Merge branch 'jk/remote-helper-with-signed-tags'
[git] / 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         N_("git checkout [options] <branch>"),
26         N_("git checkout [options] [<branch>] -- <file>..."),
27         NULL,
28 };
29
30 struct checkout_opts {
31         int patch_mode;
32         int quiet;
33         int merge;
34         int force;
35         int force_detach;
36         int writeout_stage;
37         int overwrite_ignore;
38         int ignore_skipworktree;
39
40         const char *new_branch;
41         const char *new_branch_force;
42         const char *new_orphan_branch;
43         int new_branch_log;
44         enum branch_track track;
45         struct diff_options diff_options;
46
47         int branch_exists;
48         const char *prefix;
49         const char **pathspec;
50         struct tree *source_tree;
51 };
52
53 static int post_checkout_hook(struct commit *old, struct commit *new,
54                               int changed)
55 {
56         return run_hook(NULL, "post-checkout",
57                         sha1_to_hex(old ? old->object.sha1 : null_sha1),
58                         sha1_to_hex(new ? new->object.sha1 : null_sha1),
59                         changed ? "1" : "0", NULL);
60         /* "new" can be NULL when checking out from the index before
61            a commit exists. */
62
63 }
64
65 static int update_some(const unsigned char *sha1, const char *base, int baselen,
66                 const char *pathname, unsigned mode, int stage, void *context)
67 {
68         int len;
69         struct cache_entry *ce;
70
71         if (S_ISDIR(mode))
72                 return READ_TREE_RECURSIVE;
73
74         len = baselen + strlen(pathname);
75         ce = xcalloc(1, cache_entry_size(len));
76         hashcpy(ce->sha1, sha1);
77         memcpy(ce->name, base, baselen);
78         memcpy(ce->name + baselen, pathname, len - baselen);
79         ce->ce_flags = create_ce_flags(0) | CE_UPDATE;
80         ce->ce_namelen = len;
81         ce->ce_mode = create_ce_mode(mode);
82         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
83         return 0;
84 }
85
86 static int read_tree_some(struct tree *tree, const char **pathspec)
87 {
88         struct pathspec ps;
89         init_pathspec(&ps, pathspec);
90         read_tree_recursive(tree, "", 0, 0, &ps, update_some, NULL);
91         free_pathspec(&ps);
92
93         /* update the index with the given tree's info
94          * for all args, expanding wildcards, and exit
95          * with any non-zero return code.
96          */
97         return 0;
98 }
99
100 static int skip_same_name(struct cache_entry *ce, int pos)
101 {
102         while (++pos < active_nr &&
103                !strcmp(active_cache[pos]->name, ce->name))
104                 ; /* skip */
105         return pos;
106 }
107
108 static int check_stage(int stage, struct cache_entry *ce, int pos)
109 {
110         while (pos < active_nr &&
111                !strcmp(active_cache[pos]->name, ce->name)) {
112                 if (ce_stage(active_cache[pos]) == stage)
113                         return 0;
114                 pos++;
115         }
116         if (stage == 2)
117                 return error(_("path '%s' does not have our version"), ce->name);
118         else
119                 return error(_("path '%s' does not have their version"), ce->name);
120 }
121
122 static int check_stages(unsigned stages, struct cache_entry *ce, int pos)
123 {
124         unsigned seen = 0;
125         const char *name = ce->name;
126
127         while (pos < active_nr) {
128                 ce = active_cache[pos];
129                 if (strcmp(name, ce->name))
130                         break;
131                 seen |= (1 << ce_stage(ce));
132                 pos++;
133         }
134         if ((stages & seen) != stages)
135                 return error(_("path '%s' does not have all necessary versions"),
136                              name);
137         return 0;
138 }
139
140 static int checkout_stage(int stage, struct cache_entry *ce, int pos,
141                           struct checkout *state)
142 {
143         while (pos < active_nr &&
144                !strcmp(active_cache[pos]->name, ce->name)) {
145                 if (ce_stage(active_cache[pos]) == stage)
146                         return checkout_entry(active_cache[pos], state, NULL);
147                 pos++;
148         }
149         if (stage == 2)
150                 return error(_("path '%s' does not have our version"), ce->name);
151         else
152                 return error(_("path '%s' does not have their version"), ce->name);
153 }
154
155 static int checkout_merged(int pos, struct checkout *state)
156 {
157         struct cache_entry *ce = active_cache[pos];
158         const char *path = ce->name;
159         mmfile_t ancestor, ours, theirs;
160         int status;
161         unsigned char sha1[20];
162         mmbuffer_t result_buf;
163         unsigned char threeway[3][20];
164         unsigned mode = 0;
165
166         memset(threeway, 0, sizeof(threeway));
167         while (pos < active_nr) {
168                 int stage;
169                 stage = ce_stage(ce);
170                 if (!stage || strcmp(path, ce->name))
171                         break;
172                 hashcpy(threeway[stage - 1], ce->sha1);
173                 if (stage == 2)
174                         mode = create_ce_mode(ce->ce_mode);
175                 pos++;
176                 ce = active_cache[pos];
177         }
178         if (is_null_sha1(threeway[1]) || is_null_sha1(threeway[2]))
179                 return error(_("path '%s' does not have necessary versions"), path);
180
181         read_mmblob(&ancestor, threeway[0]);
182         read_mmblob(&ours, threeway[1]);
183         read_mmblob(&theirs, threeway[2]);
184
185         /*
186          * NEEDSWORK: re-create conflicts from merges with
187          * merge.renormalize set, too
188          */
189         status = ll_merge(&result_buf, path, &ancestor, "base",
190                           &ours, "ours", &theirs, "theirs", NULL);
191         free(ancestor.ptr);
192         free(ours.ptr);
193         free(theirs.ptr);
194         if (status < 0 || !result_buf.ptr) {
195                 free(result_buf.ptr);
196                 return error(_("path '%s': cannot merge"), path);
197         }
198
199         /*
200          * NEEDSWORK:
201          * There is absolutely no reason to write this as a blob object
202          * and create a phony cache entry just to leak.  This hack is
203          * primarily to get to the write_entry() machinery that massages
204          * the contents to work-tree format and writes out which only
205          * allows it for a cache entry.  The code in write_entry() needs
206          * to be refactored to allow us to feed a <buffer, size, mode>
207          * instead of a cache entry.  Such a refactoring would help
208          * merge_recursive as well (it also writes the merge result to the
209          * object database even when it may contain conflicts).
