Merge branch 'dl/doc-submodule-wo-subcommand'
[git] / unpack-trees.c
1 #include "cache.h"
2 #include "argv-array.h"
3 #include "repository.h"
4 #include "config.h"
5 #include "dir.h"
6 #include "tree.h"
7 #include "tree-walk.h"
8 #include "cache-tree.h"
9 #include "unpack-trees.h"
10 #include "progress.h"
11 #include "refs.h"
12 #include "attr.h"
13 #include "split-index.h"
14 #include "dir.h"
15 #include "submodule.h"
16 #include "submodule-config.h"
17 #include "fsmonitor.h"
18 #include "object-store.h"
19 #include "fetch-object.h"
20
21 /*
22  * Error messages expected by scripts out of plumbing commands such as
23  * read-tree.  Non-scripted Porcelain is not required to use these messages
24  * and in fact are encouraged to reword them to better suit their particular
25  * situation better.  See how "git checkout" and "git merge" replaces
26  * them using setup_unpack_trees_porcelain(), for example.
27  */
28 static const char *unpack_plumbing_errors[NB_UNPACK_TREES_ERROR_TYPES] = {
29         /* ERROR_WOULD_OVERWRITE */
30         "Entry '%s' would be overwritten by merge. Cannot merge.",
31
32         /* ERROR_NOT_UPTODATE_FILE */
33         "Entry '%s' not uptodate. Cannot merge.",
34
35         /* ERROR_NOT_UPTODATE_DIR */
36         "Updating '%s' would lose untracked files in it",
37
38         /* ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN */
39         "Untracked working tree file '%s' would be overwritten by merge.",
40
41         /* ERROR_WOULD_LOSE_UNTRACKED_REMOVED */
42         "Untracked working tree file '%s' would be removed by merge.",
43
44         /* ERROR_BIND_OVERLAP */
45         "Entry '%s' overlaps with '%s'.  Cannot bind.",
46
47         /* ERROR_SPARSE_NOT_UPTODATE_FILE */
48         "Entry '%s' not uptodate. Cannot update sparse checkout.",
49
50         /* ERROR_WOULD_LOSE_ORPHANED_OVERWRITTEN */
51         "Working tree file '%s' would be overwritten by sparse checkout update.",
52
53         /* ERROR_WOULD_LOSE_ORPHANED_REMOVED */
54         "Working tree file '%s' would be removed by sparse checkout update.",
55
56         /* ERROR_WOULD_LOSE_SUBMODULE */
57         "Submodule '%s' cannot checkout new HEAD.",
58 };
59
60 #define ERRORMSG(o,type) \
61         ( ((o) && (o)->msgs[(type)]) \
62           ? ((o)->msgs[(type)])      \
63           : (unpack_plumbing_errors[(type)]) )
64
65 static const char *super_prefixed(const char *path)
66 {
67         /*
68          * It is necessary and sufficient to have two static buffers
69          * here, as the return value of this function is fed to
70          * error() using the unpack_*_errors[] templates we see above.
71          */
72         static struct strbuf buf[2] = {STRBUF_INIT, STRBUF_INIT};
73         static int super_prefix_len = -1;
74         static unsigned idx = ARRAY_SIZE(buf) - 1;
75
76         if (super_prefix_len < 0) {
77                 const char *super_prefix = get_super_prefix();
78                 if (!super_prefix) {
79                         super_prefix_len = 0;
80                 } else {
81                         int i;
82                         for (i = 0; i < ARRAY_SIZE(buf); i++)
83                                 strbuf_addstr(&buf[i], super_prefix);
84                         super_prefix_len = buf[0].len;
85                 }
86         }
87
88         if (!super_prefix_len)
89                 return path;
90
91         if (++idx >= ARRAY_SIZE(buf))
92                 idx = 0;
93
94         strbuf_setlen(&buf[idx], super_prefix_len);
95         strbuf_addstr(&buf[idx], path);
96
97         return buf[idx].buf;
98 }
99
100 void setup_unpack_trees_porcelain(struct unpack_trees_options *opts,
101                                   const char *cmd)
102 {
103         int i;
104         const char **msgs = opts->msgs;
105         const char *msg;
106
107         argv_array_init(&opts->msgs_to_free);
108
109         if (!strcmp(cmd, "checkout"))
110                 msg = advice_commit_before_merge
111                       ? _("Your local changes to the following files would be overwritten by checkout:\n%%s"
112                           "Please commit your changes or stash them before you switch branches.")
113                       : _("Your local changes to the following files would be overwritten by checkout:\n%%s");
114         else if (!strcmp(cmd, "merge"))
115                 msg = advice_commit_before_merge
116                       ? _("Your local changes to the following files would be overwritten by merge:\n%%s"
117                           "Please commit your changes or stash them before you merge.")
118                       : _("Your local changes to the following files would be overwritten by merge:\n%%s");
119         else
120                 msg = advice_commit_before_merge
121                       ? _("Your local changes to the following files would be overwritten by %s:\n%%s"
122                           "Please commit your changes or stash them before you %s.")
123                       : _("Your local changes to the following files would be overwritten by %s:\n%%s");
124         msgs[ERROR_WOULD_OVERWRITE] = msgs[ERROR_NOT_UPTODATE_FILE] =
125                 argv_array_pushf(&opts->msgs_to_free, msg, cmd, cmd);
126
127         msgs[ERROR_NOT_UPTODATE_DIR] =
128                 _("Updating the following directories would lose untracked files in them:\n%s");
129
130         if (!strcmp(cmd, "checkout"))
131                 msg = advice_commit_before_merge
132                       ? _("The following untracked working tree files would be removed by checkout:\n%%s"
133                           "Please move or remove them before you switch branches.")
134                       : _("The following untracked working tree files would be removed by checkout:\n%%s");
135         else if (!strcmp(cmd, "merge"))
136                 msg = advice_commit_before_merge
137                       ? _("The following untracked working tree files would be removed by merge:\n%%s"
138                           "Please move or remove them before you merge.")
139                       : _("The following untracked working tree files would be removed by merge:\n%%s");
140         else
141                 msg = advice_commit_before_merge
142                       ? _("The following untracked working tree files would be removed by %s:\n%%s"
143                           "Please move or remove them before you %s.")
144                       : _("The following untracked working tree files would be removed by %s:\n%%s");
145         msgs[ERROR_WOULD_LOSE_UNTRACKED_REMOVED] =
146                 argv_array_pushf(&opts->msgs_to_free, msg, cmd, cmd);
147
148         if (!strcmp(cmd, "checkout"))
149                 msg = advice_commit_before_merge
150                       ? _("The following untracked working tree files would be overwritten by checkout:\n%%s"
151                           "Please move or remove them before you switch branches.")
152                       : _("The following untracked working tree files would be overwritten by checkout:\n%%s");
153         else if (!strcmp(cmd, "merge"))
154                 msg = advice_commit_before_merge
155                       ? _("The following untracked working tree files would be overwritten by merge:\n%%s"
156                           "Please move or remove them before you merge.")
157                       : _("The following untracked working tree files would be overwritten by merge:\n%%s");
158         else
159                 msg = advice_commit_before_merge
160                       ? _("The following untracked working tree files would be overwritten by %s:\n%%s"
161                           "Please move or remove them before you %s.")
162                       : _("The following untracked working tree files would be overwritten by %s:\n%%s");
163         msgs[ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN] =
164                 argv_array_pushf(&opts->msgs_to_free, msg, cmd, cmd);
165
166         /*
167          * Special case: ERROR_BIND_OVERLAP refers to a pair of paths, we
168          * cannot easily display it as a list.
169          */
170         msgs[ERROR_BIND_OVERLAP] = _("Entry '%s' overlaps with '%s'.  Cannot bind.");
171
172         msgs[ERROR_SPARSE_NOT_UPTODATE_FILE] =
173                 _("Cannot update sparse checkout: the following entries are not up to date:\n%s");
174         msgs[ERROR_WOULD_LOSE_ORPHANED_OVERWRITTEN] =
175                 _("The following working tree files would be overwritten by sparse checkout update:\n%s");
176         msgs[ERROR_WOULD_LOSE_ORPHANED_REMOVED] =
177                 _("The following working tree files would be removed by sparse checkout update:\n%s");
178         msgs[ERROR_WOULD_LOSE_SUBMODULE] =
179                 _("Cannot update submodule:\n%s");
180
181         opts->show_all_errors = 1;
182         /* rejected paths may not have a static buffer */
183         for (i = 0; i < ARRAY_SIZE(opts->unpack_rejects); i++)
184                 opts->unpack_rejects[i].strdup_strings = 1;
185 }
186
187 void clear_unpack_trees_porcelain(struct unpack_trees_options *opts)
188 {
189         argv_array_clear(&opts->msgs_to_free);
190         memset(opts->msgs, 0, sizeof(opts->msgs));
191 }
192
193 static int do_add_entry(struct unpack_trees_options *o, struct cache_entry *ce,
194                          unsigned int set, unsigned int clear)
195 {
196         clear |= CE_HASHED;
197
198         if (set & CE_REMOVE)
199                 set |= CE_WT_REMOVE;
200
201         ce->ce_flags = (ce->ce_flags & ~clear) | set;
202         return add_index_entry(&o->result, ce,
203                                ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
204 }
205
206 static void add_entry(struct unpack_trees_options *o,
207                       const struct cache_entry *ce,
208                       unsigned int set, unsigned int clear)
209 {
210         do_add_entry(o, dup_cache_entry(ce, &o->result), set, clear);
211 }
212
213 /*
214  * add error messages on path <path>
215  * corresponding to the type <e> with the message <msg>
216  * indicating if it should be display in porcelain or not
217  */
218 static int add_rejected_path(struct unpack_trees_options *o,
219                              enum unpack_trees_error_types e,
220                              const char *path)
221 {
222         if (!o->show_all_errors)
223                 return error(ERRORMSG(o, e), super_prefixed(path));
224
225         /*
226          * Otherwise, insert in a list for future display by
227          * display_error_msgs()
228          */
229         string_list_append(&o->unpack_rejects[e], path);
230         return -1;
231 }
232
233 /*
234  * display all the error messages stored in a nice way
235  */
236 static void display_error_msgs(struct unpack_trees_options *o)
237 {
238         int e, i;
239         int something_displayed = 0;
240         for (e = 0; e < NB_UNPACK_TREES_ERROR_TYPES; e++) {
241                 struct string_list *rejects = &o->unpack_rejects[e];
242                 if (rejects->nr > 0) {
243                         struct strbuf path = STRBUF_INIT;
244                         something_displayed = 1;
245                         for (i = 0; i < rejects->nr; i++)
246                                 strbuf_addf(&path, "\t%s\n", rejects->items[i].string);
247                         error(ERRORMSG(o, e), super_prefixed(path.buf));
248                         strbuf_release(&path);
249                 }
250                 string_list_clear(rejects, 0);
251         }
252         if (something_displayed)
253                 fprintf(stderr, _("Aborting\n"));
254 }
255
256 static int check_submodule_move_head(const struct cache_entry *ce,
257                                      const char *old_id,
258                                      const char *new_id,
259                                      struct unpack_trees_options *o)
260 {
261         unsigned flags = SUBMODULE_MOVE_HEAD_DRY_RUN;
262         const struct submodule *sub = submodule_from_ce(ce);
263
264         if (!sub)
265                 return 0;
266
267         if (o->reset)
268                 flags |= SUBMODULE_MOVE_HEAD_FORCE;
269
270         if (submodule_move_head(ce->name, old_id, new_id, flags))
271                 return o->gently ? -1 :
272                                    add_rejected_path(o, ERROR_WOULD_LOSE_SUBMODULE, ce->name);
273         return 0;
274 }
275
276 /*
277  * Preform the loading of the repository's gitmodules file.  This function is
278  * used by 'check_update()' to perform loading of the gitmodules file in two
279  * differnt situations:
280  * (1) before removing entries from the working tree if the gitmodules file has
281  *     been marked for removal.  This situation is specified by 'state' == NULL.
