Merge branch 'jc/mktree' into sb/opt-filename
[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
21 static const char * const checkout_usage[] = {
22         "git checkout [options] <branch>",
23         "git checkout [options] [<branch>] -- <file>...",
24         NULL,
25 };
26
27 struct checkout_opts {
28         int quiet;
29         int merge;
30         int force;
31         int writeout_stage;
32         int writeout_error;
33
34         const char *new_branch;
35         int new_branch_log;
36         enum branch_track track;
37 };
38
39 static int post_checkout_hook(struct commit *old, struct commit *new,
40                               int changed)
41 {
42         return run_hook(NULL, "post-checkout",
43                         sha1_to_hex(old ? old->object.sha1 : null_sha1),
44                         sha1_to_hex(new ? new->object.sha1 : null_sha1),
45                         changed ? "1" : "0", NULL);
46         /* "new" can be NULL when checking out from the index before
47            a commit exists. */
48
49 }
50
51 static int update_some(const unsigned char *sha1, const char *base, int baselen,
52                 const char *pathname, unsigned mode, int stage, void *context)
53 {
54         int len;
55         struct cache_entry *ce;
56
57         if (S_ISDIR(mode))
58                 return READ_TREE_RECURSIVE;
59
60         len = baselen + strlen(pathname);
61         ce = xcalloc(1, cache_entry_size(len));
62         hashcpy(ce->sha1, sha1);
63         memcpy(ce->name, base, baselen);
64         memcpy(ce->name + baselen, pathname, len - baselen);
65         ce->ce_flags = create_ce_flags(len, 0);
66         ce->ce_mode = create_ce_mode(mode);
67         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
68         return 0;
69 }
70
71 static int read_tree_some(struct tree *tree, const char **pathspec)
72 {
73         read_tree_recursive(tree, "", 0, 0, pathspec, update_some, NULL);
74
75         /* update the index with the given tree's info
76          * for all args, expanding wildcards, and exit
77          * with any non-zero return code.
78          */
79         return 0;
80 }
81
82 static int skip_same_name(struct cache_entry *ce, int pos)
83 {
84         while (++pos < active_nr &&
85                !strcmp(active_cache[pos]->name, ce->name))
86                 ; /* skip */
87         return pos;
88 }
89
90 static int check_stage(int stage, struct cache_entry *ce, int pos)
91 {
92         while (pos < active_nr &&
93                !strcmp(active_cache[pos]->name, ce->name)) {
94                 if (ce_stage(active_cache[pos]) == stage)
95                         return 0;
96                 pos++;
97         }
98         return error("path '%s' does not have %s version",
99                      ce->name,
100                      (stage == 2) ? "our" : "their");
101 }
102
103 static int check_all_stages(struct cache_entry *ce, int pos)
104 {
105         if (ce_stage(ce) != 1 ||
106             active_nr <= pos + 2 ||
107             strcmp(active_cache[pos+1]->name, ce->name) ||
108             ce_stage(active_cache[pos+1]) != 2 ||
109             strcmp(active_cache[pos+2]->name, ce->name) ||
110             ce_stage(active_cache[pos+2]) != 3)
111                 return error("path '%s' does not have all three versions",
112                              ce->name);
113         return 0;
114 }
115
116 static int checkout_stage(int stage, struct cache_entry *ce, int pos,
117                           struct checkout *state)
118 {
119         while (pos < active_nr &&
120                !strcmp(active_cache[pos]->name, ce->name)) {
121                 if (ce_stage(active_cache[pos]) == stage)
122                         return checkout_entry(active_cache[pos], state, NULL);
123                 pos++;
124         }
125         return error("path '%s' does not have %s version",
126                      ce->name,
127                      (stage == 2) ? "our" : "their");
128 }
129
130 /* NEEDSWORK: share with merge-recursive */
131 static void fill_mm(const unsigned char *sha1, mmfile_t *mm)
132 {
133         unsigned long size;
134         enum object_type type;
135
136         if (!hashcmp(sha1, null_sha1)) {
137                 mm->ptr = xstrdup("");
138                 mm->size = 0;
139                 return;
140         }
141
142         mm->ptr = read_sha1_file(sha1, &type, &size);
143         if (!mm->ptr || type != OBJ_BLOB)
144                 die("unable to read blob object %s", sha1_to_hex(sha1));
145         mm->size = size;
146 }
147
148 static int checkout_merged(int pos, struct checkout *state)
149 {
150         struct cache_entry *ce = active_cache[pos];
151         const char *path = ce->name;
152         mmfile_t ancestor, ours, theirs;
153         int status;
154         unsigned char sha1[20];
155         mmbuffer_t result_buf;
156
157         if (ce_stage(ce) != 1 ||
158             active_nr <= pos + 2 ||
159             strcmp(active_cache[pos+1]->name, path) ||
160             ce_stage(active_cache[pos+1]) != 2 ||
161             strcmp(active_cache[pos+2]->name, path) ||
162             ce_stage(active_cache[pos+2]) != 3)
163                 return error("path '%s' does not have all 3 versions", path);
164
165         fill_mm(active_cache[pos]->sha1, &ancestor);