210          */
211         if (write_sha1_file(result_buf.ptr, result_buf.size,
212                             blob_type, sha1))
213                 die(_("Unable to add merge result for '%s'"), path);
214         ce = make_cache_entry(mode, sha1, path, 2, 0);
215         if (!ce)
216                 die(_("make_cache_entry failed for path '%s'"), path);
217         status = checkout_entry(ce, state, NULL);
218         return status;
219 }
220
221 static int checkout_paths(const struct checkout_opts *opts,
222                           const char *revision)
223 {
224         int pos;
225         struct checkout state;
226         static char *ps_matched;
227         unsigned char rev[20];
228         int flag;
229         struct commit *head;
230         int errs = 0;
231         int stage = opts->writeout_stage;
232         int merge = opts->merge;
233         int newfd;
234         struct lock_file *lock_file;
235
236         if (opts->track != BRANCH_TRACK_UNSPECIFIED)
237                 die(_("'%s' cannot be used with updating paths"), "--track");
238
239         if (opts->new_branch_log)
240                 die(_("'%s' cannot be used with updating paths"), "-l");
241
242         if (opts->force && opts->patch_mode)
243                 die(_("'%s' cannot be used with updating paths"), "-f");
244
245         if (opts->force_detach)
246                 die(_("'%s' cannot be used with updating paths"), "--detach");
247
248         if (opts->merge && opts->patch_mode)
249                 die(_("'%s' cannot be used with %s"), "--merge", "--patch");
250
251         if (opts->force && opts->merge)
252                 die(_("'%s' cannot be used with %s"), "-f", "-m");
253
254         if (opts->new_branch)
255                 die(_("Cannot update paths and switch to branch '%s' at the same time."),
256                     opts->new_branch);
257
258         if (opts->patch_mode)
259                 return run_add_interactive(revision, "--patch=checkout",
260                                            opts->pathspec);
261
262         lock_file = xcalloc(1, sizeof(struct lock_file));
263
264         newfd = hold_locked_index(lock_file, 1);
265         if (read_cache_preload(opts->pathspec) < 0)
266                 return error(_("corrupt index file"));
267
268         if (opts->source_tree)
269                 read_tree_some(opts->source_tree, opts->pathspec);
270
271         for (pos = 0; opts->pathspec[pos]; pos++)
272                 ;
273         ps_matched = xcalloc(1, pos);
274
275         /*
276          * Make sure all pathspecs participated in locating the paths
277          * to be checked out.
278          */
279         for (pos = 0; pos < active_nr; pos++) {
280                 struct cache_entry *ce = active_cache[pos];
281                 ce->ce_flags &= ~CE_MATCHED;
282                 if (!opts->ignore_skipworktree && ce_skip_worktree(ce))
283                         continue;
284                 if (opts->source_tree && !(ce->ce_flags & CE_UPDATE))
285                         /*
286                          * "git checkout tree-ish -- path", but this entry
287                          * is in the original index; it will not be checked
288                          * out to the working tree and it does not matter
289                          * if pathspec matched this entry.  We will not do
290                          * anything to this entry at all.
291                          */
292                         continue;
293                 /*
294                  * Either this entry came from the tree-ish we are
295                  * checking the paths out of, or we are checking out
296                  * of the index.
297                  *
298                  * If it comes from the tree-ish, we already know it
299                  * matches the pathspec and could just stamp
300                  * CE_MATCHED to it from update_some(). But we still
301                  * need ps_matched and read_tree_recursive (and
302                  * eventually tree_entry_interesting) cannot fill
303                  * ps_matched yet. Once it can, we can avoid calling
304                  * match_pathspec() for _all_ entries when
305                  * opts->source_tree != NULL.