282  * (2) before checking out entries to the working tree if the gitmodules file
283  *     has been marked for update.  This situation is specified by 'state' != NULL.
284  */
285 static void load_gitmodules_file(struct index_state *index,
286                                  struct checkout *state)
287 {
288         int pos = index_name_pos(index, GITMODULES_FILE, strlen(GITMODULES_FILE));
289
290         if (pos >= 0) {
291                 struct cache_entry *ce = index->cache[pos];
292                 if (!state && ce->ce_flags & CE_WT_REMOVE) {
293                         repo_read_gitmodules(the_repository);
294                 } else if (state && (ce->ce_flags & CE_UPDATE)) {
295                         submodule_free(the_repository);
296                         checkout_entry(ce, state, NULL, NULL);
297                         repo_read_gitmodules(the_repository);
298                 }
299         }
300 }
301
302 static struct progress *get_progress(struct unpack_trees_options *o)
303 {
304         unsigned cnt = 0, total = 0;
305         struct index_state *index = &o->result;
306
307         if (!o->update || !o->verbose_update)
308                 return NULL;
309
310         for (; cnt < index->cache_nr; cnt++) {
311                 const struct cache_entry *ce = index->cache[cnt];
312                 if (ce->ce_flags & (CE_UPDATE | CE_WT_REMOVE))
313                         total++;
314         }
315
316         return start_delayed_progress(_("Checking out files"), total);
317 }
318
319 static void setup_collided_checkout_detection(struct checkout *state,
320                                               struct index_state *index)
321 {
322         int i;
323
324         state->clone = 1;
325         for (i = 0; i < index->cache_nr; i++)
326                 index->cache[i]->ce_flags &= ~CE_MATCHED;
327 }
328
329 static void report_collided_checkout(struct index_state *index)
330 {
331         struct string_list list = STRING_LIST_INIT_NODUP;
332         int i;
333
334         for (i = 0; i < index->cache_nr; i++) {
335                 struct cache_entry *ce = index->cache[i];
336
337                 if (!(ce->ce_flags & CE_MATCHED))
338                         continue;
339
340                 string_list_append(&list, ce->name);
341                 ce->ce_flags &= ~CE_MATCHED;
342         }
343
344         list.cmp = fspathcmp;
345         string_list_sort(&list);
346
347         if (list.nr) {
348                 warning(_("the following paths have collided (e.g. case-sensitive paths\n"
349                           "on a case-insensitive filesystem) and only one from the same\n"
350                           "colliding group is in the working tree:\n"));
351
352                 for (i = 0; i < list.nr; i++)
353                         fprintf(stderr, "  '%s'\n", list.items[i].string);
354         }
355
356         string_list_clear(&list, 0);
357 }
358
359 static int check_updates(struct unpack_trees_options *o)
360 {
361         unsigned cnt = 0;
362         int errs = 0;
363         struct progress *progress;
364         struct index_state *index = &o->result;
365         struct checkout state = CHECKOUT_INIT;
366         int i;
367
368         trace_performance_enter();
369         state.force = 1;
370         state.quiet = 1;
371         state.refresh_cache = 1;
372         state.istate = index;
373
374         if (o->clone)
375                 setup_collided_checkout_detection(&state, index);
376
377         progress = get_progress(o);
378
379         if (o->update)
380                 git_attr_set_direction(GIT_ATTR_CHECKOUT);
381
382         if (should_update_submodules() && o->update && !o->dry_run)
383                 load_gitmodules_file(index, NULL);
384
385         for (i = 0; i < index->cache_nr; i++) {
386                 const struct cache_entry *ce = index->cache[i];
387
388                 if (ce->ce_flags & CE_WT_REMOVE) {
389                         display_progress(progress, ++cnt);
390                         if (o->update && !o->dry_run)
391                                 unlink_entry(ce);
392                 }
393         }
394         remove_marked_cache_entries(index, 0);
395         remove_scheduled_dirs();
396
397         if (should_update_submodules() && o->update && !o->dry_run)
398                 load_gitmodules_file(index, &state);
399
400         enable_delayed_checkout(&state);
401         if (repository_format_partial_clone && o->update && !o->dry_run) {
402                 /*
403                  * Prefetch the objects that are to be checked out in the loop
404                  * below.
405                  */
406                 struct oid_array to_fetch = OID_ARRAY_INIT;
407                 int fetch_if_missing_store = fetch_if_missing;
408                 fetch_if_missing = 0;
409                 for (i = 0; i < index->cache_nr; i++) {
410                         struct cache_entry *ce = index->cache[i];
411                         if ((ce->ce_flags & CE_UPDATE) &&
412                             !S_ISGITLINK(ce->ce_mode)) {
413                                 if (!has_object_file(&ce->oid))
414                                         oid_array_append(&to_fetch, &ce->oid);
415                         }
416                 }
417                 if (to_fetch.nr)
418                         fetch_objects(repository_format_partial_clone,
419                                       to_fetch.oid, to_fetch.nr);
420                 fetch_if_missing = fetch_if_missing_store;
421                 oid_array_clear(&to_fetch);
422         }
423         for (i = 0; i < index->cache_nr; i++) {
424                 struct cache_entry *ce = index->cache[i];
425
426                 if (ce->ce_flags & CE_UPDATE) {
427                         if (ce->ce_flags & CE_WT_REMOVE)
428                                 BUG("both update and delete flags are set on %s",
429                                     ce->name);
430                         display_progress(progress, ++cnt);
431                         ce->ce_flags &= ~CE_UPDATE;
432                         if (o->update && !o->dry_run) {
433                                 errs |= checkout_entry(ce, &state, NULL, NULL);
434                         }
435                 }
436         }
437         stop_progress(&progress);
438         errs |= finish_delayed_checkout(&state, NULL);
439         if (o->update)
440                 git_attr_set_direction(GIT_ATTR_CHECKIN);
441
442         if (o->clone)
443                 report_collided_checkout(index);
444
445         trace_performance_leave("check_updates");
446         return errs != 0;
447 }
448
449 static int verify_uptodate_sparse(const struct cache_entry *ce,
450                                   struct unpack_trees_options *o);
451 static int verify_absent_sparse(const struct cache_entry *ce,
452                                 enum unpack_trees_error_types,
453                                 struct unpack_trees_options *o);
454
455 static int apply_sparse_checkout(struct index_state *istate,
456                                  struct cache_entry *ce,
457                                  struct unpack_trees_options *o)
458 {
459         int was_skip_worktree = ce_skip_worktree(ce);
460
461         if (ce->ce_flags & CE_NEW_SKIP_WORKTREE)
462                 ce->ce_flags |= CE_SKIP_WORKTREE;
463         else
464                 ce->ce_flags &= ~CE_SKIP_WORKTREE;
465         if (was_skip_worktree != ce_skip_worktree(ce)) {
466                 ce->ce_flags |= CE_UPDATE_IN_BASE;
467                 mark_fsmonitor_invalid(istate, ce);
468                 istate->cache_changed |= CE_ENTRY_CHANGED;
469         }
470
471         /*
472          * if (!was_skip_worktree && !ce_skip_worktree()) {
473          *      This is perfectly normal. Move on;
474          * }
475          */
476
477         /*
478          * Merge strategies may set CE_UPDATE|CE_REMOVE outside checkout
479          * area as a result of ce_skip_worktree() shortcuts in
480          * verify_absent() and verify_uptodate().
481          * Make sure they don't modify worktree if they are already
482          * outside checkout area
483          */
484         if (was_skip_worktree && ce_skip_worktree(ce)) {
485                 ce->ce_flags &= ~CE_UPDATE;
486
487                 /*
488                  * By default, when CE_REMOVE is on, CE_WT_REMOVE is also
489                  * on to get that file removed from both index and worktree.
490                  * If that file is already outside worktree area, don't
491                  * bother remove it.
