builtin / pull.con commit Merge branch 'gp/status-rebase-i-info' (178d2c7)
   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 "lockfile.h"
  19
  20enum rebase_type {
  21        REBASE_INVALID = -1,
  22        REBASE_FALSE = 0,
  23        REBASE_TRUE,
  24        REBASE_PRESERVE
  25};
  26
  27/**
  28 * Parses the value of --rebase. If value is a false value, returns
  29 * REBASE_FALSE. If value is a true value, returns REBASE_TRUE. If value is
  30 * "preserve", returns REBASE_PRESERVE. If value is a invalid value, dies with
  31 * a fatal error if fatal is true, otherwise returns REBASE_INVALID.
  32 */
  33static enum rebase_type parse_config_rebase(const char *key, const char *value,
  34                int fatal)
  35{
  36        int v = git_config_maybe_bool("pull.rebase", value);
  37
  38        if (!v)
  39                return REBASE_FALSE;
  40        else if (v > 0)
  41                return REBASE_TRUE;
  42        else if (!strcmp(value, "preserve"))
  43                return REBASE_PRESERVE;
  44
  45        if (fatal)
  46                die(_("Invalid value for %s: %s"), key, value);
  47        else
  48                error(_("Invalid value for %s: %s"), key, value);
  49
  50        return REBASE_INVALID;
  51}
  52
  53/**
  54 * Callback for --rebase, which parses arg with parse_config_rebase().
  55 */
  56static int parse_opt_rebase(const struct option *opt, const char *arg, int unset)
  57{
  58        enum rebase_type *value = opt->value;
  59
  60        if (arg)
  61                *value = parse_config_rebase("--rebase", arg, 0);
  62        else
  63                *value = unset ? REBASE_FALSE : REBASE_TRUE;
  64        return *value == REBASE_INVALID ? -1 : 0;
  65}
  66
  67static const char * const pull_usage[] = {
  68        N_("git pull [options] [<repository> [<refspec>...]]"),
  69        NULL
  70};
  71
  72/* Shared options */
  73static int opt_verbosity;
  74static char *opt_progress;
  75
  76/* Options passed to git-merge or git-rebase */
  77static enum rebase_type opt_rebase = -1;
  78static char *opt_diffstat;
  79static char *opt_log;
  80static char *opt_squash;
  81static char *opt_commit;
  82static char *opt_edit;
  83static char *opt_ff;
  84static char *opt_verify_signatures;
  85static struct argv_array opt_strategies = ARGV_ARRAY_INIT;
  86static struct argv_array opt_strategy_opts = ARGV_ARRAY_INIT;
  87static char *opt_gpg_sign;
  88
  89/* Options passed to git-fetch */
  90static char *opt_all;
  91static char *opt_append;
  92static char *opt_upload_pack;
  93static int opt_force;
  94static char *opt_tags;
  95static char *opt_prune;
  96static char *opt_recurse_submodules;
  97static int opt_dry_run;
  98static char *opt_keep;
  99static char *opt_depth;
 100static char *opt_unshallow;
 101static char *opt_update_shallow;
 102static char *opt_refmap;
 103
 104static struct option pull_options[] = {
 105        /* Shared options */
 106        OPT__VERBOSITY(&opt_verbosity),
 107        OPT_PASSTHRU(0, "progress", &opt_progress, NULL,
 108                N_("force progress reporting"),
 109                PARSE_OPT_NOARG),
 110
 111        /* Options passed to git-merge or git-rebase */
 112        OPT_GROUP(N_("Options related to merging")),
 113        { OPTION_CALLBACK, 'r', "rebase", &opt_rebase,
 114          N_("false|true|preserve"),
 115          N_("incorporate changes by rebasing rather than merging"),
 116          PARSE_OPT_OPTARG, parse_opt_rebase },
 117        OPT_PASSTHRU('n', NULL, &opt_diffstat, NULL,
 118                N_("do not show a diffstat at the end of the merge"),
 119                PARSE_OPT_NOARG | PARSE_OPT_NONEG),
 120        OPT_PASSTHRU(0, "stat", &opt_diffstat, NULL,
 121                N_("show a diffstat at the end of the merge"),
 122                PARSE_OPT_NOARG),
 123        OPT_PASSTHRU(0, "summary", &opt_diffstat, NULL,
 124                N_("(synonym to --stat)"),
