Merge branch 'jd/subtree'
[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         struct pathspec 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_le(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 struct pathspec *pathspec)
87 {
88         read_tree_recursive(tree, "", 0, 0, pathspec, update_some, NULL);
89
90         /* update the index with the given tree's info
91          * for all args, expanding wildcards, and exit
92          * with any non-zero return code.
93          */
94         return 0;
95 }
96
97 static int skip_same_name(const struct cache_entry *ce, int pos)
98 {
99         while (++pos < active_nr &&
100                !strcmp(active_cache[pos]->name, ce->name))
101                 ; /* skip */
102         return pos;
103 }
104
105 static int check_stage(int stage, const struct cache_entry *ce, int pos)
106 {
107         while (pos < active_nr &&
108                !strcmp(active_cache[pos]->name, ce->name)) {
109                 if (ce_stage(active_cache[pos]) == stage)
110                         return 0;
111                 pos++;
112         }
113         if (stage == 2)
114                 return error(_("path '%s' does not have our version"), ce->name);
115         else
116                 return error(_("path '%s' does not have their version"), ce->name);
117 }
118
119 static int check_stages(unsigned stages, const struct cache_entry *ce, int pos)
120 {
121         unsigned seen = 0;
122         const char *name = ce->name;
123
124         while (pos < active_nr) {
125                 ce = active_cache[pos];
126                 if (strcmp(name, ce->name))
127                         break;
128                 seen |= (1 << ce_stage(ce));
129                 pos++;
130         }
131         if ((stages & seen) != stages)
132                 return error(_("path '%s' does not have all necessary versions"),
133                              name);
134         return 0;
135 }
136
137 static int checkout_stage(int stage, struct cache_entry *ce, int pos,
138                           struct checkout *state)
139 {
140         while (pos < active_nr &&
141                !strcmp(active_cache[pos]->name, ce->name)) {
142                 if (ce_stage(active_cache[pos]) == stage)
143                         return checkout_entry(active_cache[pos], state, NULL);
144                 pos++;
145         }
146         if (stage == 2)
147                 return error(_("path '%s' does not have our version"), ce->name);
148         else
149                 return error(_("path '%s' does not have their version"), ce->name);
150 }
151
152 static int checkout_merged(int pos, struct checkout *state)
153 {
154         struct cache_entry *ce = active_cache[pos];
155         const char *path = ce->name;
156         mmfile_t ancestor, ours, theirs;
157         int status;
158         unsigned char sha1[20];
159         mmbuffer_t result_buf;
160         unsigned char threeway[3][20];
161         unsigned mode = 0;
162
163         memset(threeway, 0, sizeof(threeway));
164         while (pos < active_nr) {
165                 int stage;
166                 stage = ce_stage(ce);
167                 if (!stage || strcmp(path, ce->name))
168                         break;
169                 hashcpy(threeway[stage - 1], ce->sha1);
170                 if (stage == 2)
171                         mode = create_ce_mode(ce->ce_mode);
172                 pos++;
173                 ce = active_cache[pos];
174         }
175         if (is_null_sha1(threeway[1]) || is_null_sha1(threeway[2]))
176                 return error(_("path '%s' does not have necessary versions"), path);
177
178         read_mmblob(&ancestor, threeway[0]);
179         read_mmblob(&ours, threeway[1]);
180         read_mmblob(&theirs, threeway[2]);
181
182         /*
183          * NEEDSWORK: re-create conflicts from merges with
184          * merge.renormalize set, too
185          */
186         status = ll_merge(&result_buf, path, &ancestor, "base",
187                           &ours, "ours", &theirs, "theirs", NULL);
188         free(ancestor.ptr);
189         free(ours.ptr);
190         free(theirs.ptr);
191         if (status < 0 || !result_buf.ptr) {
192                 free(result_buf.ptr);
193                 return error(_("path '%s': cannot merge"), path);
194         }
195
196         /*
197          * NEEDSWORK:
198          * There is absolutely no reason to write this as a blob object
199          * and create a phony cache entry just to leak.  This hack is
200          * primarily to get to the write_entry() machinery that massages
201          * the contents to work-tree format and writes out which only
202          * allows it for a cache entry.  The code in write_entry() needs
203          * to be refactored to allow us to feed a <buffer, size, mode>
204          * instead of a cache entry.  Such a refactoring would help
205          * merge_recursive as well (it also writes the merge result to the
206          * object database even when it may contain conflicts).