492                  */
493                 if (ce->ce_flags & CE_REMOVE)
494                         ce->ce_flags &= ~CE_WT_REMOVE;
495         }
496
497         if (!was_skip_worktree && ce_skip_worktree(ce)) {
498                 /*
499                  * If CE_UPDATE is set, verify_uptodate() must be called already
500                  * also stat info may have lost after merged_entry() so calling
501                  * verify_uptodate() again may fail
502                  */
503                 if (!(ce->ce_flags & CE_UPDATE) && verify_uptodate_sparse(ce, o))
504                         return -1;
505                 ce->ce_flags |= CE_WT_REMOVE;
506                 ce->ce_flags &= ~CE_UPDATE;
507         }
508         if (was_skip_worktree && !ce_skip_worktree(ce)) {
509                 if (verify_absent_sparse(ce, ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN, o))
510                         return -1;
511                 ce->ce_flags |= CE_UPDATE;
512         }
513         return 0;
514 }
515
516 static inline int call_unpack_fn(const struct cache_entry * const *src,
517                                  struct unpack_trees_options *o)
518 {
519         int ret = o->fn(src, o);
520         if (ret > 0)
521                 ret = 0;
522         return ret;
523 }
524
525 static void mark_ce_used(struct cache_entry *ce, struct unpack_trees_options *o)
526 {
527         ce->ce_flags |= CE_UNPACKED;
528
529         if (o->cache_bottom < o->src_index->cache_nr &&
530             o->src_index->cache[o->cache_bottom] == ce) {
531                 int bottom = o->cache_bottom;
532                 while (bottom < o->src_index->cache_nr &&
533                        o->src_index->cache[bottom]->ce_flags & CE_UNPACKED)
534                         bottom++;
535                 o->cache_bottom = bottom;
536         }
537 }
538
539 static void mark_all_ce_unused(struct index_state *index)
540 {
541         int i;
542         for (i = 0; i < index->cache_nr; i++)
543                 index->cache[i]->ce_flags &= ~(CE_UNPACKED | CE_ADDED | CE_NEW_SKIP_WORKTREE);
544 }
545
546 static int locate_in_src_index(const struct cache_entry *ce,
547                                struct unpack_trees_options *o)
548 {
549         struct index_state *index = o->src_index;
550         int len = ce_namelen(ce);
551         int pos = index_name_pos(index, ce->name, len);
552         if (pos < 0)
553                 pos = -1 - pos;
554         return pos;
555 }
556
557 /*
558  * We call unpack_index_entry() with an unmerged cache entry
559  * only in diff-index, and it wants a single callback.  Skip
560  * the other unmerged entry with the same name.
561  */
562 static void mark_ce_used_same_name(struct cache_entry *ce,
563                                    struct unpack_trees_options *o)
564 {
565         struct index_state *index = o->src_index;
566         int len = ce_namelen(ce);
567         int pos;
568
569         for (pos = locate_in_src_index(ce, o); pos < index->cache_nr; pos++) {
570                 struct cache_entry *next = index->cache[pos];
571                 if (len != ce_namelen(next) ||
572                     memcmp(ce->name, next->name, len))
573                         break;
574                 mark_ce_used(next, o);
575         }
576 }
577
578 static struct cache_entry *next_cache_entry(struct unpack_trees_options *o)
579 {
580         const struct index_state *index = o->src_index;
581         int pos = o->cache_bottom;
582
583         while (pos < index->cache_nr) {
584                 struct cache_entry *ce = index->cache[pos];
585                 if (!(ce->ce_flags & CE_UNPACKED))
586                         return ce;
587                 pos++;
588         }
589         return NULL;
590 }
591
592 static void add_same_unmerged(const struct cache_entry *ce,
593                               struct unpack_trees_options *o)
594 {
595         struct index_state *index = o->src_index;
596         int len = ce_namelen(ce);
597         int pos = index_name_pos(index, ce->name, len);
598
599         if (0 <= pos)
600                 die("programming error in a caller of mark_ce_used_same_name");
601         for (pos = -pos - 1; pos < index->cache_nr; pos++) {
602                 struct cache_entry *next = index->cache[pos];
603                 if (len != ce_namelen(next) ||
604                     memcmp(ce->name, next->name, len))
605                         break;
606                 add_entry(o, next, 0, 0);
607                 mark_ce_used(next, o);
608         }
609 }
610
611 static int unpack_index_entry(struct cache_entry *ce,
612                               struct unpack_trees_options *o)
613 {
614         const struct cache_entry *src[MAX_UNPACK_TREES + 1] = { NULL, };
615         int ret;
616
617         src[0] = ce;
618
619         mark_ce_used(ce, o);
620         if (ce_stage(ce)) {
621                 if (o->skip_unmerged) {
622                         add_entry(o, ce, 0, 0);
623                         return 0;
624                 }
625         }
626         ret = call_unpack_fn(src, o);
627         if (ce_stage(ce))
628                 mark_ce_used_same_name(ce, o);
629         return ret;
630 }
631
632 static int find_cache_pos(struct traverse_info *, const struct name_entry *);
633
634 static void restore_cache_bottom(struct traverse_info *info, int bottom)
635 {
636         struct unpack_trees_options *o = info->data;
637
638         if (o->diff_index_cached)
639                 return;
640         o->cache_bottom = bottom;
641 }
642
643 static int switch_cache_bottom(struct traverse_info *info)
644 {
645         struct unpack_trees_options *o = info->data;
646         int ret, pos;
647
648         if (o->diff_index_cached)
649                 return 0;
650         ret = o->cache_bottom;
651         pos = find_cache_pos(info->prev, &info->name);
652
653         if (pos < -1)
654                 o->cache_bottom = -2 - pos;
655         else if (pos < 0)
656                 o->cache_bottom = o->src_index->cache_nr;
657         return ret;
658 }
659
660 static inline int are_same_oid(struct name_entry *name_j, struct name_entry *name_k)
661 {
662         return !is_null_oid(&name_j->oid) && !is_null_oid(&name_k->oid) && oideq(&name_j->oid, &name_k->oid);
663 }
664
665 static int all_trees_same_as_cache_tree(int n, unsigned long dirmask,
666                                         struct name_entry *names,
667                                         struct traverse_info *info)
668 {
669         struct unpack_trees_options *o = info->data;
670         int i;
671
672         if (!o->merge || dirmask != ((1 << n) - 1))
673                 return 0;
674
675         for (i = 1; i < n; i++)
676                 if (!are_same_oid(names, names + i))
677                         return 0;
678
679         return cache_tree_matches_traversal(o->src_index->cache_tree, names, info);
680 }
681
682 static int index_pos_by_traverse_info(struct name_entry *names,
683                                       struct traverse_info *info)
684 {
685         struct unpack_trees_options *o = info->data;
686         int len = traverse_path_len(info, names);
687         char *name = xmalloc(len + 1 /* slash */ + 1 /* NUL */);
688         int pos;
689
690         make_traverse_path(name, info, names);
691         name[len++] = '/';
692         name[len] = '\0';
693         pos = index_name_pos(o->src_index, name, len);
694         if (pos >= 0)
695                 BUG("This is a directory and should not exist in index");
696         pos = -pos - 1;
697         if (!starts_with(o->src_index->cache[pos]->name, name) ||
698             (pos > 0 && starts_with(o->src_index->cache[pos-1]->name, name)))
699                 BUG("pos must point at the first entry in this directory");
700         free(name);
701         return pos;
702 }
703
704 /*
705  * Fast path if we detect that all trees are the same as cache-tree at this
706  * path. We'll walk these trees in an iterative loop using cache-tree/index
707  * instead of ODB since we already know what these trees contain.
708  */
709 static int traverse_by_cache_tree(int pos, int nr_entries, int nr_names,
710                                   struct name_entry *names,
711                                   struct traverse_info *info)
712 {
713         struct cache_entry *src[MAX_UNPACK_TREES + 1] = { NULL, };
714         struct unpack_trees_options *o = info->data;
715         struct cache_entry *tree_ce = NULL;
716         int ce_len = 0;
717         int i, d;
718
719         if (!o->merge)
720                 BUG("We need cache-tree to do this optimization");
721
722         /*
723          * Do what unpack_callback() and unpack_nondirectories() normally
724          * do. But we walk all paths in an iterative loop instead.
725          *
726          * D/F conflicts and higher stage entries are not a concern
727          * because cache-tree would be invalidated and we would never
728          * get here in the first place.
729          */
730         for (i = 0; i < nr_entries; i++) {
731                 int new_ce_len, len, rc;
732
733                 src[0] = o->src_index->cache[pos + i];
734
735                 len = ce_namelen(src[0]);
736                 new_ce_len = cache_entry_size(len);
737
738                 if (new_ce_len > ce_len) {
739                         new_ce_len <<= 1;
740                         tree_ce = xrealloc(tree_ce, new_ce_len);
741                         memset(tree_ce, 0, new_ce_len);
742                         ce_len = new_ce_len;
743
744                         tree_ce->ce_flags = create_ce_flags(0);
745
746                         for (d = 1; d <= nr_names; d++)
747                                 src[d] = tree_ce;
748                 }
749
750                 tree_ce->ce_mode = src[0]->ce_mode;
751                 tree_ce->ce_namelen = len;
752                 oidcpy(&tree_ce->oid, &src[0]->oid);
753                 memcpy(tree_ce->name, src[0]->name, len + 1);
754
755                 rc = call_unpack_fn((const struct cache_entry * const *)src, o);
756                 if (rc < 0) {
757                         free(tree_ce);
758                         return rc;
759                 }
760
761                 mark_ce_used(src[0], o);
762         }
763         free(tree_ce);
764         if (o->debug_unpack)
765                 printf("Unpacked %d entries from %s to %s using cache-tree\n",
766                        nr_entries,
767                        o->src_index->cache[pos]->name,
768                        o->src_index->cache[pos + nr_entries - 1]->name);
769         return 0;
770 }
771
772 static int traverse_trees_recursive(int n, unsigned long dirmask,
773                                     unsigned long df_conflicts,
774                                     struct name_entry *names,
775                                     struct traverse_info *info)
776 {
777         struct unpack_trees_options *o = info->data;
778         int i, ret, bottom;
779         int nr_buf = 0;
780         struct tree_desc t[MAX_UNPACK_TREES];
781         void *buf[MAX_UNPACK_TREES];
782         struct traverse_info newinfo;
783         struct name_entry *p;
784         int nr_entries;
785
786         nr_entries = all_trees_same_as_cache_tree(n, dirmask, names, info);
787         if (nr_entries > 0) {
788                 int pos = index_pos_by_traverse_info(names, info);
789
790                 if (!o->merge || df_conflicts)
791                         BUG("Wrong condition to get here buddy");
792
793                 /*
794                  * All entries up to 'pos' must have been processed
795                  * (i.e. marked CE_UNPACKED) at this point. But to be safe,
796                  * save and restore cache_bottom anyway to not miss
797                  * unprocessed entries before 'pos'.
798                  */
799                 bottom = o->cache_bottom;
800                 ret = traverse_by_cache_tree(pos, nr_entries, n, names, info);
801                 o->cache_bottom = bottom;
802                 return ret;
803         }
804
805         p = names;
806         while (!p->mode)
807                 p++;
808
809         newinfo = *info;
810         newinfo.prev = info;
811         newinfo.pathspec = info->pathspec;
812         newinfo.name = *p;
813         newinfo.pathlen += tree_entry_len(p) + 1;
814         newinfo.df_conflicts |= df_conflicts;
815
816         /*
817          * Fetch the tree from the ODB for each peer directory in the
818          * n commits.