 125                PARSE_OPT_NOARG | PARSE_OPT_HIDDEN),
 126        OPT_PASSTHRU(0, "log", &opt_log, N_("n"),
 127                N_("add (at most <n>) entries from shortlog to merge commit message"),
 128                PARSE_OPT_OPTARG),
 129        OPT_PASSTHRU(0, "squash", &opt_squash, NULL,
 130                N_("create a single commit instead of doing a merge"),
 131                PARSE_OPT_NOARG),
 132        OPT_PASSTHRU(0, "commit", &opt_commit, NULL,
 133                N_("perform a commit if the merge succeeds (default)"),
 134                PARSE_OPT_NOARG),
 135        OPT_PASSTHRU(0, "edit", &opt_edit, NULL,
 136                N_("edit message before committing"),
 137                PARSE_OPT_NOARG),
 138        OPT_PASSTHRU(0, "ff", &opt_ff, NULL,
 139                N_("allow fast-forward"),
 140                PARSE_OPT_NOARG),
 141        OPT_PASSTHRU(0, "ff-only", &opt_ff, NULL,
 142                N_("abort if fast-forward is not possible"),
 143                PARSE_OPT_NOARG | PARSE_OPT_NONEG),
 144        OPT_PASSTHRU(0, "verify-signatures", &opt_verify_signatures, NULL,
 145                N_("verify that the named commit has a valid GPG signature"),
 146                PARSE_OPT_NOARG),
 147        OPT_PASSTHRU_ARGV('s', "strategy", &opt_strategies, N_("strategy"),
 148                N_("merge strategy to use"),
 149                0),
 150        OPT_PASSTHRU_ARGV('X', "strategy-option", &opt_strategy_opts,
 151                N_("option=value"),
 152                N_("option for selected merge strategy"),
 153                0),
 154        OPT_PASSTHRU('S', "gpg-sign", &opt_gpg_sign, N_("key-id"),
 155                N_("GPG sign commit"),
 156                PARSE_OPT_OPTARG),
 157
 158        /* Options passed to git-fetch */
 159        OPT_GROUP(N_("Options related to fetching")),
 160        OPT_PASSTHRU(0, "all", &opt_all, NULL,
 161                N_("fetch from all remotes"),
 162                PARSE_OPT_NOARG),
 163        OPT_PASSTHRU('a', "append", &opt_append, NULL,
 164                N_("append to .git/FETCH_HEAD instead of overwriting"),
 165                PARSE_OPT_NOARG),
 166        OPT_PASSTHRU(0, "upload-pack", &opt_upload_pack, N_("path"),
 167                N_("path to upload pack on remote end"),
 168                0),
 169        OPT__FORCE(&opt_force, N_("force overwrite of local branch")),
 170        OPT_PASSTHRU('t', "tags", &opt_tags, NULL,
 171                N_("fetch all tags and associated objects"),
 172                PARSE_OPT_NOARG),
 173        OPT_PASSTHRU('p', "prune", &opt_prune, NULL,
 174                N_("prune remote-tracking branches no longer on remote"),
 175                PARSE_OPT_NOARG),
 176        OPT_PASSTHRU(0, "recurse-submodules", &opt_recurse_submodules,
 177                N_("on-demand"),
 178                N_("control recursive fetching of submodules"),
 179                PARSE_OPT_OPTARG),
 180        OPT_BOOL(0, "dry-run", &opt_dry_run,
 181                N_("dry run")),
 182        OPT_PASSTHRU('k', "keep", &opt_keep, NULL,
 183                N_("keep downloaded pack"),
 184                PARSE_OPT_NOARG),
 185        OPT_PASSTHRU(0, "depth", &opt_depth, N_("depth"),
 186                N_("deepen history of shallow clone"),
 187                0),
 188        OPT_PASSTHRU(0, "unshallow", &opt_unshallow, NULL,
 189                N_("convert to a complete repository"),
 190                PARSE_OPT_NONEG | PARSE_OPT_NOARG),
 191        OPT_PASSTHRU(0, "update-shallow", &opt_update_shallow, NULL,
 192                N_("accept refs that update .git/shallow"),
 193                PARSE_OPT_NOARG),
 194        OPT_PASSTHRU(0, "refmap", &opt_refmap, N_("refmap"),
 195                N_("specify fetch refmap"),
 196                PARSE_OPT_NONEG),
 197
 198        OPT_END()
 199};
 200
 201/**
 202 * Pushes "-q" or "-v" switches into arr to match the opt_verbosity level.