207          */
208         if (write_sha1_file(result_buf.ptr, result_buf.size,
209                             blob_type, sha1))
210                 die(_("Unable to add merge result for '%s'"), path);
211         ce = make_cache_entry(mode, sha1, path, 2, 0);
212         if (!ce)
213                 die(_("make_cache_entry failed for path '%s'"), path);
214         status = checkout_entry(ce, state, NULL);
215         return status;
216 }
217
218 static int checkout_paths(const struct checkout_opts *opts,
219                           const char *revision)
220 {
221         int pos;
222         struct checkout state;
223         static char *ps_matched;
224         unsigned char rev[20];
225         int flag;
226         struct commit *head;
227         int errs = 0;
228         int newfd;
229         struct lock_file *lock_file;
230
231         if (opts->track != BRANCH_TRACK_UNSPECIFIED)
232                 die(_("'%s' cannot be used with updating paths"), "--track");
233
234         if (opts->new_branch_log)
235                 die(_("'%s' cannot be used with updating paths"), "-l");
236
237         if (opts->force && opts->patch_mode)
238                 die(_("'%s' cannot be used with updating paths"), "-f");
239
240         if (opts->force_detach)
241                 die(_("'%s' cannot be used with updating paths"), "--detach");
242
243         if (opts->merge && opts->patch_mode)
244                 die(_("'%s' cannot be used with %s"), "--merge", "--patch");
245
246         if (opts->force && opts->merge)
247                 die(_("'%s' cannot be used with %s"), "-f", "-m");
248
249         if (opts->new_branch)
250                 die(_("Cannot update paths and switch to branch '%s' at the same time."),
251                     opts->new_branch);
252
253         if (opts->patch_mode)
254                 return run_add_interactive(revision, "--patch=checkout",
255                                            &opts->pathspec);
256
257         lock_file = xcalloc(1, sizeof(struct lock_file));
258
259         newfd = hold_locked_index(lock_file, 1);
260         if (read_cache_preload(&opts->pathspec) < 0)
261                 return error(_("corrupt index file"));
262
263         if (opts->source_tree)
264                 read_tree_some(opts->source_tree, &opts->pathspec);
265
266         ps_matched = xcalloc(1, opts->pathspec.nr);
267
268         /*
269          * Make sure all pathspecs participated in locating the paths
270          * to be checked out.
271          */
272         for (pos = 0; pos < active_nr; pos++) {
273                 struct cache_entry *ce = active_cache[pos];
274                 ce->ce_flags &= ~CE_MATCHED;
275                 if (!opts->ignore_skipworktree && ce_skip_worktree(ce))
276                         continue;
277                 if (opts->source_tree && !(ce->ce_flags & CE_UPDATE))
278                         /*
279                          * "git checkout tree-ish -- path", but this entry
280                          * is in the original index; it will not be checked
281                          * out to the working tree and it does not matter
282                          * if pathspec matched this entry.  We will not do
283                          * anything to this entry at all.
284                          */
285                         continue;
286                 /*
287                  * Either this entry came from the tree-ish we are
288                  * checking the paths out of, or we are checking out
289                  * of the index.
290                  *
291                  * If it comes from the tree-ish, we already know it
292                  * matches the pathspec and could just stamp
293                  * CE_MATCHED to it from update_some(). But we still
294                  * need ps_matched and read_tree_recursive (and
295                  * eventually tree_entry_interesting) cannot fill
296                  * ps_matched yet. Once it can, we can avoid calling
297                  * match_pathspec() for _all_ entries when
298                  * opts->source_tree != NULL.
299                  */
300                 if (ce_path_match(ce, &opts->pathspec, ps_matched))
301                         ce->ce_flags |= CE_MATCHED;
302         }
303
304         if (report_path_error(ps_matched, &opts->pathspec, opts->prefix)) {
305                 free(ps_matched);
306                 return 1;
307         }
308         free(ps_matched);
309
310         /* "checkout -m path" to recreate conflicted state */
311         if (opts->merge)
312                 unmerge_marked_index(&the_index);
313
314         /* Any unmerged paths? */
315         for (pos = 0; pos < active_nr; pos++) {
316                 const struct cache_entry *ce = active_cache[pos];
317                 if (ce->ce_flags & CE_MATCHED) {
318                         if (!ce_stage(ce))
319                                 continue;
320                         if (opts->force) {
321                                 warning(_("path '%s' is unmerged"), ce->name);
322                         } else if (opts->writeout_stage) {
323                                 errs |= check_stage(opts->writeout_stage, ce, pos);
324                         } else if (opts->merge) {
325                                 errs |= check_stages((1<<2) | (1<<3), ce, pos);
326                         } else {
327                                 errs = 1;
328                                 error(_("path '%s' is unmerged"), ce->name);
329                         }
330                         pos = skip_same_name(ce, pos) - 1;
331                 }
332         }
333         if (errs)
334                 return 1;
335
336         /* Now we are committed to check them out */
337         memset(&state, 0, sizeof(state));
338         state.force = 1;
339         state.refresh_cache = 1;
340         for (pos = 0; pos < active_nr; pos++) {
341                 struct cache_entry *ce = active_cache[pos];
342                 if (ce->ce_flags & CE_MATCHED) {
343                         if (!ce_stage(ce)) {
344                                 errs |= checkout_entry(ce, &state, NULL);
345                                 continue;
346                         }
347                         if (opts->writeout_stage)
348                                 errs |= checkout_stage(opts->writeout_stage, ce, pos, &state);
349                         else if (opts->merge)
350                                 errs |= checkout_merged(pos, &state);
351                         pos = skip_same_name(ce, pos) - 1;
352                 }
353         }
354
355         if (write_cache(newfd, active_cache, active_nr) ||
356             commit_locked_index(lock_file))
357                 die(_("unable to write new index file"));
358
359         read_ref_full("HEAD", rev, 0, &flag);
360         head = lookup_commit_reference_gently(rev, 1);
361
