NULL if
 625  * `remote` does not name a valid remote, HEAD does not point to a branch,
 626  * remote is not the branch's configured remote or the branch does not have any
 627  * configured upstream branch.
 628  */
 629 static const char *get_upstream_branch(const char *remote)
 630 {
 631         struct remote *rm;
 632         struct branch *curr_branch;
 633         const char *curr_branch_remote;
 634
 635         rm = remote_get(remote);
 636         if (!rm)
 637                 return NULL;
 638
 639         curr_branch = branch_get("HEAD");
 640         if (!curr_branch)
 641                 return NULL;
 642
 643         curr_branch_remote = remote_for_branch(curr_branch, NULL);
 644         assert(curr_branch_remote);
 645
 646         if (strcmp(curr_branch_remote, rm->name))
 647                 return NULL;
 648
 649         return branch_get_upstream(curr_branch, NULL);
 650 }
 651
 652 /**
 653  * Derives the remote tracking branch from the remote and refspec.
 654  *
 655  * FIXME: The current implementation assumes the default mapping of
 656  * refs/heads/<branch_name> to refs/remotes/<remote_name>/<branch_name>.
 657  */
 658 static const char *get_tracking_branch(const char *remote, const char *refspec)
 659 {
 660         struct refspec *spec;
 661         const char *spec_src;
 662         const char *merge_branch;
 663
 664         spec = parse_fetch_refspec(1, &refspec);
 665         spec_src = spec->src;
 666         if (!*spec_src || !strcmp(spec_src, "HEAD"))
 667                 spec_src = "HEAD";
 668         else if (skip_prefix(spec_src, "heads/", &spec_src))
 669                 ;
 670         else if (skip_prefix(spec_src, "refs/heads/", &spec_src))
 671                 ;
 672         else if (starts_with(spec_src, "refs/") ||
 673                 starts_with(spec_src, "tags/") ||
 674                 starts_with(spec_src, "remotes/"))
 675                 spec_src = "";
 676
 677         if (*spec_src) {
 678                 if (!strcmp(remote, "."))
 679                         merge_branch = mkpath("refs/heads/%s", spec_src);
 680                 else
 681                         merge_branch = mkpath("refs/remotes/%s/%s", remote, spec_src);
 682         } else
 683                 merge_branch = NULL;
 684
 685         free_refspec(1, spec);
 686         return merge_branch;
 687 }
 688
 689 /**
 690  * Given the repo and refspecs, sets fork_point to the point at which the
 691  * current branch forked from its remote tracking branch. Returns 0 on success,
 692  * -1 on failure.
 693  */
 694 static int get_rebase_fork_point(unsigned char *fork_point, const char *repo,
 695                 const char *refspec)
 696 {
 697         int ret;
 698         struct branch *curr_branch;
 699         const char *remote_branch;
 700         struct child_process cp = CHILD_PROCESS_INIT;
 701         struct strbuf sb = STRBUF_INIT;
 702
 703         curr_branch = branch_get("HEAD");
 704         if (!curr_branch)
 705                 return -1;
 706
 707         if (refspec)
 708                 remote_branch = get_tracking_branch(repo, refspec);
 709         else
 710                 remote_branch = get_upstream_branch(repo);
 711
 712         if (!remote_branch)
 713                 return -1;
 714
 715         argv_array_pushl(&cp.args, "merge-base", "--fork-point",
 716                         remote_branch, curr_branch->name, NULL);
 717         cp.no_stdin = 1;
 718         cp.no_stderr = 1;
 719         cp.git_cmd = 1;
 720
 721         ret = capture_command(&cp, &sb, GIT_SHA1_HEXSZ);
 722         if (ret)
 723                 goto cleanup;
 724
 725         ret = get_sha1_hex(sb.buf, fork_point);
 726         if (ret)
 727                 goto cleanup;
 728
 729 cleanup:
 730         strbuf_release(&sb);
 731         return ret ? -1 : 0;
 732 }
 733
 734 /**
 735  * Sets merge_base to the octopus merge base of curr_head, merge_head and
 736  * fork_point. Returns 0 if a merge base is found, 1 otherwise.
 737  */
 738 static int get_octopus_merge_base(unsigned char *merge_base,
 739                 const unsigned char *curr_head,
 740                 const unsigned char *merge_head,
 741                 const unsigned char *fork_point)
 742 {
 743         struct commit_list *revs = NULL, *result;
 744
 745         commit_list_insert(lookup_commit_reference(curr_head), &revs);
 746         commit_list_insert(lookup_commit_reference(merge_head), &revs);
 747         if (!is_null_sha1(fork_point))
 748                 commit_list_insert(lookup_commit_reference(fork_point), &revs);
 749
 750         result = reduce_heads(get_octopus_merge_bases(revs));
 751         free_commit_list(revs);
 752         if (!result)
 753                 return 1;
 754
 755         hashcpy(merge_base, result->item->object.oid.hash);
 756         return 0;
 757 }
 758
 759 /**
 760  * Given the current HEAD SHA1, the merge head returned from git-fetch and the
 761  * fork point calculated by get_rebase_fork_point(), runs git-rebase with the
 762  * appropriate arguments and returns its exit status.
