builtin/checkout.c

   1 #include "cache.h"
   2 #include "builtin.h"
   3 #include "parse-options.h"
   4 #include "refs.h"
   5 #include "commit.h"
   6 #include "tree.h"
   7 #include "tree-walk.h"
   8 #include "cache-tree.h"
   9 #include "unpack-trees.h"
  10 #include "dir.h"
  11 #include "run-command.h"
  12 #include "merge-recursive.h"
  13 #include "branch.h"
  14 #include "diff.h"
  15 #include "revision.h"
  16 #include "remote.h"
  17 #include "blob.h"
  18 #include "xdiff-interface.h"
  19 #include "ll-merge.h"
  20 #include "resolve-undo.h"
  21 #include "submodule.h"
  22 #include "argv-array.h"
  23
  24 static const char * const checkout_usage[] = {
  25         "git checkout [options] <branch>",
  26         "git checkout [options] [<branch>] -- <file>...",
  27         NULL,
  28 };
  29
  30 struct checkout_opts {
  31         int quiet;
  32         int merge;
  33         int force;
  34         int force_detach;
  35         int writeout_stage;
  36         int writeout_error;
  37         int overwrite_ignore;
  38
  39         /* not set by parse_options */
  40         int branch_exists;
  41
  42         const char *new_branch;
  43         const char *new_branch_force;
  44         const char *new_orphan_branch;
  45         int new_branch_log;
  46         enum branch_track track;
  47         struct diff_options diff_options;
  48 };
  49
  50 static int post_checkout_hook(struct commit *old, struct commit *new,
  51                               int changed)
  52 {
  53         return run_hook(NULL, "post-checkout",
  54                         sha1_to_hex(old ? old->object.sha1 : null_sha1),
  55                         sha1_to_hex(new ? new->object.sha1 : null_sha1),
  56                         changed ? "1" : "0", NULL);
  57         /* "new" can be NULL when checking out from the index before
  58            a commit exists. */
  59
  60 }
  61
  62 static int update_some(const unsigned char *sha1, const char *base, int baselen,
  63                 const char *pathname, unsigned mode, int stage, void *context)
  64 {
  65         int len;
  66         struct cache_entry *ce;
  67
  68         if (S_ISDIR(mode))
  69                 return READ_TREE_RECURSIVE;
  70
  71         len = baselen + strlen(pathname);
  72         ce = xcalloc(1, cache_entry_size(len));
  73         hashcpy(ce->sha1, sha1);
  74         memcpy(ce->name, base, baselen);
  75         memcpy(ce->name + baselen, pathname, len - baselen);
  76         ce->ce_flags = create_ce_flags(0) | CE_UPDATE;
  77         ce->ce_namelen = len;
  78         ce->ce_mode = create_ce_mode(mode);
  79         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
  80         return 0;
  81 }
  82
  83 static int read_tree_some(struct tree *tree, const char **pathspec)
  84 {
  85         struct pathspec ps;
  86         init_pathspec(&ps, pathspec);
  87         read_tree_recursive(tree, "", 0, 0, &ps, update_some, NULL);
  88         free_pathspec(&ps);
  89
  90         /* update the index with the given tree's info
  91          * for all args, expanding wildcards, and exit
  92          * with any non-zero return code.
  93          */
  94         return 0;
  95 }
  96
  97 static int skip_same_name(struct cache_entry *ce, int pos)
  98 {
  99         while (++pos < active_nr &&
 100                !strcmp(active_cache[pos]->name, ce->name))
 101                 ; /* skip */
 102         return pos;
 103 }
 104
 105 static int check_stage(int stage, struct cache_entry *ce, int pos)
 106 {
 107         while (pos < active_nr &&
 108                !strcmp(active_cache[pos]->name, ce->name)) {
 109                 if (ce_stage(active_cache[pos]) == stage)
 110                         return 0;
 111                 pos++;
 112         }
 113         if (stage == 2)
 114                 return error(_("path '%s' does not have our version"), ce->name);
 115         else
 116                 return error(_("path '%s' does not have their version"), ce->name);
 117 }
 118
 119 static int check_stages(unsigned stages, struct cache_entry *ce, int pos)
 120 {
 121         unsigned seen = 0;
 122         const char *name = ce->name;
 123
 124         while (pos < active_nr) {
 125                 ce = active_cache[pos];
 126                 if (strcmp(name, ce->name))
 127                         break;
 128                 seen |= (1 << ce_stage(ce));
 129                 pos++;
 130         }
 131         if ((stages & seen) != stages)
 132                 return error(_("path '%s' does not have all necessary versions"),
 133                              name);
 134         return 0;
 135 }
 136
 137 static int checkout_stage(int stage, struct cache_entry *ce, int pos,
 138                           struct checkout *state)
 139 {
 140         while (pos < active_nr &&
 141                !strcmp(active_cache[pos]->name, ce->name)) {
 142                 if (ce_stage(active_cache[pos]) == stage)
 143                         return checkout_entry(active_cache[pos], state, NULL);
 144                 pos++;
 145         }
 146         if (stage == 2)
 147                 return error(_("path '%s' does not have our version"), ce->name);
 148         else
 149                 return error(_("path '%s' does not have their version"), ce->name);
 150 }
 151
 152 static int checkout_merged(int pos, struct checkout *state)
 153 {
 154         struct cache_entry *ce = active_cache[pos];
 155         const char *path = ce->name;
 156         mmfile_t ancestor, ours, theirs;
 157         int status;
 158         unsigned char sha1[20];
 159         mmbuffer_t result_buf;
 160         unsigned char threeway[3][20];
 161         unsigned mode = 0;
 162