362         errs |= post_checkout_hook(head, head, 0);
363         return errs;
364 }
365
366 static void show_local_changes(struct object *head,
367                                const struct diff_options *opts)
368 {
369         struct rev_info rev;
370         /* I think we want full paths, even if we're in a subdirectory. */
371         init_revisions(&rev, NULL);
372         rev.diffopt.flags = opts->flags;
373         rev.diffopt.output_format |= DIFF_FORMAT_NAME_STATUS;
374         diff_setup_done(&rev.diffopt);
375         add_pending_object(&rev, head, NULL);
376         run_diff_index(&rev, 0);
377 }
378
379 static void describe_detached_head(const char *msg, struct commit *commit)
380 {
381         struct strbuf sb = STRBUF_INIT;
382         if (!parse_commit(commit))
383                 pp_commit_easy(CMIT_FMT_ONELINE, commit, &sb);
384         fprintf(stderr, "%s %s... %s\n", msg,
385                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV), sb.buf);
386         strbuf_release(&sb);
387 }
388
389 static int reset_tree(struct tree *tree, const struct checkout_opts *o,
390                       int worktree, int *writeout_error)
391 {
392         struct unpack_trees_options opts;
393         struct tree_desc tree_desc;
394
395         memset(&opts, 0, sizeof(opts));
396         opts.head_idx = -1;
397         opts.update = worktree;
398         opts.skip_unmerged = !worktree;
399         opts.reset = 1;
400         opts.merge = 1;
401         opts.fn = oneway_merge;
402         opts.verbose_update = !o->quiet && isatty(2);
403         opts.src_index = &the_index;
404         opts.dst_index = &the_index;
405         parse_tree(tree);
406         init_tree_desc(&tree_desc, tree->buffer, tree->size);
407         switch (unpack_trees(1, &tree_desc, &opts)) {
408         case -2:
409                 *writeout_error = 1;
410                 /*
411                  * We return 0 nevertheless, as the index is all right
412                  * and more importantly we have made best efforts to
413                  * update paths in the work tree, and we cannot revert
414                  * them.
415                  */
416         case 0:
417                 return 0;
418         default:
419                 return 128;
420         }
421 }
422
423 struct branch_info {
424         const char *name; /* The short name used */
425         const char *path; /* The full name of a real branch */
426         struct commit *commit; /* The named commit */
427 };
428
429 static void setup_branch_path(struct branch_info *branch)
430 {
431         struct strbuf buf = STRBUF_INIT;
432
433         strbuf_branchname(&buf, branch->name);
434         if (strcmp(buf.buf, branch->name))
435                 branch->name = xstrdup(buf.buf);
436         strbuf_splice(&buf, 0, 0, "refs/heads/", 11);
437         branch->path = strbuf_detach(&buf, NULL);
438 }
439
440 static int merge_working_tree(const struct checkout_opts *opts,
441                               struct branch_info *old,
442                               struct branch_info *new,
443                               int *writeout_error)
444 {
445         int ret;
446         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
447         int newfd = hold_locked_index(lock_file, 1);
448
449         if (read_cache_preload(NULL) < 0)
450                 return error(_("corrupt index file"));
451
452         resolve_undo_clear();
453         if (opts->force) {
454                 ret = reset_tree(new->commit->tree, opts, 1, writeout_error);
455                 if (ret)
456                         return ret;
457         } else {
458                 struct tree_desc trees[2];
459                 struct tree *tree;
460                 struct unpack_trees_options topts;
461
462                 memset(&topts, 0, sizeof(topts));
463                 topts.head_idx = -1;
464                 topts.src_index = &the_index;
465                 topts.dst_index = &the_index;
466
467                 setup_unpack_trees_porcelain(&topts, "checkout");
468
469                 refresh_cache(REFRESH_QUIET);
470
471                 if (unmerged_cache()) {
472                         error(_("you need to resolve your current index first"));
473                         return 1;
474                 }
475
476                 /* 2-way merge to the new branch */
477                 topts.initial_checkout = is_cache_unborn();
478                 topts.update = 1;
479                 topts.merge = 1;
480                 topts.gently = opts->merge && old->commit;
481                 topts.verbose_update = !opts->quiet && isatty(2);
482                 topts.fn = twoway_merge;
483                 if (opts->overwrite_ignore) {
484                         topts.dir = xcalloc(1, sizeof(*topts.dir));
485                         topts.dir->flags |= DIR_SHOW_IGNORED;
486                         setup_standard_excludes(topts.dir);
487                 }
488                 tree = parse_tree_indirect(old->commit ?
489                                            old->commit->object.sha1 :
490                                            EMPTY_TREE_SHA1_BIN);
491                 init_tree_desc(&trees[0], tree->buffer, tree->size);
492                 tree = parse_tree_indirect(new->commit->object.sha1);
493                 init_tree_desc(&trees[1], tree->buffer, tree->size);
494
495                 ret = unpack_trees(2, trees, &topts);
496                 if (ret == -1) {
497                         /*
498                          * Unpack couldn't do a trivial merge; either
499                          * give up or do a real merge, depending on
500                          * whether the merge flag was used.
501                          */
502                         struct tree *result;
503                         struct tree *work;
504                         struct merge_options o;
505                         if (!opts->merge)
506                                 return 1;
507
508                         /*
509                          * Without old->commit, the below is the same as
510                          * the two-tree unpack we already tried and failed.
511                          */
512                         if (!old->commit)
513                                 return 1;
514
515                         /* Do more real merge */
516
517                         /*
518                          * We update the index fully, then write the
519                          * tree from the index, then merge the new
520                          * branch with the current tree, with the old
521                          * branch as the base. Then we reset the index
522                          * (but not the working tree) to the new
523                          * branch, leaving the working tree as the
524                          * merged version, but skipping unmerged
525                          * entries in the index.