306                  */
307                 if (match_pathspec(opts->pathspec, ce->name, ce_namelen(ce),
308                                    0, ps_matched))
309                         ce->ce_flags |= CE_MATCHED;
310         }
311
312         if (report_path_error(ps_matched, opts->pathspec, opts->prefix)) {
313                 free(ps_matched);
314                 return 1;
315         }
316         free(ps_matched);
317
318         /* "checkout -m path" to recreate conflicted state */
319         if (opts->merge)
320                 unmerge_marked_index(&the_index);
321
322         /* Any unmerged paths? */
323         for (pos = 0; pos < active_nr; pos++) {
324                 struct cache_entry *ce = active_cache[pos];
325                 if (ce->ce_flags & CE_MATCHED) {
326                         if (!ce_stage(ce))
327                                 continue;
328                         if (opts->force) {
329                                 warning(_("path '%s' is unmerged"), ce->name);
330                         } else if (stage) {
331                                 errs |= check_stage(stage, ce, pos);
332                         } else if (opts->merge) {
333                                 errs |= check_stages((1<<2) | (1<<3), ce, pos);
334                         } else {
335                                 errs = 1;
336                                 error(_("path '%s' is unmerged"), ce->name);
337                         }
338                         pos = skip_same_name(ce, pos) - 1;
339                 }
340         }
341         if (errs)
342                 return 1;
343
344         /* Now we are committed to check them out */
345         memset(&state, 0, sizeof(state));
346         state.force = 1;
347         state.refresh_cache = 1;
348         for (pos = 0; pos < active_nr; pos++) {
349                 struct cache_entry *ce = active_cache[pos];
350                 if (ce->ce_flags & CE_MATCHED) {
351                         if (!ce_stage(ce)) {
352                                 errs |= checkout_entry(ce, &state, NULL);
353                                 continue;
354                         }
355                         if (stage)
356                                 errs |= checkout_stage(stage, ce, pos, &state);
357                         else if (merge)
358                                 errs |= checkout_merged(pos, &state);
359                         pos = skip_same_name(ce, pos) - 1;
360                 }
361         }
362
363         if (write_cache(newfd, active_cache, active_nr) ||
364             commit_locked_index(lock_file))
365                 die(_("unable to write new index file"));
366
367         read_ref_full("HEAD", rev, 0, &flag);
368         head = lookup_commit_reference_gently(rev, 1);
369
370         errs |= post_checkout_hook(head, head, 0);
371         return errs;
372 }
373
374 static void show_local_changes(struct object *head,
375                                const struct diff_options *opts)
376 {
377         struct rev_info rev;
378         /* I think we want full paths, even if we're in a subdirectory. */
379         init_revisions(&rev, NULL);
380         rev.diffopt.flags = opts->flags;
381         rev.diffopt.output_format |= DIFF_FORMAT_NAME_STATUS;
382         diff_setup_done(&rev.diffopt);
383         add_pending_object(&rev, head, NULL);
384         run_diff_index(&rev, 0);
385 }
386
387 static void describe_detached_head(const char *msg, struct commit *commit)
388 {
389         struct strbuf sb = STRBUF_INIT;
390         parse_commit(commit);
391         pp_commit_easy(CMIT_FMT_ONELINE, commit, &sb);
392         fprintf(stderr, "%s %s... %s\n", msg,
393                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV), sb.buf);
394         strbuf_release(&sb);
395 }
396
397 static int reset_tree(struct tree *tree, const struct checkout_opts *o,
398                       int worktree, int *writeout_error)
399 {
400         struct unpack_trees_options opts;
401         struct tree_desc tree_desc;
402
403         memset(&opts, 0, sizeof(opts));
404         opts.head_idx = -1;
405         opts.update = worktree;
406         opts.skip_unmerged = !worktree;
407         opts.reset = 1;
408         opts.merge = 1;
409         opts.fn = oneway_merge;
410         opts.verbose_update = !o->quiet && isatty(2);
411         opts.src_index = &the_index;
412         opts.dst_index = &the_index;
413         parse_tree(tree);
414         init_tree_desc(&tree_desc, tree->buffer, tree->size);
415         switch (unpack_trees(1, &tree_desc, &opts)) {
416         case -2:
417                 *writeout_error = 1;
418                 /*
419                  * We return 0 nevertheless, as the index is all right
420                  * and more importantly we have made best efforts to
421                  * update paths in the work tree, and we cannot revert
422                  * them.
423                  */
424         case 0:
425                 return 0;
426         default:
427                 return 128;
428         }
429 }
430
431 struct branch_info {
432         const char *name; /* The short name used */
433         const char *path; /* The full name of a real branch */
434         struct commit *commit; /* The named commit */
435 };
436
437 static void setup_branch_path(struct branch_info *branch)
438 {
439         struct strbuf buf = STRBUF_INIT;
440
441         strbuf_branchname(&buf, branch->name);
442         if (strcmp(buf.buf, branch->name))
443                 branch->name = xstrdup(buf.buf);
444         strbuf_splice(&buf, 0, 0, "refs/heads/", 11);
445         branch->path = strbuf_detach(&buf, NULL);
446 }
447
448 static int merge_working_tree(const struct checkout_opts *opts,
449                               struct branch_info *old,
450                               struct branch_info *new,
451                               int *writeout_error)
452 {
453         int ret;
454         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
455         int newfd = hold_locked_index(lock_file, 1);
456
457         if (read_cache_preload(NULL) < 0)
458                 return error(_("corrupt index file"));
459
460         resolve_undo_clear();
461         if (opts->force) {
462                 ret = reset_tree(new->commit->tree, opts, 1, writeout_error);
463                 if (ret)
464                         return ret;
465         } else {
466                 struct tree_desc trees[2];
467                 struct tree *tree;
468                 struct unpack_trees_options topts;
469
470                 memset(&topts, 0, sizeof(topts));
471                 topts.head_idx = -1;
472                 topts.src_index = &the_index;
473                 topts.dst_index = &the_index;
474
475                 setup_unpack_trees_porcelain(&topts, "checkout");
476
477                 refresh_cache(REFRESH_QUIET);
478
479                 if (unmerged_cache()) {
480                         error(_("you need to resolve your current index first"));
481                         return 1;
482                 }
483
484                 /* 2-way merge to the new branch */
485                 topts.initial_checkout = is_cache_unborn();
486                 topts.update = 1;
487                 topts.merge = 1;
488                 topts.gently = opts->merge && old->commit;
489                 topts.verbose_update = !opts->quiet && isatty(2);
490                 topts.fn = twoway_merge;
491                 if (opts->overwrite_ignore) {
492                         topts.dir = xcalloc(1, sizeof(*topts.dir));
493                         topts.dir->flags |= DIR_SHOW_IGNORED;
494                         setup_standard_excludes(topts.dir);
495                 }
496                 tree = parse_tree_indirect(old->commit ?