 203 */
 204static void argv_push_verbosity(struct argv_array *arr)
 205{
 206        int verbosity;
 207
 208        for (verbosity = opt_verbosity; verbosity > 0; verbosity--)
 209                argv_array_push(arr, "-v");
 210
 211        for (verbosity = opt_verbosity; verbosity < 0; verbosity++)
 212                argv_array_push(arr, "-q");
 213}
 214
 215/**
 216 * Pushes "-f" switches into arr to match the opt_force level.
 217 */
 218static void argv_push_force(struct argv_array *arr)
 219{
 220        int force = opt_force;
 221        while (force-- > 0)
 222                argv_array_push(arr, "-f");
 223}
 224
 225/**
 226 * Sets the GIT_REFLOG_ACTION environment variable to the concatenation of argv
 227 */
 228static void set_reflog_message(int argc, const char **argv)
 229{
 230        int i;
 231        struct strbuf msg = STRBUF_INIT;
 232
 233        for (i = 0; i < argc; i++) {
 234                if (i)
 235                        strbuf_addch(&msg, ' ');
 236                strbuf_addstr(&msg, argv[i]);
 237        }
 238
 239        setenv("GIT_REFLOG_ACTION", msg.buf, 0);
 240
 241        strbuf_release(&msg);
 242}
 243
 244/**
 245 * If pull.ff is unset, returns NULL. If pull.ff is "true", returns "--ff". If
 246 * pull.ff is "false", returns "--no-ff". If pull.ff is "only", returns
 247 * "--ff-only". Otherwise, if pull.ff is set to an invalid value, die with an
 248 * error.
 249 */
 250static const char *config_get_ff(void)
 251{
 252        const char *value;
 253
 254        if (git_config_get_value("pull.ff", &value))
 255                return NULL;
 256
 257        switch (git_config_maybe_bool("pull.ff", value)) {
 258        case 0:
 259                return "--no-ff";
 260        case 1:
 261                return "--ff";
 262        }
 263
 264        if (!strcmp(value, "only"))
 265                return "--ff-only";
 266
 267        die(_("Invalid value for pull.ff: %s"), value);
 268}
 269
 270/**
 271 * Returns the default configured value for --rebase. It first looks for the
 272 * value of "branch.$curr_branch.rebase", where $curr_branch is the current
 273 * branch, and if HEAD is detached or the configuration key does not exist,
 274 * looks for the value of "pull.rebase". If both configuration keys do not
 275 * exist, returns REBASE_FALSE.
 276 */
 277static enum rebase_type config_get_rebase(void)
 278{
 279        struct branch *curr_branch = branch_get("HEAD");
 280        const char *value;
 281
 282        if (curr_branch) {
 283                char *key = xstrfmt("branch.%s.rebase", curr_branch->name);
 284
 285                if (!git_config_get_value(key, &value)) {
 286                        enum rebase_type ret = parse_config_rebase(key, value, 1);
 287                        free(key);
 288                        return ret;
 289                }
 290
 291                free(key);
 292        }
 293
 294        if (!git_config_get_value("pull.rebase", &value))
 295                return parse_config_rebase("pull.rebase", value, 1);
 296
 297        return REBASE_FALSE;
 298}
 299
 300/**
 301 * Returns 1 if there are unstaged changes, 0 otherwise.
 302 */
 303static int has_unstaged_changes(const char *prefix)
 304{
 305        struct rev_info rev_info;
 306        int result;
 307
 308        init_revisions(&rev_info, prefix);
 309        DIFF_OPT_SET(&rev_info.diffopt, IGNORE_SUBMODULES);
 310        DIFF_OPT_SET(&rev_info.diffopt, QUICK);
 311        diff_setup_done(&rev_info.diffopt);
 312        result = run_diff_files(&rev_info, 0);
 313        return diff_result_code(&rev_info.diffopt, result);
 314}
 315
 316/**
 317 * Returns 1 if there are uncommitted changes, 0 otherwise.
 318 */
 319static int has_uncommitted_changes(const char *prefix)
 320{
 321        struct rev_info rev_info;
 322        int result;
 323
 324        if (is_cache_unborn())
 325                return 0;
 326
 327        init_revisions(&rev_info, prefix);
 328        DIFF_OPT_SET(&rev_info.diffopt, IGNORE_SUBMODULES);
 329        DIFF_OPT_SET(&rev_info.diffopt, QUICK);
 330        add_head_to_pending(&rev_info);
 331        diff_setup_done(&rev_info.diffopt);
 332        result = run_diff_index(&rev_info, 1);
 333        return diff_result_code(&rev_info.diffopt, result);
 334}
 335
 336/**
 337 * If the work tree has unstaged or uncommitted changes, dies with the
 338 * appropriate message.