526                          */
527
528                         add_files_to_cache(NULL, NULL, 0);
529                         /*
530                          * NEEDSWORK: carrying over local changes
531                          * when branches have different end-of-line
532                          * normalization (or clean+smudge rules) is
533                          * a pain; plumb in an option to set
534                          * o.renormalize?
535                          */
536                         init_merge_options(&o);
537                         o.verbosity = 0;
538                         work = write_tree_from_memory(&o);
539
540                         ret = reset_tree(new->commit->tree, opts, 1,
541                                          writeout_error);
542                         if (ret)
543                                 return ret;
544                         o.ancestor = old->name;
545                         o.branch1 = new->name;
546                         o.branch2 = "local";
547                         merge_trees(&o, new->commit->tree, work,
548                                 old->commit->tree, &result);
549                         ret = reset_tree(new->commit->tree, opts, 0,
550                                          writeout_error);
551                         if (ret)
552                                 return ret;
553                 }
554         }
555
556         if (write_cache(newfd, active_cache, active_nr) ||
557             commit_locked_index(lock_file))
558                 die(_("unable to write new index file"));
559
560         if (!opts->force && !opts->quiet)
561                 show_local_changes(&new->commit->object, &opts->diff_options);
562
563         return 0;
564 }
565
566 static void report_tracking(struct branch_info *new)
567 {
568         struct strbuf sb = STRBUF_INIT;
569         struct branch *branch = branch_get(new->name);
570
571         if (!format_tracking_info(branch, &sb))
572                 return;
573         fputs(sb.buf, stdout);
574         strbuf_release(&sb);
575 }
576
577 static void update_refs_for_switch(const struct checkout_opts *opts,
578                                    struct branch_info *old,
579                                    struct branch_info *new)
580 {
581         struct strbuf msg = STRBUF_INIT;
582         const char *old_desc, *reflog_msg;
583         if (opts->new_branch) {
584                 if (opts->new_orphan_branch) {
585                         if (opts->new_branch_log && !log_all_ref_updates) {
586                                 int temp;
587                                 char log_file[PATH_MAX];
588                                 char *ref_name = mkpath("refs/heads/%s", opts->new_orphan_branch);
589
590                                 temp = log_all_ref_updates;
591                                 log_all_ref_updates = 1;
592                                 if (log_ref_setup(ref_name, log_file, sizeof(log_file))) {
593                                         fprintf(stderr, _("Can not do reflog for '%s'\n"),
594                                             opts->new_orphan_branch);
595                                         log_all_ref_updates = temp;
596                                         return;
597                                 }
598                                 log_all_ref_updates = temp;
599                         }
600                 }
601                 else
602                         create_branch(old->name, opts->new_branch, new->name,
603                                       opts->new_branch_force ? 1 : 0,
604                                       opts->new_branch_log,
605                                       opts->new_branch_force ? 1 : 0,
606                                       opts->quiet,
607                                       opts->track);
608                 new->name = opts->new_branch;
609                 setup_branch_path(new);
610         }
611
612         old_desc = old->name;
613         if (!old_desc && old->commit)
614                 old_desc = sha1_to_hex(old->commit->object.sha1);
615
616         reflog_msg = getenv("GIT_REFLOG_ACTION");
617         if (!reflog_msg)
618                 strbuf_addf(&msg, "checkout: moving from %s to %s",
619                         old_desc ? old_desc : "(invalid)", new->name);
620         else
621                 strbuf_insert(&msg, 0, reflog_msg, strlen(reflog_msg));
622
623         if (!strcmp(new->name, "HEAD") && !new->path && !opts->force_detach) {
624                 /* Nothing to do. */
625         } else if (opts->force_detach || !new->path) {  /* No longer on any branch. */
626                 update_ref(msg.buf, "HEAD", new->commit->object.sha1, NULL,
627                            REF_NODEREF, UPDATE_REFS_DIE_ON_ERR);
628                 if (!opts->quiet) {
629                         if (old->path && advice_detached_head)
630                                 detach_advice(new->name);
631                         describe_detached_head(_("HEAD is now at"), new->commit);
632                 }
633         } else if (new->path) { /* Switch branches. */
634                 create_symref("HEAD", new->path, msg.buf);
635                 if (!opts->quiet) {
636                         if (old->path && !strcmp(new->path, old->path)) {
637                                 if (opts->new_branch_force)
638                                         fprintf(stderr, _("Reset branch '%s'\n"),
639                                                 new->name);
640                                 else
641                                         fprintf(stderr, _("Already on '%s'\n"),
642                                                 new->name);
643                         } else if (opts->new_branch) {
644                                 if (opts->branch_exists)
645                                         fprintf(stderr, _("Switched to and reset branch '%s'\n"), new->name);
646                                 else
647                                         fprintf(stderr, _("Switched to a new branch '%s'\n"), new->name);
648                         } else {
649                                 fprintf(stderr, _("Switched to branch '%s'\n"),
650                                         new->name);
651                         }