819          *
820          * For 2- and 3-way traversals, we try to avoid hitting the
821          * ODB twice for the same OID.  This should yield a nice speed
822          * up in checkouts and merges when the commits are similar.
823          *
824          * We don't bother doing the full O(n^2) search for larger n,
825          * because wider traversals don't happen that often and we
826          * avoid the search setup.
827          *
828          * When 2 peer OIDs are the same, we just copy the tree
829          * descriptor data.  This implicitly borrows the buffer
830          * data from the earlier cell.
831          */
832         for (i = 0; i < n; i++, dirmask >>= 1) {
833                 if (i > 0 && are_same_oid(&names[i], &names[i - 1]))
834                         t[i] = t[i - 1];
835                 else if (i > 1 && are_same_oid(&names[i], &names[i - 2]))
836                         t[i] = t[i - 2];
837                 else {
838                         const struct object_id *oid = NULL;
839                         if (dirmask & 1)
840                                 oid = &names[i].oid;
841                         buf[nr_buf++] = fill_tree_descriptor(t + i, oid);
842                 }
843         }
844
845         bottom = switch_cache_bottom(&newinfo);
846         ret = traverse_trees(o->src_index, n, t, &newinfo);
847         restore_cache_bottom(&newinfo, bottom);
848
849         for (i = 0; i < nr_buf; i++)
850                 free(buf[i]);
851
852         return ret;
853 }
854
855 /*
856  * Compare the traverse-path to the cache entry without actually
857  * having to generate the textual representation of the traverse
858  * path.
859  *
860  * NOTE! This *only* compares up to the size of the traverse path
861  * itself - the caller needs to do the final check for the cache
862  * entry having more data at the end!
863  */
864 static int do_compare_entry_piecewise(const struct cache_entry *ce, const struct traverse_info *info, const struct name_entry *n)
865 {
866         int len, pathlen, ce_len;
867         const char *ce_name;
868
869         if (info->prev) {
870                 int cmp = do_compare_entry_piecewise(ce, info->prev,
871                                                      &info->name);
872                 if (cmp)
873                         return cmp;
874         }
875         pathlen = info->pathlen;
876         ce_len = ce_namelen(ce);
877
878         /* If ce_len < pathlen then we must have previously hit "name == directory" entry */
879         if (ce_len < pathlen)
880                 return -1;
881
882         ce_len -= pathlen;
883         ce_name = ce->name + pathlen;
884
885         len = tree_entry_len(n);
886         return df_name_compare(ce_name, ce_len, S_IFREG, n->path, len, n->mode);
887 }
888
889 static int do_compare_entry(const struct cache_entry *ce,
890                             const struct traverse_info *info,
891                             const struct name_entry *n)
892 {
893         int len, pathlen, ce_len;
894         const char *ce_name;
895         int cmp;
896
897         /*
898          * If we have not precomputed the traverse path, it is quicker
899          * to avoid doing so.  But if we have precomputed it,
900          * it is quicker to use the precomputed version.
901          */
902         if (!info->traverse_path)
903                 return do_compare_entry_piecewise(ce, info, n);
904
905         cmp = strncmp(ce->name, info->traverse_path, info->pathlen);
906         if (cmp)
907                 return cmp;
908
909         pathlen = info->pathlen;
910         ce_len = ce_namelen(ce);
911
912         if (ce_len < pathlen)
913                 return -1;
914
915         ce_len -= pathlen;
916         ce_name = ce->name + pathlen;
917
918         len = tree_entry_len(n);
919         return df_name_compare(ce_name, ce_len, S_IFREG, n->path, len, n->mode);
920 }
921
922 static int compare_entry(const struct cache_entry *ce, const struct traverse_info *info, const struct name_entry *n)
923 {
924         int cmp = do_compare_entry(ce, info, n);
925         if (cmp)
926                 return cmp;
927
928         /*
929          * Even if the beginning compared identically, the ce should
930          * compare as bigger than a directory leading up to it!
931          */
932         return ce_namelen(ce) > traverse_path_len(info, n);
933 }
934
935 static int ce_in_traverse_path(const struct cache_entry *ce,
936                                const struct traverse_info *info)
937 {
938         if (!info->prev)
939                 return 1;
940         if (do_compare_entry(ce, info->prev, &info->name))
941                 return 0;
942         /*
943          * If ce (blob) is the same name as the path (which is a tree
944          * we will be descending into), it won't be inside it.
945          */
946         return (info->pathlen < ce_namelen(ce));
947 }
948
949 static struct cache_entry *create_ce_entry(const struct traverse_info *info,
950         const struct name_entry *n,
951         int stage,
952         struct index_state *istate,
953         int is_transient)
954 {
955         int len = traverse_path_len(info, n);
956         struct cache_entry *ce =
957                 is_transient ?
958                 make_empty_transient_cache_entry(len) :
959                 make_empty_cache_entry(istate, len);
960
961         ce->ce_mode = create_ce_mode(n->mode);
962         ce->ce_flags = create_ce_flags(stage);
963         ce->ce_namelen = len;
964         oidcpy(&ce->oid, &n->oid);
965         make_traverse_path(ce->name, info, n);
966
967         return ce;
968 }
969
970 /*
971  * Note that traverse_by_cache_tree() duplicates some logic in this function
972  * without actually calling it. If you change the logic here you may need to
973  * check and change there as well.
974  */
975 static int unpack_nondirectories(int n, unsigned long mask,
976                                  unsigned long dirmask,
977                                  struct cache_entry **src,
978                                  const struct name_entry *names,
979                                  const struct traverse_info *info)
980 {
981         int i;
982         struct unpack_trees_options *o = info->data;
983         unsigned long conflicts = info->df_conflicts | dirmask;
984
985         /* Do we have *only* directories? Nothing to do */
986         if (mask == dirmask && !src[0])
987                 return 0;
988
989         /*
990          * Ok, we've filled in up to any potential index entry in src[0],
991          * now do the rest.
992          */
993         for (i = 0; i < n; i++) {
994                 int stage;
995                 unsigned int bit = 1ul << i;
996                 if (conflicts & bit) {
997                         src[i + o->merge] = o->df_conflict_entry;
998                         continue;
999                 }
1000                 if (!(mask & bit))
1001                         continue;
1002                 if (!o->merge)
1003                         stage = 0;
1004                 else if (i + 1 < o->head_idx)
1005                         stage = 1;
1006                 else if (i + 1 > o->head_idx)
1007                         stage = 3;
1008                 else
1009                         stage = 2;
1010
1011                 /*
1012                  * If the merge bit is set, then the cache entries are
1013                  * discarded in the following block.  In this case,
1014                  * construct "transient" cache_entries, as they are
1015                  * not stored in the index.  otherwise construct the
1016                  * cache entry from the index aware logic.
1017                  */
1018                 src[i + o->merge] = create_ce_entry(info, names + i, stage, &o->result, o->merge);
1019         }
1020
1021         if (o->merge) {
1022                 int rc = call_unpack_fn((const struct cache_entry * const *)src,
1023                                         o);
1024                 for (i = 0; i < n; i++) {
1025                         struct cache_entry *ce = src[i + o->merge];
1026                         if (ce != o->df_conflict_entry)
1027                                 discard_cache_entry(ce);
1028                 }
1029                 return rc;
1030         }
1031
1032         for (i = 0; i < n; i++)
1033                 if (src[i] && src[i] != o->df_conflict_entry)
1034                         if (do_add_entry(o, src[i], 0, 0))
1035                                 return -1;
1036
1037         return 0;
1038 }
1039
1040 static int unpack_failed(struct unpack_trees_options *o, const char *message)
1041 {
1042         discard_index(&o->result);
1043         if (!o->gently && !o->exiting_early) {
1044                 if (message)
1045                         return error("%s", message);
1046                 return -1;
1047         }
1048         return -1;
1049 }
1050
1051 /*
1052  * The tree traversal is looking at name p.  If we have a matching entry,
1053  * return it.  If name p is a directory in the index, do not return
1054  * anything, as we will want to match it when the traversal descends into
1055  * the directory.
1056  */
1057 static int find_cache_pos(struct traverse_info *info,
1058                           const struct name_entry *p)
1059 {
1060         int pos;
1061         struct unpack_trees_options *o = info->data;
1062         struct index_state *index = o->src_index;
1063         int pfxlen = info->pathlen;
1064         int p_len = tree_entry_len(p);
1065
1066         for (pos = o->cache_bottom; pos < index->cache_nr; pos++) {
1067                 const struct cache_entry *ce = index->cache[pos];
1068                 const char *ce_name, *ce_slash;
1069                 int cmp, ce_len;
1070
1071                 if (ce->ce_flags & CE_UNPACKED) {
1072                         /*
1073                          * cache_bottom entry is already unpacked, so
1074                          * we can never match it; don't check it
1075                          * again.
1076                          */
1077                         if (pos == o->cache_bottom)
1078                                 ++o->cache_bottom;
1079                         continue;
1080                 }
1081                 if (!ce_in_traverse_path(ce, info)) {
1082                         /*
1083                          * Check if we can skip future cache checks
1084                          * (because we're already past all possible
1085                          * entries in the traverse path).
1086                          */
1087                         if (info->traverse_path) {
1088                                 if (strncmp(ce->name, info->traverse_path,
1089                                             info->pathlen) > 0)
1090                                         break;
1091                         }
1092                         continue;
1093                 }
1094                 ce_name = ce->name + pfxlen;
1095                 ce_slash = strchr(ce_name, '/');
1096                 if (ce_slash)
1097                         ce_len = ce_slash - ce_name;
1098                 else
1099                         ce_len = ce_namelen(ce) - pfxlen;
1100                 cmp = name_compare(p->path, p_len, ce_name, ce_len);
1101                 /*
1102                  * Exact match; if we have a directory we need to
1103                  * delay returning it.
1104                  */
1105                 if (!cmp)
1106                         return ce_slash ? -2 - pos : pos;
1107                 if (0 < cmp)
1108                         continue; /* keep looking */
1109                 /*
1110                  * ce_name sorts after p->path; could it be that we
1111                  * have files under p->path directory in the index?
1112                  * E.g.  ce_name == "t-i", and p->path == "t"; we may
1113                  * have "t/a" in the index.