 339 */
 340static void die_on_unclean_work_tree(const char *prefix)
 341{
 342        struct lock_file *lock_file = xcalloc(1, sizeof(*lock_file));
 343        int do_die = 0;
 344
 345        hold_locked_index(lock_file, 0);
 346        refresh_cache(REFRESH_QUIET);
 347        update_index_if_able(&the_index, lock_file);
 348        rollback_lock_file(lock_file);
 349
 350        if (has_unstaged_changes(prefix)) {
 351                error(_("Cannot pull with rebase: You have unstaged changes."));
 352                do_die = 1;
 353        }
 354
 355        if (has_uncommitted_changes(prefix)) {
 356                if (do_die)
 357                        error(_("Additionally, your index contains uncommitted changes."));
 358                else
 359                        error(_("Cannot pull with rebase: Your index contains uncommitted changes."));
 360                do_die = 1;
 361        }
 362
 363        if (do_die)
 364                exit(1);
 365}
 366
 367/**
 368 * Appends merge candidates from FETCH_HEAD that are not marked not-for-merge
 369 * into merge_heads.
 370 */
 371static void get_merge_heads(struct sha1_array *merge_heads)
 372{
 373        const char *filename = git_path("FETCH_HEAD");
 374        FILE *fp;
 375        struct strbuf sb = STRBUF_INIT;
 376        unsigned char sha1[GIT_SHA1_RAWSZ];
 377
 378        if (!(fp = fopen(filename, "r")))
 379                die_errno(_("could not open '%s' for reading"), filename);
 380        while (strbuf_getline(&sb, fp, '\n') != EOF) {
 381                if (get_sha1_hex(sb.buf, sha1))
 382                        continue;  /* invalid line: does not start with SHA1 */
 383                if (starts_with(sb.buf + GIT_SHA1_HEXSZ, "\tnot-for-merge\t"))
 384                        continue;  /* ref is not-for-merge */
 385                sha1_array_append(merge_heads, sha1);
 386        }
 387        fclose(fp);
 388        strbuf_release(&sb);
 389}
 390
 391/**
 392 * Used by die_no_merge_candidates() as a for_each_remote() callback to
 393 * retrieve the name of the remote if the repository only has one remote.
 394 */
 395static int get_only_remote(struct remote *remote, void *cb_data)
 396{
 397        const char **remote_name = cb_data;
 398
 399        if (*remote_name)
 400                return -1;
 401
 402        *remote_name = remote->name;
 403        return 0;
 404}
 405
 406/**
 407 * Dies with the appropriate reason for why there are no merge candidates:
 408 *
 409 * 1. We fetched from a specific remote, and a refspec was given, but it ended
 410 *    up not fetching anything. This is usually because the user provided a
 411 *    wildcard refspec which had no matches on the remote end.
 412 *
 413 * 2. We fetched from a non-default remote, but didn't specify a branch to
 414 *    merge. We can't use the configured one because it applies to the default
 415 *    remote, thus the user must specify the branches to merge.
 416 *
 417 * 3. We fetched from the branch's or repo's default remote, but:
 418 *
 419 *    a. We are not on a branch, so there will never be a configured branch to
 420 *       merge with.
 421 *
 422 *    b. We are on a branch, but there is no configured branch to merge with.
 423 *
 424 * 4. We fetched from the branch's or repo's default remote, but the configured
 425 *    branch to merge didn't get fetched. (Either it doesn't exist, or wasn't
 426 *    part of the configured fetch refspec.)
