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