652                 }
653                 if (old->path && old->name) {
654                         if (!ref_exists(old->path) && reflog_exists(old->path))
655                                 delete_reflog(old->path);
656                 }
657         }
658         remove_branch_state();
659         strbuf_release(&msg);
660         if (!opts->quiet &&
661             (new->path || (!opts->force_detach && !strcmp(new->name, "HEAD"))))
662                 report_tracking(new);
663 }
664
665 static int add_pending_uninteresting_ref(const char *refname,
666                                          const unsigned char *sha1,
667                                          int flags, void *cb_data)
668 {
669         add_pending_sha1(cb_data, refname, sha1, UNINTERESTING);
670         return 0;
671 }
672
673 static void describe_one_orphan(struct strbuf *sb, struct commit *commit)
674 {
675         strbuf_addstr(sb, "  ");
676         strbuf_addstr(sb,
677                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
678         strbuf_addch(sb, ' ');
679         if (!parse_commit(commit))
680                 pp_commit_easy(CMIT_FMT_ONELINE, commit, sb);
681         strbuf_addch(sb, '\n');
682 }
683
684 #define ORPHAN_CUTOFF 4
685 static void suggest_reattach(struct commit *commit, struct rev_info *revs)
686 {
687         struct commit *c, *last = NULL;
688         struct strbuf sb = STRBUF_INIT;
689         int lost = 0;
690         while ((c = get_revision(revs)) != NULL) {
691                 if (lost < ORPHAN_CUTOFF)
692                         describe_one_orphan(&sb, c);
693                 last = c;
694                 lost++;
695         }
696         if (ORPHAN_CUTOFF < lost) {
697                 int more = lost - ORPHAN_CUTOFF;
698                 if (more == 1)
699                         describe_one_orphan(&sb, last);
700                 else
701                         strbuf_addf(&sb, _(" ... and %d more.\n"), more);
702         }
703
704         fprintf(stderr,
705                 Q_(
706                 /* The singular version */
707                 "Warning: you are leaving %d commit behind, "
708                 "not connected to\n"
709                 "any of your branches:\n\n"
710                 "%s\n",
711                 /* The plural version */
712                 "Warning: you are leaving %d commits behind, "
713                 "not connected to\n"
714                 "any of your branches:\n\n"
715                 "%s\n",
716                 /* Give ngettext() the count */
717                 lost),
718                 lost,
719                 sb.buf);
720         strbuf_release(&sb);
721
722         if (advice_detached_head)
723                 fprintf(stderr,
724                         _(
725                         "If you want to keep them by creating a new branch, "
726                         "this may be a good time\nto do so with:\n\n"
727                         " git branch new_branch_name %s\n\n"),
728                         find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
729 }
730
731 /*
732  * We are about to leave commit that was at the tip of a detached
733  * HEAD.  If it is not reachable from any ref, this is the last chance
734  * for the user to do so without resorting to reflog.
735  */
736 static void orphaned_commit_warning(struct commit *old, struct commit *new)
737 {
738         struct rev_info revs;
739         struct object *object = &old->object;
740         struct object_array refs;
741
742         init_revisions(&revs, NULL);
743         setup_revisions(0, NULL, &revs, NULL);
744
745         object->flags &= ~UNINTERESTING;
746         add_pending_object(&revs, object, sha1_to_hex(object->sha1));
747
748         for_each_ref(add_pending_uninteresting_ref, &revs);
749         add_pending_sha1(&revs, "HEAD", new->object.sha1, UNINTERESTING);
750
751         refs = revs.pending;
752         revs.leak_pending = 1;
753
754         if (prepare_revision_walk(&revs))
755                 die(_("internal error in revision walk"));
756         if (!(old->object.flags & UNINTERESTING))
757                 suggest_reattach(old, &revs);
758         else
759                 describe_detached_head(_("Previous HEAD position was"), old);
760
761         clear_commit_marks_for_object_array(&refs, ALL_REV_FLAGS);
762         free(refs.objects);
763 }
764
765 static int switch_branches(const struct checkout_opts *opts,
766                            struct branch_info *new)
767 {
768         int ret = 0;
769         struct branch_info old;
770         void *path_to_free;
771         unsigned char rev[20];
772         int flag, writeout_error = 0;
773         memset(&old, 0, sizeof(old));
774         old.path = path_to_free = resolve_refdup("HEAD", rev, 0, &flag);
775         old.commit = lookup_commit_reference_gently(rev, 1);
776         if (!(flag & REF_ISSYMREF))
777                 old.path = NULL;
778
779         if (old.path && starts_with(old.path, "refs/heads/"))
780                 old.name = old.path + strlen("refs/heads/");
781
782         if (!new->name) {
783                 new->name = "HEAD";
784                 new->commit = old.commit;
785                 if (!new->commit)
786                         die(_("You are on a branch yet to be born"));
787                 parse_commit_or_die(new->commit);
788         }
789
790         ret = merge_working_tree(opts, &old, new, &writeout_error);
791         if (ret) {
792                 free(path_to_free);
793                 return ret;
794         }
795
796         if (!opts->quiet && !old.path && old.commit && new->commit != old.commit)
797                 orphaned_commit_warning(old.commit, new->commit);
798
799         update_refs_for_switch(opts, &old, new);
800
801         ret = post_checkout_hook(old.commit, new->commit, 1);
802         free(path_to_free);
803         return ret || writeout_error;
804 }
805
806 static int git_checkout_config(const char *var, const char *value, void *cb)
807 {
808         if (!strcmp(var, "diff.ignoresubmodules")) {
809                 struct checkout_opts *opts = cb;
810                 handle_ignore_submodules_arg(&opts->diff_options, value);
811                 return 0;
812         }
813
814         if (starts_with(var, "submodule."))