 163         memset(threeway, 0, sizeof(threeway));
 164         while (pos < active_nr) {
 165                 int stage;
 166                 stage = ce_stage(ce);
 167                 if (!stage || strcmp(path, ce->name))
 168                         break;
 169                 hashcpy(threeway[stage - 1], ce->sha1);
 170                 if (stage == 2)
 171                         mode = create_ce_mode(ce->ce_mode);
 172                 pos++;
 173                 ce = active_cache[pos];
 174         }
 175         if (is_null_sha1(threeway[1]) || is_null_sha1(threeway[2]))
 176                 return error(_("path '%s' does not have necessary versions"), path);
 177
 178         read_mmblob(&ancestor, threeway[0]);
 179         read_mmblob(&ours, threeway[1]);
 180         read_mmblob(&theirs, threeway[2]);
 181
 182         /*
 183          * NEEDSWORK: re-create conflicts from merges with
 184          * merge.renormalize set, too
 185          */
 186         status = ll_merge(&result_buf, path, &ancestor, "base",
 187                           &ours, "ours", &theirs, "theirs", NULL);
 188         free(ancestor.ptr);
 189         free(ours.ptr);
 190         free(theirs.ptr);
 191         if (status < 0 || !result_buf.ptr) {
 192                 free(result_buf.ptr);
 193                 return error(_("path '%s': cannot merge"), path);
 194         }
 195
 196         /*
 197          * NEEDSWORK:
 198          * There is absolutely no reason to write this as a blob object
 199          * and create a phony cache entry just to leak.  This hack is
 200          * primarily to get to the write_entry() machinery that massages
 201          * the contents to work-tree format and writes out which only
 202          * allows it for a cache entry.  The code in write_entry() needs
 203          * to be refactored to allow us to feed a <buffer, size, mode>
 204          * instead of a cache entry.  Such a refactoring would help
 205          * merge_recursive as well (it also writes the merge result to the
 206          * object database even when it may contain conflicts).
 207          */
 208         if (write_sha1_file(result_buf.ptr, result_buf.size,
 209                             blob_type, sha1))
 210                 die(_("Unable to add merge result for '%s'"), path);
 211         ce = make_cache_entry(mode, sha1, path, 2, 0);
 212         if (!ce)
 213                 die(_("make_cache_entry failed for path '%s'"), path);
 214         status = checkout_entry(ce, state, NULL);
 215         return status;
 216 }
 217
 218 static int checkout_paths(struct tree *source_tree, const char **pathspec,
 219                           const char *prefix, struct checkout_opts *opts)
 220 {
 221         int pos;
 222         struct checkout state;
 223         static char *ps_matched;
 224         unsigned char rev[20];
 225         int flag;
 226         struct commit *head;
 227         int errs = 0;
 228         int stage = opts->writeout_stage;
 229         int merge = opts->merge;
 230         int newfd;
 231         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 232
 233         newfd = hold_locked_index(lock_file, 1);
 234         if (read_cache_preload(pathspec) < 0)
 235                 return error(_("corrupt index file"));
 236
 237         if (source_tree)
 238                 read_tree_some(source_tree, pathspec);
 239
 240         for (pos = 0; pathspec[pos]; pos++)
 241                 ;
 242         ps_matched = xcalloc(1, pos);
 243
 244         for (pos = 0; pos < active_nr; pos++) {
 245                 struct cache_entry *ce = active_cache[pos];
 246                 if (source_tree && !(ce->ce_flags & CE_UPDATE))
 247                         continue;
 248                 match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, ps_matched);
 249         }
 250
 251         if (report_path_error(ps_matched, pathspec, prefix))
 252                 return 1;
 253
 254         /* "checkout -m path" to recreate conflicted state */
 255         if (opts->merge)
 256                 unmerge_cache(pathspec);
 257
 258         /* Any unmerged paths? */
 259         for (pos = 0; pos < active_nr; pos++) {
 260                 struct cache_entry *ce = active_cache[pos];
 261                 if (match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, NULL)) {
 262                         if (!ce_stage(ce))
 263                                 continue;
 264                         if (opts->force) {
 265                                 warning(_("path '%s' is unmerged"), ce->name);
 266                         } else if (stage) {
 267                                 errs |= check_stage(stage, ce, pos);
 268                         } else if (opts->merge) {
 269                                 errs |= check_stages((1<<2) | (1<<3), ce, pos);
 270                         } else {
 271                                 errs = 1;
 272                                 error(_("path '%s' is unmerged"), ce->name);
 273                         }
 274                         pos = skip_same_name(ce, pos) - 1;
 275                 }
 276         }
 277         if (errs)
 278                 return 1;
 279
 280         /* Now we are committed to check them out */
 281         memset(&state, 0, sizeof(state));
 282         state.force = 1;
 283         state.refresh_cache = 1;
 284         for (pos = 0; pos < active_nr; pos++) {
 285                 struct cache_entry *ce = active_cache[pos];
 286                 if (source_tree && !(ce->ce_flags & CE_UPDATE))
 287                         continue;
 288                 if (match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, NULL)) {
 289                         if (!ce_stage(ce)) {
