Merge branch 'rs/plug-leak-in-pack-bitmaps'
[git] / builtin / checkout.c
1 #include "builtin.h"
2 #include "lockfile.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 #include "sigchain.h"
24
25 static const char * const checkout_usage[] = {
26         N_("git checkout [<options>] <branch>"),
27         N_("git checkout [<options>] [<branch>] -- <file>..."),
28         NULL,
29 };
30
31 struct checkout_opts {
32         int patch_mode;
33         int quiet;
34         int merge;
35         int force;
36         int force_detach;
37         int writeout_stage;
38         int overwrite_ignore;
39         int ignore_skipworktree;
40         int ignore_other_worktrees;
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         int branch_exists;
50         const char *prefix;
51         struct pathspec pathspec;
52         struct tree *source_tree;
53
54         const char *new_worktree;
55         const char **saved_argv;
56         int new_worktree_mode;
57 };
58
59 static int post_checkout_hook(struct commit *old, struct commit *new,
60                               int changed)
61 {
62         return run_hook_le(NULL, "post-checkout",
63                            sha1_to_hex(old ? old->object.sha1 : null_sha1),
64                            sha1_to_hex(new ? new->object.sha1 : null_sha1),
65                            changed ? "1" : "0", NULL);
66         /* "new" can be NULL when checking out from the index before
67            a commit exists. */
68
69 }
70
71 static int update_some(const unsigned char *sha1, struct strbuf *base,
72                 const char *pathname, unsigned mode, int stage, void *context)
73 {
74         int len;
75         struct cache_entry *ce;
76         int pos;
77
78         if (S_ISDIR(mode))
79                 return READ_TREE_RECURSIVE;
80
81         len = base->len + strlen(pathname);
82         ce = xcalloc(1, cache_entry_size(len));
83         hashcpy(ce->sha1, sha1);
84         memcpy(ce->name, base->buf, base->len);
85         memcpy(ce->name + base->len, pathname, len - base->len);
86         ce->ce_flags = create_ce_flags(0) | CE_UPDATE;
87         ce->ce_namelen = len;
88         ce->ce_mode = create_ce_mode(mode);
89
90         /*
91          * If the entry is the same as the current index, we can leave the old
92          * entry in place. Whether it is UPTODATE or not, checkout_entry will
93          * do the right thing.
94          */
95         pos = cache_name_pos(ce->name, ce->ce_namelen);
96         if (pos >= 0) {
97                 struct cache_entry *old = active_cache[pos];
98                 if (ce->ce_mode == old->ce_mode &&
99                     !hashcmp(ce->sha1, old->sha1)) {
100                         old->ce_flags |= CE_UPDATE;
101                         free(ce);
102                         return 0;
103                 }
104         }
105
106         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
107         return 0;
108 }
109
110 static int read_tree_some(struct tree *tree, const struct pathspec *pathspec)
111 {
112         read_tree_recursive(tree, "", 0, 0, pathspec, update_some, NULL);
113
114         /* update the index with the given tree's info
115          * for all args, expanding wildcards, and exit
116          * with any non-zero return code.
117          */
118         return 0;
119 }
120
121 static int skip_same_name(const struct cache_entry *ce, int pos)
122 {
123         while (++pos < active_nr &&
124                !strcmp(active_cache[pos]->name, ce->name))
125                 ; /* skip */
126         return pos;
127 }
128
129 static int check_stage(int stage, const struct cache_entry *ce, int pos)
130 {
131         while (pos < active_nr &&
132                !strcmp(active_cache[pos]->name, ce->name)) {
133                 if (ce_stage(active_cache[pos]) == stage)
134                         return 0;
135                 pos++;
136         }
137         if (stage == 2)
138                 return error(_("path '%s' does not have our version"), ce->name);
139         else
140                 return error(_("path '%s' does not have their version"), ce->name);
141 }
142
143 static int check_stages(unsigned stages, const struct cache_entry *ce, int pos)
144 {
145         unsigned seen = 0;
146         const char *name = ce->name;
147
148         while (pos < active_nr) {
149                 ce = active_cache[pos];
150                 if (strcmp(name, ce->name))
151                         break;
152                 seen |= (1 << ce_stage(ce));
153                 pos++;
154         }
155         if ((stages & seen) != stages)
156                 return error(_("path '%s' does not have all necessary versions"),
157                              name);
158         return 0;
159 }
160
161 static int checkout_stage(int stage, struct cache_entry *ce, int pos,
162                           struct checkout *state)
163 {
164         while (pos < active_nr &&
165                !strcmp(active_cache[pos]->name, ce->name)) {
166                 if (ce_stage(active_cache[pos]) == stage)
167                         return checkout_entry(active_cache[pos], state, NULL);
168                 pos++;
169         }
170         if (stage == 2)
171                 return error(_("path '%s' does not have our version"), ce->name);
172         else
173                 return error(_("path '%s' does not have their version"), ce->name);
174 }
175
176 static int checkout_merged(int pos, struct checkout *state)
177 {
178         struct cache_entry *ce = active_cache[pos];
179         const char *path = ce->name;
180         mmfile_t ancestor, ours, theirs;
181         int status;
182         unsigned char sha1[20];
183         mmbuffer_t result_buf;
184         unsigned char threeway[3][20];
185         unsigned mode = 0;
186
187         memset(threeway, 0, sizeof(threeway));
188         while (pos < active_nr) {
189                 int stage;
190                 stage = ce_stage(ce);
191                 if (!stage || strcmp(path, ce->name))
192                         break;
193                 hashcpy(threeway[stage - 1], ce->sha1);
194                 if (stage == 2)
195                         mode = create_ce_mode(ce->ce_mode);
196                 pos++;
197                 ce = active_cache[pos];
198         }
199         if (is_null_sha1(threeway[1]) || is_null_sha1(threeway[2]))
200                 return error(_("path '%s' does not have necessary versions"), path);
201
202         read_mmblob(&ancestor, threeway[0]);
203         read_mmblob(&ours, threeway[1]);
204         read_mmblob(&theirs, threeway[2]);
205
206         /*
207          * NEEDSWORK: re-create conflicts from merges with
208          * merge.renormalize set, too
209          */
210         status = ll_merge(&result_buf, path, &ancestor, "base",
211                           &ours, "ours", &theirs, "theirs", NULL);
212         free(ancestor.ptr);
213         free(ours.ptr);
214         free(theirs.ptr);
215         if (status < 0 || !result_buf.ptr) {
216                 free(result_buf.ptr);
217                 return error(_("path '%s': cannot merge"), path);
218         }
219
220         /*
221          * NEEDSWORK:
222          * There is absolutely no reason to write this as a blob object
223          * and create a phony cache entry just to leak.  This hack is
224          * primarily to get to the write_entry() machinery that massages
225          * the contents to work-tree format and writes out which only
226          * allows it for a cache entry.  The code in write_entry() needs
227          * to be refactored to allow us to feed a <buffer, size, mode>
228          * instead of a cache entry.  Such a refactoring would help
229          * merge_recursive as well (it also writes the merge result to the
230          * object database even when it may contain conflicts).