815                 return parse_submodule_config_option(var, value);
816
817         return git_xmerge_config(var, value, NULL);
818 }
819
820 struct tracking_name_data {
821         /* const */ char *src_ref;
822         char *dst_ref;
823         unsigned char *dst_sha1;
824         int unique;
825 };
826
827 static int check_tracking_name(struct remote *remote, void *cb_data)
828 {
829         struct tracking_name_data *cb = cb_data;
830         struct refspec query;
831         memset(&query, 0, sizeof(struct refspec));
832         query.src = cb->src_ref;
833         if (remote_find_tracking(remote, &query) ||
834             get_sha1(query.dst, cb->dst_sha1)) {
835                 free(query.dst);
836                 return 0;
837         }
838         if (cb->dst_ref) {
839                 free(query.dst);
840                 cb->unique = 0;
841                 return 0;
842         }
843         cb->dst_ref = query.dst;
844         return 0;
845 }
846
847 static const char *unique_tracking_name(const char *name, unsigned char *sha1)
848 {
849         struct tracking_name_data cb_data = { NULL, NULL, NULL, 1 };
850         char src_ref[PATH_MAX];
851         snprintf(src_ref, PATH_MAX, "refs/heads/%s", name);
852         cb_data.src_ref = src_ref;
853         cb_data.dst_sha1 = sha1;
854         for_each_remote(check_tracking_name, &cb_data);
855         if (cb_data.unique)
856                 return cb_data.dst_ref;
857         free(cb_data.dst_ref);
858         return NULL;
859 }
860
861 static int parse_branchname_arg(int argc, const char **argv,
862                                 int dwim_new_local_branch_ok,
863                                 struct branch_info *new,
864                                 struct tree **source_tree,
865                                 unsigned char rev[20],
866                                 const char **new_branch)
867 {
868         int argcount = 0;
869         unsigned char branch_rev[20];
870         const char *arg;
871         int dash_dash_pos;
872         int has_dash_dash = 0;
873         int i;
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> [--]
886          *
887          *   (a) 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          *   (b) If <something> is _not_ a commit, either "--" is present
894          *       or <something> is not a path, no -t or -b was given, and
895          *       and there is a tracking branch whose name is <something>
896          *       in one and only one remote, then this is a short-hand to
897          *       fork local <something> from that remote-tracking branch.
898          *
899          *   (c) Otherwise, if "--" is present, treat it like case (1).
900          *
901          *   (d) Otherwise :
902          *       - if it's a reference, treat it like case (1)
903          *       - else if it's a path, treat it like case (2)
904          *       - else: fail.
905          *
906          * case 4: git checkout <something> <paths>
907          *
908          *   The first argument must not be ambiguous.
909          *   - If it's *only* a reference, treat it like case (1).
910          *   - If it's only a path, treat it like case (2).
911          *   - else: fail.
912          *
913          */
914         if (!argc)
915                 return 0;
916
917         arg = argv[0];
918         dash_dash_pos = -1;
919         for (i = 0; i < argc; i++) {
920                 if (!strcmp(argv[i], "--")) {
921                         dash_dash_pos = i;
922                         break;
923                 }
924         }
925         if (dash_dash_pos == 0)
926                 return 1; /* case (2) */
927         else if (dash_dash_pos == 1)
928                 has_dash_dash = 1; /* case (3) or (1) */
929         else if (dash_dash_pos >= 2)
930                 die(_("only one reference expected, %d given."), dash_dash_pos);
931
932         if (!strcmp(arg, "-"))
933                 arg = "@{-1}";
934
935         if (get_sha1_mb(arg, rev)) {
936                 /*
937                  * Either case (3) or (4), with <something> not being
938                  * a commit, or an attempt to use case (1) with an
939                  * invalid ref.
940                  *
941                  * It's likely an error, but we need to find out if
942                  * we should auto-create the branch, case (3).(b).
943                  */
944                 int recover_with_dwim = dwim_new_local_branch_ok;
945
946                 if (check_filename(NULL, arg) && !has_dash_dash)
947                         recover_with_dwim = 0;
948                 /*
949                  * Accept "git checkout foo" and "git checkout foo --"
950                  * as candidates for dwim.
951                  */
952                 if (!(argc == 1 && !has_dash_dash) &&
953                     !(argc == 2 && has_dash_dash))
954                         recover_with_dwim = 0;
955
956                 if (recover_with_dwim) {
957                         const char *remote = unique_tracking_name(arg, rev);
958                         if (remote) {
959                                 *new_branch = arg;
960                                 arg = remote;
961                                 /* DWIMmed to create local branch, case (3).(b) */
962                         } else {
963                                 recover_with_dwim = 0;
964                         }
965                 }
966
967                 if (!recover_with_dwim) {
968                         if (has_dash_dash)
969                                 die(_("invalid reference: %s"), arg);
970                         return argcount;
971                 }
972         }
973
974         /* we can't end up being in (2) anymore, eat the argument */
975         argcount++;
976         argv++;
977         argc--;
978
979         new->name = arg;
980         setup_branch_path(new);
981
982         if (!check_refname_format(new->path, 0) &&
983             !read_ref(new->path, branch_rev))
984                 hashcpy(rev, branch_rev);
985         else
986                 new->path = NULL; /* not an existing branch */
987
988         new->commit = lookup_commit_reference_gently(rev, 1);
989         if (!new->commit) {
990                 /* not a commit */
991                 *source_tree = parse_tree_indirect(rev);
992         } else {
993                 parse_commit_or_die(new->commit);
994                 *source_tree = new->commit->tree;
995         }
996
997         if (!*source_tree)                   /* case (1): want a tree */
998                 die(_("reference is not a tree: %s"), arg);
999         if (!has_dash_dash) {/* case (3).(d) -> (1) */
1000                 /*
1001                  * Do not complain the most common case
1002                  *      git checkout branch
1003                  * even if there happen to be a file called 'branch';
1004                  * it would be extremely annoying.