497                                            old->commit->object.sha1 :
498                                            EMPTY_TREE_SHA1_BIN);
499                 init_tree_desc(&trees[0], tree->buffer, tree->size);
500                 tree = parse_tree_indirect(new->commit->object.sha1);
501                 init_tree_desc(&trees[1], tree->buffer, tree->size);
502
503                 ret = unpack_trees(2, trees, &topts);
504                 if (ret == -1) {
505                         /*
506                          * Unpack couldn't do a trivial merge; either
507                          * give up or do a real merge, depending on
508                          * whether the merge flag was used.
509                          */
510                         struct tree *result;
511                         struct tree *work;
512                         struct merge_options o;
513                         if (!opts->merge)
514                                 return 1;
515
516                         /*
517                          * Without old->commit, the below is the same as
518                          * the two-tree unpack we already tried and failed.
519                          */
520                         if (!old->commit)
521                                 return 1;
522
523                         /* Do more real merge */
524
525                         /*
526                          * We update the index fully, then write the
527                          * tree from the index, then merge the new
528                          * branch with the current tree, with the old
529                          * branch as the base. Then we reset the index
530                          * (but not the working tree) to the new
531                          * branch, leaving the working tree as the
532                          * merged version, but skipping unmerged
533                          * entries in the index.
534                          */
535
536                         add_files_to_cache(NULL, NULL, 0);
537                         /*
538                          * NEEDSWORK: carrying over local changes
539                          * when branches have different end-of-line
540                          * normalization (or clean+smudge rules) is
541                          * a pain; plumb in an option to set
542                          * o.renormalize?
543                          */
544                         init_merge_options(&o);
545                         o.verbosity = 0;
546                         work = write_tree_from_memory(&o);
547
548                         ret = reset_tree(new->commit->tree, opts, 1,
549                                          writeout_error);
550                         if (ret)
551                                 return ret;
552                         o.ancestor = old->name;
553                         o.branch1 = new->name;
554                         o.branch2 = "local";
555                         merge_trees(&o, new->commit->tree, work,
556                                 old->commit->tree, &result);
557                         ret = reset_tree(new->commit->tree, opts, 0,
558                                          writeout_error);
559                         if (ret)
560                                 return ret;
561                 }
562         }
563
564         if (write_cache(newfd, active_cache, active_nr) ||
565             commit_locked_index(lock_file))
566                 die(_("unable to write new index file"));
567
568         if (!opts->force && !opts->quiet)
569                 show_local_changes(&new->commit->object, &opts->diff_options);
570
571         return 0;
572 }
573
574 static void report_tracking(struct branch_info *new)
575 {
576         struct strbuf sb = STRBUF_INIT;
577         struct branch *branch = branch_get(new->name);
578
579         if (!format_tracking_info(branch, &sb))
580                 return;
581         fputs(sb.buf, stdout);
582         strbuf_release(&sb);
583 }
584
585 static void update_refs_for_switch(const struct checkout_opts *opts,
586                                    struct branch_info *old,
587                                    struct branch_info *new)
588 {
589         struct strbuf msg = STRBUF_INIT;
590         const char *old_desc;
591         if (opts->new_branch) {
592                 if (opts->new_orphan_branch) {
593                         if (opts->new_branch_log && !log_all_ref_updates) {
594                                 int temp;
595                                 char log_file[PATH_MAX];
596                                 char *ref_name = mkpath("refs/heads/%s", opts->new_orphan_branch);
597
598                                 temp = log_all_ref_updates;
599                                 log_all_ref_updates = 1;
600                                 if (log_ref_setup(ref_name, log_file, sizeof(log_file))) {
601                                         fprintf(stderr, _("Can not do reflog for '%s'\n"),
602                                             opts->new_orphan_branch);
603                                         log_all_ref_updates = temp;
604                                         return;
605                                 }
606                                 log_all_ref_updates = temp;
607                         }
608                 }
609                 else
610                         create_branch(old->name, opts->new_branch, new->name,
611                                       opts->new_branch_force ? 1 : 0,
612                                       opts->new_branch_log,
613                                       opts->new_branch_force ? 1 : 0,
614                                       opts->quiet,
615                                       opts->track);