231          */
232         if (write_sha1_file(result_buf.ptr, result_buf.size,
233                             blob_type, sha1))
234                 die(_("Unable to add merge result for '%s'"), path);
235         ce = make_cache_entry(mode, sha1, path, 2, 0);
236         if (!ce)
237                 die(_("make_cache_entry failed for path '%s'"), path);
238         status = checkout_entry(ce, state, NULL);
239         return status;
240 }
241
242 static int checkout_paths(const struct checkout_opts *opts,
243                           const char *revision)
244 {
245         int pos;
246         struct checkout state;
247         static char *ps_matched;
248         unsigned char rev[20];
249         int flag;
250         struct commit *head;
251         int errs = 0;
252         struct lock_file *lock_file;
253
254         if (opts->track != BRANCH_TRACK_UNSPECIFIED)
255                 die(_("'%s' cannot be used with updating paths"), "--track");
256
257         if (opts->new_branch_log)
258                 die(_("'%s' cannot be used with updating paths"), "-l");
259
260         if (opts->force && opts->patch_mode)
261                 die(_("'%s' cannot be used with updating paths"), "-f");
262
263         if (opts->force_detach)
264                 die(_("'%s' cannot be used with updating paths"), "--detach");
265
266         if (opts->merge && opts->patch_mode)
267                 die(_("'%s' cannot be used with %s"), "--merge", "--patch");
268
269         if (opts->force && opts->merge)
270                 die(_("'%s' cannot be used with %s"), "-f", "-m");
271
272         if (opts->new_branch)
273                 die(_("Cannot update paths and switch to branch '%s' at the same time."),
274                     opts->new_branch);
275
276         if (opts->new_worktree)
277                 die(_("'%s' cannot be used with updating paths"), "--to");
278
279         if (opts->patch_mode)
280                 return run_add_interactive(revision, "--patch=checkout",
281                                            &opts->pathspec);
282
283         lock_file = xcalloc(1, sizeof(struct lock_file));
284
285         hold_locked_index(lock_file, 1);
286         if (read_cache_preload(&opts->pathspec) < 0)
287                 return error(_("corrupt index file"));
288
289         if (opts->source_tree)
290                 read_tree_some(opts->source_tree, &opts->pathspec);
291
292         ps_matched = xcalloc(1, opts->pathspec.nr);
293
294         /*
295          * Make sure all pathspecs participated in locating the paths
296          * to be checked out.
297          */
298         for (pos = 0; pos < active_nr; pos++) {
299                 struct cache_entry *ce = active_cache[pos];
300                 ce->ce_flags &= ~CE_MATCHED;
301                 if (!opts->ignore_skipworktree && ce_skip_worktree(ce))
302                         continue;
303                 if (opts->source_tree && !(ce->ce_flags & CE_UPDATE))
304                         /*
305                          * "git checkout tree-ish -- path", but this entry
306                          * is in the original index; it will not be checked
307                          * out to the working tree and it does not matter
308                          * if pathspec matched this entry.  We will not do
309                          * anything to this entry at all.
310                          */
311                         continue;
312                 /*
313                  * Either this entry came from the tree-ish we are
314                  * checking the paths out of, or we are checking out
315                  * of the index.
316                  *
317                  * If it comes from the tree-ish, we already know it
318                  * matches the pathspec and could just stamp
319                  * CE_MATCHED to it from update_some(). But we still
320                  * need ps_matched and read_tree_recursive (and
321                  * eventually tree_entry_interesting) cannot fill
322                  * ps_matched yet. Once it can, we can avoid calling
323                  * match_pathspec() for _all_ entries when
324                  * opts->source_tree != NULL.
325                  */
326                 if (ce_path_match(ce, &opts->pathspec, ps_matched))
327                         ce->ce_flags |= CE_MATCHED;
328         }
329
330         if (report_path_error(ps_matched, &opts->pathspec, opts->prefix)) {
331                 free(ps_matched);
332                 return 1;
333         }
334         free(ps_matched);
335
336         /* "checkout -m path" to recreate conflicted state */
337         if (opts->merge)
338                 unmerge_marked_index(&the_index);
339
340         /* Any unmerged paths? */
341         for (pos = 0; pos < active_nr; pos++) {
342                 const struct cache_entry *ce = active_cache[pos];
343                 if (ce->ce_flags & CE_MATCHED) {
344                         if (!ce_stage(ce))
345                                 continue;
346                         if (opts->force) {
347                                 warning(_("path '%s' is unmerged"), ce->name);
348                         } else if (opts->writeout_stage) {
349                                 errs |= check_stage(opts->writeout_stage, ce, pos);
350                         } else if (opts->merge) {
351                                 errs |= check_stages((1<<2) | (1<<3), ce, pos);
352                         } else {
353                                 errs = 1;
354                                 error(_("path '%s' is unmerged"), ce->name);
355                         }
356                         pos = skip_same_name(ce, pos) - 1;
357                 }
358         }
359         if (errs)
360                 return 1;
361
362         /* Now we are committed to check them out */
363         memset(&state, 0, sizeof(state));
364         state.force = 1;
365         state.refresh_cache = 1;
366         state.istate = &the_index;
367         for (pos = 0; pos < active_nr; pos++) {
368                 struct cache_entry *ce = active_cache[pos];
369                 if (ce->ce_flags & CE_MATCHED) {
370                         if (!ce_stage(ce)) {
371                                 errs |= checkout_entry(ce, &state, NULL);
372                                 continue;
373                         }
374                         if (opts->writeout_stage)
375                                 errs |= checkout_stage(opts->writeout_stage, ce, pos, &state);
376                         else if (opts->merge)
377                                 errs |= checkout_merged(pos, &state);
378                         pos = skip_same_name(ce, pos) - 1;
379                 }
380         }
381
382         if (write_locked_index(&the_index, lock_file, COMMIT_LOCK))
383                 die(_("unable to write new index file"));
384
385         read_ref_full("HEAD", 0, rev, &flag);
386         head = lookup_commit_reference_gently(rev, 1);
387
388         errs |= post_checkout_hook(head, head, 0);
389         return errs;
390 }
391
392 static void show_local_changes(struct object *head,
393                                const struct diff_options *opts)
394 {
395         struct rev_info rev;
396         /* I think we want full paths, even if we're in a subdirectory. */
397         init_revisions(&rev, NULL);
398         rev.diffopt.flags = opts->flags;
399         rev.diffopt.output_format |= DIFF_FORMAT_NAME_STATUS;
400         diff_setup_done(&rev.diffopt);
401         add_pending_object(&rev, head, NULL);
402         run_diff_index(&rev, 0);
403 }
404
405 static void describe_detached_head(const char *msg, struct commit *commit)
406 {
407         struct strbuf sb = STRBUF_INIT;
408         if (!parse_commit(commit))
409                 pp_commit_easy(CMIT_FMT_ONELINE, commit, &sb);
410         fprintf(stderr, "%s %s... %s\n", msg,
411                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV), sb.buf);
412         strbuf_release(&sb);
413 }
414
415 static int reset_tree(struct tree *tree, const struct checkout_opts *o,
416                       int worktree, int *writeout_error)
417 {
418         struct unpack_trees_options opts;
419         struct tree_desc tree_desc;
420
421         memset(&opts, 0, sizeof(opts));
422         opts.head_idx = -1;
423         opts.update = worktree;
424         opts.skip_unmerged = !worktree;
425         opts.reset = 1;
426         opts.merge = 1;
427         opts.fn = oneway_merge;
428         opts.verbose_update = !o->quiet && isatty(2);
429         opts.src_index = &the_index;
430         opts.dst_index = &the_index;
431         parse_tree(tree);
432         init_tree_desc(&tree_desc, tree->buffer, tree->size);
433         switch (unpack_trees(1, &tree_desc, &opts)) {
434         case -2:
435                 *writeout_error = 1;
436                 /*
437                  * We return 0 nevertheless, as the index is all right
438                  * and more importantly we have made best efforts to
439                  * update paths in the work tree, and we cannot revert
440                  * them.