 427 */
 428static void NORETURN die_no_merge_candidates(const char *repo, const char **refspecs)
 429{
 430        struct branch *curr_branch = branch_get("HEAD");
 431        const char *remote = curr_branch ? curr_branch->remote_name : NULL;
 432
 433        if (*refspecs) {
 434                if (opt_rebase)
 435                        fprintf_ln(stderr, _("There is no candidate for rebasing against among the refs that you just fetched."));
 436                else
 437                        fprintf_ln(stderr, _("There are no candidates for merging among the refs that you just fetched."));
 438                fprintf_ln(stderr, _("Generally this means that you provided a wildcard refspec which had no\n"
 439                                        "matches on the remote end."));
 440        } else if (repo && curr_branch && (!remote || strcmp(repo, remote))) {
 441                fprintf_ln(stderr, _("You asked to pull from the remote '%s', but did not specify\n"
 442                        "a branch. Because this is not the default configured remote\n"
 443                        "for your current branch, you must specify a branch on the command line."),
 444                        repo);
 445        } else if (!curr_branch) {
 446                fprintf_ln(stderr, _("You are not currently on a branch."));
 447                if (opt_rebase)
 448                        fprintf_ln(stderr, _("Please specify which branch you want to rebase against."));
 449                else
 450                        fprintf_ln(stderr, _("Please specify which branch you want to merge with."));
 451                fprintf_ln(stderr, _("See git-pull(1) for details."));
 452                fprintf(stderr, "\n");
 453                fprintf_ln(stderr, "    git pull <remote> <branch>");
 454                fprintf(stderr, "\n");
 455        } else if (!curr_branch->merge_nr) {
 456                const char *remote_name = NULL;
 457
 458                if (for_each_remote(get_only_remote, &remote_name) || !remote_name)
 459                        remote_name = "<remote>";
 460
 461                fprintf_ln(stderr, _("There is no tracking information for the current branch."));
 462                if (opt_rebase)
 463                        fprintf_ln(stderr, _("Please specify which branch you want to rebase against."));
 464                else
 465                        fprintf_ln(stderr, _("Please specify which branch you want to merge with."));
 466                fprintf_ln(stderr, _("See git-pull(1) for details."));
 467                fprintf(stderr, "\n");
 468                fprintf_ln(stderr, "    git pull <remote> <branch>");
 469                fprintf(stderr, "\n");
 470                fprintf_ln(stderr, _("If you wish to set tracking information for this branch you can do so with:\n"
 471                                "\n"
 472                                "    git branch --set-upstream-to=%s/<branch> %s\n"),
 473                                remote_name, curr_branch->name);
 474        } else
 475                fprintf_ln(stderr, _("Your configuration specifies to merge with the ref '%s'\n"
 476                        "from the remote, but no such ref was fetched."),
 477                        *curr_branch->merge_name);
 478        exit(1);
 479}
 480
 481/**
 482 * Parses argv into [<repo> [<refspecs>...]], returning their values in `repo`
 483 * as a string and `refspecs` as a null-terminated array of strings. If `repo`
 484 * is not provided in argv, it is set to NULL.
 485 */
 486static void parse_repo_refspecs(int argc, const char **argv, const char **repo,
 487                const char ***refspecs)
 488{
 489        if (argc > 0) {
 490                *repo = *argv++;
 491                argc--;
 492        } else
 493                *repo = NULL;
 494        *refspecs = argv;
 495}
 496
 497/**
 498 * Runs git-fetch, returning its exit status. `repo` and `refspecs` are the
 499 * repository and refspecs to fetch, or NULL if they are not provided.
 500 */
 501static int run_fetch(const char *repo, const char **refspecs)
 502{
 503        struct argv_array args = ARGV_ARRAY_INIT;
 504        int ret;
 505
 506        argv_array_pushl(&args, "fetch", "--update-head-ok", NULL);
 507
 508        /* Shared options */
 509        argv_push_verbosity(&args);
 510        if (opt_progress)
 511                argv_array_push(&args, opt_progress);
 512
 513        /* Options passed to git-fetch */
 514        if (opt_all)
 515                argv_array_push(&args, opt_all);
 516        if (opt_append)
 517                argv_array_push(&args, opt_append);
 518        if (opt_upload_pack)
 519                argv_array_push(&args, opt_upload_pack);
 520        argv_push_force(&args);
 521        if (opt_tags)
 522                argv_array_push(&args, opt_tags);
 523        if (opt_prune)
 524                argv_array_push(&args, opt_prune);
 525        if (opt_recurse_submodules)
 526                argv_array_push(&args, opt_recurse_submodules);
 527        if (opt_dry_run)
 528                argv_array_push(&args, "--dry-run");
 529        if (opt_keep)
 530                argv_array_push(&args, opt_keep);
 531        if (opt_depth)
 532                argv_array_push(&args, opt_depth);
 533        if (opt_unshallow)
 534                argv_array_push(&args, opt_unshallow);
 535        if (opt_update_shallow)
 536                argv_array_push(&args, opt_update_shallow);
 537        if (opt_refmap)
 538                argv_array_push(&args, opt_refmap);
 539
 540        if (repo) {
 541                argv_array_push(&args, repo);
 542                argv_array_pushv(&args, refspecs);
 543        } else if (*refspecs)
 544                die("BUG: refspecs without repo?");
 545        ret = run_command_v_opt(args.argv, RUN_GIT_CMD);
 546        argv_array_clear(&args);
 547        return ret;
 548}
 549
 550/**
 551 * "Pulls into void" by branching off merge_head.