616                 new->name = opts->new_branch;
617                 setup_branch_path(new);
618         }
619
620         old_desc = old->name;
621         if (!old_desc && old->commit)
622                 old_desc = sha1_to_hex(old->commit->object.sha1);
623         strbuf_addf(&msg, "checkout: moving from %s to %s",
624                     old_desc ? old_desc : "(invalid)", new->name);
625
626         if (!strcmp(new->name, "HEAD") && !new->path && !opts->force_detach) {
627                 /* Nothing to do. */
628         } else if (opts->force_detach || !new->path) {  /* No longer on any branch. */
629                 update_ref(msg.buf, "HEAD", new->commit->object.sha1, NULL,
630                            REF_NODEREF, DIE_ON_ERR);
631                 if (!opts->quiet) {
632                         if (old->path && advice_detached_head)
633                                 detach_advice(new->name);
634                         describe_detached_head(_("HEAD is now at"), new->commit);
635                 }
636         } else if (new->path) { /* Switch branches. */
637                 create_symref("HEAD", new->path, msg.buf);
638                 if (!opts->quiet) {
639                         if (old->path && !strcmp(new->path, old->path)) {
640                                 if (opts->new_branch_force)
641                                         fprintf(stderr, _("Reset branch '%s'\n"),
642                                                 new->name);
643                                 else
644                                         fprintf(stderr, _("Already on '%s'\n"),
645                                                 new->name);
646                         } else if (opts->new_branch) {
647                                 if (opts->branch_exists)
648                                         fprintf(stderr, _("Switched to and reset branch '%s'\n"), new->name);
649                                 else
650                                         fprintf(stderr, _("Switched to a new branch '%s'\n"), new->name);
651                         } else {
652                                 fprintf(stderr, _("Switched to branch '%s'\n"),
653                                         new->name);
654                         }
655                 }
656                 if (old->path && old->name) {
657                         char log_file[PATH_MAX], ref_file[PATH_MAX];
658
659                         git_snpath(log_file, sizeof(log_file), "logs/%s", old->path);
660                         git_snpath(ref_file, sizeof(ref_file), "%s", old->path);
661                         if (!file_exists(ref_file) && file_exists(log_file))
662                                 remove_path(log_file);
663                 }
664         }
665         remove_branch_state();
666         strbuf_release(&msg);
667         if (!opts->quiet &&
668             (new->path || (!opts->force_detach && !strcmp(new->name, "HEAD"))))
669                 report_tracking(new);
670 }
671
672 static int add_pending_uninteresting_ref(const char *refname,
673                                          const unsigned char *sha1,
674                                          int flags, void *cb_data)
675 {
676         add_pending_sha1(cb_data, refname, sha1, UNINTERESTING);
677         return 0;
678 }
679
680 static void describe_one_orphan(struct strbuf *sb, struct commit *commit)
681 {
682         parse_commit(commit);
683         strbuf_addstr(sb, "  ");
684         strbuf_addstr(sb,
685                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
686         strbuf_addch(sb, ' ');
687         pp_commit_easy(CMIT_FMT_ONELINE, commit, sb);
688         strbuf_addch(sb, '\n');
689 }
690
691 #define ORPHAN_CUTOFF 4
692 static void suggest_reattach(struct commit *commit, struct rev_info *revs)
693 {
694         struct commit *c, *last = NULL;
695         struct strbuf sb = STRBUF_INIT;
696         int lost = 0;
697         while ((c = get_revision(revs)) != NULL) {
698                 if (lost < ORPHAN_CUTOFF)
699                         describe_one_orphan(&sb, c);
700                 last = c;
701                 lost++;
702         }
703         if (ORPHAN_CUTOFF < lost) {
704                 int more = lost - ORPHAN_CUTOFF;
705                 if (more == 1)
706                         describe_one_orphan(&sb, last);
707                 else
708                         strbuf_addf(&sb, _(" ... and %d more.\n"), more);
709         }
710
711         fprintf(stderr,
712                 Q_(
713                 /* The singular version */
714                 "Warning: you are leaving %d commit behind, "
715                 "not connected to\n"
716                 "any of your branches:\n\n"
717                 "%s\n",
718                 /* The plural version */
719                 "Warning: you are leaving %d commits behind, "
720                 "not connected to\n"
721                 "any of your branches:\n\n"
722                 "%s\n",
723                 /* Give ngettext() the count */
724                 lost),
725                 lost,
726                 sb.buf);
727         strbuf_release(&sb);
728
729         if (advice_detached_head)
730                 fprintf(stderr,
731                         _(
732                         "If you want to keep them by creating a new branch, "
733                         "this may be a good time\nto do so with:\n\n"
734                         " git branch new_branch_name %s\n\n"),
735                         find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
736 }
737
738 /*
739  * We are about to leave commit that was at the tip of a detached
740  * HEAD.  If it is not reachable from any ref, this is the last chance
741  * for the user to do so without resorting to reflog.