 290                                 errs |= checkout_entry(ce, &state, NULL);
 291                                 continue;
 292                         }
 293                         if (stage)
 294                                 errs |= checkout_stage(stage, ce, pos, &state);
 295                         else if (merge)
 296                                 errs |= checkout_merged(pos, &state);
 297                         pos = skip_same_name(ce, pos) - 1;
 298                 }
 299         }
 300
 301         if (write_cache(newfd, active_cache, active_nr) ||
 302             commit_locked_index(lock_file))
 303                 die(_("unable to write new index file"));
 304
 305         read_ref_full("HEAD", rev, 0, &flag);
 306         head = lookup_commit_reference_gently(rev, 1);
 307
 308         errs |= post_checkout_hook(head, head, 0);
 309         return errs;
 310 }
 311
 312 static void show_local_changes(struct object *head, struct diff_options *opts)
 313 {
 314         struct rev_info rev;
 315         /* I think we want full paths, even if we're in a subdirectory. */
 316         init_revisions(&rev, NULL);
 317         rev.diffopt.flags = opts->flags;
 318         rev.diffopt.output_format |= DIFF_FORMAT_NAME_STATUS;
 319         diff_setup_done(&rev.diffopt);
 320         add_pending_object(&rev, head, NULL);
 321         run_diff_index(&rev, 0);
 322 }
 323
 324 static void describe_detached_head(const char *msg, struct commit *commit)
 325 {
 326         struct strbuf sb = STRBUF_INIT;
 327         parse_commit(commit);
 328         pp_commit_easy(CMIT_FMT_ONELINE, commit, &sb);
 329         fprintf(stderr, "%s %s... %s\n", msg,
 330                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV), sb.buf);
 331         strbuf_release(&sb);
 332 }
 333
 334 static int reset_tree(struct tree *tree, struct checkout_opts *o, int worktree)
 335 {
 336         struct unpack_trees_options opts;
 337         struct tree_desc tree_desc;
 338
 339         memset(&opts, 0, sizeof(opts));
 340         opts.head_idx = -1;
 341         opts.update = worktree;
 342         opts.skip_unmerged = !worktree;
 343         opts.reset = 1;
 344         opts.merge = 1;
 345         opts.fn = oneway_merge;
 346         opts.verbose_update = !o->quiet && isatty(2);
 347         opts.src_index = &the_index;
 348         opts.dst_index = &the_index;
 349         parse_tree(tree);
 350         init_tree_desc(&tree_desc, tree->buffer, tree->size);
 351         switch (unpack_trees(1, &tree_desc, &opts)) {
 352         case -2:
 353                 o->writeout_error = 1;
 354                 /*
 355                  * We return 0 nevertheless, as the index is all right
 356                  * and more importantly we have made best efforts to
 357                  * update paths in the work tree, and we cannot revert
 358                  * them.
 359                  */
 360         case 0:
 361                 return 0;
 362         default:
 363                 return 128;
 364         }
 365 }
 366
 367 struct branch_info {
 368         const char *name; /* The short name used */
 369         const char *path; /* The full name of a real branch */
 370         struct commit *commit; /* The named commit */
 371 };
 372
 373 static void setup_branch_path(struct branch_info *branch)
 374 {
 375         struct strbuf buf = STRBUF_INIT;
 376
 377         strbuf_branchname(&buf, branch->name);
 378         if (strcmp(buf.buf, branch->name))
 379                 branch->name = xstrdup(buf.buf);
 380         strbuf_splice(&buf, 0, 0, "refs/heads/", 11);
 381         branch->path = strbuf_detach(&buf, NULL);
 382 }
 383
 384 static int merge_working_tree(struct checkout_opts *opts,
 385                               struct branch_info *old, struct branch_info *new)
 386 {
 387         int ret;
 388         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 389         int newfd = hold_locked_index(lock_file, 1);
 390
 391         if (read_cache_preload(NULL) < 0)
 392                 return error(_("corrupt index file"));
 393
 394         resolve_undo_clear();
 395         if (opts->force) {
 396                 ret = reset_tree(new->commit->tree, opts, 1);
 397                 if (ret)
 398                         return ret;
 399         } else {
 400                 struct tree_desc trees[2];
 401                 struct tree *tree;
 402                 struct unpack_trees_options topts;
 403
 404                 memset(&topts, 0, sizeof(topts));
 405                 topts.head_idx = -1;
 406                 topts.src_index = &the_index;
 407                 topts.dst_index = &the_index;
 408
 409                 setup_unpack_trees_porcelain(&topts, "checkout");
 410
 411                 refresh_cache(REFRESH_QUIET);
 412
 413                 if (unmerged_cache()) {
 414                         error(_("you need to resolve your current index first"));
 415                         return 1;
 416                 }
 417
 418                 /* 2-way merge to the new branch */
 419                 topts.initial_checkout = is_cache_unborn();
 420                 topts.update = 1;
 421                 topts.merge = 1;
 422                 topts.gently = opts->merge && old->commit;
 423                 topts.verbose_update = !opts->quiet && isatty(2);
 424                 topts.fn = twoway_merge;
 425                 if (opts->overwrite_ignore) {
 426                         topts.dir = xcalloc(1, sizeof(*topts.dir));
 427                         topts.dir->flags |= DIR_SHOW_IGNORED;
 428                         setup_standard_excludes(topts.dir);
 429                 }
 430                 tree = parse_tree_indirect(old->commit ?