1114                  */
1115                 if (p_len < ce_len && !memcmp(ce_name, p->path, p_len) &&
1116                     ce_name[p_len] < '/')
1117                         continue; /* keep looking */
1118                 break;
1119         }
1120         return -1;
1121 }
1122
1123 static struct cache_entry *find_cache_entry(struct traverse_info *info,
1124                                             const struct name_entry *p)
1125 {
1126         int pos = find_cache_pos(info, p);
1127         struct unpack_trees_options *o = info->data;
1128
1129         if (0 <= pos)
1130                 return o->src_index->cache[pos];
1131         else
1132                 return NULL;
1133 }
1134
1135 static void debug_path(struct traverse_info *info)
1136 {
1137         if (info->prev) {
1138                 debug_path(info->prev);
1139                 if (*info->prev->name.path)
1140                         putchar('/');
1141         }
1142         printf("%s", info->name.path);
1143 }
1144
1145 static void debug_name_entry(int i, struct name_entry *n)
1146 {
1147         printf("ent#%d %06o %s\n", i,
1148                n->path ? n->mode : 0,
1149                n->path ? n->path : "(missing)");
1150 }
1151
1152 static void debug_unpack_callback(int n,
1153                                   unsigned long mask,
1154                                   unsigned long dirmask,
1155                                   struct name_entry *names,
1156                                   struct traverse_info *info)
1157 {
1158         int i;
1159         printf("* unpack mask %lu, dirmask %lu, cnt %d ",
1160                mask, dirmask, n);
1161         debug_path(info);
1162         putchar('\n');
1163         for (i = 0; i < n; i++)
1164                 debug_name_entry(i, names + i);
1165 }
1166
1167 /*
1168  * Note that traverse_by_cache_tree() duplicates some logic in this function
1169  * without actually calling it. If you change the logic here you may need to
1170  * check and change there as well.
1171  */
1172 static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *names, struct traverse_info *info)
1173 {
1174         struct cache_entry *src[MAX_UNPACK_TREES + 1] = { NULL, };
1175         struct unpack_trees_options *o = info->data;
1176         const struct name_entry *p = names;
1177
1178         /* Find first entry with a real name (we could use "mask" too) */
1179         while (!p->mode)
1180                 p++;
1181
1182         if (o->debug_unpack)
1183                 debug_unpack_callback(n, mask, dirmask, names, info);
1184
1185         /* Are we supposed to look at the index too? */
1186         if (o->merge) {
1187                 while (1) {
1188                         int cmp;
1189                         struct cache_entry *ce;
1190
1191                         if (o->diff_index_cached)
1192                                 ce = next_cache_entry(o);
1193                         else
1194                                 ce = find_cache_entry(info, p);
1195
1196                         if (!ce)
1197                                 break;
1198                         cmp = compare_entry(ce, info, p);
1199                         if (cmp < 0) {
1200                                 if (unpack_index_entry(ce, o) < 0)
1201                                         return unpack_failed(o, NULL);
1202                                 continue;
1203                         }
1204                         if (!cmp) {
1205                                 if (ce_stage(ce)) {
1206                                         /*
1207                                          * If we skip unmerged index
1208                                          * entries, we'll skip this
1209                                          * entry *and* the tree
1210                                          * entries associated with it!
1211                                          */
1212                                         if (o->skip_unmerged) {
1213                                                 add_same_unmerged(ce, o);
1214                                                 return mask;
1215                                         }
1216                                 }
1217                                 src[0] = ce;
1218                         }
1219                         break;
1220                 }
1221         }
1222
1223         if (unpack_nondirectories(n, mask, dirmask, src, names, info) < 0)
1224                 return -1;
1225
1226         if (o->merge && src[0]) {
1227                 if (ce_stage(src[0]))
1228                         mark_ce_used_same_name(src[0], o);
1229                 else
1230                         mark_ce_used(src[0], o);
1231         }
1232
1233         /* Now handle any directories.. */
1234         if (dirmask) {
1235                 /* special case: "diff-index --cached" looking at a tree */
1236                 if (o->diff_index_cached &&
1237                     n == 1 && dirmask == 1 && S_ISDIR(names->mode)) {
1238                         int matches;
1239                         matches = cache_tree_matches_traversal(o->src_index->cache_tree,
1240                                                                names, info);
1241                         /*
1242                          * Everything under the name matches; skip the
1243                          * entire hierarchy.  diff_index_cached codepath
1244                          * special cases D/F conflicts in such a way that
1245                          * it does not do any look-ahead, so this is safe.
1246                          */
1247                         if (matches) {
1248                                 o->cache_bottom += matches;
1249                                 return mask;
1250                         }
1251                 }
1252
1253                 if (traverse_trees_recursive(n, dirmask, mask & ~dirmask,
1254                                              names, info) < 0)
1255                         return -1;
1256                 return mask;
1257         }
1258
1259         return mask;
1260 }
1261
1262 static int clear_ce_flags_1(struct index_state *istate,
1263                             struct cache_entry **cache, int nr,
1264                             struct strbuf *prefix,
1265                             int select_mask, int clear_mask,
1266                             struct exclude_list *el, int defval);
1267
1268 /* Whole directory matching */
1269 static int clear_ce_flags_dir(struct index_state *istate,
1270                               struct cache_entry **cache, int nr,
1271                               struct strbuf *prefix,
1272                               char *basename,
1273                               int select_mask, int clear_mask,
1274                               struct exclude_list *el, int defval)
1275 {
1276         struct cache_entry **cache_end;
1277         int dtype = DT_DIR;
1278         int ret = is_excluded_from_list(prefix->buf, prefix->len,
1279                                         basename, &dtype, el, istate);
1280         int rc;
1281
1282         strbuf_addch(prefix, '/');
1283
1284         /* If undecided, use matching result of parent dir in defval */
1285         if (ret < 0)
1286                 ret = defval;
1287
1288         for (cache_end = cache; cache_end != cache + nr; cache_end++) {
1289                 struct cache_entry *ce = *cache_end;
1290                 if (strncmp(ce->name, prefix->buf, prefix->len))
1291                         break;
1292         }
1293
1294         /*
1295          * TODO: check el, if there are no patterns that may conflict
1296          * with ret (iow, we know in advance the incl/excl
1297          * decision for the entire directory), clear flag here without
1298          * calling clear_ce_flags_1(). That function will call
1299          * the expensive is_excluded_from_list() on every entry.
1300          */
1301         rc = clear_ce_flags_1(istate, cache, cache_end - cache,
1302                               prefix,
1303                               select_mask, clear_mask,
1304                               el, ret);
1305         strbuf_setlen(prefix, prefix->len - 1);
1306         return rc;
1307 }
1308
1309 /*
1310  * Traverse the index, find every entry that matches according to
1311  * o->el. Do "ce_flags &= ~clear_mask" on those entries. Return the
1312  * number of traversed entries.
1313  *
1314  * If select_mask is non-zero, only entries whose ce_flags has on of
1315  * those bits enabled are traversed.
1316  *
1317  * cache        : pointer to an index entry
1318  * prefix_len   : an offset to its path
1319  *
1320  * The current path ("prefix") including the trailing '/' is
1321  *   cache[0]->name[0..(prefix_len-1)]
1322  * Top level path has prefix_len zero.
1323  */
1324 static int clear_ce_flags_1(struct index_state *istate,
1325                             struct cache_entry **cache, int nr,
1326                             struct strbuf *prefix,
1327                             int select_mask, int clear_mask,
1328                             struct exclude_list *el, int defval)
1329 {
1330         struct cache_entry **cache_end = cache + nr;
1331
1332         /*
1333          * Process all entries that have the given prefix and meet
1334          * select_mask condition
1335          */
1336         while(cache != cache_end) {
1337                 struct cache_entry *ce = *cache;
1338                 const char *name, *slash;
1339                 int len, dtype, ret;
1340
1341                 if (select_mask && !(ce->ce_flags & select_mask)) {
1342                         cache++;
1343                         continue;
1344                 }
1345
1346                 if (prefix->len && strncmp(ce->name, prefix->buf, prefix->len))
1347                         break;
1348
1349                 name = ce->name + prefix->len;
1350                 slash = strchr(name, '/');
1351
1352                 /* If it's a directory, try whole directory match first */
1353                 if (slash) {
1354                         int processed;
1355
1356                         len = slash - name;
1357                         strbuf_add(prefix, name, len);
1358
1359                         processed = clear_ce_flags_dir(istate, cache, cache_end - cache,
1360                                                        prefix,
1361                                                        prefix->buf + prefix->len - len,
1362                                                        select_mask, clear_mask,
1363                                                        el, defval);
1364
1365                         /* clear_c_f_dir eats a whole dir already? */
1366                         if (processed) {
1367                                 cache += processed;
1368                                 strbuf_setlen(prefix, prefix->len - len);
1369                                 continue;
1370                         }
1371
1372                         strbuf_addch(prefix, '/');
1373                         cache += clear_ce_flags_1(istate, cache, cache_end - cache,
1374                                                   prefix,
1375                                                   select_mask, clear_mask, el, defval);
1376                         strbuf_setlen(prefix, prefix->len - len - 1);
1377                         continue;
1378                 }
1379
1380                 /* Non-directory */
1381                 dtype = ce_to_dtype(ce);
1382                 ret = is_excluded_from_list(ce->name, ce_namelen(ce),
1383                                             name, &dtype, el, istate);
1384                 if (ret < 0)
1385                         ret = defval;
1386                 if (ret > 0)
1387                         ce->ce_flags &= ~clear_mask;
1388                 cache++;
1389         }
1390         return nr - (cache_end - cache);
1391 }
1392
1393 static int clear_ce_flags(struct index_state *istate,
1394                           int select_mask, int clear_mask,
1395                           struct exclude_list *el)
1396 {
1397         static struct strbuf prefix = STRBUF_INIT;
1398
1399         strbuf_reset(&prefix);
1400
1401         return clear_ce_flags_1(istate,
1402                                 istate->cache,
1403                                 istate->cache_nr,
1404                                 &prefix,
1405                                 select_mask, clear_mask,
1406                                 el, 0);
1407 }
1408
1409 /*
1410  * Set/Clear CE_NEW_SKIP_WORKTREE according to $GIT_DIR/info/sparse-checkout
1411  */
1412 static void mark_new_skip_worktree(struct exclude_list *el,
1413                                    struct index_state *istate,
1414                                    int select_flag, int skip_wt_flag)
1415 {
1416         int i;
1417
1418         /*
1419          * 1. Pretend the narrowest worktree: only unmerged entries
1420          * are checked out
1421          */
1422         for (i = 0; i < istate->cache_nr; i++) {
1423                 struct cache_entry *ce = istate->cache[i];
1424
1425                 if (select_flag && !(ce->ce_flags & select_flag))
1426                         continue;
1427
1428                 if (!ce_stage(ce) && !(ce->ce_flags & CE_CONFLICTED))
1429                         ce->ce_flags |= skip_wt_flag;
1430                 else
1431                         ce->ce_flags &= ~skip_wt_flag;
1432         }
1433
1434         /*
1435          * 2. Widen worktree according to sparse-checkout file.
