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 "config.h"
  10 #include "builtin.h"
  11 #include "parse-options.h"
  12 #include "exec_cmd.h"
  13 #include "run-command.h"
  14 #include "sha1-array.h"
  15 #include "remote.h"
  16 #include "dir.h"
  17 #include "refs.h"
  18 #include "revision.h"
  19 #include "submodule.h"
  20 #include "submodule-config.h"
  21 #include "tempfile.h"
  22 #include "lockfile.h"
  23 #include "wt-status.h"
  24
  25 enum rebase_type {
  26         REBASE_INVALID = -1,
  27         REBASE_FALSE = 0,
  28         REBASE_TRUE,
  29         REBASE_PRESERVE,
  30         REBASE_INTERACTIVE
  31 };
  32
  33 /**
  34  * Parses the value of --rebase. If value is a false value, returns
  35  * REBASE_FALSE. If value is a true value, returns REBASE_TRUE. If value is
  36  * "preserve", returns REBASE_PRESERVE. If value is a invalid value, dies with
  37  * a fatal error if fatal is true, otherwise returns REBASE_INVALID.
  38  */
  39 static enum rebase_type parse_config_rebase(const char *key, const char *value,
  40                 int fatal)
  41 {
  42         int v = git_parse_maybe_bool(value);
  43
  44         if (!v)
  45                 return REBASE_FALSE;
  46         else if (v > 0)
  47                 return REBASE_TRUE;
  48         else if (!strcmp(value, "preserve"))
  49                 return REBASE_PRESERVE;
  50         else if (!strcmp(value, "interactive"))
  51                 return REBASE_INTERACTIVE;
  52
  53         if (fatal)
  54                 die(_("Invalid value for %s: %s"), key, value);
  55         else
  56                 error(_("Invalid value for %s: %s"), key, value);
  57
  58         return REBASE_INVALID;
  59 }
  60
  61 /**
  62  * Callback for --rebase, which parses arg with parse_config_rebase().
  63  */
  64 static int parse_opt_rebase(const struct option *opt, const char *arg, int unset)
  65 {
  66         enum rebase_type *value = opt->value;
  67
  68         if (arg)
  69                 *value = parse_config_rebase("--rebase", arg, 0);
  70         else
  71                 *value = unset ? REBASE_FALSE : REBASE_TRUE;
  72         return *value == REBASE_INVALID ? -1 : 0;
  73 }
  74
  75 static const char * const pull_usage[] = {
  76         N_("git pull [<options>] [<repository> [<refspec>...]]"),
  77         NULL
  78 };
  79
  80 /* Shared options */
  81 static int opt_verbosity;
  82 static char *opt_progress;
  83 static int recurse_submodules = RECURSE_SUBMODULES_DEFAULT;
  84
  85 /* Options passed to git-merge or git-rebase */
  86 static enum rebase_type opt_rebase = -1;
  87 static char *opt_diffstat;
  88 static char *opt_log;
  89 static char *opt_squash;
  90 static char *opt_commit;
  91 static char *opt_edit;
  92 static char *opt_ff;
  93 static char *opt_verify_signatures;
  94 static int opt_autostash = -1;
  95 static int config_autostash;
  96 static struct argv_array opt_strategies = ARGV_ARRAY_INIT;
  97 static struct argv_array opt_strategy_opts = ARGV_ARRAY_INIT;
  98 static char *opt_gpg_sign;
  99 static int opt_allow_unrelated_histories;
 100
 101 /* Options passed to git-fetch */
 102 static char *opt_all;
 103 static char *opt_append;
 104 static char *opt_upload_pack;
 105 static int opt_force;
 106 static char *opt_tags;
 107 static char *opt_prune;
 108 static char *max_children;
 109 static int opt_dry_run;
 110 static char *opt_keep;
 111 static char *opt_depth;
 112 static char *opt_unshallow;
 113 static char *opt_update_shallow;
 114 static char *opt_refmap;
 115 static char *opt_ipv4;
 116 static char *opt_ipv6;
 117
 118 static struct option pull_options[] = {
 119         /* Shared options */
 120         OPT__VERBOSITY(&opt_verbosity),
 121         OPT_PASSTHRU(0, "progress", &opt_progress, NULL,
 122                 N_("force progress reporting"),
 123                 PARSE_OPT_NOARG),
 124         { OPTION_CALLBACK, 0, "recurse-submodules",
 125                    &recurse_submodules, N_("on-demand"),
 126                    N_("control for recursive fetching of submodules"),
 127                    PARSE_OPT_OPTARG, option_fetch_parse_recurse_submodules },
 128
 129         /* Options passed to git-merge or git-rebase */
 130         OPT_GROUP(N_("Options related to merging")),
 131         { OPTION_CALLBACK, 'r', "rebase", &opt_rebase,
 132           "false|true|preserve|interactive",
 133           N_("incorporate changes by rebasing rather than merging"),
 134           PARSE_OPT_OPTARG, parse_opt_rebase },
 135         OPT_PASSTHRU('n', NULL, &opt_diffstat, NULL,
 136                 N_("do not show a diffstat at the end of the merge"),
 137                 PARSE_OPT_NOARG | PARSE_OPT_NONEG),
 138         OPT_PASSTHRU(0, "stat", &opt_diffstat, NULL,