166         fill_mm(active_cache[pos+1]->sha1, &ours);
167         fill_mm(active_cache[pos+2]->sha1, &theirs);
168
169         status = ll_merge(&result_buf, path, &ancestor,
170                           &ours, "ours", &theirs, "theirs", 1);
171         free(ancestor.ptr);
172         free(ours.ptr);
173         free(theirs.ptr);
174         if (status < 0 || !result_buf.ptr) {
175                 free(result_buf.ptr);
176                 return error("path '%s': cannot merge", path);
177         }
178
179         /*
180          * NEEDSWORK:
181          * There is absolutely no reason to write this as a blob object
182          * and create a phony cache entry just to leak.  This hack is
183          * primarily to get to the write_entry() machinery that massages
184          * the contents to work-tree format and writes out which only
185          * allows it for a cache entry.  The code in write_entry() needs
186          * to be refactored to allow us to feed a <buffer, size, mode>
187          * instead of a cache entry.  Such a refactoring would help
188          * merge_recursive as well (it also writes the merge result to the
189          * object database even when it may contain conflicts).
190          */
191         if (write_sha1_file(result_buf.ptr, result_buf.size,
192                             blob_type, sha1))
193                 die("Unable to add merge result for '%s'", path);
194         ce = make_cache_entry(create_ce_mode(active_cache[pos+1]->ce_mode),
195                               sha1,
196                               path, 2, 0);
197         if (!ce)
198                 die("make_cache_entry failed for path '%s'", path);
199         status = checkout_entry(ce, state, NULL);
200         return status;
201 }
202
203 static int checkout_paths(struct tree *source_tree, const char **pathspec,
204                           struct checkout_opts *opts)
205 {
206         int pos;
207         struct checkout state;
208         static char *ps_matched;
209         unsigned char rev[20];
210         int flag;
211         struct commit *head;
212         int errs = 0;
213         int stage = opts->writeout_stage;
214         int merge = opts->merge;
215         int newfd;
216         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
217
218         newfd = hold_locked_index(lock_file, 1);
219         if (read_cache_preload(pathspec) < 0)
220                 return error("corrupt index file");
221
222         if (source_tree)
223                 read_tree_some(source_tree, pathspec);
224
225         for (pos = 0; pathspec[pos]; pos++)
226                 ;
227         ps_matched = xcalloc(1, pos);
228
229         for (pos = 0; pos < active_nr; pos++) {
230                 struct cache_entry *ce = active_cache[pos];
231                 match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, ps_matched);
232         }
233
234         if (report_path_error(ps_matched, pathspec, 0))
235                 return 1;
236
237         /* Any unmerged paths? */
238         for (pos = 0; pos < active_nr; pos++) {
239                 struct cache_entry *ce = active_cache[pos];
240                 if (match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, NULL)) {
241                         if (!ce_stage(ce))
242                                 continue;
243                         if (opts->force) {
244                                 warning("path '%s' is unmerged", ce->name);
245                         } else if (stage) {
246                                 errs |= check_stage(stage, ce, pos);
247                         } else if (opts->merge) {
248                                 errs |= check_all_stages(ce, pos);
249                         } else {
250                                 errs = 1;
251                                 error("path '%s' is unmerged", ce->name);
252                         }
253                         pos = skip_same_name(ce, pos) - 1;
254                 }
255         }
256         if (errs)
257                 return 1;
258
259         /* Now we are committed to check them out */
260         memset(&state, 0, sizeof(state));
261         state.force = 1;
262         state.refresh_cache = 1;
263         for (pos = 0; pos < active_nr; pos++) {
264                 struct cache_entry *ce = active_cache[pos];
265                 if (match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, NULL)) {
266                         if (!ce_stage(ce)) {
267                                 errs |= checkout_entry(ce, &state, NULL);
268                                 continue;
269                         }
270                         if (stage)
271                                 errs |= checkout_stage(stage, ce, pos, &state);
272                         else if (merge)
273                                 errs |= checkout_merged(pos, &state);
274                         pos = skip_same_name(ce, pos) - 1;
275                 }
276         }
277
278         if (write_cache(newfd, active_cache, active_nr) ||
279             commit_locked_index(lock_file))
280                 die("unable to write new index file");
281
282         resolve_ref("HEAD", rev, 0, &flag);
283         head = lookup_commit_reference_gently(rev, 1);
284