441                  */
442         case 0:
443                 return 0;
444         default:
445                 return 128;
446         }
447 }
448
449 struct branch_info {
450         const char *name; /* The short name used */
451         const char *path; /* The full name of a real branch */
452         struct commit *commit; /* The named commit */
453         /*
454          * if not null the branch is detached because it's already
455          * checked out in this checkout
456          */
457         char *checkout;
458 };
459
460 static void setup_branch_path(struct branch_info *branch)
461 {
462         struct strbuf buf = STRBUF_INIT;
463
464         strbuf_branchname(&buf, branch->name);
465         if (strcmp(buf.buf, branch->name))
466                 branch->name = xstrdup(buf.buf);
467         strbuf_splice(&buf, 0, 0, "refs/heads/", 11);
468         branch->path = strbuf_detach(&buf, NULL);
469 }
470
471 static int merge_working_tree(const struct checkout_opts *opts,
472                               struct branch_info *old,
473                               struct branch_info *new,
474                               int *writeout_error)
475 {
476         int ret;
477         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
478
479         hold_locked_index(lock_file, 1);
480         if (read_cache_preload(NULL) < 0)
481                 return error(_("corrupt index file"));
482
483         resolve_undo_clear();
484         if (opts->force) {
485                 ret = reset_tree(new->commit->tree, opts, 1, writeout_error);
486                 if (ret)
487                         return ret;
488         } else {
489                 struct tree_desc trees[2];
490                 struct tree *tree;
491                 struct unpack_trees_options topts;
492
493                 memset(&topts, 0, sizeof(topts));
494                 topts.head_idx = -1;
495                 topts.src_index = &the_index;
496                 topts.dst_index = &the_index;
497
498                 setup_unpack_trees_porcelain(&topts, "checkout");
499
500                 refresh_cache(REFRESH_QUIET);
501
502                 if (unmerged_cache()) {
503                         error(_("you need to resolve your current index first"));
504                         return 1;
505                 }
506
507                 /* 2-way merge to the new branch */
508                 topts.initial_checkout = is_cache_unborn();
509                 topts.update = 1;
510                 topts.merge = 1;
511                 topts.gently = opts->merge && old->commit;
512                 topts.verbose_update = !opts->quiet && isatty(2);
513                 topts.fn = twoway_merge;
514                 if (opts->overwrite_ignore) {
515                         topts.dir = xcalloc(1, sizeof(*topts.dir));
516                         topts.dir->flags |= DIR_SHOW_IGNORED;
517                         setup_standard_excludes(topts.dir);
518                 }
519                 tree = parse_tree_indirect(old->commit && !opts->new_worktree_mode ?
520                                            old->commit->object.sha1 :
521                                            EMPTY_TREE_SHA1_BIN);
522                 init_tree_desc(&trees[0], tree->buffer, tree->size);
523                 tree = parse_tree_indirect(new->commit->object.sha1);
524                 init_tree_desc(&trees[1], tree->buffer, tree->size);
525
526                 ret = unpack_trees(2, trees, &topts);
527                 if (ret == -1) {
528                         /*
529                          * Unpack couldn't do a trivial merge; either
530                          * give up or do a real merge, depending on
531                          * whether the merge flag was used.
532                          */
533                         struct tree *result;
534                         struct tree *work;
535                         struct merge_options o;
536                         if (!opts->merge)
537                                 return 1;
538
539                         /*
540                          * Without old->commit, the below is the same as
541                          * the two-tree unpack we already tried and failed.
542                          */
543                         if (!old->commit)
544                                 return 1;
545
546                         /* Do more real merge */
547
548                         /*
549                          * We update the index fully, then write the
550                          * tree from the index, then merge the new
551                          * branch with the current tree, with the old
552                          * branch as the base. Then we reset the index
553                          * (but not the working tree) to the new
554                          * branch, leaving the working tree as the
555                          * merged version, but skipping unmerged
556                          * entries in the index.
557                          */
558
559                         add_files_to_cache(NULL, NULL, 0);
560                         /*
561                          * NEEDSWORK: carrying over local changes
562                          * when branches have different end-of-line
563                          * normalization (or clean+smudge rules) is
564                          * a pain; plumb in an option to set
565                          * o.renormalize?