 431                                            old->commit->object.sha1 :
 432                                            EMPTY_TREE_SHA1_BIN);
 433                 init_tree_desc(&trees[0], tree->buffer, tree->size);
 434                 tree = parse_tree_indirect(new->commit->object.sha1);
 435                 init_tree_desc(&trees[1], tree->buffer, tree->size);
 436
 437                 ret = unpack_trees(2, trees, &topts);
 438                 if (ret == -1) {
 439                         /*
 440                          * Unpack couldn't do a trivial merge; either
 441                          * give up or do a real merge, depending on
 442                          * whether the merge flag was used.
 443                          */
 444                         struct tree *result;
 445                         struct tree *work;
 446                         struct merge_options o;
 447                         if (!opts->merge)
 448                                 return 1;
 449
 450                         /*
 451                          * Without old->commit, the below is the same as
 452                          * the two-tree unpack we already tried and failed.
 453                          */
 454                         if (!old->commit)
 455                                 return 1;
 456
 457                         /* Do more real merge */
 458
 459                         /*
 460                          * We update the index fully, then write the
 461                          * tree from the index, then merge the new
 462                          * branch with the current tree, with the old
 463                          * branch as the base. Then we reset the index
 464                          * (but not the working tree) to the new
 465                          * branch, leaving the working tree as the
 466                          * merged version, but skipping unmerged
 467                          * entries in the index.
 468                          */
 469
 470                         add_files_to_cache(NULL, NULL, 0);
 471                         /*
 472                          * NEEDSWORK: carrying over local changes
 473                          * when branches have different end-of-line
 474                          * normalization (or clean+smudge rules) is
 475                          * a pain; plumb in an option to set
 476                          * o.renormalize?
 477                          */
 478                         init_merge_options(&o);
 479                         o.verbosity = 0;
 480                         work = write_tree_from_memory(&o);
 481
 482                         ret = reset_tree(new->commit->tree, opts, 1);
 483                         if (ret)
 484                                 return ret;
 485                         o.ancestor = old->name;
 486                         o.branch1 = new->name;
 487                         o.branch2 = "local";
 488                         merge_trees(&o, new->commit->tree, work,
 489                                 old->commit->tree, &result);
 490                         ret = reset_tree(new->commit->tree, opts, 0);
 491                         if (ret)
 492                                 return ret;
 493                 }
 494         }
 495
 496         if (write_cache(newfd, active_cache, active_nr) ||
 497             commit_locked_index(lock_file))
 498                 die(_("unable to write new index file"));
 499
 500         if (!opts->force && !opts->quiet)
 501                 show_local_changes(&new->commit->object, &opts->diff_options);
 502
 503         return 0;
 504 }
 505
 506 static void report_tracking(struct branch_info *new)
 507 {
 508         struct strbuf sb = STRBUF_INIT;
 509         struct branch *branch = branch_get(new->name);
 510
 511         if (!format_tracking_info(branch, &sb))
 512                 return;
 513         fputs(sb.buf, stdout);
 514         strbuf_release(&sb);
 515 }
 516
 517 static void update_refs_for_switch(struct checkout_opts *opts,
 518                                    struct branch_info *old,
 519                                    struct branch_info *new)
 520 {
 521         struct strbuf msg = STRBUF_INIT;
 522         const char *old_desc;
 523         if (opts->new_branch) {
 524                 if (opts->new_orphan_branch) {
 525                         if (opts->new_branch_log && !log_all_ref_updates) {
 526                                 int temp;
 527                                 char log_file[PATH_MAX];
 528                                 char *ref_name = mkpath("refs/heads/%s", opts->new_orphan_branch);
 529
 530                                 temp = log_all_ref_updates;
 531                                 log_all_ref_updates = 1;
 532                                 if (log_ref_setup(ref_name, log_file, sizeof(log_file))) {
 533                                         fprintf(stderr, _("Can not do reflog for '%s'\n"),
 534                                             opts->new_orphan_branch);
 535                                         log_all_ref_updates = temp;
 536                                         return;
 537                                 }
 538                                 log_all_ref_updates = temp;
 539                         }
 540                 }
 541                 else
 542                         create_branch(old->name, opts->new_branch, new->name,
 543                                       opts->new_branch_force ? 1 : 0,
 544                                       opts->new_branch_log,
 545                                       opts->new_branch_force ? 1 : 0,
 546                                       opts->quiet,
 547                                       opts->track);
 548                 new->name = opts->new_branch;