 552 */
 553static int pull_into_void(const unsigned char *merge_head,
 554                const unsigned char *curr_head)
 555{
 556        /*
 557         * Two-way merge: we treat the index as based on an empty tree,
 558         * and try to fast-forward to HEAD. This ensures we will not lose
 559         * index/worktree changes that the user already made on the unborn
 560         * branch.
 561         */
 562        if (checkout_fast_forward(EMPTY_TREE_SHA1_BIN, merge_head, 0))
 563                return 1;
 564
 565        if (update_ref("initial pull", "HEAD", merge_head, curr_head, 0, UPDATE_REFS_DIE_ON_ERR))
 566                return 1;
 567
 568        return 0;
 569}
 570
 571/**
 572 * Runs git-merge, returning its exit status.
 573 */
 574static int run_merge(void)
 575{
 576        int ret;
 577        struct argv_array args = ARGV_ARRAY_INIT;
 578
 579        argv_array_pushl(&args, "merge", NULL);
 580
 581        /* Shared options */
 582        argv_push_verbosity(&args);
 583        if (opt_progress)
 584                argv_array_push(&args, opt_progress);
 585
 586        /* Options passed to git-merge */
 587        if (opt_diffstat)
 588                argv_array_push(&args, opt_diffstat);
 589        if (opt_log)
 590                argv_array_push(&args, opt_log);
 591        if (opt_squash)
 592                argv_array_push(&args, opt_squash);
 593        if (opt_commit)
 594                argv_array_push(&args, opt_commit);
 595        if (opt_edit)
 596                argv_array_push(&args, opt_edit);
 597        if (opt_ff)
 598                argv_array_push(&args, opt_ff);
 599        if (opt_verify_signatures)
 600                argv_array_push(&args, opt_verify_signatures);
 601        argv_array_pushv(&args, opt_strategies.argv);
 602        argv_array_pushv(&args, opt_strategy_opts.argv);
 603        if (opt_gpg_sign)
 604                argv_array_push(&args, opt_gpg_sign);
 605
 606        argv_array_push(&args, "FETCH_HEAD");
 607        ret = run_command_v_opt(args.argv, RUN_GIT_CMD);
 608        argv_array_clear(&args);
 609        return ret;
 610}
 611
 612/**
 613 * Returns remote's upstream branch for the current branch. If remote is NULL,
 614 * the current branch's configured default remote is used. Returns NULL if
 615 * `remote` does not name a valid remote, HEAD does not point to a branch,
 616 * remote is not the branch's configured remote or the branch does not have any
 617 * configured upstream branch.
 618 */
 619static const char *get_upstream_branch(const char *remote)
 620{
 621        struct remote *rm;
 622        struct branch *curr_branch;
 623        const char *curr_branch_remote;
 624
 625        rm = remote_get(remote);
 626        if (!rm)
 627                return NULL;
 628
 629        curr_branch = branch_get("HEAD");
 630        if (!curr_branch)
 631                return NULL;
 632
 633        curr_branch_remote = remote_for_branch(curr_branch, NULL);
 634        assert(curr_branch_remote);
 635
 636        if (strcmp(curr_branch_remote, rm->name))
 637                return NULL;
 638
 639        return branch_get_upstream(curr_branch, NULL);
 640}
 641
 642/**
 643 * Derives the remote tracking branch from the remote and refspec.
 644 *
 645 * FIXME: The current implementation assumes the default mapping of
 646 * refs/heads/<branch_name> to refs/remotes/<remote_name>/<branch_name>.