566                          */
567                         init_merge_options(&o);
568                         o.verbosity = 0;
569                         work = write_tree_from_memory(&o);
570
571                         ret = reset_tree(new->commit->tree, opts, 1,
572                                          writeout_error);
573                         if (ret)
574                                 return ret;
575                         o.ancestor = old->name;
576                         o.branch1 = new->name;
577                         o.branch2 = "local";
578                         merge_trees(&o, new->commit->tree, work,
579                                 old->commit->tree, &result);
580                         ret = reset_tree(new->commit->tree, opts, 0,
581                                          writeout_error);
582                         if (ret)
583                                 return ret;
584                 }
585         }
586
587         if (!active_cache_tree)
588                 active_cache_tree = cache_tree();
589
590         if (!cache_tree_fully_valid(active_cache_tree))
591                 cache_tree_update(&the_index, WRITE_TREE_SILENT | WRITE_TREE_REPAIR);
592
593         if (write_locked_index(&the_index, lock_file, COMMIT_LOCK))
594                 die(_("unable to write new index file"));
595
596         if (!opts->force && !opts->quiet)
597                 show_local_changes(&new->commit->object, &opts->diff_options);
598
599         return 0;
600 }
601
602 static void report_tracking(struct branch_info *new)
603 {
604         struct strbuf sb = STRBUF_INIT;
605         struct branch *branch = branch_get(new->name);
606
607         if (!format_tracking_info(branch, &sb))
608                 return;
609         fputs(sb.buf, stdout);
610         strbuf_release(&sb);
611 }
612
613 static void update_refs_for_switch(const struct checkout_opts *opts,
614                                    struct branch_info *old,
615                                    struct branch_info *new)
616 {
617         struct strbuf msg = STRBUF_INIT;
618         const char *old_desc, *reflog_msg;
619         if (opts->new_branch) {
620                 if (opts->new_orphan_branch) {
621                         if (opts->new_branch_log && !log_all_ref_updates) {
622                                 int temp;
623                                 struct strbuf log_file = STRBUF_INIT;
624                                 int ret;
625                                 const char *ref_name;
626
627                                 ref_name = mkpath("refs/heads/%s", opts->new_orphan_branch);
628                                 temp = log_all_ref_updates;
629                                 log_all_ref_updates = 1;
630                                 ret = log_ref_setup(ref_name, &log_file);
631                                 log_all_ref_updates = temp;
632                                 strbuf_release(&log_file);
633                                 if (ret) {
634                                         fprintf(stderr, _("Can not do reflog for '%s'\n"),
635                                             opts->new_orphan_branch);
636                                         return;
637                                 }
638                         }
639                 }
640                 else
641                         create_branch(old->name, opts->new_branch, new->name,
642                                       opts->new_branch_force ? 1 : 0,
643                                       opts->new_branch_log,
644                                       opts->new_branch_force ? 1 : 0,
645                                       opts->quiet,
646                                       opts->track);
647                 new->name = opts->new_branch;
648                 setup_branch_path(new);
649         }
650
651         old_desc = old->name;
652         if (!old_desc && old->commit)
653                 old_desc = sha1_to_hex(old->commit->object.sha1);
654
655         reflog_msg = getenv("GIT_REFLOG_ACTION");
656         if (!reflog_msg)
657                 strbuf_addf(&msg, "checkout: moving from %s to %s",
658                         old_desc ? old_desc : "(invalid)", new->name);
659         else
660                 strbuf_insert(&msg, 0, reflog_msg, strlen(reflog_msg));
661
662         if (!strcmp(new->name, "HEAD") && !new->path && !opts->force_detach) {
663                 /* Nothing to do. */
664         } else if (opts->force_detach || !new->path) {  /* No longer on any branch. */
665                 update_ref(msg.buf, "HEAD", new->commit->object.sha1, NULL,
666                            REF_NODEREF, UPDATE_REFS_DIE_ON_ERR);
667                 if (!opts->quiet) {
668                         if (old->path && advice_detached_head)
669                                 detach_advice(new->name);
670                         describe_detached_head(_("HEAD is now at"), new->commit);
671                 }
672         } else if (new->path) { /* Switch branches. */
673                 create_symref("HEAD", new->path, msg.buf);
674                 if (!opts->quiet) {
675                         if (old->path && !strcmp(new->path, old->path)) {
676                                 if (opts->new_branch_force)
677                                         fprintf(stderr, _("Reset branch '%s'\n"),
678                                                 new->name);
679                                 else
680                                         fprintf(stderr, _("Already on '%s'\n"),
681                                                 new->name);
682                         } else if (opts->new_branch) {
683                                 if (opts->branch_exists)
684                                         fprintf(stderr, _("Switched to and reset branch '%s'\n"), new->name);
685                                 else
686                                         fprintf(stderr, _("Switched to a new branch '%s'\n"), new->name);
687                         } else {
688                                 fprintf(stderr, _("Switched to branch '%s'\n"),
689                                         new->name);
690                         }
691                 }
692                 if (old->path && old->name) {
693                         if (!ref_exists(old->path) && reflog_exists(old->path))
694                                 delete_reflog(old->path);
695                 }
696         }
697         remove_branch_state();
698         strbuf_release(&msg);
699         if (!opts->quiet &&
700             (new->path || (!opts->force_detach && !strcmp(new->name, "HEAD"))))
701                 report_tracking(new);
702 }
703
704 static int add_pending_uninteresting_ref(const char *refname,
705                                          const unsigned char *sha1,
706                                          int flags, void *cb_data)
707 {
708         add_pending_sha1(cb_data, refname, sha1, UNINTERESTING);
709         return 0;
710 }
711
712 static void describe_one_orphan(struct strbuf *sb, struct commit *commit)
713 {
714         strbuf_addstr(sb, "  ");
715         strbuf_addstr(sb,
716                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
717         strbuf_addch(sb, ' ');
718         if (!parse_commit(commit))
719                 pp_commit_easy(CMIT_FMT_ONELINE, commit, sb);
720         strbuf_addch(sb, '\n');
721 }
722
723 #define ORPHAN_CUTOFF 4
724 static void suggest_reattach(struct commit *commit, struct rev_info *revs)
725 {
726         struct commit *c, *last = NULL;
727         struct strbuf sb = STRBUF_INIT;
728         int lost = 0;
729         while ((c = get_revision(revs)) != NULL) {
730                 if (lost < ORPHAN_CUTOFF)
731                         describe_one_orphan(&sb, c);
732                 last = c;
733                 lost++;
734         }
735         if (ORPHAN_CUTOFF < lost) {
736                 int more = lost - ORPHAN_CUTOFF;
737                 if (more == 1)
738                         describe_one_orphan(&sb, last);
739                 else
740                         strbuf_addf(&sb, _(" ... and %d more.\n"), more);
741         }
742
743         fprintf(stderr,
744                 Q_(
745                 /* The singular version */
746                 "Warning: you are leaving %d commit behind, "
747                 "not connected to\n"
748                 "any of your branches:\n\n"
749                 "%s\n",
750                 /* The plural version */
751                 "Warning: you are leaving %d commits behind, "
752                 "not connected to\n"
753                 "any of your branches:\n\n"
754                 "%s\n",
755                 /* Give ngettext() the count */
756                 lost),
757                 lost,
758                 sb.buf);
759         strbuf_release(&sb);
760
761         if (advice_detached_head)
762                 fprintf(stderr,
763                         Q_(
764                         /* The singular version */
765                         "If you want to keep it by creating a new branch, "
766                         "this may be a good time\nto do so with:\n\n"
767                         " git branch <new-branch-name> %s\n\n",
768                         /* The plural version */
769                         "If you want to keep them by creating a new branch, "
770                         "this may be a good time\nto do so with:\n\n"
771                         " git branch <new-branch-name> %s\n\n",
772                         /* Give ngettext() the count */
773                         lost),
774                         find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
775 }
776
777 /*
778  * We are about to leave commit that was at the tip of a detached
779  * HEAD.  If it is not reachable from any ref, this is the last chance
780  * for the user to do so without resorting to reflog.