 139                 N_("show a diffstat at the end of the merge"),
 140                 PARSE_OPT_NOARG),
 141         OPT_PASSTHRU(0, "summary", &opt_diffstat, NULL,
 142                 N_("(synonym to --stat)"),
 143                 PARSE_OPT_NOARG | PARSE_OPT_HIDDEN),
 144         OPT_PASSTHRU(0, "log", &opt_log, N_("n"),
 145                 N_("add (at most <n>) entries from shortlog to merge commit message"),
 146                 PARSE_OPT_OPTARG),
 147         OPT_PASSTHRU(0, "squash", &opt_squash, NULL,
 148                 N_("create a single commit instead of doing a merge"),
 149                 PARSE_OPT_NOARG),
 150         OPT_PASSTHRU(0, "commit", &opt_commit, NULL,
 151                 N_("perform a commit if the merge succeeds (default)"),
 152                 PARSE_OPT_NOARG),
 153         OPT_PASSTHRU(0, "edit", &opt_edit, NULL,
 154                 N_("edit message before committing"),
 155                 PARSE_OPT_NOARG),
 156         OPT_PASSTHRU(0, "ff", &opt_ff, NULL,
 157                 N_("allow fast-forward"),
 158                 PARSE_OPT_NOARG),
 159         OPT_PASSTHRU(0, "ff-only", &opt_ff, NULL,
 160                 N_("abort if fast-forward is not possible"),
 161                 PARSE_OPT_NOARG | PARSE_OPT_NONEG),
 162         OPT_PASSTHRU(0, "verify-signatures", &opt_verify_signatures, NULL,
 163                 N_("verify that the named commit has a valid GPG signature"),
 164                 PARSE_OPT_NOARG),
 165         OPT_BOOL(0, "autostash", &opt_autostash,
 166                 N_("automatically stash/stash pop before and after rebase")),
 167         OPT_PASSTHRU_ARGV('s', "strategy", &opt_strategies, N_("strategy"),
 168                 N_("merge strategy to use"),
 169                 0),
 170         OPT_PASSTHRU_ARGV('X', "strategy-option", &opt_strategy_opts,
 171                 N_("option=value"),
 172                 N_("option for selected merge strategy"),
 173                 0),
 174         OPT_PASSTHRU('S', "gpg-sign", &opt_gpg_sign, N_("key-id"),
 175                 N_("GPG sign commit"),
 176                 PARSE_OPT_OPTARG),
 177         OPT_SET_INT(0, "allow-unrelated-histories",
 178                     &opt_allow_unrelated_histories,
 179                     N_("allow merging unrelated histories"), 1),
 180
 181         /* Options passed to git-fetch */
 182         OPT_GROUP(N_("Options related to fetching")),
 183         OPT_PASSTHRU(0, "all", &opt_all, NULL,
 184                 N_("fetch from all remotes"),
 185                 PARSE_OPT_NOARG),
 186         OPT_PASSTHRU('a', "append", &opt_append, NULL,
 187                 N_("append to .git/FETCH_HEAD instead of overwriting"),
 188                 PARSE_OPT_NOARG),
 189         OPT_PASSTHRU(0, "upload-pack", &opt_upload_pack, N_("path"),
 190                 N_("path to upload pack on remote end"),
 191                 0),
 192         OPT__FORCE(&opt_force, N_("force overwrite of local branch")),
 193         OPT_PASSTHRU('t', "tags", &opt_tags, NULL,
 194                 N_("fetch all tags and associated objects"),
 195                 PARSE_OPT_NOARG),
 196         OPT_PASSTHRU('p', "prune", &opt_prune, NULL,
 197                 N_("prune remote-tracking branches no longer on remote"),
 198                 PARSE_OPT_NOARG),
 199         OPT_PASSTHRU('j', "jobs", &max_children, N_("n"),
 200                 N_("number of submodules pulled in parallel"),
 201                 PARSE_OPT_OPTARG),
 202         OPT_BOOL(0, "dry-run", &opt_dry_run,
 203                 N_("dry run")),
 204         OPT_PASSTHRU('k', "keep", &opt_keep, NULL,
 205                 N_("keep downloaded pack"),
 206                 PARSE_OPT_NOARG),
 207         OPT_PASSTHRU(0, "depth", &opt_depth, N_("depth"),
 208                 N_("deepen history of shallow clone"),
 209                 0),
 210         OPT_PASSTHRU(0, "unshallow", &opt_unshallow, NULL,
 211                 N_("convert to a complete repository"),
 212                 PARSE_OPT_NONEG | PARSE_OPT_NOARG),
 213         OPT_PASSTHRU(0, "update-shallow", &opt_update_shallow, NULL,
 214                 N_("accept refs that update .git/shallow"),
 215                 PARSE_OPT_NOARG),
 216         OPT_PASSTHRU(0, "refmap", &opt_refmap, N_("refmap"),
 217                 N_("specify fetch refmap"),
 218                 PARSE_OPT_NONEG),
 219         OPT_PASSTHRU('4',  "ipv4", &opt_ipv4, NULL,
 220                 N_("use IPv4 addresses only"),
 221                 PARSE_OPT_NOARG),
 222         OPT_PASSTHRU('6',  "ipv6", &opt_ipv6, NULL,
 223                 N_("use IPv6 addresses only"),
 224                 PARSE_OPT_NOARG),
 225
 226         OPT_END()
 227 };
 228
 229 /**
 230  * Pushes "-q" or "-v" switches into arr to match the opt_verbosity level.