742  */
743 static void orphaned_commit_warning(struct commit *old, struct commit *new)
744 {
745         struct rev_info revs;
746         struct object *object = &old->object;
747         struct object_array refs;
748
749         init_revisions(&revs, NULL);
750         setup_revisions(0, NULL, &revs, NULL);
751
752         object->flags &= ~UNINTERESTING;
753         add_pending_object(&revs, object, sha1_to_hex(object->sha1));
754
755         for_each_ref(add_pending_uninteresting_ref, &revs);
756         add_pending_sha1(&revs, "HEAD", new->object.sha1, UNINTERESTING);
757
758         refs = revs.pending;
759         revs.leak_pending = 1;
760
761         if (prepare_revision_walk(&revs))
762                 die(_("internal error in revision walk"));
763         if (!(old->object.flags & UNINTERESTING))
764                 suggest_reattach(old, &revs);
765         else
766                 describe_detached_head(_("Previous HEAD position was"), old);
767
768         clear_commit_marks_for_object_array(&refs, ALL_REV_FLAGS);
769         free(refs.objects);
770 }
771
772 static int switch_branches(const struct checkout_opts *opts,
773                            struct branch_info *new)
774 {
775         int ret = 0;
776         struct branch_info old;
777         void *path_to_free;
778         unsigned char rev[20];
779         int flag, writeout_error = 0;
780         memset(&old, 0, sizeof(old));
781         old.path = path_to_free = resolve_refdup("HEAD", rev, 0, &flag);
782         old.commit = lookup_commit_reference_gently(rev, 1);
783         if (!(flag & REF_ISSYMREF))
784                 old.path = NULL;
785
786         if (old.path && !prefixcmp(old.path, "refs/heads/"))
787                 old.name = old.path + strlen("refs/heads/");
788
789         if (!new->name) {
790                 new->name = "HEAD";
791                 new->commit = old.commit;
792                 if (!new->commit)
793                         die(_("You are on a branch yet to be born"));
794                 parse_commit(new->commit);
795         }
796
797         ret = merge_working_tree(opts, &old, new, &writeout_error);
798         if (ret) {
799                 free(path_to_free);
800                 return ret;
801         }
802
803         if (!opts->quiet && !old.path && old.commit && new->commit != old.commit)
804                 orphaned_commit_warning(old.commit, new->commit);
805
806         update_refs_for_switch(opts, &old, new);
807
808         ret = post_checkout_hook(old.commit, new->commit, 1);
809         free(path_to_free);
810         return ret || writeout_error;
811 }
812
813 static int git_checkout_config(const char *var, const char *value, void *cb)
814 {
815         if (!strcmp(var, "diff.ignoresubmodules")) {
816                 struct checkout_opts *opts = cb;
817                 handle_ignore_submodules_arg(&opts->diff_options, value);
818                 return 0;
819         }
820
821         if (!prefixcmp(var, "submodule."))
822                 return parse_submodule_config_option(var, value);
823
824         return git_xmerge_config(var, value, NULL);
825 }
826
827 struct tracking_name_data {
828         const char *name;
829         char *remote;
830         int unique;
831 };
832
833 static int check_tracking_name(const char *refname, const unsigned char *sha1,
834                                int flags, void *cb_data)
835 {
836         struct tracking_name_data *cb = cb_data;
837         const char *slash;
838
839         if (prefixcmp(refname, "refs/remotes/"))
840                 return 0;
841         slash = strchr(refname + 13, '/');
842         if (!slash || strcmp(slash + 1, cb->name))
843                 return 0;
844         if (cb->remote) {
845                 cb->unique = 0;
846                 return 0;
847         }
848         cb->remote = xstrdup(refname);
849         return 0;
850 }
851
852 static const char *unique_tracking_name(const char *name)
853 {
854         struct tracking_name_data cb_data = { NULL, NULL, 1 };
855         cb_data.name = name;
856         for_each_ref(check_tracking_name, &cb_data);
857         if (cb_data.unique)
858                 return cb_data.remote;
859         free(cb_data.remote);
860         return NULL;
861 }
862
863 static int parse_branchname_arg(int argc, const char **argv,
864                                 int dwim_new_local_branch_ok,
865                                 struct branch_info *new,
866                                 struct tree **source_tree,
867                                 unsigned char rev[20],
868                                 const char **new_branch)
869 {
870         int argcount = 0;
871         unsigned char branch_rev[20];
872         const char *arg;
873         int has_dash_dash;
874
875         /*
876          * case 1: git checkout <ref> -- [<paths>]
877          *
878          *   <ref> must be a valid tree, everything after the '--' must be
879          *   a path.
880          *
881          * case 2: git checkout -- [<paths>]
882          *
883          *   everything after the '--' must be paths.
884          *
885          * case 3: git checkout <something> [<paths>]
886          *
887          *   With no paths, if <something> is a commit, that is to
888          *   switch to the branch or detach HEAD at it.  As a special case,
889          *   if <something> is A...B (missing A or B means HEAD but you can
890          *   omit at most one side), and if there is a unique merge base
891          *   between A and B, A...B names that merge base.
892          *
893          *   With no paths, if <something> is _not_ a commit, no -t nor -b
894          *   was given, and there is a tracking branch whose name is
895          *   <something> in one and only one remote, then this is a short-hand
896          *   to fork local <something> from that remote-tracking branch.
897          *
898          *   Otherwise <something> shall not be ambiguous.
899          *   - If it's *only* a reference, treat it like case (1).
900          *   - If it's only a path, treat it like case (2).
901          *   - else: fail.