285         errs |= post_checkout_hook(head, head, 0);
286         return errs;
287 }
288
289 static void show_local_changes(struct object *head)
290 {
291         struct rev_info rev;
292         /* I think we want full paths, even if we're in a subdirectory. */
293         init_revisions(&rev, NULL);
294         rev.abbrev = 0;
295         rev.diffopt.output_format |= DIFF_FORMAT_NAME_STATUS;
296         if (diff_setup_done(&rev.diffopt) < 0)
297                 die("diff_setup_done failed");
298         add_pending_object(&rev, head, NULL);
299         run_diff_index(&rev, 0);
300 }
301
302 static void describe_detached_head(char *msg, struct commit *commit)
303 {
304         struct strbuf sb = STRBUF_INIT;
305         parse_commit(commit);
306         pretty_print_commit(CMIT_FMT_ONELINE, commit, &sb, 0, NULL, NULL, 0, 0);
307         fprintf(stderr, "%s %s... %s\n", msg,
308                 find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV), sb.buf);
309         strbuf_release(&sb);
310 }
311
312 static int reset_tree(struct tree *tree, struct checkout_opts *o, int worktree)
313 {
314         struct unpack_trees_options opts;
315         struct tree_desc tree_desc;
316
317         memset(&opts, 0, sizeof(opts));
318         opts.head_idx = -1;
319         opts.update = worktree;
320         opts.skip_unmerged = !worktree;
321         opts.reset = 1;
322         opts.merge = 1;
323         opts.fn = oneway_merge;
324         opts.verbose_update = !o->quiet;
325         opts.src_index = &the_index;
326         opts.dst_index = &the_index;
327         parse_tree(tree);
328         init_tree_desc(&tree_desc, tree->buffer, tree->size);
329         switch (unpack_trees(1, &tree_desc, &opts)) {
330         case -2:
331                 o->writeout_error = 1;
332                 /*
333                  * We return 0 nevertheless, as the index is all right
334                  * and more importantly we have made best efforts to
335                  * update paths in the work tree, and we cannot revert
336                  * them.
337                  */
338         case 0:
339                 return 0;
340         default:
341                 return 128;
342         }
343 }
344
345 struct branch_info {
346         const char *name; /* The short name used */
347         const char *path; /* The full name of a real branch */
348         struct commit *commit; /* The named commit */
349 };
350
351 static void setup_branch_path(struct branch_info *branch)
352 {
353         struct strbuf buf = STRBUF_INIT;
354
355         strbuf_branchname(&buf, branch->name);
356         if (strcmp(buf.buf, branch->name))
357                 branch->name = xstrdup(buf.buf);
358         strbuf_splice(&buf, 0, 0, "refs/heads/", 11);
359         branch->path = strbuf_detach(&buf, NULL);
360 }
361
362 static int merge_working_tree(struct checkout_opts *opts,
363                               struct branch_info *old, struct branch_info *new)
364 {
365         int ret;
366         struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
367         int newfd = hold_locked_index(lock_file, 1);
368
369         if (read_cache_preload(NULL) < 0)
370                 return error("corrupt index file");
371
372         if (opts->force) {
373                 ret = reset_tree(new->commit->tree, opts, 1);
374                 if (ret)
375                         return ret;
376         } else {
377                 struct tree_desc trees[2];
378                 struct tree *tree;
379                 struct unpack_trees_options topts;
380
381                 memset(&topts, 0, sizeof(topts));
382                 topts.head_idx = -1;
383                 topts.src_index = &the_index;
384                 topts.dst_index = &the_index;
385
386                 topts.msgs.not_uptodate_file = "You have local changes to '%s'; cannot switch branches.";
387
388                 refresh_cache(REFRESH_QUIET);
389
390                 if (unmerged_cache()) {
391                         error("you need to resolve your current index first");
392                         return 1;
393                 }
394
395                 /* 2-way merge to the new branch */
396                 topts.initial_checkout = is_cache_unborn();
397                 topts.update = 1;
398                 topts.merge = 1;
399                 topts.gently = opts->merge;
400                 topts.verbose_update = !opts->quiet;
401                 topts.fn = twoway_merge;
402                 topts.dir = xcalloc(1, sizeof(*topts.dir));
403                 topts.dir->flags |= DIR_SHOW_IGNORED;
404                 topts.dir->exclude_per_dir = ".gitignore";
405                 tree = parse_tree_indirect(old->commit->object.sha1);
406                 init_tree_desc(&trees[0], tree->buffer, tree->size);
407                 tree = parse_tree_indirect(new->commit->object.sha1);
408                 init_tree_desc(&trees[1], tree->buffer, tree->size);
409
410                 ret = unpack_trees(2, trees, &topts);
411                 if (ret == -1) {
412                         /*
413                          * Unpack couldn't do a trivial merge; either
414                          * give up or do a real merge, depending on
415                          * whether the merge flag was used.