 231  */
 232 static void argv_push_verbosity(struct argv_array *arr)
 233 {
 234         int verbosity;
 235
 236         for (verbosity = opt_verbosity; verbosity > 0; verbosity--)
 237                 argv_array_push(arr, "-v");
 238
 239         for (verbosity = opt_verbosity; verbosity < 0; verbosity++)
 240                 argv_array_push(arr, "-q");
 241 }
 242
 243 /**
 244  * Pushes "-f" switches into arr to match the opt_force level.
 245  */
 246 static void argv_push_force(struct argv_array *arr)
 247 {
 248         int force = opt_force;
 249         while (force-- > 0)
 250                 argv_array_push(arr, "-f");
 251 }
 252
 253 /**
 254  * Sets the GIT_REFLOG_ACTION environment variable to the concatenation of argv
 255  */
 256 static void set_reflog_message(int argc, const char **argv)
 257 {
 258         int i;
 259         struct strbuf msg = STRBUF_INIT;
 260
 261         for (i = 0; i < argc; i++) {
 262                 if (i)
 263                         strbuf_addch(&msg, ' ');
 264                 strbuf_addstr(&msg, argv[i]);
 265         }
 266
 267         setenv("GIT_REFLOG_ACTION", msg.buf, 0);
 268
 269         strbuf_release(&msg);
 270 }
 271
 272 /**
 273  * If pull.ff is unset, returns NULL. If pull.ff is "true", returns "--ff". If
 274  * pull.ff is "false", returns "--no-ff". If pull.ff is "only", returns
 275  * "--ff-only". Otherwise, if pull.ff is set to an invalid value, die with an
 276  * error.
 277  */
 278 static const char *config_get_ff(void)
 279 {
 280         const char *value;
 281
 282         if (git_config_get_value("pull.ff", &value))
 283                 return NULL;
 284
 285         switch (git_parse_maybe_bool(value)) {
 286         case 0:
 287                 return "--no-ff";
 288         case 1:
 289                 return "--ff";
 290         }
 291
 292         if (!strcmp(value, "only"))
 293                 return "--ff-only";
 294
 295         die(_("Invalid value for pull.ff: %s"), value);
 296 }
 297
 298 /**
 299  * Returns the default configured value for --rebase. It first looks for the
 300  * value of "branch.$curr_branch.rebase", where $curr_branch is the current
 301  * branch, and if HEAD is detached or the configuration key does not exist,
 302  * looks for the value of "pull.rebase". If both configuration keys do not
 303  * exist, returns REBASE_FALSE.
 304  */
 305 static enum rebase_type config_get_rebase(void)
 306 {
 307         struct branch *curr_branch = branch_get("HEAD");
 308         const char *value;
 309
 310         if (curr_branch) {
 311                 char *key = xstrfmt("branch.%s.rebase", curr_branch->name);
 312
 313                 if (!git_config_get_value(key, &value)) {
 314                         enum rebase_type ret = parse_config_rebase(key, value, 1);
 315                         free(key);
 316                         return ret;
 317                 }
 318
 319                 free(key);
 320         }
 321
 322         if (!git_config_get_value("pull.rebase", &value))
 323                 return parse_config_rebase("pull.rebase", value, 1);
 324
 325         return REBASE_FALSE;
 326 }
 327
 328 /**
 329  * Read config variables.
 330  */
 331 static int git_pull_config(const char *var, const char *value, void *cb)
 332 {
 333         if (!strcmp(var, "rebase.autostash")) {
 334                 config_autostash = git_config_bool(var, value);
 335                 return 0;
 336         } else if (!strcmp(var, "submodule.recurse")) {
 337                 recurse_submodules = git_config_bool(var, value) ?
 338                         RECURSE_SUBMODULES_ON : RECURSE_SUBMODULES_OFF;
 339                 return 0;
 340         }
 341         return git_default_config(var, value, cb);
 342 }
 343
 344 /**
 345  * Appends merge candidates from FETCH_HEAD that are not marked not-for-merge
 346  * into merge_heads.