 647 */
 648static const char *get_tracking_branch(const char *remote, const char *refspec)
 649{
 650        struct refspec *spec;
 651        const char *spec_src;
 652        const char *merge_branch;
 653
 654        spec = parse_fetch_refspec(1, &refspec);
 655        spec_src = spec->src;
 656        if (!*spec_src || !strcmp(spec_src, "HEAD"))
 657                spec_src = "HEAD";
 658        else if (skip_prefix(spec_src, "heads/", &spec_src))
 659                ;
 660        else if (skip_prefix(spec_src, "refs/heads/", &spec_src))
 661                ;
 662        else if (starts_with(spec_src, "refs/") ||
 663                starts_with(spec_src, "tags/") ||
 664                starts_with(spec_src, "remotes/"))
 665                spec_src = "";
 666
 667        if (*spec_src) {
 668                if (!strcmp(remote, "."))
 669                        merge_branch = mkpath("refs/heads/%s", spec_src);
 670                else
 671                        merge_branch = mkpath("refs/remotes/%s/%s", remote, spec_src);
 672        } else
 673                merge_branch = NULL;
 674
 675        free_refspec(1, spec);
 676        return merge_branch;
 677}
 678
 679/**
 680 * Given the repo and refspecs, sets fork_point to the point at which the
 681 * current branch forked from its remote tracking branch. Returns 0 on success,
 682 * -1 on failure.
 683 */
 684static int get_rebase_fork_point(unsigned char *fork_point, const char *repo,
 685                const char *refspec)
 686{
 687        int ret;
 688        struct branch *curr_branch;
 689        const char *remote_branch;
 690        struct child_process cp = CHILD_PROCESS_INIT;
 691        struct strbuf sb = STRBUF_INIT;
 692
 693        curr_branch = branch_get("HEAD");
 694        if (!curr_branch)
 695                return -1;
 696
 697        if (refspec)
 698                remote_branch = get_tracking_branch(repo, refspec);
 699        else
 700                remote_branch = get_upstream_branch(repo);
 701
 702        if (!remote_branch)
 703                return -1;
 704
 705        argv_array_pushl(&cp.args, "merge-base", "--fork-point",
 706                        remote_branch, curr_branch->name, NULL);
 707        cp.no_stdin = 1;
 708        cp.no_stderr = 1;
 709        cp.git_cmd = 1;
 710
 711        ret = capture_command(&cp, &sb, GIT_SHA1_HEXSZ);
 712        if (ret)
 713                goto cleanup;
 714
 715        ret = get_sha1_hex(sb.buf, fork_point);
 716        if (ret)
 717                goto cleanup;
 718
 719cleanup:
 720        strbuf_release(&sb);
 721        return ret ? -1 : 0;
 722}
 723
 724/**
 725 * Sets merge_base to the octopus merge base of curr_head, merge_head and
 726 * fork_point. Returns 0 if a merge base is found, 1 otherwise.
 727 */
 728static int get_octopus_merge_base(unsigned char *merge_base,
 729                const unsigned char *curr_head,
 730                const unsigned char *merge_head,
 731                const unsigned char *fork_point)
 732{
 733        struct commit_list *revs = NULL, *result;
 734
 735        commit_list_insert(lookup_commit_reference(curr_head), &revs);
 736        commit_list_insert(lookup_commit_reference(merge_head), &revs);
 737        if (!is_null_sha1(fork_point))
 738                commit_list_insert(lookup_commit_reference(fork_point), &revs);
 739
 740        result = reduce_heads(get_octopus_merge_bases(revs));
 741        free_commit_list(revs);
 742        if (!result)
 743                return 1;
 744
 745        hashcpy(merge_base, result->item->object.sha1);
 746        return 0;
 747}
 748
 749/**
 750 * Given the current HEAD SHA1, the merge head returned from git-fetch and the
 751 * fork point calculated by get_rebase_fork_point(), runs git-rebase with the
 752 * appropriate arguments and returns its exit status.