416                          */
417                         struct tree *result;
418                         struct tree *work;
419                         struct merge_options o;
420                         if (!opts->merge)
421                                 return 1;
422                         parse_commit(old->commit);
423
424                         /* Do more real merge */
425
426                         /*
427                          * We update the index fully, then write the
428                          * tree from the index, then merge the new
429                          * branch with the current tree, with the old
430                          * branch as the base. Then we reset the index
431                          * (but not the working tree) to the new
432                          * branch, leaving the working tree as the
433                          * merged version, but skipping unmerged
434                          * entries in the index.
435                          */
436
437                         add_files_to_cache(NULL, NULL, 0);
438                         init_merge_options(&o);
439                         o.verbosity = 0;
440                         work = write_tree_from_memory(&o);
441
442                         ret = reset_tree(new->commit->tree, opts, 1);
443                         if (ret)
444                                 return ret;
445                         o.branch1 = new->name;
446                         o.branch2 = "local";
447                         merge_trees(&o, new->commit->tree, work,
448                                 old->commit->tree, &result);
449                         ret = reset_tree(new->commit->tree, opts, 0);
450                         if (ret)
451                                 return ret;
452                 }
453         }
454
455         if (write_cache(newfd, active_cache, active_nr) ||
456             commit_locked_index(lock_file))
457                 die("unable to write new index file");
458
459         if (!opts->force && !opts->quiet)
460                 show_local_changes(&new->commit->object);
461
462         return 0;
463 }
464
465 static void report_tracking(struct branch_info *new)
466 {
467         struct strbuf sb = STRBUF_INIT;
468         struct branch *branch = branch_get(new->name);
469
470         if (!format_tracking_info(branch, &sb))
471                 return;
472         fputs(sb.buf, stdout);
473         strbuf_release(&sb);
474 }
475
476 static void update_refs_for_switch(struct checkout_opts *opts,
477                                    struct branch_info *old,
478                                    struct branch_info *new)
479 {
480         struct strbuf msg = STRBUF_INIT;
481         const char *old_desc;
482         if (opts->new_branch) {
483                 create_branch(old->name, opts->new_branch, new->name, 0,
484                               opts->new_branch_log, opts->track);
485                 new->name = opts->new_branch;
486                 setup_branch_path(new);
487         }
488
489         old_desc = old->name;
490         if (!old_desc && old->commit)
491                 old_desc = sha1_to_hex(old->commit->object.sha1);
492         strbuf_addf(&msg, "checkout: moving from %s to %s",
493                     old_desc ? old_desc : "(invalid)", new->name);
494
495         if (new->path) {
496                 create_symref("HEAD", new->path, msg.buf);
497                 if (!opts->quiet) {
498                         if (old->path && !strcmp(new->path, old->path))
499                                 fprintf(stderr, "Already on '%s'\n",
500                                         new->name);
501                         else
502                                 fprintf(stderr, "Switched to%s branch '%s'\n",
503                                         opts->new_branch ? " a new" : "",
504                                         new->name);
505                 }
506         } else if (strcmp(new->name, "HEAD")) {
507                 update_ref(msg.buf, "HEAD", new->commit->object.sha1, NULL,
508                            REF_NODEREF, DIE_ON_ERR);
509                 if (!opts->quiet) {
510                         if (old->path)
511                                 fprintf(stderr, "Note: moving to '%s' which isn't a local branch\nIf you want to create a new branch from this checkout, you may do so\n(now or later) by using -b with the checkout command again. Example:\n  git checkout -b <new_branch_name>\n", new->name);
512                         describe_detached_head("HEAD is now at", new->commit);
513                 }
514         }
515         remove_branch_state();
516         strbuf_release(&msg);
517         if (!opts->quiet && (new->path || !strcmp(new->name, "HEAD")))
518                 report_tracking(new);
519 }
520
521 static int switch_branches(struct checkout_opts *opts, struct branch_info *new)