 347  */
 348 static void get_merge_heads(struct oid_array *merge_heads)
 349 {
 350         const char *filename = git_path_fetch_head();
 351         FILE *fp;
 352         struct strbuf sb = STRBUF_INIT;
 353         struct object_id oid;
 354
 355         fp = xfopen(filename, "r");
 356         while (strbuf_getline_lf(&sb, fp) != EOF) {
 357                 if (get_oid_hex(sb.buf, &oid))
 358                         continue;  /* invalid line: does not start with SHA1 */
 359                 if (starts_with(sb.buf + GIT_SHA1_HEXSZ, "\tnot-for-merge\t"))
 360                         continue;  /* ref is not-for-merge */
 361                 oid_array_append(merge_heads, &oid);
 362         }
 363         fclose(fp);
 364         strbuf_release(&sb);
 365 }
 366
 367 /**
 368  * Used by die_no_merge_candidates() as a for_each_remote() callback to
 369  * retrieve the name of the remote if the repository only has one remote.
 370  */
 371 static int get_only_remote(struct remote *remote, void *cb_data)
 372 {
 373         const char **remote_name = cb_data;
 374
 375         if (*remote_name)
 376                 return -1;
 377
 378         *remote_name = remote->name;
 379         return 0;
 380 }
 381
 382 /**
 383  * Dies with the appropriate reason for why there are no merge candidates:
 384  *
 385  * 1. We fetched from a specific remote, and a refspec was given, but it ended
 386  *    up not fetching anything. This is usually because the user provided a
 387  *    wildcard refspec which had no matches on the remote end.
 388  *
 389  * 2. We fetched from a non-default remote, but didn't specify a branch to
 390  *    merge. We can't use the configured one because it applies to the default
 391  *    remote, thus the user must specify the branches to merge.
 392  *
 393  * 3. We fetched from the branch's or repo's default remote, but:
 394  *
 395  *    a. We are not on a branch, so there will never be a configured branch to
 396  *       merge with.
 397  *
 398  *    b. We are on a branch, but there is no configured branch to merge with.
 399  *
 400  * 4. We fetched from the branch's or repo's default remote, but the configured
 401  *    branch to merge didn't get fetched. (Either it doesn't exist, or wasn't
 402  *    part of the configured fetch refspec.)
 403  */
 404 static void NORETURN die_no_merge_candidates(const char *repo, const char **refspecs)
 405 {
 406         struct branch *curr_branch = branch_get("HEAD");
 407         const char *remote = curr_branch ? curr_branch->remote_name : NULL;
 408
 409         if (*refspecs) {
 410                 if (opt_rebase)
 411                         fprintf_ln(stderr, _("There is no candidate for rebasing against among the refs that you just fetched."));
 412                 else
 413                         fprintf_ln(stderr, _("There are no candidates for merging among the refs that you just fetched."));
 414                 fprintf_ln(stderr, _("Generally this means that you provided a wildcard refspec which had no\n"
 415                                         "matches on the remote end."));
 416         } else if (repo && curr_branch && (!remote || strcmp(repo, remote))) {
 417                 fprintf_ln(stderr, _("You asked to pull from the remote '%s', but did not specify\n"
 418                         "a branch. Because this is not the default configured remote\n"
 419                         "for your current branch, you must specify a branch on the command line."),
 420                         repo);
 421         } else if (!curr_branch) {
 422                 fprintf_ln(stderr, _("You are not currently on a 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         } else if (!curr_branch->merge_nr) {
 432                 const char *remote_name = NULL;
 433
 434                 if (for_each_remote(get_only_remote, &remote_name) || !remote_name)
 435                         remote_name = _("<remote>");
 436
 437                 fprintf_ln(stderr, _("There is no tracking information for the current branch."));
 438                 if (opt_rebase)
 439                         fprintf_ln(stderr, _("Please specify which branch you want to rebase against."));
 440                 else
 441                         fprintf_ln(stderr, _("Please specify which branch you want to merge with."));
 442                 fprintf_ln(stderr, _("See git-pull(1) for details."));
 443                 fprintf(stderr, "\n");
 444                 fprintf_ln(stderr, "    git pull %s %s", _("<remote>"), _("<branch>"));
 445                 fprintf(stderr, "\n");
 446                 fprintf_ln(stderr, _("If you wish to set tracking information for this branch you can do so with:"));
 447                 fprintf(stderr, "\n");
 448                 fprintf_ln(stderr, "    git branch --set-upstream-to=%s/%s %s\n",
 449                                 remote_name, _("<branch>"), curr_branch->name);
 450         } else
 451                 fprintf_ln(stderr, _("Your configuration specifies to merge with the ref '%s'\n"
 452                         "from the remote, but no such ref was fetched."),
 453                         *curr_branch->merge_name);
 454         exit(1);
 455 }
 456
 457 /**
 458  * Parses argv into [<repo> [<refspecs>...]], returning their values in `repo`
 459  * as a string and `refspecs` as a null-terminated array of strings. If `repo`
 460  * is not provided in argv, it is set to NULL.