781  */
782 static void orphaned_commit_warning(struct commit *old, struct commit *new)
783 {
784         struct rev_info revs;
785         struct object *object = &old->object;
786         struct object_array refs;
787
788         init_revisions(&revs, NULL);
789         setup_revisions(0, NULL, &revs, NULL);
790
791         object->flags &= ~UNINTERESTING;
792         add_pending_object(&revs, object, sha1_to_hex(object->sha1));
793
794         for_each_ref(add_pending_uninteresting_ref, &revs);
795         add_pending_sha1(&revs, "HEAD", new->object.sha1, UNINTERESTING);
796
797         refs = revs.pending;
798         revs.leak_pending = 1;
799
800         if (prepare_revision_walk(&revs))
801                 die(_("internal error in revision walk"));
802         if (!(old->object.flags & UNINTERESTING))
803                 suggest_reattach(old, &revs);
804         else
805                 describe_detached_head(_("Previous HEAD position was"), old);
806
807         clear_commit_marks_for_object_array(&refs, ALL_REV_FLAGS);
808         free(refs.objects);
809 }
810
811 static int switch_branches(const struct checkout_opts *opts,
812                            struct branch_info *new)
813 {
814         int ret = 0;
815         struct branch_info old;
816         void *path_to_free;
817         unsigned char rev[20];
818         int flag, writeout_error = 0;
819         memset(&old, 0, sizeof(old));
820         old.path = path_to_free = resolve_refdup("HEAD", 0, rev, &flag);
821         old.commit = lookup_commit_reference_gently(rev, 1);
822         if (!(flag & REF_ISSYMREF))
823                 old.path = NULL;
824
825         if (old.path)
826                 skip_prefix(old.path, "refs/heads/", &old.name);
827
828         if (!new->name) {
829                 new->name = "HEAD";
830                 new->commit = old.commit;
831                 if (!new->commit)
832                         die(_("You are on a branch yet to be born"));
833                 parse_commit_or_die(new->commit);
834         }
835
836         ret = merge_working_tree(opts, &old, new, &writeout_error);
837         if (ret) {
838                 free(path_to_free);
839                 return ret;
840         }
841
842         if (!opts->quiet && !old.path && old.commit &&
843             new->commit != old.commit && !opts->new_worktree_mode)
844                 orphaned_commit_warning(old.commit, new->commit);
845
846         update_refs_for_switch(opts, &old, new);
847
848         ret = post_checkout_hook(old.commit, new->commit, 1);
849         free(path_to_free);
850         return ret || writeout_error;
851 }
852
853 static char *junk_work_tree;
854 static char *junk_git_dir;
855 static int is_junk;
856 static pid_t junk_pid;
857
858 static void remove_junk(void)
859 {
860         struct strbuf sb = STRBUF_INIT;
861         if (!is_junk || getpid() != junk_pid)
862                 return;
863         if (junk_git_dir) {
864                 strbuf_addstr(&sb, junk_git_dir);
865                 remove_dir_recursively(&sb, 0);
866                 strbuf_reset(&sb);
867         }
868         if (junk_work_tree) {
869                 strbuf_addstr(&sb, junk_work_tree);
870                 remove_dir_recursively(&sb, 0);
871         }
872         strbuf_release(&sb);
873 }
874
875 static void remove_junk_on_signal(int signo)
876 {
877         remove_junk();
878         sigchain_pop(signo);
879         raise(signo);
880 }
881
882 static int prepare_linked_checkout(const struct checkout_opts *opts,
883                                    struct branch_info *new)
884 {
885         struct strbuf sb_git = STRBUF_INIT, sb_repo = STRBUF_INIT;
886         struct strbuf sb = STRBUF_INIT;
887         const char *path = opts->new_worktree, *name;
888         struct stat st;
889         struct child_process cp;
890         int counter = 0, len, ret;
891
892         if (!new->commit)
893                 die(_("no branch specified"));
894         if (file_exists(path) && !is_empty_dir(path))
895                 die(_("'%s' already exists"), path);
896
897         len = strlen(path);
898         while (len && is_dir_sep(path[len - 1]))
899                 len--;
900
901         for (name = path + len - 1; name > path; name--)
902                 if (is_dir_sep(*name)) {
903                         name++;
904                         break;
905                 }
906         strbuf_addstr(&sb_repo,
907                       git_path("worktrees/%.*s", (int)(path + len - name), name));
908         len = sb_repo.len;
909         if (safe_create_leading_directories_const(sb_repo.buf))
910                 die_errno(_("could not create leading directories of '%s'"),
911                           sb_repo.buf);
912         while (!stat(sb_repo.buf, &st)) {
913                 counter++;
914                 strbuf_setlen(&sb_repo, len);
915                 strbuf_addf(&sb_repo, "%d", counter);
916         }
917         name = strrchr(sb_repo.buf, '/') + 1;
918
919         junk_pid = getpid();
920         atexit(remove_junk);
921         sigchain_push_common(remove_junk_on_signal);
922
923         if (mkdir(sb_repo.buf, 0777))
924                 die_errno(_("could not create directory of '%s'"), sb_repo.buf);
925         junk_git_dir = xstrdup(sb_repo.buf);
926         is_junk = 1;
927
928         /*
929          * lock the incomplete repo so prune won't delete it, unlock
930          * after the preparation is over.
931          */
932         strbuf_addf(&sb, "%s/locked", sb_repo.buf);
933         write_file(sb.buf, 1, "initializing\n");
934
935         strbuf_addf(&sb_git, "%s/.git", path);
936         if (safe_create_leading_directories_const(sb_git.buf))
937                 die_errno(_("could not create leading directories of '%s'"),
938                           sb_git.buf);
939         junk_work_tree = xstrdup(path);
940
941         strbuf_reset(&sb);
942         strbuf_addf(&sb, "%s/gitdir", sb_repo.buf);
943         write_file(sb.buf, 1, "%s\n", real_path(sb_git.buf));
944         write_file(sb_git.buf, 1, "gitdir: %s/worktrees/%s\n",
945                    real_path(get_git_common_dir()), name);
946         /*
947          * This is to keep resolve_ref() happy. We need a valid HEAD
948          * or is_git_directory() will reject the directory. Any valid
949          * value would do because this value will be ignored and
950          * replaced at the next (real) checkout.
951          */
952         strbuf_reset(&sb);
953         strbuf_addf(&sb, "%s/HEAD", sb_repo.buf);
954         write_file(sb.buf, 1, "%s\n", sha1_to_hex(new->commit->object.sha1));
955         strbuf_reset(&sb);
956         strbuf_addf(&sb, "%s/commondir", sb_repo.buf);
957         write_file(sb.buf, 1, "../..\n");
958
959         if (!opts->quiet)
960                 fprintf_ln(stderr, _("Enter %s (identifier %s)"), path, name);
961
962         setenv("GIT_CHECKOUT_NEW_WORKTREE", "1", 1);
963         setenv(GIT_DIR_ENVIRONMENT, sb_git.buf, 1);
964         setenv(GIT_WORK_TREE_ENVIRONMENT, path, 1);
965         memset(&cp, 0, sizeof(cp));
966         cp.git_cmd = 1;
967         cp.argv = opts->saved_argv;
968         ret = run_command(&cp);
969         if (!ret) {
970                 is_junk = 0;
971                 free(junk_work_tree);
972                 free(junk_git_dir);
973                 junk_work_tree = NULL;
974                 junk_git_dir = NULL;
975         }
976         strbuf_reset(&sb);
977         strbuf_addf(&sb, "%s/locked", sb_repo.buf);
978         unlink_or_warn(sb.buf);
979         strbuf_release(&sb);
980         strbuf_release(&sb_repo);
981         strbuf_release(&sb_git);
982         return ret;
983 }
984
985 static int git_checkout_config(const char *var, const char *value, void *cb)
986 {
987         if (!strcmp(var, "diff.ignoresubmodules")) {
988                 struct checkout_opts *opts = cb;
989                 handle_ignore_submodules_arg(&opts->diff_options, value);
990                 return 0;
991         }
992
993         if (starts_with(var, "submodule."))