902          *
903          */
904         if (!argc)
905                 return 0;
906
907         if (!strcmp(argv[0], "--"))     /* case (2) */
908                 return 1;
909
910         arg = argv[0];
911         has_dash_dash = (argc > 1) && !strcmp(argv[1], "--");
912
913         if (!strcmp(arg, "-"))
914                 arg = "@{-1}";
915
916         if (get_sha1_mb(arg, rev)) {
917                 if (has_dash_dash)          /* case (1) */
918                         die(_("invalid reference: %s"), arg);
919                 if (dwim_new_local_branch_ok &&
920                     !check_filename(NULL, arg) &&
921                     argc == 1) {
922                         const char *remote = unique_tracking_name(arg);
923                         if (!remote || get_sha1(remote, rev))
924                                 return argcount;
925                         *new_branch = arg;
926                         arg = remote;
927                         /* DWIMmed to create local branch */
928                 } else {
929                         return argcount;
930                 }
931         }
932
933         /* we can't end up being in (2) anymore, eat the argument */
934         argcount++;
935         argv++;
936         argc--;
937
938         new->name = arg;
939         setup_branch_path(new);
940
941         if (!check_refname_format(new->path, 0) &&
942             !read_ref(new->path, branch_rev))
943                 hashcpy(rev, branch_rev);
944         else
945                 new->path = NULL; /* not an existing branch */
946
947         new->commit = lookup_commit_reference_gently(rev, 1);
948         if (!new->commit) {
949                 /* not a commit */
950                 *source_tree = parse_tree_indirect(rev);
951         } else {
952                 parse_commit(new->commit);
953                 *source_tree = new->commit->tree;
954         }
955
956         if (!*source_tree)                   /* case (1): want a tree */
957                 die(_("reference is not a tree: %s"), arg);
958         if (!has_dash_dash) {/* case (3 -> 1) */
959                 /*
960                  * Do not complain the most common case
961                  *      git checkout branch
962                  * even if there happen to be a file called 'branch';
963                  * it would be extremely annoying.
964                  */
965                 if (argc)
966                         verify_non_filename(NULL, arg);
967         } else {
968                 argcount++;
969                 argv++;
970                 argc--;
971         }
972
973         return argcount;
974 }
975
976 static int switch_unborn_to_new_branch(const struct checkout_opts *opts)
977 {
978         int status;
979         struct strbuf branch_ref = STRBUF_INIT;
980
981         if (!opts->new_branch)
982                 die(_("You are on a branch yet to be born"));
983         strbuf_addf(&branch_ref, "refs/heads/%s", opts->new_branch);
984         status = create_symref("HEAD", branch_ref.buf, "checkout -b");
985         strbuf_release(&branch_ref);
986         if (!opts->quiet)
987                 fprintf(stderr, _("Switched to a new branch '%s'\n"),
988                         opts->new_branch);
989         return status;
990 }
991
992 static int checkout_branch(struct checkout_opts *opts,
993                            struct branch_info *new)
994 {
995         if (opts->pathspec)
996                 die(_("paths cannot be used with switching branches"));
997
998         if (opts->patch_mode)
999                 die(_("'%s' cannot be used with switching branches"),
1000                     "--patch");
1001
1002         if (opts->writeout_stage)
1003                 die(_("'%s' cannot be used with switching branches"),
1004                     "--ours/--theirs");
1005
1006         if (opts->force && opts->merge)
1007                 die(_("'%s' cannot be used with '%s'"), "-f", "-m");
1008
1009         if (opts->force_detach && opts->new_branch)
1010                 die(_("'%s' cannot be used with '%s'"),
1011                     "--detach", "-b/-B/--orphan");
1012
1013         if (opts->new_orphan_branch) {
1014                 if (opts->track != BRANCH_TRACK_UNSPECIFIED)
1015                         die(_("'%s' cannot be used with '%s'"), "--orphan", "-t");
1016         } else if (opts->force_detach) {
1017                 if (opts->track != BRANCH_TRACK_UNSPECIFIED)
1018                         die(_("'%s' cannot be used with '%s'"), "--detach", "-t");
1019         } else if (opts->track == BRANCH_TRACK_UNSPECIFIED)
1020                 opts->track = git_branch_track;
1021
1022         if (new->name && !new->commit)
1023                 die(_("Cannot switch branch to a non-commit '%s'"),
1024                     new->name);
1025
1026         if (!new->commit && opts->new_branch) {
1027                 unsigned char rev[20];
1028                 int flag;
1029
1030                 if (!read_ref_full("HEAD", rev, 0, &flag) &&
1031                     (flag & REF_ISSYMREF) && is_null_sha1(rev))
1032                         return switch_unborn_to_new_branch(opts);
1033         }
1034         return switch_branches(opts, new);
1035 }
1036
1037 int cmd_checkout(int argc, const char **argv, const char *prefix)
1038 {
1039         struct checkout_opts opts;
1040         struct branch_info new;
1041         char *conflict_style = NULL;
1042         int dwim_new_local_branch = 1;
1043         struct option options[] = {
1044                 OPT__QUIET(&opts.quiet, N_("suppress progress reporting")),
1045                 OPT_STRING('b', NULL, &opts.new_branch, N_("branch"),
1046                            N_("create and checkout a new branch")),
1047                 OPT_STRING('B', NULL, &opts.new_branch_force, N_("branch"),
1048                            N_("create/reset and checkout a branch")),
1049                 OPT_BOOLEAN('l', NULL, &opts.new_branch_log, N_("create reflog for new branch")),
1050                 OPT_BOOLEAN(0, "detach", &opts.force_detach, N_("detach the HEAD at named commit")),
1051                 OPT_SET_INT('t', "track",  &opts.track, N_("set upstream info for new branch"),
1052                         BRANCH_TRACK_EXPLICIT),
1053                 OPT_STRING(0, "orphan", &opts.new_orphan_branch, N_("new branch"), N_("new unparented branch")),
