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