994                 return parse_submodule_config_option(var, value);
995
996         return git_xmerge_config(var, value, NULL);
997 }
998
999 struct tracking_name_data {
1000         /* const */ char *src_ref;
1001         char *dst_ref;
1002         unsigned char *dst_sha1;
1003         int unique;
1004 };
1005
1006 static int check_tracking_name(struct remote *remote, void *cb_data)
1007 {
1008         struct tracking_name_data *cb = cb_data;
1009         struct refspec query;
1010         memset(&query, 0, sizeof(struct refspec));
1011         query.src = cb->src_ref;
1012         if (remote_find_tracking(remote, &query) ||
1013             get_sha1(query.dst, cb->dst_sha1)) {
1014                 free(query.dst);
1015                 return 0;
1016         }
1017         if (cb->dst_ref) {
1018                 free(query.dst);
1019                 cb->unique = 0;
1020                 return 0;
1021         }
1022         cb->dst_ref = query.dst;
1023         return 0;
1024 }
1025
1026 static const char *unique_tracking_name(const char *name, unsigned char *sha1)
1027 {
1028         struct tracking_name_data cb_data = { NULL, NULL, NULL, 1 };
1029         char src_ref[PATH_MAX];
1030         snprintf(src_ref, PATH_MAX, "refs/heads/%s", name);
1031         cb_data.src_ref = src_ref;
1032         cb_data.dst_sha1 = sha1;
1033         for_each_remote(check_tracking_name, &cb_data);
1034         if (cb_data.unique)
1035                 return cb_data.dst_ref;
1036         free(cb_data.dst_ref);
1037         return NULL;
1038 }
1039
1040 static void check_linked_checkout(struct branch_info *new, const char *id)
1041 {
1042         struct strbuf sb = STRBUF_INIT;
1043         struct strbuf path = STRBUF_INIT;
1044         struct strbuf gitdir = STRBUF_INIT;
1045         const char *start, *end;
1046
1047         if (id)
1048                 strbuf_addf(&path, "%s/worktrees/%s/HEAD", get_git_common_dir(), id);
1049         else
1050                 strbuf_addf(&path, "%s/HEAD", get_git_common_dir());
1051
1052         if (strbuf_read_file(&sb, path.buf, 0) < 0 ||
1053             !skip_prefix(sb.buf, "ref:", &start))
1054                 goto done;
1055         while (isspace(*start))
1056                 start++;
1057         end = start;
1058         while (*end && !isspace(*end))
1059                 end++;
1060         if (strncmp(start, new->path, end - start) || new->path[end - start] != '\0')
1061                 goto done;
1062         if (id) {
1063                 strbuf_reset(&path);
1064                 strbuf_addf(&path, "%s/worktrees/%s/gitdir", get_git_common_dir(), id);
1065                 if (strbuf_read_file(&gitdir, path.buf, 0) <= 0)
1066                         goto done;
1067                 strbuf_rtrim(&gitdir);
1068         } else
1069                 strbuf_addstr(&gitdir, get_git_common_dir());
1070         die(_("'%s' is already checked out at '%s'"), new->name, gitdir.buf);
1071 done:
1072         strbuf_release(&path);
1073         strbuf_release(&sb);
1074         strbuf_release(&gitdir);
1075 }
1076
1077 static void check_linked_checkouts(struct branch_info *new)
1078 {
1079         struct strbuf path = STRBUF_INIT;
1080         DIR *dir;
1081         struct dirent *d;
1082
1083         strbuf_addf(&path, "%s/worktrees", get_git_common_dir());
1084         if ((dir = opendir(path.buf)) == NULL) {
1085                 strbuf_release(&path);
1086                 return;
1087         }
1088
1089         /*
1090          * $GIT_COMMON_DIR/HEAD is practically outside
1091          * $GIT_DIR so resolve_ref_unsafe() won't work (it
1092          * uses git_path). Parse the ref ourselves.
1093          */
1094         check_linked_checkout(new, NULL);
1095
1096         while ((d = readdir(dir)) != NULL) {
1097                 if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, ".."))
1098                         continue;
1099                 check_linked_checkout(new, d->d_name);
1100         }
1101         strbuf_release(&path);
1102         closedir(dir);
1103 }
1104
1105 static int parse_branchname_arg(int argc, const char **argv,
1106                                 int dwim_new_local_branch_ok,
1107                                 struct branch_info *new,
1108                                 struct checkout_opts *opts,
1109                                 unsigned char rev[20])
1110 {
1111         struct tree **source_tree = &opts->source_tree;
1112         const char **new_branch = &opts->new_branch;
1113         int force_detach = opts->force_detach;
1114         int argcount = 0;
1115         unsigned char branch_rev[20];
1116         const char *arg;
1117         int dash_dash_pos;
1118         int has_dash_dash = 0;
1119         int i;
1120
1121         /*
1122          * case 1: git checkout <ref> -- [<paths>]
1123          *
1124          *   <ref> must be a valid tree, everything after the '--' must be
1125          *   a path.
1126          *
1127          * case 2: git checkout -- [<paths>]
1128          *
1129          *   everything after the '--' must be paths.
1130          *
1131          * case 3: git checkout <something> [--]
1132          *
1133          *   (a) If <something> is a commit, that is to
1134          *       switch to the branch or detach HEAD at it.  As a special case,
1135          *       if <something> is A...B (missing A or B means HEAD but you can
1136          *       omit at most one side), and if there is a unique merge base
1137          *       between A and B, A...B names that merge base.
1138          *
1139          *   (b) If <something> is _not_ a commit, either "--" is present
1140          *       or <something> is not a path, no -t or -b was given, and
1141          *       and there is a tracking branch whose name is <something>
1142          *       in one and only one remote, then this is a short-hand to
1143          *       fork local <something> from that remote-tracking branch.
1144          *
1145          *   (c) Otherwise, if "--" is present, treat it like case (1).
1146          *
1147          *   (d) Otherwise :
1148          *       - if it's a reference, treat it like case (1)
1149          *       - else if it's a path, treat it like case (2)
1150          *       - else: fail.
1151          *
1152          * case 4: git checkout <something> <paths>
1153          *
1154          *   The first argument must not be ambiguous.
1155          *   - If it's *only* a reference, treat it like case (1).
1156          *   - If it's only a path, treat it like case (2).
1157          *   - else: fail.