522 {
523         int ret = 0;
524         struct branch_info old;
525         unsigned char rev[20];
526         int flag;
527         memset(&old, 0, sizeof(old));
528         old.path = resolve_ref("HEAD", rev, 0, &flag);
529         old.commit = lookup_commit_reference_gently(rev, 1);
530         if (!(flag & REF_ISSYMREF))
531                 old.path = NULL;
532
533         if (old.path && !prefixcmp(old.path, "refs/heads/"))
534                 old.name = old.path + strlen("refs/heads/");
535
536         if (!new->name) {
537                 new->name = "HEAD";
538                 new->commit = old.commit;
539                 if (!new->commit)
540                         die("You are on a branch yet to be born");
541                 parse_commit(new->commit);
542         }
543
544         if (!old.commit && !opts->force) {
545                 if (!opts->quiet) {
546                         warning("You appear to be on a branch yet to be born.");
547                         warning("Forcing checkout of %s.", new->name);
548                 }
549                 opts->force = 1;
550         }
551
552         ret = merge_working_tree(opts, &old, new);
553         if (ret)
554                 return ret;
555
556         /*
557          * If we were on a detached HEAD, but have now moved to
558          * a new commit, we want to mention the old commit once more
559          * to remind the user that it might be lost.
560          */
561         if (!opts->quiet && !old.path && old.commit && new->commit != old.commit)
562                 describe_detached_head("Previous HEAD position was", old.commit);
563
564         update_refs_for_switch(opts, &old, new);
565
566         ret = post_checkout_hook(old.commit, new->commit, 1);
567         return ret || opts->writeout_error;
568 }
569
570 static int git_checkout_config(const char *var, const char *value, void *cb)
571 {
572         return git_xmerge_config(var, value, cb);
573 }
574
575 int cmd_checkout(int argc, const char **argv, const char *prefix)
576 {
577         struct checkout_opts opts;
578         unsigned char rev[20];
579         const char *arg;
580         struct branch_info new;
581         struct tree *source_tree = NULL;
582         char *conflict_style = NULL;
583         struct option options[] = {
584                 OPT__QUIET(&opts.quiet),
585                 OPT_STRING('b', NULL, &opts.new_branch, "new branch", "branch"),
586                 OPT_BOOLEAN('l', NULL, &opts.new_branch_log, "log for new branch"),
587                 OPT_SET_INT('t', "track",  &opts.track, "track",
588                         BRANCH_TRACK_EXPLICIT),
589                 OPT_SET_INT('2', "ours", &opts.writeout_stage, "stage",
590                             2),
591                 OPT_SET_INT('3', "theirs", &opts.writeout_stage, "stage",
592                             3),
593                 OPT_BOOLEAN('f', NULL, &opts.force, "force"),
594                 OPT_BOOLEAN('m', "merge", &opts.merge, "merge"),
595                 OPT_STRING(0, "conflict", &conflict_style, "style",
596                            "conflict style (merge or diff3)"),
597                 OPT_END(),
598         };
599         int has_dash_dash;
600
601         memset(&opts, 0, sizeof(opts));
602         memset(&new, 0, sizeof(new));
603
604         git_config(git_checkout_config, NULL);
605
606         opts.track = BRANCH_TRACK_UNSPECIFIED;
607
608         argc = parse_options(argc, argv, options, checkout_usage,
609                              PARSE_OPT_KEEP_DASHDASH);
610
611         /* --track without -b should DWIM */
612         if (0 < opts.track && !opts.new_branch) {
613                 const char *argv0 = argv[0];
614                 if (!argc || !strcmp(argv0, "--"))
615                         die ("--track needs a branch name");
616                 if (!prefixcmp(argv0, "refs/"))
617                         argv0 += 5;
618                 if (!prefixcmp(argv0, "remotes/"))
619                         argv0 += 8;
620                 argv0 = strchr(argv0, '/');
621                 if (!argv0 || !argv0[1])
622                         die ("Missing branch name; try -b");
623                 opts.new_branch = argv0 + 1;
624         }
625
626         if (opts.track == BRANCH_TRACK_UNSPECIFIED)
627                 opts.track = git_branch_track;
628         if (conflict_style) {
629                 opts.merge = 1; /* implied */
630                 git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
631         }
632
633         if (opts.force && opts.merge)
634                 die("git checkout: -f and -m are incompatible");
635
636         /*
637          * case 1: git checkout <ref> -- [<paths>]
638          *
639          *   <ref> must be a valid tree, everything after the '--' must be
640          *   a path.