 549                 setup_branch_path(new);
 550         }
 551
 552         old_desc = old->name;
 553         if (!old_desc && old->commit)
 554                 old_desc = sha1_to_hex(old->commit->object.sha1);
 555         strbuf_addf(&msg, "checkout: moving from %s to %s",
 556                     old_desc ? old_desc : "(invalid)", new->name);
 557
 558         if (!strcmp(new->name, "HEAD") && !new->path && !opts->force_detach) {
 559                 /* Nothing to do. */
 560         } else if (opts->force_detach || !new->path) {  /* No longer on any branch. */
 561                 update_ref(msg.buf, "HEAD", new->commit->object.sha1, NULL,
 562                            REF_NODEREF, DIE_ON_ERR);
 563                 if (!opts->quiet) {
 564                         if (old->path && advice_detached_head)
 565                                 detach_advice(new->name);
 566                         describe_detached_head(_("HEAD is now at"), new->commit);
 567                 }
 568         } else if (new->path) { /* Switch branches. */
 569                 create_symref("HEAD", new->path, msg.buf);
 570                 if (!opts->quiet) {
 571                         if (old->path && !strcmp(new->path, old->path)) {
 572                                 if (opts->new_branch_force)
 573                                         fprintf(stderr, _("Reset branch '%s'\n"),
 574                                                 new->name);
 575                                 else
 576                                         fprintf(stderr, _("Already on '%s'\n"),
 577                                                 new->name);
 578                         } else if (opts->new_branch) {
 579                                 if (opts->branch_exists)
 580                                         fprintf(stderr, _("Switched to and reset branch '%s'\n"), new->name);
 581                                 else
 582                                         fprintf(stderr, _("Switched to a new branch '%s'\n"), new->name);
 583                         } else {
 584                                 fprintf(stderr, _("Switched to branch '%s'\n"),
 585                                         new->name);
 586                         }
 587                 }
 588                 if (old->path && old->name) {
 589                         char log_file[PATH_MAX], ref_file[PATH_MAX];
 590
 591                         git_snpath(log_file, sizeof(log_file), "logs/%s", old->path);
 592                         git_snpath(ref_file, sizeof(ref_file), "%s", old->path);
 593                         if (!file_exists(ref_file) && file_exists(log_file))
 594                                 remove_path(log_file);
 595                 }
 596         }
 597         remove_branch_state();
 598         strbuf_release(&msg);
 599         if (!opts->quiet &&
 600             (new->path || (!opts->force_detach && !strcmp(new->name, "HEAD"))))
 601                 report_tracking(new);
 602 }
 603
 604 static int add_pending_uninteresting_ref(const char *refname,
 605                                          const unsigned char *sha1,
 606                                          int flags, void *cb_data)
 607 {
 608         add_pending_sha1(cb_data, refname, sha1, UNINTERESTING);
 609         return 0;
 610 }
 611
 612 static void describe_one_orphan(struct strbuf *sb, struct commit *commit)
 613 {
 614         parse_commit(commit);
 615         strbuf_addstr(sb, "  ");
 616         strbuf_addstr(sb,
 617                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
 618         strbuf_addch(sb, ' ');
 619         pp_commit_easy(CMIT_FMT_ONELINE, commit, sb);
 620         strbuf_addch(sb, '\n');
 621 }
 622
 623 #define ORPHAN_CUTOFF 4
 624 static void suggest_reattach(struct commit *commit, struct rev_info *revs)
 625 {
 626         struct commit *c, *last = NULL;
 627         struct strbuf sb = STRBUF_INIT;
 628         int lost = 0;
 629         while ((c = get_revision(revs)) != NULL) {
 630                 if (lost < ORPHAN_CUTOFF)
 631                         describe_one_orphan(&sb, c);
 632                 last = c;
 633                 lost++;
 634         }
 635         if (ORPHAN_CUTOFF < lost) {
 636                 int more = lost - ORPHAN_CUTOFF;
 637                 if (more == 1)
 638                         describe_one_orphan(&sb, last);
 639                 else
 640                         strbuf_addf(&sb, _(" ... and %d more.\n"), more);
 641         }
 642
 643         fprintf(stderr,
 644                 Q_(
 645                 /* The singular version */
 646                 "Warning: you are leaving %d commit behind, "
 647                 "not connected to\n"
 648                 "any of your branches:\n\n"
 649                 "%s\n",
 650                 /* The plural version */
 651                 "Warning: you are leaving %d commits behind, "
 652                 "not connected to\n"
 653                 "any of your branches:\n\n"
 654                 "%s\n",
 655                 /* Give ngettext() the count */
 656                 lost),
 657                 lost,
 658                 sb.buf);
 659         strbuf_release(&sb);
 660
 661         if (advice_detached_head)
 662                 fprintf(stderr,
 663                         _(
 664                         "If you want to keep them by creating a new branch, "
 665                         "this may be a good time\nto do so with:\n\n"
 666                         " git branch new_branch_name %s\n\n"),
 667                         sha1_to_hex(commit->object.sha1));
 668 }
 669
 670 /*
 671  * We are about to leave commit that was at the tip of a detached
 672  * HEAD.  If it is not reachable from any ref, this is the last chance
 673  * for the user to do so without resorting to reflog.