1158          *
1159          */
1160         if (!argc)
1161                 return 0;
1162
1163         arg = argv[0];
1164         dash_dash_pos = -1;
1165         for (i = 0; i < argc; i++) {
1166                 if (!strcmp(argv[i], "--")) {
1167                         dash_dash_pos = i;
1168                         break;
1169                 }
1170         }
1171         if (dash_dash_pos == 0)
1172                 return 1; /* case (2) */
1173         else if (dash_dash_pos == 1)
1174                 has_dash_dash = 1; /* case (3) or (1) */
1175         else if (dash_dash_pos >= 2)
1176                 die(_("only one reference expected, %d given."), dash_dash_pos);
1177
1178         if (!strcmp(arg, "-"))
1179                 arg = "@{-1}";
1180
1181         if (get_sha1_mb(arg, rev)) {
1182                 /*
1183                  * Either case (3) or (4), with <something> not being
1184                  * a commit, or an attempt to use case (1) with an
1185                  * invalid ref.
1186                  *
1187                  * It's likely an error, but we need to find out if
1188                  * we should auto-create the branch, case (3).(b).
1189                  */
1190                 int recover_with_dwim = dwim_new_local_branch_ok;
1191
1192                 if (check_filename(NULL, arg) && !has_dash_dash)
1193                         recover_with_dwim = 0;
1194                 /*
1195                  * Accept "git checkout foo" and "git checkout foo --"
1196                  * as candidates for dwim.
1197                  */
1198                 if (!(argc == 1 && !has_dash_dash) &&
1199                     !(argc == 2 && has_dash_dash))
1200                         recover_with_dwim = 0;
1201
1202                 if (recover_with_dwim) {
1203                         const char *remote = unique_tracking_name(arg, rev);
1204                         if (remote) {
1205                                 *new_branch = arg;
1206                                 arg = remote;
1207                                 /* DWIMmed to create local branch, case (3).(b) */
1208                         } else {
1209                                 recover_with_dwim = 0;
1210                         }
1211                 }
1212
1213                 if (!recover_with_dwim) {
1214                         if (has_dash_dash)
1215                                 die(_("invalid reference: %s"), arg);
1216                         return argcount;
1217                 }
1218         }
1219
1220         /* we can't end up being in (2) anymore, eat the argument */
1221         argcount++;
1222         argv++;
1223         argc--;
1224
1225         new->name = arg;
1226         setup_branch_path(new);
1227
1228         if (!check_refname_format(new->path, 0) &&
1229             !read_ref(new->path, branch_rev))
1230                 hashcpy(rev, branch_rev);
1231         else
1232                 new->path = NULL; /* not an existing branch */
1233
1234         if (new->path && !force_detach && !*new_branch) {
1235                 unsigned char sha1[20];
1236                 int flag;
1237                 char *head_ref = resolve_refdup("HEAD", 0, sha1, &flag);
1238                 if (head_ref &&
1239                     (!(flag & REF_ISSYMREF) || strcmp(head_ref, new->path)) &&
1240                     !opts->ignore_other_worktrees)
1241                         check_linked_checkouts(new);
1242                 free(head_ref);
1243         }
1244
1245         new->commit = lookup_commit_reference_gently(rev, 1);
1246         if (!new->commit) {
1247                 /* not a commit */
1248                 *source_tree = parse_tree_indirect(rev);
1249         } else {
1250                 parse_commit_or_die(new->commit);
1251                 *source_tree = new->commit->tree;
1252         }
1253
1254         if (!*source_tree)                   /* case (1): want a tree */
1255                 die(_("reference is not a tree: %s"), arg);
1256         if (!has_dash_dash) {/* case (3).(d) -> (1) */
1257                 /*
1258                  * Do not complain the most common case
1259                  *      git checkout branch
1260                  * even if there happen to be a file called 'branch';
1261                  * it would be extremely annoying.
1262                  */
1263                 if (argc)
1264                         verify_non_filename(NULL, arg);
1265         } else {
1266                 argcount++;
1267                 argv++;
1268                 argc--;
1269         }
1270
1271         return argcount;
1272 }
1273
1274 static int switch_unborn_to_new_branch(const struct checkout_opts *opts)
1275 {
1276         int status;
1277         struct strbuf branch_ref = STRBUF_INIT;
1278
1279         if (!opts->new_branch)
1280                 die(_("You are on a branch yet to be born"));
1281         strbuf_addf(&branch_ref, "refs/heads/%s", opts->new_branch);
1282         status = create_symref("HEAD", branch_ref.buf, "checkout -b");
1283         strbuf_release(&branch_ref);
1284         if (!opts->quiet)
1285                 fprintf(stderr, _("Switched to a new branch '%s'\n"),
1286                         opts->new_branch);
1287         return status;
1288 }
1289
1290 static int checkout_branch(struct checkout_opts *opts,
1291                            struct branch_info *new)
1292 {
1293         if (opts->pathspec.nr)
1294                 die(_("paths cannot be used with switching branches"));
1295
1296         if (opts->patch_mode)
1297                 die(_("'%s' cannot be used with switching branches"),
1298                     "--patch");
1299
1300         if (opts->writeout_stage)
1301                 die(_("'%s' cannot be used with switching branches"),
1302                     "--ours/--theirs");
1303
1304         if (opts->force && opts->merge)
1305                 die(_("'%s' cannot be used with '%s'"), "-f", "-m");
1306
1307         if (opts->force_detach && opts->new_branch)
1308                 die(_("'%s' cannot be used with '%s'"),
1309                     "--detach", "-b/-B/--orphan");
1310
1311         if (opts->new_orphan_branch) {
1312                 if (opts->track != BRANCH_TRACK_UNSPECIFIED)
1313                         die(_("'%s' cannot be used with '%s'"), "--orphan", "-t");
1314         } else if (opts->force_detach) {
1315                 if (opts->track != BRANCH_TRACK_UNSPECIFIED)
1316                         die(_("'%s' cannot be used with '%s'"), "--detach", "-t");
1317         } else if (opts->track == BRANCH_TRACK_UNSPECIFIED)
1318                 opts->track = git_branch_track;
1319
1320         if (new->name && !new->commit)
1321                 die(_("Cannot switch branch to a non-commit '%s'"),
1322                     new->name);
1323
1324         if (opts->new_worktree)
1325                 return prepare_linked_checkout(opts, new);
1326
1327         if (!new->commit && opts->new_branch) {
1328                 unsigned char rev[20];
1329                 int flag;
1330
1331                 if (!read_ref_full("HEAD", 0, rev, &flag) &&
1332                     (flag & REF_ISSYMREF) && is_null_sha1(rev))
1333                         return switch_unborn_to_new_branch(opts);
1334         }
1335         return switch_branches(opts, new);
1336 }
1337
1338 int cmd_checkout(int argc, const char **argv, const char *prefix)
1339 {
1340         struct checkout_opts opts;
1341         struct branch_info new;
1342         char *conflict_style = NULL;
1343         int dwim_new_local_branch = 1;
1344         struct option options[] = {
1345                 OPT__QUIET(&opts.quiet, N_("suppress progress reporting")),
1346                 OPT_STRING('b', NULL, &opts.new_branch, N_("branch"),