1005                  */
1006                 if (argc)
1007                         verify_non_filename(NULL, arg);
1008         } else {
1009                 argcount++;
1010                 argv++;
1011                 argc--;
1012         }
1013
1014         return argcount;
1015 }
1016
1017 static int switch_unborn_to_new_branch(const struct checkout_opts *opts)
1018 {
1019         int status;
1020         struct strbuf branch_ref = STRBUF_INIT;
1021
1022         if (!opts->new_branch)
1023                 die(_("You are on a branch yet to be born"));
1024         strbuf_addf(&branch_ref, "refs/heads/%s", opts->new_branch);
1025         status = create_symref("HEAD", branch_ref.buf, "checkout -b");
1026         strbuf_release(&branch_ref);
1027         if (!opts->quiet)
1028                 fprintf(stderr, _("Switched to a new branch '%s'\n"),
1029                         opts->new_branch);
1030         return status;
1031 }
1032
1033 static int checkout_branch(struct checkout_opts *opts,
1034                            struct branch_info *new)
1035 {
1036         if (opts->pathspec.nr)
1037                 die(_("paths cannot be used with switching branches"));
1038
1039         if (opts->patch_mode)
1040                 die(_("'%s' cannot be used with switching branches"),
1041                     "--patch");
1042
1043         if (opts->writeout_stage)
1044                 die(_("'%s' cannot be used with switching branches"),
1045                     "--ours/--theirs");
1046
1047         if (opts->force && opts->merge)
1048                 die(_("'%s' cannot be used with '%s'"), "-f", "-m");
1049
1050         if (opts->force_detach && opts->new_branch)
1051                 die(_("'%s' cannot be used with '%s'"),
1052                     "--detach", "-b/-B/--orphan");
1053
1054         if (opts->new_orphan_branch) {
1055                 if (opts->track != BRANCH_TRACK_UNSPECIFIED)
1056                         die(_("'%s' cannot be used with '%s'"), "--orphan", "-t");
1057         } else if (opts->force_detach) {
1058                 if (opts->track != BRANCH_TRACK_UNSPECIFIED)
1059                         die(_("'%s' cannot be used with '%s'"), "--detach", "-t");
1060         } else if (opts->track == BRANCH_TRACK_UNSPECIFIED)
1061                 opts->track = git_branch_track;
1062
1063         if (new->name && !new->commit)
1064                 die(_("Cannot switch branch to a non-commit '%s'"),
1065                     new->name);
1066
1067         if (!new->commit && opts->new_branch) {
1068                 unsigned char rev[20];
1069                 int flag;
1070
1071                 if (!read_ref_full("HEAD", rev, 0, &flag) &&
1072                     (flag & REF_ISSYMREF) && is_null_sha1(rev))
1073                         return switch_unborn_to_new_branch(opts);
1074         }
1075         return switch_branches(opts, new);
1076 }
1077
1078 int cmd_checkout(int argc, const char **argv, const char *prefix)
1079 {
1080         struct checkout_opts opts;
1081         struct branch_info new;
1082         char *conflict_style = NULL;
1083         int dwim_new_local_branch = 1;
1084         struct option options[] = {
1085                 OPT__QUIET(&opts.quiet, N_("suppress progress reporting")),
1086                 OPT_STRING('b', NULL, &opts.new_branch, N_("branch"),
1087                            N_("create and checkout a new branch")),
1088                 OPT_STRING('B', NULL, &opts.new_branch_force, N_("branch"),
1089                            N_("create/reset and checkout a branch")),
1090                 OPT_BOOL('l', NULL, &opts.new_branch_log, N_("create reflog for new branch")),
1091                 OPT_BOOL(0, "detach", &opts.force_detach, N_("detach the HEAD at named commit")),
1092                 OPT_SET_INT('t', "track",  &opts.track, N_("set upstream info for new branch"),
1093                         BRANCH_TRACK_EXPLICIT),
1094                 OPT_STRING(0, "orphan", &opts.new_orphan_branch, N_("new-branch"), N_("new unparented branch")),
1095                 OPT_SET_INT('2', "ours", &opts.writeout_stage, N_("checkout our version for unmerged files"),
1096                             2),
1097                 OPT_SET_INT('3', "theirs", &opts.writeout_stage, N_("checkout their version for unmerged files"),
1098                             3),
1099                 OPT__FORCE(&opts.force, N_("force checkout (throw away local modifications)")),
1100                 OPT_BOOL('m', "merge", &opts.merge, N_("perform a 3-way merge with the new branch")),
1101                 OPT_BOOL(0, "overwrite-ignore", &opts.overwrite_ignore, N_("update ignored files (default)")),
1102                 OPT_STRING(0, "conflict", &conflict_style, N_("style"),
1103                            N_("conflict style (merge or diff3)")),
1104                 OPT_BOOL('p', "patch", &opts.patch_mode, N_("select hunks interactively")),
1105                 OPT_BOOL(0, "ignore-skip-worktree-bits", &opts.ignore_skipworktree,
1106                          N_("do not limit pathspecs to sparse entries only")),
1107                 OPT_HIDDEN_BOOL(0, "guess", &dwim_new_local_branch,
1108                                 N_("second guess 'git checkout no-such-branch'")),