 763  */
 764 static int run_rebase(const unsigned char *curr_head,
 765                 const unsigned char *merge_head,
 766                 const unsigned char *fork_point)
 767 {
 768         int ret;
 769         unsigned char oct_merge_base[GIT_SHA1_RAWSZ];
 770         struct argv_array args = ARGV_ARRAY_INIT;
 771
 772         if (!get_octopus_merge_base(oct_merge_base, curr_head, merge_head, fork_point))
 773                 if (!is_null_sha1(fork_point) && !hashcmp(oct_merge_base, fork_point))
 774                         fork_point = NULL;
 775
 776         argv_array_push(&args, "rebase");
 777
 778         /* Shared options */
 779         argv_push_verbosity(&args);
 780
 781         /* Options passed to git-rebase */
 782         if (opt_rebase == REBASE_PRESERVE)
 783                 argv_array_push(&args, "--preserve-merges");
 784         else if (opt_rebase == REBASE_INTERACTIVE)
 785                 argv_array_push(&args, "--interactive");
 786         if (opt_diffstat)
 787                 argv_array_push(&args, opt_diffstat);
 788         argv_array_pushv(&args, opt_strategies.argv);
 789         argv_array_pushv(&args, opt_strategy_opts.argv);
 790         if (opt_gpg_sign)
 791                 argv_array_push(&args, opt_gpg_sign);
 792
 793         argv_array_push(&args, "--onto");
 794         argv_array_push(&args, sha1_to_hex(merge_head));
 795
 796         if (fork_point && !is_null_sha1(fork_point))
 797                 argv_array_push(&args, sha1_to_hex(fork_point));
 798         else
 799                 argv_array_push(&args, sha1_to_hex(merge_head));
 800
 801         ret = run_command_v_opt(args.argv, RUN_GIT_CMD);
 802         argv_array_clear(&args);
 803         return ret;
 804 }
 805
 806 int cmd_pull(int argc, const char **argv, const char *prefix)
 807 {
 808         const char *repo, **refspecs;
 809         struct sha1_array merge_heads = SHA1_ARRAY_INIT;
 810         unsigned char orig_head[GIT_SHA1_RAWSZ], curr_head[GIT_SHA1_RAWSZ];
 811         unsigned char rebase_fork_point[GIT_SHA1_RAWSZ];
 812
 813         if (!getenv("GIT_REFLOG_ACTION"))
 814                 set_reflog_message(argc, argv);
 815
 816         argc = parse_options(argc, argv, prefix, pull_options, pull_usage, 0);
 817
 818         parse_repo_refspecs(argc, argv, &repo, &refspecs);
 819
 820         if (!opt_ff)
 821                 opt_ff = xstrdup_or_null(config_get_ff());
 822
 823         if (opt_rebase < 0)
 824                 opt_rebase = config_get_rebase();
 825
 826         git_config(git_default_config, NULL);
 827
 828         if (read_cache_unmerged())
 829                 die_resolve_conflict("Pull");
 830
 831         if (file_exists(git_path("MERGE_HEAD")))
 832                 die_conclude_merge();
 833
 834         if (get_sha1("HEAD", orig_head))
 835                 hashclr(orig_head);
 836
 837         if (opt_rebase) {
 838                 int autostash = 0;
 839
 840                 if (is_null_sha1(orig_head) && !is_cache_unborn())
 841                         die(_("Updating an unborn branch with changes added to the index."));
 842
 843                 git_config_get_bool("rebase.autostash", &autostash);
 844                 if (!autostash)
 845                         die_on_unclean_work_tree(prefix);
 846
 847                 if (get_rebase_fork_point(rebase_fork_point, repo, *refspecs))
 848                         hashclr(rebase_fork_point);
 849         }
 850
 851         if (run_fetch(repo, refspecs))
 852                 return 1;
 853
 854         if (opt_dry_run)
 855                 return 0;
 856
 857         if (get_sha1("HEAD", curr_head))
 858                 hashclr(curr_head);
 859
 860         if (!is_null_sha1(orig_head) && !is_null_sha1(curr_head) &&
 861                         hashcmp(orig_head, curr_head)) {
 862                 /*
 863                  * The fetch involved updating the current branch.
 864                  *
 865                  * The working tree and the index file are still based on
 866                  * orig_head commit, but we are merging into curr_head.
 867                  * Update the working tree to match curr_head.
 868                  */
 869
 870                 warning(_("fetch updated the current branch head.\n"
 871                         "fast-forwarding your working tree from\n"
 872                         "commit %s."), sha1_to_hex(orig_head));
 873
 874                 if (checkout_fast_forward(orig_head, curr_head, 0))
 875                         die(_("Cannot fast-forward your working tree.\n"
 876                                 "After making sure that you saved anything precious from\n"
 877                                 "$ git diff %s\n"
 878                                 "output, run\n"
 879                                 "$ git reset --hard\n"
 880                                 "to recover."), sha1_to_hex(orig_head));
 881         }
 882
 883         get_merge_heads(&merge_heads);
 884
 885         if (!merge_heads.nr)
 886                 die_no_merge_candidates(repo, refspecs);
 887
 888         if (is_null_sha1(orig_head)) {
 889                 if (merge_heads.nr > 1)
 890                         die(_("Cannot merge multiple branches into empty head."));
 891                 return pull_into_void(*merge_heads.sha1, curr_head);
 892         } else if (opt_rebase) {
 893                 if (merge_heads.nr > 1)
 894                         die(_("Cannot rebase onto multiple branches."));
 895                 return run_rebase(curr_head, *merge_heads.sha1, rebase_fork_point);
 896         } else
 897                 return run_merge();
 898 }