1436          * Matched entries will have skip_wt_flag cleared (i.e. "in")
1437          */
1438         clear_ce_flags(istate, select_flag, skip_wt_flag, el);
1439 }
1440
1441 static int verify_absent(const struct cache_entry *,
1442                          enum unpack_trees_error_types,
1443                          struct unpack_trees_options *);
1444 /*
1445  * N-way merge "len" trees.  Returns 0 on success, -1 on failure to manipulate the
1446  * resulting index, -2 on failure to reflect the changes to the work tree.
1447  *
1448  * CE_ADDED, CE_UNPACKED and CE_NEW_SKIP_WORKTREE are used internally
1449  */
1450 int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options *o)
1451 {
1452         int i, ret;
1453         static struct cache_entry *dfc;
1454         struct exclude_list el;
1455
1456         if (len > MAX_UNPACK_TREES)
1457                 die("unpack_trees takes at most %d trees", MAX_UNPACK_TREES);
1458
1459         trace_performance_enter();
1460         memset(&el, 0, sizeof(el));
1461         if (!core_apply_sparse_checkout || !o->update)
1462                 o->skip_sparse_checkout = 1;
1463         if (!o->skip_sparse_checkout) {
1464                 char *sparse = git_pathdup("info/sparse-checkout");
1465                 if (add_excludes_from_file_to_list(sparse, "", 0, &el, NULL) < 0)
1466                         o->skip_sparse_checkout = 1;
1467                 else
1468                         o->el = &el;
1469                 free(sparse);
1470         }
1471
1472         memset(&o->result, 0, sizeof(o->result));
1473         o->result.initialized = 1;
1474         o->result.timestamp.sec = o->src_index->timestamp.sec;
1475         o->result.timestamp.nsec = o->src_index->timestamp.nsec;
1476         o->result.version = o->src_index->version;
1477         if (!o->src_index->split_index) {
1478                 o->result.split_index = NULL;
1479         } else if (o->src_index == o->dst_index) {
1480                 /*
1481                  * o->dst_index (and thus o->src_index) will be discarded
1482                  * and overwritten with o->result at the end of this function,
1483                  * so just use src_index's split_index to avoid having to
1484                  * create a new one.
1485                  */
1486                 o->result.split_index = o->src_index->split_index;
1487                 o->result.split_index->refcount++;
1488         } else {
1489                 o->result.split_index = init_split_index(&o->result);
1490         }
1491         oidcpy(&o->result.oid, &o->src_index->oid);
1492         o->merge_size = len;
1493         mark_all_ce_unused(o->src_index);
1494
1495         /*
1496          * Sparse checkout loop #1: set NEW_SKIP_WORKTREE on existing entries
1497          */
1498         if (!o->skip_sparse_checkout)
1499                 mark_new_skip_worktree(o->el, o->src_index, 0, CE_NEW_SKIP_WORKTREE);
1500
1501         if (!dfc)
1502                 dfc = xcalloc(1, cache_entry_size(0));
1503         o->df_conflict_entry = dfc;
1504
1505         if (len) {
1506                 const char *prefix = o->prefix ? o->prefix : "";
1507                 struct traverse_info info;
1508
1509                 setup_traverse_info(&info, prefix);
1510                 info.fn = unpack_callback;
1511                 info.data = o;
1512                 info.show_all_errors = o->show_all_errors;
1513                 info.pathspec = o->pathspec;
1514
1515                 if (o->prefix) {
1516                         /*
1517                          * Unpack existing index entries that sort before the
1518                          * prefix the tree is spliced into.  Note that o->merge
1519                          * is always true in this case.
1520                          */
1521                         while (1) {
1522                                 struct cache_entry *ce = next_cache_entry(o);
1523                                 if (!ce)
1524                                         break;
1525                                 if (ce_in_traverse_path(ce, &info))
1526                                         break;
1527                                 if (unpack_index_entry(ce, o) < 0)
1528                                         goto return_failed;
1529                         }
1530                 }
1531
1532                 trace_performance_enter();
1533                 ret = traverse_trees(o->src_index, len, t, &info);
1534                 trace_performance_leave("traverse_trees");
1535                 if (ret < 0)
1536                         goto return_failed;
1537         }
1538
1539         /* Any left-over entries in the index? */
1540         if (o->merge) {
1541                 while (1) {
1542                         struct cache_entry *ce = next_cache_entry(o);
1543                         if (!ce)
1544                                 break;
1545                         if (unpack_index_entry(ce, o) < 0)
1546                                 goto return_failed;
1547                 }
1548         }
1549         mark_all_ce_unused(o->src_index);
1550
1551         if (o->trivial_merges_only && o->nontrivial_merge) {
1552                 ret = unpack_failed(o, "Merge requires file-level merging");
1553                 goto done;
1554         }
1555
1556         if (!o->skip_sparse_checkout) {
1557                 int empty_worktree = 1;
1558
1559                 /*
1560                  * Sparse checkout loop #2: set NEW_SKIP_WORKTREE on entries not in loop #1
1561                  * If the will have NEW_SKIP_WORKTREE, also set CE_SKIP_WORKTREE
1562                  * so apply_sparse_checkout() won't attempt to remove it from worktree
1563                  */
1564                 mark_new_skip_worktree(o->el, &o->result, CE_ADDED, CE_SKIP_WORKTREE | CE_NEW_SKIP_WORKTREE);
1565
1566                 ret = 0;
1567                 for (i = 0; i < o->result.cache_nr; i++) {
1568                         struct cache_entry *ce = o->result.cache[i];
1569
1570                         /*
1571                          * Entries marked with CE_ADDED in merged_entry() do not have
1572                          * verify_absent() check (the check is effectively disabled
1573                          * because CE_NEW_SKIP_WORKTREE is set unconditionally).
1574                          *
1575                          * Do the real check now because we have had
1576                          * correct CE_NEW_SKIP_WORKTREE
1577                          */
1578                         if (ce->ce_flags & CE_ADDED &&
1579                             verify_absent(ce, ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN, o)) {
1580                                 if (!o->show_all_errors)
1581                                         goto return_failed;
1582                                 ret = -1;
1583                         }
1584
1585                         if (apply_sparse_checkout(&o->result, ce, o)) {
1586                                 if (!o->show_all_errors)
1587                                         goto return_failed;
1588                                 ret = -1;
1589                         }
1590                         if (!ce_skip_worktree(ce))
1591                                 empty_worktree = 0;
1592
1593                 }
1594                 if (ret < 0)
1595                         goto return_failed;
1596                 /*
1597                  * Sparse checkout is meant to narrow down checkout area
1598                  * but it does not make sense to narrow down to empty working
1599                  * tree. This is usually a mistake in sparse checkout rules.
1600                  * Do not allow users to do that.
1601                  */
1602                 if (o->result.cache_nr && empty_worktree) {
1603                         ret = unpack_failed(o, "Sparse checkout leaves no entry on working directory");
1604                         goto done;
1605                 }
1606         }
1607
1608         ret = check_updates(o) ? (-2) : 0;
1609         if (o->dst_index) {
1610                 move_index_extensions(&o->result, o->src_index);
1611                 if (!ret) {
1612                         if (git_env_bool("GIT_TEST_CHECK_CACHE_TREE", 0))
1613                                 cache_tree_verify(the_repository, &o->result);
1614                         if (!o->result.cache_tree)
1615                                 o->result.cache_tree = cache_tree();
1616                         if (!cache_tree_fully_valid(o->result.cache_tree))
1617                                 cache_tree_update(&o->result,
1618                                                   WRITE_TREE_SILENT |
1619                                                   WRITE_TREE_REPAIR);
1620                 }
1621                 discard_index(o->dst_index);
1622                 *o->dst_index = o->result;
1623         } else {
1624                 discard_index(&o->result);
1625         }
1626         o->src_index = NULL;
1627
1628 done:
1629         trace_performance_leave("unpack_trees");
1630         clear_exclude_list(&el);
1631         return ret;
1632
1633 return_failed:
1634         if (o->show_all_errors)
1635                 display_error_msgs(o);
1636         mark_all_ce_unused(o->src_index);
1637         ret = unpack_failed(o, NULL);
1638         if (o->exiting_early)
1639                 ret = 0;
1640         goto done;
1641 }
1642
1643 /* Here come the merge functions */
1644
1645 static int reject_merge(const struct cache_entry *ce,
1646                         struct unpack_trees_options *o)
1647 {
1648         return o->gently ? -1 :
1649                 add_rejected_path(o, ERROR_WOULD_OVERWRITE, ce->name);
1650 }
1651
1652 static int same(const struct cache_entry *a, const struct cache_entry *b)
1653 {
1654         if (!!a != !!b)
1655                 return 0;
1656         if (!a && !b)
1657                 return 1;
1658         if ((a->ce_flags | b->ce_flags) & CE_CONFLICTED)
1659                 return 0;
1660         return a->ce_mode == b->ce_mode &&
1661                oideq(&a->oid, &b->oid);
1662 }
1663
1664
1665 /*
1666  * When a CE gets turned into an unmerged entry, we
1667  * want it to be up-to-date
1668  */
1669 static int verify_uptodate_1(const struct cache_entry *ce,
1670                              struct unpack_trees_options *o,
1671                              enum unpack_trees_error_types error_type)
1672 {
1673         struct stat st;
1674
1675         if (o->index_only)
1676                 return 0;
1677
1678         /*
1679          * CE_VALID and CE_SKIP_WORKTREE cheat, we better check again
1680          * if this entry is truly up-to-date because this file may be
1681          * overwritten.
1682          */
1683         if ((ce->ce_flags & CE_VALID) || ce_skip_worktree(ce))
1684                 ; /* keep checking */
1685         else if (o->reset || ce_uptodate(ce))
1686                 return 0;
1687
1688         if (!lstat(ce->name, &st)) {
1689                 int flags = CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE;
1690                 unsigned changed = ie_match_stat(o->src_index, ce, &st, flags);
1691
1692                 if (submodule_from_ce(ce)) {
1693                         int r = check_submodule_move_head(ce,
1694                                 "HEAD", oid_to_hex(&ce->oid), o);
1695                         if (r)
1696                                 return o->gently ? -1 :
1697                                         add_rejected_path(o, error_type, ce->name);
1698                         return 0;
1699                 }
1700
1701                 if (!changed)
1702                         return 0;
1703                 /*
1704                  * Historic default policy was to allow submodule to be out
1705                  * of sync wrt the superproject index. If the submodule was
1706                  * not considered interesting above, we don't care here.