 674  */
 675 static void orphaned_commit_warning(struct commit *old, struct commit *new)
 676 {
 677         struct rev_info revs;
 678         struct object *object = &old->object;
 679         struct object_array refs;
 680
 681         init_revisions(&revs, NULL);
 682         setup_revisions(0, NULL, &revs, NULL);
 683
 684         object->flags &= ~UNINTERESTING;
 685         add_pending_object(&revs, object, sha1_to_hex(object->sha1));
 686
 687         for_each_ref(add_pending_uninteresting_ref, &revs);
 688         add_pending_sha1(&revs, "HEAD", new->object.sha1, UNINTERESTING);
 689
 690         refs = revs.pending;
 691         revs.leak_pending = 1;
 692
 693         if (prepare_revision_walk(&revs))
 694                 die(_("internal error in revision walk"));
 695         if (!(old->object.flags & UNINTERESTING))
 696                 suggest_reattach(old, &revs);
 697         else
 698                 describe_detached_head(_("Previous HEAD position was"), old);
 699
 700         clear_commit_marks_for_object_array(&refs, ALL_REV_FLAGS);
 701         free(refs.objects);
 702 }
 703
 704 static int switch_branches(struct checkout_opts *opts, struct branch_info *new)
 705 {
 706         int ret = 0;
 707         struct branch_info old;
 708         void *path_to_free;
 709         unsigned char rev[20];
 710         int flag;
 711         memset(&old, 0, sizeof(old));
 712         old.path = path_to_free = resolve_refdup("HEAD", rev, 0, &flag);
 713         old.commit = lookup_commit_reference_gently(rev, 1);
 714         if (!(flag & REF_ISSYMREF))
 715                 old.path = NULL;
 716
 717         if (old.path && !prefixcmp(old.path, "refs/heads/"))
 718                 old.name = old.path + strlen("refs/heads/");
 719
 720         if (!new->name) {
 721                 new->name = "HEAD";
 722                 new->commit = old.commit;
 723                 if (!new->commit)
 724                         die(_("You are on a branch yet to be born"));
 725                 parse_commit(new->commit);
 726         }
 727
 728         ret = merge_working_tree(opts, &old, new);
 729         if (ret) {
 730                 free(path_to_free);
 731                 return ret;
 732         }
 733
 734         if (!opts->quiet && !old.path && old.commit && new->commit != old.commit)
 735                 orphaned_commit_warning(old.commit, new->commit);
 736
 737         update_refs_for_switch(opts, &old, new);
 738
 739         ret = post_checkout_hook(old.commit, new->commit, 1);
 740         free(path_to_free);
 741         return ret || opts->writeout_error;
 742 }
 743
 744 static int git_checkout_config(const char *var, const char *value, void *cb)
 745 {
 746         if (!strcmp(var, "diff.ignoresubmodules")) {
 747                 struct checkout_opts *opts = cb;
 748                 handle_ignore_submodules_arg(&opts->diff_options, value);
 749                 return 0;
 750         }
 751
 752         if (!prefixcmp(var, "submodule."))
 753                 return parse_submodule_config_option(var, value);
 754
 755         return git_xmerge_config(var, value, NULL);
 756 }
 757
 758 static int interactive_checkout(const char *revision, const char **pathspec,
 759                                 struct checkout_opts *opts)
 760 {
 761         return run_add_interactive(revision, "--patch=checkout", pathspec);
 762 }
 763
 764 struct tracking_name_data {
 765         const char *name;
 766         char *remote;
 767         int unique;
 768 };
 769
 770 static int check_tracking_name(const char *refname, const unsigned char *sha1,
 771                                int flags, void *cb_data)
 772 {
 773         struct tracking_name_data *cb = cb_data;
 774         const char *slash;
 775
 776         if (prefixcmp(refname, "refs/remotes/"))
 777                 return 0;
 778         slash = strchr(refname + 13, '/');
 779         if (!slash || strcmp(slash + 1, cb->name))
 780                 return 0;
 781         if (cb->remote) {
 782                 cb->unique = 0;
 783                 return 0;
 784         }
 785         cb->remote = xstrdup(refname);
 786         return 0;
 787 }
 788
 789 static const char *unique_tracking_name(const char *name)
 790 {
 791         struct tracking_name_data cb_data = { NULL, NULL, 1 };
 792         cb_data.name = name;
 793         for_each_ref(check_tracking_name, &cb_data);
 794         if (cb_data.unique)
 795                 return cb_data.remote;
 796         free(cb_data.remote);
 797         return NULL;
 798 }
 799
 800 static int parse_branchname_arg(int argc, const char **argv,
 801                                 int dwim_new_local_branch_ok,
 802                                 struct branch_info *new,
 803                                 struct tree **source_tree,
 804                                 unsigned char rev[20],
 805                                 const char **new_branch)
 806 {
 807         int argcount = 0;
 808         unsigned char branch_rev[20];
 809         const char *arg;
 810         int has_dash_dash;
 811
 812         /*
 813          * case 1: git checkout <ref> -- [<paths>]
 814          *
 815          *   <ref> must be a valid tree, everything after the '--' must be
 816          *   a path.
 817          *
 818          * case 2: git checkout -- [<paths>]
 819          *
 820          *   everything after the '--' must be paths.
 821          *
 822          * case 3: git checkout <something> [<paths>]
 823          *
 824          *   With no paths, if <something> is a commit, that is to
 825          *   switch to the branch or detach HEAD at it.  As a special case,
 826          *   if <something> is A...B (missing A or B means HEAD but you can
 827          *   omit at most one side), and if there is a unique merge base
 828          *   between A and B, A...B names that merge base.
 829          *
 830          *   With no paths, if <something> is _not_ a commit, no -t nor -b
 831          *   was given, and there is a tracking branch whose name is
 832          *   <something> in one and only one remote, then this is a short-hand
 833          *   to fork local <something> from that remote-tracking branch.
 834          *
 835          *   Otherwise <something> shall not be ambiguous.
 836          *   - If it's *only* a reference, treat it like case (1).
 837          *   - If it's only a path, treat it like case (2).
 838          *   - else: fail.