641          *
642          * case 2: git checkout -- [<paths>]
643          *
644          *   everything after the '--' must be paths.
645          *
646          * case 3: git checkout <something> [<paths>]
647          *
648          *   With no paths, if <something> is a commit, that is to
649          *   switch to the branch or detach HEAD at it.
650          *
651          *   Otherwise <something> shall not be ambiguous.
652          *   - If it's *only* a reference, treat it like case (1).
653          *   - If it's only a path, treat it like case (2).
654          *   - else: fail.
655          *
656          */
657         if (argc) {
658                 if (!strcmp(argv[0], "--")) {       /* case (2) */
659                         argv++;
660                         argc--;
661                         goto no_reference;
662                 }
663
664                 arg = argv[0];
665                 has_dash_dash = (argc > 1) && !strcmp(argv[1], "--");
666
667                 if (!strcmp(arg, "-"))
668                         arg = "@{-1}";
669
670                 if (get_sha1(arg, rev)) {
671                         if (has_dash_dash)          /* case (1) */
672                                 die("invalid reference: %s", arg);
673                         goto no_reference;          /* case (3 -> 2) */
674                 }
675
676                 /* we can't end up being in (2) anymore, eat the argument */
677                 argv++;
678                 argc--;
679
680                 new.name = arg;
681                 if ((new.commit = lookup_commit_reference_gently(rev, 1))) {
682                         setup_branch_path(&new);
683                         if (resolve_ref(new.path, rev, 1, NULL))
684                                 new.commit = lookup_commit_reference(rev);
685                         else
686                                 new.path = NULL;
687                         parse_commit(new.commit);
688                         source_tree = new.commit->tree;
689                 } else
690                         source_tree = parse_tree_indirect(rev);
691
692                 if (!source_tree)                   /* case (1): want a tree */
693                         die("reference is not a tree: %s", arg);
694                 if (!has_dash_dash) {/* case (3 -> 1) */
695                         /*
696                          * Do not complain the most common case
697                          *      git checkout branch
698                          * even if there happen to be a file called 'branch';
699                          * it would be extremely annoying.
700                          */
701                         if (argc)
702                                 verify_non_filename(NULL, arg);
703                 }
704                 else {
705                         argv++;
706                         argc--;
707                 }
708         }
709
710 no_reference:
711         if (argc) {
712                 const char **pathspec = get_pathspec(prefix, argv);
713
714                 if (!pathspec)
715                         die("invalid path specification");
716
717                 /* Checkout paths */
718                 if (opts.new_branch) {
719                         if (argc == 1) {
720                                 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]);
721                         } else {
722                                 die("git checkout: updating paths is incompatible with switching branches.");
723                         }
724                 }
725
726                 if (1 < !!opts.writeout_stage + !!opts.force + !!opts.merge)
727                         die("git checkout: --ours/--theirs, --force and --merge are incompatible when\nchecking out of the index.");
728
729                 return checkout_paths(source_tree, pathspec, &opts);
730         }
731
732         if (opts.new_branch) {
733                 struct strbuf buf = STRBUF_INIT;
734                 if (strbuf_check_branch_ref(&buf, opts.new_branch))
735                         die("git checkout: we do not like '%s' as a branch name.",
736                             opts.new_branch);
737                 if (!get_sha1(buf.buf, rev))
738                         die("git checkout: branch %s already exists", opts.new_branch);
739                 strbuf_release(&buf);
740         }
741
742         if (new.name && !new.commit) {
743                 die("Cannot switch branch to a non-commit.");
744         }
745         if (opts.writeout_stage)
746                 die("--ours/--theirs is incompatible with switching branches.");
747
748         return switch_branches(&opts, &new);
749 }