1707                  */
1708                 if (S_ISGITLINK(ce->ce_mode))
1709                         return 0;
1710
1711                 errno = 0;
1712         }
1713         if (errno == ENOENT)
1714                 return 0;
1715         return o->gently ? -1 :
1716                 add_rejected_path(o, error_type, ce->name);
1717 }
1718
1719 int verify_uptodate(const struct cache_entry *ce,
1720                     struct unpack_trees_options *o)
1721 {
1722         if (!o->skip_sparse_checkout && (ce->ce_flags & CE_NEW_SKIP_WORKTREE))
1723                 return 0;
1724         return verify_uptodate_1(ce, o, ERROR_NOT_UPTODATE_FILE);
1725 }
1726
1727 static int verify_uptodate_sparse(const struct cache_entry *ce,
1728                                   struct unpack_trees_options *o)
1729 {
1730         return verify_uptodate_1(ce, o, ERROR_SPARSE_NOT_UPTODATE_FILE);
1731 }
1732
1733 /*
1734  * TODO: We should actually invalidate o->result, not src_index [1].
1735  * But since cache tree and untracked cache both are not copied to
1736  * o->result until unpacking is complete, we invalidate them on
1737  * src_index instead with the assumption that they will be copied to
1738  * dst_index at the end.
1739  *
1740  * [1] src_index->cache_tree is also used in unpack_callback() so if
1741  * we invalidate o->result, we need to update it to use
1742  * o->result.cache_tree as well.
1743  */
1744 static void invalidate_ce_path(const struct cache_entry *ce,
1745                                struct unpack_trees_options *o)
1746 {
1747         if (!ce)
1748                 return;
1749         cache_tree_invalidate_path(o->src_index, ce->name);
1750         untracked_cache_invalidate_path(o->src_index, ce->name, 1);
1751 }
1752
1753 /*
1754  * Check that checking out ce->sha1 in subdir ce->name is not
1755  * going to overwrite any working files.
1756  *
1757  * Currently, git does not checkout subprojects during a superproject
1758  * checkout, so it is not going to overwrite anything.
1759  */
1760 static int verify_clean_submodule(const char *old_sha1,
1761                                   const struct cache_entry *ce,
1762                                   enum unpack_trees_error_types error_type,
1763                                   struct unpack_trees_options *o)
1764 {
1765         if (!submodule_from_ce(ce))
1766                 return 0;
1767
1768         return check_submodule_move_head(ce, old_sha1,
1769                                          oid_to_hex(&ce->oid), o);
1770 }
1771
1772 static int verify_clean_subdirectory(const struct cache_entry *ce,
1773                                      enum unpack_trees_error_types error_type,
1774                                      struct unpack_trees_options *o)
1775 {
1776         /*
1777          * we are about to extract "ce->name"; we would not want to lose
1778          * anything in the existing directory there.
1779          */
1780         int namelen;
1781         int i;
1782         struct dir_struct d;
1783         char *pathbuf;
1784         int cnt = 0;
1785
1786         if (S_ISGITLINK(ce->ce_mode)) {
1787                 struct object_id oid;
1788                 int sub_head = resolve_gitlink_ref(ce->name, "HEAD", &oid);
1789                 /*
1790                  * If we are not going to update the submodule, then
1791                  * we don't care.
1792                  */
1793                 if (!sub_head && oideq(&oid, &ce->oid))
1794                         return 0;
1795                 return verify_clean_submodule(sub_head ? NULL : oid_to_hex(&oid),
1796                                               ce, error_type, o);
1797         }
1798
1799         /*
1800          * First let's make sure we do not have a local modification
1801          * in that directory.
1802          */
1803         namelen = ce_namelen(ce);
1804         for (i = locate_in_src_index(ce, o);
1805              i < o->src_index->cache_nr;
1806              i++) {
1807                 struct cache_entry *ce2 = o->src_index->cache[i];
1808                 int len = ce_namelen(ce2);
1809                 if (len < namelen ||
1810                     strncmp(ce->name, ce2->name, namelen) ||
1811                     ce2->name[namelen] != '/')
1812                         break;
1813                 /*
1814                  * ce2->name is an entry in the subdirectory to be
1815                  * removed.
1816                  */
1817                 if (!ce_stage(ce2)) {
1818                         if (verify_uptodate(ce2, o))
1819                                 return -1;
1820                         add_entry(o, ce2, CE_REMOVE, 0);
1821                         invalidate_ce_path(ce, o);
1822                         mark_ce_used(ce2, o);
1823                 }
1824                 cnt++;
1825         }
1826
1827         /*
1828          * Then we need to make sure that we do not lose a locally
1829          * present file that is not ignored.
1830          */
1831         pathbuf = xstrfmt("%.*s/", namelen, ce->name);
1832
1833         memset(&d, 0, sizeof(d));
1834         if (o->dir)
1835                 d.exclude_per_dir = o->dir->exclude_per_dir;
1836         i = read_directory(&d, o->src_index, pathbuf, namelen+1, NULL);
1837         if (i)
1838                 return o->gently ? -1 :
1839                         add_rejected_path(o, ERROR_NOT_UPTODATE_DIR, ce->name);
1840         free(pathbuf);
1841         return cnt;
1842 }
1843
1844 /*
1845  * This gets called when there was no index entry for the tree entry 'dst',
1846  * but we found a file in the working tree that 'lstat()' said was fine,
1847  * and we're on a case-insensitive filesystem.
1848  *
1849  * See if we can find a case-insensitive match in the index that also
1850  * matches the stat information, and assume it's that other file!
1851  */
1852 static int icase_exists(struct unpack_trees_options *o, const char *name, int len, struct stat *st)
1853 {
1854         const struct cache_entry *src;
1855
1856         src = index_file_exists(o->src_index, name, len, 1);
1857         return src && !ie_match_stat(o->src_index, src, st, CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE);
1858 }
1859
1860 static int check_ok_to_remove(const char *name, int len, int dtype,
1861                               const struct cache_entry *ce, struct stat *st,
1862                               enum unpack_trees_error_types error_type,
1863                               struct unpack_trees_options *o)
1864 {
1865         const struct cache_entry *result;
1866
1867         /*
1868          * It may be that the 'lstat()' succeeded even though
1869          * target 'ce' was absent, because there is an old
1870          * entry that is different only in case..
1871          *
1872          * Ignore that lstat() if it matches.
1873          */
1874         if (ignore_case && icase_exists(o, name, len, st))
1875                 return 0;
1876
1877         if (o->dir &&
1878             is_excluded(o->dir, o->src_index, name, &dtype))
1879                 /*
1880                  * ce->name is explicitly excluded, so it is Ok to
1881                  * overwrite it.
1882                  */
1883                 return 0;
1884         if (S_ISDIR(st->st_mode)) {
1885                 /*
1886                  * We are checking out path "foo" and
1887                  * found "foo/." in the working tree.
1888                  * This is tricky -- if we have modified
1889                  * files that are in "foo/" we would lose
1890                  * them.
1891                  */
1892                 if (verify_clean_subdirectory(ce, error_type, o) < 0)
1893                         return -1;
1894                 return 0;
1895         }
1896
1897         /*
1898          * The previous round may already have decided to
1899          * delete this path, which is in a subdirectory that
1900          * is being replaced with a blob.
1901          */
1902         result = index_file_exists(&o->result, name, len, 0);
1903         if (result) {
1904                 if (result->ce_flags & CE_REMOVE)
1905                         return 0;
1906         }
1907
1908         return o->gently ? -1 :
1909                 add_rejected_path(o, error_type, name);
1910 }
1911
1912 /*
1913  * We do not want to remove or overwrite a working tree file that
1914  * is not tracked, unless it is ignored.
1915  */
1916 static int verify_absent_1(const struct cache_entry *ce,
1917                            enum unpack_trees_error_types error_type,
1918                            struct unpack_trees_options *o)
1919 {
1920         int len;
1921         struct stat st;
1922
1923         if (o->index_only || o->reset || !o->update)
1924                 return 0;
1925
1926         len = check_leading_path(ce->name, ce_namelen(ce));
1927         if (!len)
1928                 return 0;
1929         else if (len > 0) {
1930                 char *path;
1931                 int ret;
1932
1933                 path = xmemdupz(ce->name, len);
1934                 if (lstat(path, &st))
1935                         ret = error_errno("cannot stat '%s'", path);
1936                 else {
1937                         if (submodule_from_ce(ce))
1938                                 ret = check_submodule_move_head(ce,
1939                                                                 oid_to_hex(&ce->oid),
1940                                                                 NULL, o);
1941                         else
1942                                 ret = check_ok_to_remove(path, len, DT_UNKNOWN, NULL,
1943                                                          &st, error_type, o);
1944                 }
1945                 free(path);
1946                 return ret;
1947         } else if (lstat(ce->name, &st)) {
1948                 if (errno != ENOENT)
1949                         return error_errno("cannot stat '%s'", ce->name);
1950                 return 0;
1951         } else {
1952                 if (submodule_from_ce(ce))
1953                         return check_submodule_move_head(ce, oid_to_hex(&ce->oid),
1954                                                          NULL, o);
1955
1956                 return check_ok_to_remove(ce->name, ce_namelen(ce),
1957                                           ce_to_dtype(ce), ce, &st,
1958                                           error_type, o);
1959         }
1960 }
1961
1962 static int verify_absent(const struct cache_entry *ce,
1963                          enum unpack_trees_error_types error_type,
1964                          struct unpack_trees_options *o)
1965 {
1966         if (!o->skip_sparse_checkout && (ce->ce_flags & CE_NEW_SKIP_WORKTREE))
1967                 return 0;
1968         return verify_absent_1(ce, error_type, o);
1969 }
1970
1971 static int verify_absent_sparse(const struct cache_entry *ce,
1972                                 enum unpack_trees_error_types error_type,
1973                                 struct unpack_trees_options *o)
1974 {
1975         enum unpack_trees_error_types orphaned_error = error_type;
1976         if (orphaned_error == ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN)
1977                 orphaned_error = ERROR_WOULD_LOSE_ORPHANED_OVERWRITTEN;
1978
1979         return verify_absent_1(ce, orphaned_error, o);
1980 }
1981
1982 static int merged_entry(const struct cache_entry *ce,
1983                         const struct cache_entry *old,
1984                         struct unpack_trees_options *o)
1985 {
1986         int update = CE_UPDATE;
1987         struct cache_entry *merge = dup_cache_entry(ce, &o->result);
1988
1989         if (!old) {
1990                 /*
1991                  * New index entries. In sparse checkout, the following
1992                  * verify_absent() will be delayed until after
1993                  * traverse_trees() finishes in unpack_trees(), then:
1994                  *
1995                  *  - CE_NEW_SKIP_WORKTREE will be computed correctly
1996                  *  - verify_absent() be called again, this time with
1997                  *    correct CE_NEW_SKIP_WORKTREE
1998                  *
1999                  * verify_absent() call here does nothing in sparse
2000                  * checkout (i.e. o->skip_sparse_checkout == 0)
2001                  */
2002                 update |= CE_ADDED;
2003                 merge->ce_flags |= CE_NEW_SKIP_WORKTREE;
2004
2005                 if (verify_absent(merge,
2006                                   ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN, o)) {
2007                         discard_cache_entry(merge);
2008                         return -1;
2009                 }
2010                 invalidate_ce_path(merge, o);
2011
2012                 if (submodule_from_ce(ce)) {
2013                         int ret = check_submodule_move_head(ce, NULL,
2014                                                             oid_to_hex(&ce->oid),
2015                                                             o);
2016                         if (ret)
2017                                 return ret;
2018                 }
2019
2020         } else if (!(old->ce_flags & CE_CONFLICTED)) {
2021                 /*
2022                  * See if we can re-use the old CE directly?