1054                 OPT_SET_INT('2', "ours", &opts.writeout_stage, N_("checkout our version for unmerged files"),
1055                             2),
1056                 OPT_SET_INT('3', "theirs", &opts.writeout_stage, N_("checkout their version for unmerged files"),
1057                             3),
1058                 OPT__FORCE(&opts.force, N_("force checkout (throw away local modifications)")),
1059                 OPT_BOOLEAN('m', "merge", &opts.merge, N_("perform a 3-way merge with the new branch")),
1060                 OPT_BOOLEAN(0, "overwrite-ignore", &opts.overwrite_ignore, N_("update ignored files (default)")),
1061                 OPT_STRING(0, "conflict", &conflict_style, N_("style"),
1062                            N_("conflict style (merge or diff3)")),
1063                 OPT_BOOLEAN('p', "patch", &opts.patch_mode, N_("select hunks interactively")),
1064                 OPT_BOOL(0, "ignore-skip-worktree-bits", &opts.ignore_skipworktree,
1065                          N_("do not limit pathspecs to sparse entries only")),
1066                 { OPTION_BOOLEAN, 0, "guess", &dwim_new_local_branch, NULL,
1067                   N_("second guess 'git checkout no-such-branch'"),
1068                   PARSE_OPT_NOARG | PARSE_OPT_HIDDEN },
1069                 OPT_END(),
1070         };
1071
1072         memset(&opts, 0, sizeof(opts));
1073         memset(&new, 0, sizeof(new));
1074         opts.overwrite_ignore = 1;
1075         opts.prefix = prefix;
1076
1077         gitmodules_config();
1078         git_config(git_checkout_config, &opts);
1079
1080         opts.track = BRANCH_TRACK_UNSPECIFIED;
1081
1082         argc = parse_options(argc, argv, prefix, options, checkout_usage,
1083                              PARSE_OPT_KEEP_DASHDASH);
1084
1085         if (conflict_style) {
1086                 opts.merge = 1; /* implied */
1087                 git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
1088         }
1089
1090         if ((!!opts.new_branch + !!opts.new_branch_force + !!opts.new_orphan_branch) > 1)
1091                 die(_("-b, -B and --orphan are mutually exclusive"));
1092
1093         /*
1094          * From here on, new_branch will contain the branch to be checked out,
1095          * and new_branch_force and new_orphan_branch will tell us which one of
1096          * -b/-B/--orphan is being used.
1097          */
1098         if (opts.new_branch_force)
1099                 opts.new_branch = opts.new_branch_force;
1100
1101         if (opts.new_orphan_branch)
1102                 opts.new_branch = opts.new_orphan_branch;
1103
1104         /* --track without -b/-B/--orphan should DWIM */
1105         if (opts.track != BRANCH_TRACK_UNSPECIFIED && !opts.new_branch) {
1106                 const char *argv0 = argv[0];
1107                 if (!argc || !strcmp(argv0, "--"))
1108                         die (_("--track needs a branch name"));
1109                 if (!prefixcmp(argv0, "refs/"))
1110                         argv0 += 5;
1111                 if (!prefixcmp(argv0, "remotes/"))
1112                         argv0 += 8;
1113                 argv0 = strchr(argv0, '/');
1114                 if (!argv0 || !argv0[1])
1115                         die (_("Missing branch name; try -b"));
1116                 opts.new_branch = argv0 + 1;
1117         }
1118
1119         /*
1120          * Extract branch name from command line arguments, so
1121          * all that is left is pathspecs.
1122          *
1123          * Handle
1124          *
1125          *  1) git checkout <tree> -- [<paths>]
1126          *  2) git checkout -- [<paths>]
1127          *  3) git checkout <something> [<paths>]
1128          *
1129          * including "last branch" syntax and DWIM-ery for names of
1130          * remote branches, erroring out for invalid or ambiguous cases.
1131          */
1132         if (argc) {
1133                 unsigned char rev[20];
1134                 int dwim_ok =
1135                         !opts.patch_mode &&
1136                         dwim_new_local_branch &&
1137                         opts.track == BRANCH_TRACK_UNSPECIFIED &&
1138                         !opts.new_branch;
1139                 int n = parse_branchname_arg(argc, argv, dwim_ok,
1140                                              &new, &opts.source_tree,
1141                                              rev, &opts.new_branch);
1142                 argv += n;
1143                 argc -= n;
1144         }
1145
1146         if (argc) {
1147                 opts.pathspec = get_pathspec(prefix, argv);
1148
1149                 if (!opts.pathspec)
1150                         die(_("invalid path specification"));
1151
1152                 /*
1153                  * Try to give more helpful suggestion.
1154                  * new_branch && argc > 1 will be caught later.
1155                  */
1156                 if (opts.new_branch && argc == 1)
1157                         die(_("Cannot update paths and switch to branch '%s' at the same time.\n"
1158                               "Did you intend to checkout '%s' which can not be resolved as commit?"),
1159                             opts.new_branch, argv[0]);
1160
1161                 if (opts.force_detach)
1162                         die(_("git checkout: --detach does not take a path argument '%s'"),
1163                             argv[0]);
1164
1165                 if (1 < !!opts.writeout_stage + !!opts.force + !!opts.merge)
1166                         die(_("git checkout: --ours/--theirs, --force and --merge are incompatible when\n"
1167                               "checking out of the index."));
1168         }
1169
1170         if (opts.new_branch) {
1171                 struct strbuf buf = STRBUF_INIT;
1172
1173                 opts.branch_exists =
1174                         validate_new_branchname(opts.new_branch, &buf,
1175                                                 !!opts.new_branch_force,
1176                                                 !!opts.new_branch_force);
1177
1178                 strbuf_release(&buf);
1179         }
1180
1181         if (opts.patch_mode || opts.pathspec)
1182                 return checkout_paths(&opts, new.name);
1183         else
1184                 return checkout_branch(&opts, &new);
1185 }