 839          *
 840          */
 841         if (!argc)
 842                 return 0;
 843
 844         if (!strcmp(argv[0], "--"))     /* case (2) */
 845                 return 1;
 846
 847         arg = argv[0];
 848         has_dash_dash = (argc > 1) && !strcmp(argv[1], "--");
 849
 850         if (!strcmp(arg, "-"))
 851                 arg = "@{-1}";
 852
 853         if (get_sha1_mb(arg, rev)) {
 854                 if (has_dash_dash)          /* case (1) */
 855                         die(_("invalid reference: %s"), arg);
 856                 if (dwim_new_local_branch_ok &&
 857                     !check_filename(NULL, arg) &&
 858                     argc == 1) {
 859                         const char *remote = unique_tracking_name(arg);
 860                         if (!remote || get_sha1(remote, rev))
 861                                 return argcount;
 862                         *new_branch = arg;
 863                         arg = remote;
 864                         /* DWIMmed to create local branch */
 865                 } else {
 866                         return argcount;
 867                 }
 868         }
 869
 870         /* we can't end up being in (2) anymore, eat the argument */
 871         argcount++;
 872         argv++;
 873         argc--;
 874
 875         new->name = arg;
 876         setup_branch_path(new);
 877
 878         if (!check_refname_format(new->path, 0) &&
 879             !read_ref(new->path, branch_rev))
 880                 hashcpy(rev, branch_rev);
 881         else
 882                 new->path = NULL; /* not an existing branch */
 883
 884         new->commit = lookup_commit_reference_gently(rev, 1);
 885         if (!new->commit) {
 886                 /* not a commit */
 887                 *source_tree = parse_tree_indirect(rev);
 888         } else {
 889                 parse_commit(new->commit);
 890                 *source_tree = new->commit->tree;
 891         }
 892
 893         if (!*source_tree)                   /* case (1): want a tree */
 894                 die(_("reference is not a tree: %s"), arg);
 895         if (!has_dash_dash) {/* case (3 -> 1) */
 896                 /*
 897                  * Do not complain the most common case
 898                  *      git checkout branch
 899                  * even if there happen to be a file called 'branch';
 900                  * it would be extremely annoying.
 901                  */
 902                 if (argc)
 903                         verify_non_filename(NULL, arg);
 904         } else {
 905                 argcount++;
 906                 argv++;
 907                 argc--;
 908         }
 909
 910         return argcount;
 911 }
 912
 913 static int switch_unborn_to_new_branch(struct checkout_opts *opts)
 914 {
 915         int status;
 916         struct strbuf branch_ref = STRBUF_INIT;
 917
 918         if (!opts->new_branch)
 919                 die(_("You are on a branch yet to be born"));
 920         strbuf_addf(&branch_ref, "refs/heads/%s", opts->new_branch);
 921         status = create_symref("HEAD", branch_ref.buf, "checkout -b");
 922         strbuf_release(&branch_ref);
 923         return status;
 924 }
 925
 926 int cmd_checkout(int argc, const char **argv, const char *prefix)
 927 {
 928         struct checkout_opts opts;
 929         unsigned char rev[20];
 930         struct branch_info new;
 931         struct tree *source_tree = NULL;
 932         char *conflict_style = NULL;
 933         int patch_mode = 0;
 934         int dwim_new_local_branch = 1;
 935         struct option options[] = {
 936                 OPT__QUIET(&opts.quiet, "suppress progress reporting"),
 937                 OPT_STRING('b', NULL, &opts.new_branch, "branch",
 938                            "create and checkout a new branch"),
 939                 OPT_STRING('B', NULL, &opts.new_branch_force, "branch",
 940                            "create/reset and checkout a branch"),
 941                 OPT_BOOLEAN('l', NULL, &opts.new_branch_log, "create reflog for new branch"),
 942                 OPT_BOOLEAN(0, "detach", &opts.force_detach, "detach the HEAD at named commit"),
 943                 OPT_SET_INT('t', "track",  &opts.track, "set upstream info for new branch",
 944                         BRANCH_TRACK_EXPLICIT),
 945                 OPT_STRING(0, "orphan", &opts.new_orphan_branch, "new branch", "new unparented branch"),
 946                 OPT_SET_INT('2', "ours", &opts.writeout_stage, "checkout our version for unmerged files",
 947                             2),
 948                 OPT_SET_INT('3', "theirs", &opts.writeout_stage, "checkout their version for unmerged files",
 949                             3),
 950                 OPT__FORCE(&opts.force, "force checkout (throw away local modifications)"),
 951                 OPT_BOOLEAN('m', "merge", &opts.merge, "perform a 3-way merge with the new branch"),
 952                 OPT_BOOLEAN(0, "overwrite-ignore", &opts.overwrite_ignore, "update ignored files (default)"),
 953                 OPT_STRING(0, "conflict", &conflict_style, "style",
 954                            "conflict style (merge or diff3)"),
 955                 OPT_BOOLEAN('p', "patch", &patch_mode, "select hunks interactively"),
 956                 { OPTION_BOOLEAN, 0, "guess", &dwim_new_local_branch, NULL,
 957                   "second guess 'git checkout no-such-branch'",
 958                   PARSE_OPT_NOARG | PARSE_OPT_HIDDEN },
 959                 OPT_END(),
 960         };
 961
 962         memset(&opts, 0, sizeof(opts));
 963         memset(&new, 0, sizeof(new));
 964         opts.overwrite_ignore = 1;
 965
 966         gitmodules_config();
 967         git_config(git_checkout_config, &opts);
 968
 969         opts.track = BRANCH_TRACK_UNSPECIFIED;
 970
 971         argc = parse_options(argc, argv, prefix, options, checkout_usage,
 972                              PARSE_OPT_KEEP_DASHDASH);
 973