 753 */
 754static int run_rebase(const unsigned char *curr_head,
 755                const unsigned char *merge_head,
 756                const unsigned char *fork_point)
 757{
 758        int ret;
 759        unsigned char oct_merge_base[GIT_SHA1_RAWSZ];
 760        struct argv_array args = ARGV_ARRAY_INIT;
 761
 762        if (!get_octopus_merge_base(oct_merge_base, curr_head, merge_head, fork_point))
 763                if (!is_null_sha1(fork_point) && !hashcmp(oct_merge_base, fork_point))
 764                        fork_point = NULL;
 765
 766        argv_array_push(&args, "rebase");
 767
 768        /* Shared options */
 769        argv_push_verbosity(&args);
 770
 771        /* Options passed to git-rebase */
 772        if (opt_rebase == REBASE_PRESERVE)
 773                argv_array_push(&args, "--preserve-merges");
 774        if (opt_diffstat)
 775                argv_array_push(&args, opt_diffstat);
 776        argv_array_pushv(&args, opt_strategies.argv);
 777        argv_array_pushv(&args, opt_strategy_opts.argv);
 778        if (opt_gpg_sign)
 779                argv_array_push(&args, opt_gpg_sign);
 780
 781        argv_array_push(&args, "--onto");
 782        argv_array_push(&args, sha1_to_hex(merge_head));
 783
 784        if (fork_point && !is_null_sha1(fork_point))
 785                argv_array_push(&args, sha1_to_hex(fork_point));
 786        else
 787                argv_array_push(&args, sha1_to_hex(merge_head));
 788
 789        ret = run_command_v_opt(args.argv, RUN_GIT_CMD);
 790        argv_array_clear(&args);
 791        return ret;
 792}
 793
 794int cmd_pull(int argc, const char **argv, const char *prefix)
 795{
 796        const char *repo, **refspecs;
 797        struct sha1_array merge_heads = SHA1_ARRAY_INIT;
 798        unsigned char orig_head[GIT_SHA1_RAWSZ], curr_head[GIT_SHA1_RAWSZ];
 799        unsigned char rebase_fork_point[GIT_SHA1_RAWSZ];
 800
 801        if (!getenv("GIT_REFLOG_ACTION"))
 802                set_reflog_message(argc, argv);
 803
 804        argc = parse_options(argc, argv, prefix, pull_options, pull_usage, 0);
 805
 806        parse_repo_refspecs(argc, argv, &repo, &refspecs);
 807
 808        if (!opt_ff)
 809                opt_ff = xstrdup_or_null(config_get_ff());
 810
 811        if (opt_rebase < 0)
 812                opt_rebase = config_get_rebase();
 813
 814        git_config(git_default_config, NULL);
 815
 816        if (read_cache_unmerged())
 817                die_resolve_conflict("Pull");
 818
 819        if (file_exists(git_path("MERGE_HEAD")))
 820                die_conclude_merge();
 821
 822        if (get_sha1("HEAD", orig_head))
 823                hashclr(orig_head);
 824
 825        if (opt_rebase) {
 826                if (is_null_sha1(orig_head) && !is_cache_unborn())
 827                        die(_("Updating an unborn branch with changes added to the index."));
 828
 829                die_on_unclean_work_tree(prefix);
 830
 831                if (get_rebase_fork_point(rebase_fork_point, repo, *refspecs))
 832                        hashclr(rebase_fork_point);
 833        }
 834
 835        if (run_fetch(repo, refspecs))
 836                return 1;
 837
 838        if (opt_dry_run)
 839                return 0;
 840
 841        if (get_sha1("HEAD", curr_head))
 842                hashclr(curr_head);
 843
 844        if (!is_null_sha1(orig_head) && !is_null_sha1(curr_head) &&
 845                        hashcmp(orig_head, curr_head)) {
 846                /*
 847                 * The fetch involved updating the current branch.
 848                 *
 849                 * The working tree and the index file are still based on
 850                 * orig_head commit, but we are merging into curr_head.
 851                 * Update the working tree to match curr_head.
 852                 */
 853
 854                warning(_("fetch updated the current branch head.\n"
 855                        "fast-forwarding your working tree from\n"
 856                        "commit %s."), sha1_to_hex(orig_head));
 857
 858                if (checkout_fast_forward(orig_head, curr_head, 0))
 859                        die(_("Cannot fast-forward your working tree.\n"
 860                                "After making sure that you saved anything precious from\n"
 861                                "$ git diff %s\n"
 862                                "output, run\n"
 863                                "$ git reset --hard\n"
 864                                "to recover."), sha1_to_hex(orig_head));
 865        }
 866
 867        get_merge_heads(&merge_heads);
 868
 869        if (!merge_heads.nr)
 870                die_no_merge_candidates(repo, refspecs);
 871
 872        if (is_null_sha1(orig_head)) {
 873                if (merge_heads.nr > 1)
 874                        die(_("Cannot merge multiple branches into empty head."));
 875                return pull_into_void(*merge_heads.sha1, curr_head);
 876        } else if (opt_rebase) {
 877                if (merge_heads.nr > 1)
 878                        die(_("Cannot rebase onto multiple branches."));
 879                return run_rebase(curr_head, *merge_heads.sha1, rebase_fork_point);
 880        } else
 881                return run_merge();
 882}