 461  */
 462 static void parse_repo_refspecs(int argc, const char **argv, const char **repo,
 463                 const char ***refspecs)
 464 {
 465         if (argc > 0) {
 466                 *repo = *argv++;
 467                 argc--;
 468         } else
 469                 *repo = NULL;
 470         *refspecs = argv;
 471 }
 472
 473 /**
 474  * Runs git-fetch, returning its exit status. `repo` and `refspecs` are the
 475  * repository and refspecs to fetch, or NULL if they are not provided.
 476  */
 477 static int run_fetch(const char *repo, const char **refspecs)
 478 {
 479         struct argv_array args = ARGV_ARRAY_INIT;
 480         int ret;
 481
 482         argv_array_pushl(&args, "fetch", "--update-head-ok", NULL);
 483
 484         /* Shared options */
 485         argv_push_verbosity(&args);
 486         if (opt_progress)
 487                 argv_array_push(&args, opt_progress);
 488
 489         /* Options passed to git-fetch */
 490         if (opt_all)
 491                 argv_array_push(&args, opt_all);
 492         if (opt_append)
 493                 argv_array_push(&args, opt_append);
 494         if (opt_upload_pack)
 495                 argv_array_push(&args, opt_upload_pack);
 496         argv_push_force(&args);
 497         if (opt_tags)
 498                 argv_array_push(&args, opt_tags);
 499         if (opt_prune)
 500                 argv_array_push(&args, opt_prune);
 501         if (recurse_submodules != RECURSE_SUBMODULES_DEFAULT)
 502                 switch (recurse_submodules) {
 503                 case RECURSE_SUBMODULES_ON:
 504                         argv_array_push(&args, "--recurse-submodules=on");
 505                         break;
 506                 case RECURSE_SUBMODULES_OFF:
 507                         argv_array_push(&args, "--recurse-submodules=no");
 508                         break;
 509                 case RECURSE_SUBMODULES_ON_DEMAND:
 510                         argv_array_push(&args, "--recurse-submodules=on-demand");
 511                         break;
 512                 default:
 513                         BUG("submodule recursion option not understood");
 514                 }
 515         if (max_children)
 516                 argv_array_push(&args, max_children);
 517         if (opt_dry_run)
 518                 argv_array_push(&args, "--dry-run");
 519         if (opt_keep)
 520                 argv_array_push(&args, opt_keep);
 521         if (opt_depth)
 522                 argv_array_push(&args, opt_depth);
 523         if (opt_unshallow)
 524                 argv_array_push(&args, opt_unshallow);
 525         if (opt_update_shallow)
 526                 argv_array_push(&args, opt_update_shallow);
 527         if (opt_refmap)
 528                 argv_array_push(&args, opt_refmap);
 529         if (opt_ipv4)
 530                 argv_array_push(&args, opt_ipv4);
 531         if (opt_ipv6)
 532                 argv_array_push(&args, opt_ipv6);
 533
 534         if (repo) {
 535                 argv_array_push(&args, repo);
 536                 argv_array_pushv(&args, refspecs);
 537         } else if (*refspecs)
 538                 die("BUG: refspecs without repo?");
 539         ret = run_command_v_opt(args.argv, RUN_GIT_CMD);
 540         argv_array_clear(&args);
 541         return ret;
 542 }
 543
 544 /**
 545  * "Pulls into void" by branching off merge_head.
 546  */
 547 static int pull_into_void(const struct object_id *merge_head,
 548                 const struct object_id *curr_head)
 549 {
 550         /*
 551          * Two-way merge: we treat the index as based on an empty tree,
 552          * and try to fast-forward to HEAD. This ensures we will not lose
 553          * index/worktree changes that the user already made on the unborn
 554          * branch.
 555          */
 556         if (checkout_fast_forward(&empty_tree_oid, merge_head, 0))
 557                 return 1;
 558
 559         if (update_ref("initial pull", "HEAD", merge_head->hash, curr_head->hash, 0, UPDATE_REFS_DIE_ON_ERR))
 560                 return 1;
 561
 562         return 0;
 563 }
 564
 565 static int rebase_submodules(void)
 566 {
 567         struct child_process cp = CHILD_PROCESS_INIT;
 568
 569         cp.git_cmd = 1;
 570         cp.no_stdin = 1;
 571         argv_array_pushl(&cp.args, "submodule", "update",
 572                                    "--recursive", "--rebase", NULL);
 573
 574         return run_command(&cp);
 575 }
 576
 577 static int update_submodules(void)
 578 {
 579         struct child_process cp = CHILD_PROCESS_INIT;
 580
 581         cp.git_cmd = 1;
 582         cp.no_stdin = 1;
 583         argv_array_pushl(&cp.args, "submodule", "update",
 584                                    "--recursive", "--checkout", NULL);
 585
 586         return run_command(&cp);
 587 }
 588
 589 /**
 590  * Runs git-merge, returning its exit status.