 974         /* we can assume from now on new_branch = !new_branch_force */
 975         if (opts.new_branch && opts.new_branch_force)
 976                 die(_("-B cannot be used with -b"));
 977
 978         /* copy -B over to -b, so that we can just check the latter */
 979         if (opts.new_branch_force)
 980                 opts.new_branch = opts.new_branch_force;
 981
 982         if (patch_mode && (opts.track > 0 || opts.new_branch
 983                            || opts.new_branch_log || opts.merge || opts.force
 984                            || opts.force_detach))
 985                 die (_("--patch is incompatible with all other options"));
 986
 987         if (opts.force_detach && (opts.new_branch || opts.new_orphan_branch))
 988                 die(_("--detach cannot be used with -b/-B/--orphan"));
 989         if (opts.force_detach && 0 < opts.track)
 990                 die(_("--detach cannot be used with -t"));
 991
 992         /* --track without -b should DWIM */
 993         if (0 < opts.track && !opts.new_branch) {
 994                 const char *argv0 = argv[0];
 995                 if (!argc || !strcmp(argv0, "--"))
 996                         die (_("--track needs a branch name"));
 997                 if (!prefixcmp(argv0, "refs/"))
 998                         argv0 += 5;
 999                 if (!prefixcmp(argv0, "remotes/"))
1000                         argv0 += 8;
1001                 argv0 = strchr(argv0, '/');
1002                 if (!argv0 || !argv0[1])
1003                         die (_("Missing branch name; try -b"));
1004                 opts.new_branch = argv0 + 1;
1005         }
1006
1007         if (opts.new_orphan_branch) {
1008                 if (opts.new_branch)
1009                         die(_("--orphan and -b|-B are mutually exclusive"));
1010                 if (opts.track > 0)
1011                         die(_("--orphan cannot be used with -t"));
1012                 opts.new_branch = opts.new_orphan_branch;
1013         }
1014
1015         if (conflict_style) {
1016                 opts.merge = 1; /* implied */
1017                 git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
1018         }
1019
1020         if (opts.force && opts.merge)
1021                 die(_("git checkout: -f and -m are incompatible"));
1022
1023         /*
1024          * Extract branch name from command line arguments, so
1025          * all that is left is pathspecs.
1026          *
1027          * Handle
1028          *
1029          *  1) git checkout <tree> -- [<paths>]
1030          *  2) git checkout -- [<paths>]
1031          *  3) git checkout <something> [<paths>]
1032          *
1033          * including "last branch" syntax and DWIM-ery for names of
1034          * remote branches, erroring out for invalid or ambiguous cases.
1035          */
1036         if (argc) {
1037                 int dwim_ok =
1038                         !patch_mode &&
1039                         dwim_new_local_branch &&
1040                         opts.track == BRANCH_TRACK_UNSPECIFIED &&
1041                         !opts.new_branch;
1042                 int n = parse_branchname_arg(argc, argv, dwim_ok,
1043                                 &new, &source_tree, rev, &opts.new_branch);
1044                 argv += n;
1045                 argc -= n;
1046         }
1047
1048         if (opts.track == BRANCH_TRACK_UNSPECIFIED)
1049                 opts.track = git_branch_track;
1050
1051         if (argc) {
1052                 const char **pathspec = get_pathspec(prefix, argv);
1053
1054                 if (!pathspec)
1055                         die(_("invalid path specification"));
1056
1057                 if (patch_mode)
1058                         return interactive_checkout(new.name, pathspec, &opts);
1059
1060                 /* Checkout paths */
1061                 if (opts.new_branch) {
1062                         if (argc == 1) {
1063                                 die(_("git checkout: updating paths is incompatible with switching branches.\nDid you intend to checkout '%s' which can not be resolved as commit?"), argv[0]);
1064                         } else {
1065                                 die(_("git checkout: updating paths is incompatible with switching branches."));
1066                         }
1067                 }
1068
1069                 if (opts.force_detach)
1070                         die(_("git checkout: --detach does not take a path argument"));
1071
1072                 if (1 < !!opts.writeout_stage + !!opts.force + !!opts.merge)
1073                         die(_("git checkout: --ours/--theirs, --force and --merge are incompatible when\nchecking out of the index."));
1074
1075                 return checkout_paths(source_tree, pathspec, prefix, &opts);
1076         }
1077
1078         if (patch_mode)
1079                 return interactive_checkout(new.name, NULL, &opts);
1080
1081         if (opts.new_branch) {
1082                 struct strbuf buf = STRBUF_INIT;
1083
1084                 opts.branch_exists = validate_new_branchname(opts.new_branch, &buf,
1085                                                              !!opts.new_branch_force,
1086                                                              !!opts.new_branch_force);
1087
1088                 strbuf_release(&buf);
1089         }
1090
1091         if (new.name && !new.commit) {
1092                 die(_("Cannot switch branch to a non-commit."));
1093         }
1094         if (opts.writeout_stage)
1095                 die(_("--ours/--theirs is incompatible with switching branches."));
1096
1097         if (!new.commit && opts.new_branch) {
1098                 unsigned char rev[20];
1099                 int flag;
1100
1101                 if (!read_ref_full("HEAD", rev, 0, &flag) &&
1102                     (flag & REF_ISSYMREF) && is_null_sha1(rev))
1103                         return switch_unborn_to_new_branch(&opts);
1104         }
1105         return switch_branches(&opts, &new);
1106 }