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