 591  */
 592 static int run_merge(void)
 593 {
 594         int ret;
 595         struct argv_array args = ARGV_ARRAY_INIT;
 596
 597         argv_array_pushl(&args, "merge", NULL);
 598
 599         /* Shared options */
 600         argv_push_verbosity(&args);
 601         if (opt_progress)
 602                 argv_array_push(&args, opt_progress);
 603
 604         /* Options passed to git-merge */
 605         if (opt_diffstat)
 606                 argv_array_push(&args, opt_diffstat);
 607         if (opt_log)
 608                 argv_array_push(&args, opt_log);
 609         if (opt_squash)
 610                 argv_array_push(&args, opt_squash);
 611         if (opt_commit)
 612                 argv_array_push(&args, opt_commit);
 613         if (opt_edit)
 614                 argv_array_push(&args, opt_edit);
 615         if (opt_ff)
 616                 argv_array_push(&args, opt_ff);
 617         if (opt_verify_signatures)
 618                 argv_array_push(&args, opt_verify_signatures);
 619         argv_array_pushv(&args, opt_strategies.argv);
 620         argv_array_pushv(&args, opt_strategy_opts.argv);
 621         if (opt_gpg_sign)
 622                 argv_array_push(&args, opt_gpg_sign);
 623         if (opt_allow_unrelated_histories > 0)
 624                 argv_array_push(&args, "--allow-unrelated-histories");
 625
 626         argv_array_push(&args, "FETCH_HEAD");
 627         ret = run_command_v_opt(args.argv, RUN_GIT_CMD);
 628         argv_array_clear(&args);
 629         return ret;
 630 }
 631
 632 /**
 633  * Returns remote's upstream branch for the current branch. If remote is NULL,
 634  * the current branch's configured default remote is used. Returns NULL if
 635  * `remote` does not name a valid remote, HEAD does not point to a branch,
 636  * remote is not the branch's configured remote or the branch does not have any
 637  * configured upstream branch.
 638  */
 639 static const char *get_upstream_branch(const char *remote)
 640 {
 641         struct remote *rm;
 642         struct branch *curr_branch;
 643         const char *curr_branch_remote;
 644
 645         rm = remote_get(remote);
 646         if (!rm)
 647                 return NULL;
 648
 649         curr_branch = branch_get("HEAD");
 650         if (!curr_branch)
 651                 return NULL;
 652
 653         curr_branch_remote = remote_for_branch(curr_branch, NULL);
 654         assert(curr_branch_remote);
 655
 656         if (strcmp(curr_branch_remote, rm->name))
 657                 return NULL;
 658
 659         return branch_get_upstream(curr_branch, NULL);
 660 }
 661
 662 /**
 663  * Derives the remote tracking branch from the remote and refspec.
 664  *
 665  * FIXME: The current implementation assumes the default mapping of
 666  * refs/heads/<branch_name> to refs/remotes/<remote_name>/<branch_name>.
 667  */
 668 static const char *get_tracking_branch(const char *remote, const char *refspec)
 669 {
 670         struct refspec *spec;
 671         const char *spec_src;
 672         const char *merge_branch;
 673
 674         spec = parse_fetch_refspec(1, &refspec);
 675         spec_src = spec->src;
 676         if (!*spec_src || !strcmp(spec_src, "HEAD"))
 677                 spec_src = "HEAD";
 678         else if (skip_prefix(spec_src, "heads/", &spec_src))
 679                 ;
 680         else if (skip_prefix(spec_src, "refs/heads/", &spec_src))
 681                 ;
 682         else if (starts_with(spec_src, "refs/") ||
 683                 starts_with(spec_src, "tags/") ||
 684                 starts_with(spec_src, "remotes/"))
 685                 spec_src = "";
 686
 687         if (*spec_src) {
 688                 if (!strcmp(remote, "."))
 689                         merge_branch = mkpath("refs/heads/%s", spec_src);
 690                 else
 691                         merge_branch = mkpath("refs/remotes/%s/%s", remote, spec_src);
 692         } else
 693                 merge_branch = NULL;
 694
 695         free_refspec(1, spec);
 696         return merge_branch;
 697 }
 698
 699 /**
 700  * Given the repo and refspecs, sets fork_point to the point at which the
 701  * current branch forked from its remote tracking branch. Returns 0 on success,
 702  * -1 on failure.