1347                            N_("create and checkout a new branch")),
1348                 OPT_STRING('B', NULL, &opts.new_branch_force, N_("branch"),
1349                            N_("create/reset and checkout a branch")),
1350                 OPT_BOOL('l', NULL, &opts.new_branch_log, N_("create reflog for new branch")),
1351                 OPT_BOOL(0, "detach", &opts.force_detach, N_("detach the HEAD at named commit")),
1352                 OPT_SET_INT('t', "track",  &opts.track, N_("set upstream info for new branch"),
1353                         BRANCH_TRACK_EXPLICIT),
1354                 OPT_STRING(0, "orphan", &opts.new_orphan_branch, N_("new-branch"), N_("new unparented branch")),
1355                 OPT_SET_INT('2', "ours", &opts.writeout_stage, N_("checkout our version for unmerged files"),
1356                             2),
1357                 OPT_SET_INT('3', "theirs", &opts.writeout_stage, N_("checkout their version for unmerged files"),
1358                             3),
1359                 OPT__FORCE(&opts.force, N_("force checkout (throw away local modifications)")),
1360                 OPT_BOOL('m', "merge", &opts.merge, N_("perform a 3-way merge with the new branch")),
1361                 OPT_BOOL(0, "overwrite-ignore", &opts.overwrite_ignore, N_("update ignored files (default)")),
1362                 OPT_STRING(0, "conflict", &conflict_style, N_("style"),
1363                            N_("conflict style (merge or diff3)")),
1364                 OPT_BOOL('p', "patch", &opts.patch_mode, N_("select hunks interactively")),
1365                 OPT_BOOL(0, "ignore-skip-worktree-bits", &opts.ignore_skipworktree,
1366                          N_("do not limit pathspecs to sparse entries only")),
1367                 OPT_HIDDEN_BOOL(0, "guess", &dwim_new_local_branch,
1368                                 N_("second guess 'git checkout <no-such-branch>'")),
1369                 OPT_FILENAME(0, "to", &opts.new_worktree,
1370                            N_("check a branch out in a separate working directory")),
1371                 OPT_BOOL(0, "ignore-other-worktrees", &opts.ignore_other_worktrees,
1372                          N_("do not check if another worktree is holding the given ref")),
1373                 OPT_END(),
1374         };
1375
1376         memset(&opts, 0, sizeof(opts));
1377         memset(&new, 0, sizeof(new));
1378         opts.overwrite_ignore = 1;
1379         opts.prefix = prefix;
1380
1381         opts.saved_argv = xmalloc(sizeof(const char *) * (argc + 2));
1382         memcpy(opts.saved_argv, argv, sizeof(const char *) * (argc + 1));
1383
1384         gitmodules_config();
1385         git_config(git_checkout_config, &opts);
1386
1387         opts.track = BRANCH_TRACK_UNSPECIFIED;
1388
1389         argc = parse_options(argc, argv, prefix, options, checkout_usage,
1390                              PARSE_OPT_KEEP_DASHDASH);
1391
1392         /* recursive execution from checkout_new_worktree() */
1393         opts.new_worktree_mode = getenv("GIT_CHECKOUT_NEW_WORKTREE") != NULL;
1394         if (opts.new_worktree_mode)
1395                 opts.new_worktree = NULL;
1396
1397         if (!opts.new_worktree)
1398                 setup_work_tree();
1399
1400         if (conflict_style) {
1401                 opts.merge = 1; /* implied */
1402                 git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
1403         }
1404
1405         if ((!!opts.new_branch + !!opts.new_branch_force + !!opts.new_orphan_branch) > 1)
1406                 die(_("-b, -B and --orphan are mutually exclusive"));
1407
1408         /*
1409          * From here on, new_branch will contain the branch to be checked out,
1410          * and new_branch_force and new_orphan_branch will tell us which one of
1411          * -b/-B/--orphan is being used.
1412          */
1413         if (opts.new_branch_force)
1414                 opts.new_branch = opts.new_branch_force;
1415
1416         if (opts.new_orphan_branch)
1417                 opts.new_branch = opts.new_orphan_branch;
1418
1419         /* --track without -b/-B/--orphan should DWIM */
1420         if (opts.track != BRANCH_TRACK_UNSPECIFIED && !opts.new_branch) {
1421                 const char *argv0 = argv[0];
1422                 if (!argc || !strcmp(argv0, "--"))
1423                         die (_("--track needs a branch name"));
1424                 skip_prefix(argv0, "refs/", &argv0);
1425                 skip_prefix(argv0, "remotes/", &argv0);
1426                 argv0 = strchr(argv0, '/');
1427                 if (!argv0 || !argv0[1])
1428                         die (_("Missing branch name; try -b"));
1429                 opts.new_branch = argv0 + 1;
1430         }
1431
1432         /*
1433          * Extract branch name from command line arguments, so
1434          * all that is left is pathspecs.
1435          *
1436          * Handle
1437          *
1438          *  1) git checkout <tree> -- [<paths>]
1439          *  2) git checkout -- [<paths>]
1440          *  3) git checkout <something> [<paths>]
1441          *
1442          * including "last branch" syntax and DWIM-ery for names of
1443          * remote branches, erroring out for invalid or ambiguous cases.
1444          */
1445         if (argc) {
1446                 unsigned char rev[20];
1447                 int dwim_ok =
1448                         !opts.patch_mode &&
1449                         dwim_new_local_branch &&
1450                         opts.track == BRANCH_TRACK_UNSPECIFIED &&
1451                         !opts.new_branch;
1452                 int n = parse_branchname_arg(argc, argv, dwim_ok,
1453                                              &new, &opts, rev);
1454                 argv += n;
1455                 argc -= n;
1456         }
1457
1458         if (argc) {
1459                 parse_pathspec(&opts.pathspec, 0,
1460                                opts.patch_mode ? PATHSPEC_PREFIX_ORIGIN : 0,
1461                                prefix, argv);
1462
1463                 if (!opts.pathspec.nr)
1464                         die(_("invalid path specification"));
1465
1466                 /*
1467                  * Try to give more helpful suggestion.
1468                  * new_branch && argc > 1 will be caught later.
1469                  */
1470                 if (opts.new_branch && argc == 1)
1471                         die(_("Cannot update paths and switch to branch '%s' at the same time.\n"
1472                               "Did you intend to checkout '%s' which can not be resolved as commit?"),
1473                             opts.new_branch, argv[0]);
1474
1475                 if (opts.force_detach)
1476                         die(_("git checkout: --detach does not take a path argument '%s'"),
1477                             argv[0]);
1478
1479                 if (1 < !!opts.writeout_stage + !!opts.force + !!opts.merge)
1480                         die(_("git checkout: --ours/--theirs, --force and --merge are incompatible when\n"
1481                               "checking out of the index."));
1482         }
1483
1484         if (opts.new_branch) {
1485                 struct strbuf buf = STRBUF_INIT;
1486
1487                 opts.branch_exists =
1488                         validate_new_branchname(opts.new_branch, &buf,
1489                                                 !!opts.new_branch_force,
1490                                                 !!opts.new_branch_force);
1491
1492                 strbuf_release(&buf);
1493         }
1494
1495         if (opts.patch_mode || opts.pathspec.nr)
1496                 return checkout_paths(&opts, new.name);
1497         else
1498                 return checkout_branch(&opts, &new);
1499 }