1109                 OPT_END(),
1110         };
1111
1112         memset(&opts, 0, sizeof(opts));
1113         memset(&new, 0, sizeof(new));
1114         opts.overwrite_ignore = 1;
1115         opts.prefix = prefix;
1116
1117         gitmodules_config();
1118         git_config(git_checkout_config, &opts);
1119
1120         opts.track = BRANCH_TRACK_UNSPECIFIED;
1121
1122         argc = parse_options(argc, argv, prefix, options, checkout_usage,
1123                              PARSE_OPT_KEEP_DASHDASH);
1124
1125         if (conflict_style) {
1126                 opts.merge = 1; /* implied */
1127                 git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
1128         }
1129
1130         if ((!!opts.new_branch + !!opts.new_branch_force + !!opts.new_orphan_branch) > 1)
1131                 die(_("-b, -B and --orphan are mutually exclusive"));
1132
1133         /*
1134          * From here on, new_branch will contain the branch to be checked out,
1135          * and new_branch_force and new_orphan_branch will tell us which one of
1136          * -b/-B/--orphan is being used.
1137          */
1138         if (opts.new_branch_force)
1139                 opts.new_branch = opts.new_branch_force;
1140
1141         if (opts.new_orphan_branch)
1142                 opts.new_branch = opts.new_orphan_branch;
1143
1144         /* --track without -b/-B/--orphan should DWIM */
1145         if (opts.track != BRANCH_TRACK_UNSPECIFIED && !opts.new_branch) {
1146                 const char *argv0 = argv[0];
1147                 if (!argc || !strcmp(argv0, "--"))
1148                         die (_("--track needs a branch name"));
1149                 if (starts_with(argv0, "refs/"))
1150                         argv0 += 5;
1151                 if (starts_with(argv0, "remotes/"))
1152                         argv0 += 8;
1153                 argv0 = strchr(argv0, '/');
1154                 if (!argv0 || !argv0[1])
1155                         die (_("Missing branch name; try -b"));
1156                 opts.new_branch = argv0 + 1;
1157         }
1158
1159         /*
1160          * Extract branch name from command line arguments, so
1161          * all that is left is pathspecs.
1162          *
1163          * Handle
1164          *
1165          *  1) git checkout <tree> -- [<paths>]
1166          *  2) git checkout -- [<paths>]
1167          *  3) git checkout <something> [<paths>]
1168          *
1169          * including "last branch" syntax and DWIM-ery for names of
1170          * remote branches, erroring out for invalid or ambiguous cases.
1171          */
1172         if (argc) {
1173                 unsigned char rev[20];
1174                 int dwim_ok =
1175                         !opts.patch_mode &&
1176                         dwim_new_local_branch &&
1177                         opts.track == BRANCH_TRACK_UNSPECIFIED &&
1178                         !opts.new_branch;
1179                 int n = parse_branchname_arg(argc, argv, dwim_ok,
1180                                              &new, &opts.source_tree,
1181                                              rev, &opts.new_branch);
1182                 argv += n;
1183                 argc -= n;
1184         }
1185
1186         if (argc) {
1187                 parse_pathspec(&opts.pathspec, 0,
1188                                opts.patch_mode ? PATHSPEC_PREFIX_ORIGIN : 0,
1189                                prefix, argv);
1190
1191                 if (!opts.pathspec.nr)
1192                         die(_("invalid path specification"));
1193
1194                 /*
1195                  * Try to give more helpful suggestion.
1196                  * new_branch && argc > 1 will be caught later.
1197                  */
1198                 if (opts.new_branch && argc == 1)
1199                         die(_("Cannot update paths and switch to branch '%s' at the same time.\n"
1200                               "Did you intend to checkout '%s' which can not be resolved as commit?"),
1201                             opts.new_branch, argv[0]);
1202
1203                 if (opts.force_detach)
1204                         die(_("git checkout: --detach does not take a path argument '%s'"),
1205                             argv[0]);
1206
1207                 if (1 < !!opts.writeout_stage + !!opts.force + !!opts.merge)
1208                         die(_("git checkout: --ours/--theirs, --force and --merge are incompatible when\n"
1209                               "checking out of the index."));
1210         }
1211
1212         if (opts.new_branch) {
1213                 struct strbuf buf = STRBUF_INIT;
1214
1215                 opts.branch_exists =
1216                         validate_new_branchname(opts.new_branch, &buf,
1217                                                 !!opts.new_branch_force,
1218                                                 !!opts.new_branch_force);
1219
1220                 strbuf_release(&buf);
1221         }
1222
1223         if (opts.patch_mode || opts.pathspec.nr)
1224                 return checkout_paths(&opts, new.name);
1225         else
1226                 return checkout_branch(&opts, &new);
1227 }