 703  */
 704 static int get_rebase_fork_point(struct object_id *fork_point, const char *repo,
 705                 const char *refspec)
 706 {
 707         int ret;
 708         struct branch *curr_branch;
 709         const char *remote_branch;
 710         struct child_process cp = CHILD_PROCESS_INIT;
 711         struct strbuf sb = STRBUF_INIT;
 712
 713         curr_branch = branch_get("HEAD");
 714         if (!curr_branch)
 715                 return -1;
 716
 717         if (refspec)
 718                 remote_branch = get_tracking_branch(repo, refspec);
 719         else
 720                 remote_branch = get_upstream_branch(repo);
 721
 722         if (!remote_branch)
 723                 return -1;
 724
 725         argv_array_pushl(&cp.args, "merge-base", "--fork-point",
 726                         remote_branch, curr_branch->name, NULL);
 727         cp.no_stdin = 1;
 728         cp.no_stderr = 1;
 729         cp.git_cmd = 1;
 730
 731         ret = capture_command(&cp, &sb, GIT_SHA1_HEXSZ);
 732         if (ret)
 733                 goto cleanup;
 734
 735         ret = get_oid_hex(sb.buf, fork_point);
 736         if (ret)
 737                 goto cleanup;
 738
 739 cleanup:
 740         strbuf_release(&sb);
 741         return ret ? -1 : 0;
 742 }
 743
 744 /**
 745  * Sets merge_base to the octopus merge base of curr_head, merge_head and
 746  * fork_point. Returns 0 if a merge base is found, 1 otherwise.
 747  */
 748 static int get_octopus_merge_base(struct object_id *merge_base,
 749                 const struct object_id *curr_head,
 750                 const struct object_id *merge_head,
 751                 const struct object_id *fork_point)
 752 {
 753         struct commit_list *revs = NULL, *result;
 754
 755         commit_list_insert(lookup_commit_reference(curr_head), &revs);
 756         commit_list_insert(lookup_commit_reference(merge_head), &revs);
 757         if (!is_null_oid(fork_point))
 758                 commit_list_insert(lookup_commit_reference(fork_point), &revs);
 759
 760         result = get_octopus_merge_bases(revs);
 761         free_commit_list(revs);
 762         reduce_heads_replace(&result);
 763
 764         if (!result)
 765                 return 1;
 766
 767         oidcpy(merge_base, &result->item->object.oid);
 768         free_commit_list(result);
 769         return 0;
 770 }
 771
 772 /**
 773  * Given the current HEAD SHA1, the merge head returned from git-fetch and the
 774  * fork point calculated by get_rebase_fork_point(), runs git-rebase with the
 775  * appropriate arguments and returns its exit status.
 776  */
 777 static int run_rebase(const struct object_id *curr_head,
 778                 const struct object_id *merge_head,
 779                 const struct object_id *fork_point)
 780 {
 781         int ret;
 782         struct object_id oct_merge_base;
 783         struct argv_array args = ARGV_ARRAY_INIT;
 784
 785         if (!get_octopus_merge_base(&oct_merge_base, curr_head, merge_head, fork_point))
 786                 if (!is_null_oid(fork_point) && !oidcmp(&oct_merge_base, fork_point))
 787                         fork_point = NULL;
 788
 789         argv_array_push(&args, "rebase");
 790
 791         /* Shared options */
 792         argv_push_verbosity(&args);
 793
 794         /* Options passed to git-rebase */
 795         if (opt_rebase == REBASE_PRESERVE)
 796                 argv_array_push(&args, "--preserve-merges");
 797         else if (opt_rebase == REBASE_INTERACTIVE)
 798                 argv_array_push(&args, "--interactive");
 799         if (opt_diffstat)
 800                 argv_array_push(&args, opt_diffstat);
 801         argv_array_pushv(&args, opt_strategies.argv);
 802         argv_array_pushv(&args, opt_strategy_opts.argv);
 803         if (opt_gpg_sign)
 804                 argv_array_push(&args, opt_gpg_sign);
 805         if (opt_autostash == 0)
 806                 argv_array_push(&args, "--no-autostash");
 807         else if (opt_autostash == 1)
 808                 argv_array_push(&args, "--autostash");
 809         if (opt_verify_signatures &&
 810             !strcmp(opt_verify_signatures, "--verify-signatures"))
 811                 warning(_("ignoring --verify-signatures for rebase"));
 812
 813         argv_array_push(&args, "--onto");
 814         argv_array_push(&args, oid_to_hex(merge_head));
 815
 816         if (fork_point && !is_null_oid(fork_point))
 817                 argv_array_push(&args, oid_to_hex(fork_point));
 818         else
 819                 argv_array_push(&args, oid_to_hex(merge_head));
 820
 821         ret = run_command_v_opt(args.argv, RUN_GIT_CMD);
 822         argv_array_clear(&args);
 823         return ret;
 824 }
 825
 826 int cmd_pull(int argc, const char **argv, const char *prefix)
 827 {
 828         const char *repo, **refspecs;
 829         struct oid_array merge_heads = OID_ARRAY_INIT;
 830         struct object_id orig_head, curr_head;
 831         struct object_id rebase_fork_point;
 832         int autostash;
 833
 834         if (!getenv("GIT_REFLOG_ACTION"))
 835                 set_reflog_message(argc, argv);
 836
 837         git_config(git_pull_config, NULL);
 838
 839         argc = parse_options(argc, argv, prefix, pull_options, pull_usage, 0);
 840
 841         parse_repo_refspecs(argc, argv, &repo, &refspecs);
 842
 843         if (!opt_ff)
 844                 opt_ff = xstrdup_or_null(config_get_ff());
 845
 846         if (opt_rebase < 0)
 847                 opt_rebase = config_get_rebase();
 848
 849         if (read_cache_unmerged())
 850                 die_resolve_conflict("pull");
 851
 852         if (file_exists(git_path_merge_head()))
 853                 die_conclude_merge();
 854
 855         if (get_oid("HEAD", &orig_head))
 856                 oidclr(&orig_head);
 857
 858         if (!opt_rebase && opt_autostash != -1)
 859                 die(_("--[no-]autostash option is only valid with --rebase."));
 860
 861         autostash = config_autostash;
 862         if (opt_rebase) {
 863                 if (opt_autostash != -1)
 864                         autostash = opt_autostash;
 865
 866                 if (is_null_oid(&orig_head) && !is_cache_unborn())
 867                         die(_("Updating an unborn branch with changes added to the index."));
 868
 869                 if (!autostash)
 870                         require_clean_work_tree(N_("pull with rebase"),
 871                                 _("please commit or stash them."), 1, 0);
 872
 873                 if (get_rebase_fork_point(&rebase_fork_point, repo, *refspecs))
 874                         oidclr(&rebase_fork_point);
 875         }
 876
 877         if (run_fetch(repo, refspecs))
 878                 return 1;
 879
 880         if (opt_dry_run)
 881                 return 0;
 882
 883         if (get_oid("HEAD", &curr_head))
 884                 oidclr(&curr_head);
 885
 886         if (!is_null_oid(&orig_head) && !is_null_oid(&curr_head) &&
 887                         oidcmp(&orig_head, &curr_head)) {
 888                 /*
 889                  * The fetch involved updating the current branch.
 890                  *
 891                  * The working tree and the index file are still based on
 892                  * orig_head commit, but we are merging into curr_head.
 893                  * Update the working tree to match curr_head.
 894                  */
 895
 896                 warning(_("fetch updated the current branch head.\n"
 897                         "fast-forwarding your working tree from\n"
 898                         "commit %s."), oid_to_hex(&orig_head));
 899
 900                 if (checkout_fast_forward(&orig_head, &curr_head, 0))
 901                         die(_("Cannot fast-forward your working tree.\n"
 902                                 "After making sure that you saved anything precious from\n"
 903                                 "$ git diff %s\n"
 904                                 "output, run\n"
 905                                 "$ git reset --hard\n"
 906                                 "to recover."), oid_to_hex(&orig_head));
 907         }
 908
 909         get_merge_heads(&merge_heads);
 910
 911         if (!merge_heads.nr)
 912                 die_no_merge_candidates(repo, refspecs);
 913
 914         if (is_null_oid(&orig_head)) {
 915                 if (merge_heads.nr > 1)
 916                         die(_("Cannot merge multiple branches into empty head."));
 917                 return pull_into_void(merge_heads.oid, &curr_head);
 918         }
 919         if (opt_rebase && merge_heads.nr > 1)
 920                 die(_("Cannot rebase onto multiple branches."));
 921
 922         if (opt_rebase) {
 923                 int ret = 0;
 924                 if ((recurse_submodules == RECURSE_SUBMODULES_ON ||
 925                      recurse_submodules == RECURSE_SUBMODULES_ON_DEMAND) &&
 926                     submodule_touches_in_range(&rebase_fork_point, &curr_head))
 927                         die(_("cannot rebase with locally recorded submodule modifications"));
 928                 if (!autostash) {
 929                         struct commit_list *list = NULL;
 930                         struct commit *merge_head, *head;
 931
 932                         head = lookup_commit_reference(&orig_head);
 933                         commit_list_insert(head, &list);
 934                         merge_head = lookup_commit_reference(&merge_heads.oid[0]);
 935                         if (is_descendant_of(merge_head, list)) {
 936                                 /* we can fast-forward this without invoking rebase */
 937                                 opt_ff = "--ff-only";
 938                                 ret = run_merge();
 939                         }
 940                 }
 941                 ret = run_rebase(&curr_head, merge_heads.oid, &rebase_fork_point);
 942
 943                 if (!ret && (recurse_submodules == RECURSE_SUBMODULES_ON ||
 944                              recurse_submodules == RECURSE_SUBMODULES_ON_DEMAND))
 945                         ret = rebase_submodules();
 946
 947                 return ret;
 948         } else {
 949                 int ret = run_merge();
 950                 if (!ret && (recurse_submodules == RECURSE_SUBMODULES_ON ||
 951                              recurse_submodules == RECURSE_SUBMODULES_ON_DEMAND))
 952                         ret = update_submodules();
 953                 return ret;
 954         }
 955 }