2023                  * That way we get the uptodate stat info.
2024                  *
2025                  * This also removes the UPDATE flag on a match; otherwise
2026                  * we will end up overwriting local changes in the work tree.
2027                  */
2028                 if (same(old, merge)) {
2029                         copy_cache_entry(merge, old);
2030                         update = 0;
2031                 } else {
2032                         if (verify_uptodate(old, o)) {
2033                                 discard_cache_entry(merge);
2034                                 return -1;
2035                         }
2036                         /* Migrate old flags over */
2037                         update |= old->ce_flags & (CE_SKIP_WORKTREE | CE_NEW_SKIP_WORKTREE);
2038                         invalidate_ce_path(old, o);
2039                 }
2040
2041                 if (submodule_from_ce(ce)) {
2042                         int ret = check_submodule_move_head(ce, oid_to_hex(&old->oid),
2043                                                             oid_to_hex(&ce->oid),
2044                                                             o);
2045                         if (ret)
2046                                 return ret;
2047                 }
2048         } else {
2049                 /*
2050                  * Previously unmerged entry left as an existence
2051                  * marker by read_index_unmerged();
2052                  */
2053                 invalidate_ce_path(old, o);
2054         }
2055
2056         do_add_entry(o, merge, update, CE_STAGEMASK);
2057         return 1;
2058 }
2059
2060 static int deleted_entry(const struct cache_entry *ce,
2061                          const struct cache_entry *old,
2062                          struct unpack_trees_options *o)
2063 {
2064         /* Did it exist in the index? */
2065         if (!old) {
2066                 if (verify_absent(ce, ERROR_WOULD_LOSE_UNTRACKED_REMOVED, o))
2067                         return -1;
2068                 return 0;
2069         }
2070         if (!(old->ce_flags & CE_CONFLICTED) && verify_uptodate(old, o))
2071                 return -1;
2072         add_entry(o, ce, CE_REMOVE, 0);
2073         invalidate_ce_path(ce, o);
2074         return 1;
2075 }
2076
2077 static int keep_entry(const struct cache_entry *ce,
2078                       struct unpack_trees_options *o)
2079 {
2080         add_entry(o, ce, 0, 0);
2081         if (ce_stage(ce))
2082                 invalidate_ce_path(ce, o);
2083         return 1;
2084 }
2085
2086 #if DBRT_DEBUG
2087 static void show_stage_entry(FILE *o,
2088                              const char *label, const struct cache_entry *ce)
2089 {
2090         if (!ce)
2091                 fprintf(o, "%s (missing)\n", label);
2092         else
2093                 fprintf(o, "%s%06o %s %d\t%s\n",
2094                         label,
2095                         ce->ce_mode,
2096                         oid_to_hex(&ce->oid),
2097                         ce_stage(ce),
2098                         ce->name);
2099 }
2100 #endif
2101
2102 int threeway_merge(const struct cache_entry * const *stages,
2103                    struct unpack_trees_options *o)
2104 {
2105         const struct cache_entry *index;
2106         const struct cache_entry *head;
2107         const struct cache_entry *remote = stages[o->head_idx + 1];
2108         int count;
2109         int head_match = 0;
2110         int remote_match = 0;
2111
2112         int df_conflict_head = 0;
2113         int df_conflict_remote = 0;
2114
2115         int any_anc_missing = 0;
2116         int no_anc_exists = 1;
2117         int i;
2118
2119         for (i = 1; i < o->head_idx; i++) {
2120                 if (!stages[i] || stages[i] == o->df_conflict_entry)
2121                         any_anc_missing = 1;
2122                 else
2123                         no_anc_exists = 0;
2124         }
2125
2126         index = stages[0];
2127         head = stages[o->head_idx];
2128
2129         if (head == o->df_conflict_entry) {
2130                 df_conflict_head = 1;
2131                 head = NULL;
2132         }
2133
2134         if (remote == o->df_conflict_entry) {
2135                 df_conflict_remote = 1;
2136                 remote = NULL;
2137         }
2138
2139         /*
2140          * First, if there's a #16 situation, note that to prevent #13
2141          * and #14.
2142          */
2143         if (!same(remote, head)) {
2144                 for (i = 1; i < o->head_idx; i++) {
2145                         if (same(stages[i], head)) {
2146                                 head_match = i;
2147                         }
2148                         if (same(stages[i], remote)) {
2149                                 remote_match = i;
2150                         }
2151                 }
2152         }
2153
2154         /*
2155          * We start with cases where the index is allowed to match
2156          * something other than the head: #14(ALT) and #2ALT, where it
2157          * is permitted to match the result instead.
2158          */
2159         /* #14, #14ALT, #2ALT */
2160         if (remote && !df_conflict_head && head_match && !remote_match) {
2161                 if (index && !same(index, remote) && !same(index, head))
2162                         return reject_merge(index, o);
2163                 return merged_entry(remote, index, o);
2164         }
2165         /*
2166          * If we have an entry in the index cache, then we want to
2167          * make sure that it matches head.
2168          */
2169         if (index && !same(index, head))
2170                 return reject_merge(index, o);
2171
2172         if (head) {
2173                 /* #5ALT, #15 */
2174                 if (same(head, remote))
2175                         return merged_entry(head, index, o);
2176                 /* #13, #3ALT */
2177                 if (!df_conflict_remote && remote_match && !head_match)
2178                         return merged_entry(head, index, o);
2179         }
2180
2181         /* #1 */
2182         if (!head && !remote && any_anc_missing)
2183                 return 0;
2184
2185         /*
2186          * Under the "aggressive" rule, we resolve mostly trivial
2187          * cases that we historically had git-merge-one-file resolve.
2188          */
2189         if (o->aggressive) {
2190                 int head_deleted = !head;
2191                 int remote_deleted = !remote;
2192                 const struct cache_entry *ce = NULL;
2193
2194                 if (index)
2195                         ce = index;
2196                 else if (head)
2197                         ce = head;
2198                 else if (remote)
2199                         ce = remote;
2200                 else {
2201                         for (i = 1; i < o->head_idx; i++) {
2202                                 if (stages[i] && stages[i] != o->df_conflict_entry) {
2203                                         ce = stages[i];
2204                                         break;
2205                                 }
2206                         }
2207                 }
2208
2209                 /*
2210                  * Deleted in both.
2211                  * Deleted in one and unchanged in the other.
2212                  */
2213                 if ((head_deleted && remote_deleted) ||
2214                     (head_deleted && remote && remote_match) ||
2215                     (remote_deleted && head && head_match)) {
2216                         if (index)
2217                                 return deleted_entry(index, index, o);
2218                         if (ce && !head_deleted) {
2219                                 if (verify_absent(ce, ERROR_WOULD_LOSE_UNTRACKED_REMOVED, o))
2220                                         return -1;
2221                         }
2222                         return 0;
2223                 }
2224                 /*
2225                  * Added in both, identically.
2226                  */
2227                 if (no_anc_exists && head && remote && same(head, remote))
2228                         return merged_entry(head, index, o);
2229
2230         }
2231
2232         /* Below are "no merge" cases, which require that the index be
2233          * up-to-date to avoid the files getting overwritten with
2234          * conflict resolution files.
2235          */
2236         if (index) {
2237                 if (verify_uptodate(index, o))
2238                         return -1;
2239         }
2240
2241         o->nontrivial_merge = 1;
2242
2243         /* #2, #3, #4, #6, #7, #9, #10, #11. */
2244         count = 0;
2245         if (!head_match || !remote_match) {
2246                 for (i = 1; i < o->head_idx; i++) {
2247                         if (stages[i] && stages[i] != o->df_conflict_entry) {
2248                                 keep_entry(stages[i], o);
2249                                 count++;
2250                                 break;
2251                         }
2252                 }
2253         }
2254 #if DBRT_DEBUG
2255         else {
2256                 fprintf(stderr, "read-tree: warning #16 detected\n");
2257                 show_stage_entry(stderr, "head   ", stages[head_match]);
2258                 show_stage_entry(stderr, "remote ", stages[remote_match]);
2259         }
2260 #endif
2261         if (head) { count += keep_entry(head, o); }
2262         if (remote) { count += keep_entry(remote, o); }
2263         return count;
2264 }
2265
2266 /*
2267  * Two-way merge.
2268  *
2269  * The rule is to "carry forward" what is in the index without losing
2270  * information across a "fast-forward", favoring a successful merge
2271  * over a merge failure when it makes sense.  For details of the
2272  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
2273  *
2274  */
2275 int twoway_merge(const struct cache_entry * const *src,
2276                  struct unpack_trees_options *o)
2277 {
2278         const struct cache_entry *current = src[0];
2279         const struct cache_entry *oldtree = src[1];
2280         const struct cache_entry *newtree = src[2];
2281
2282         if (o->merge_size != 2)
2283                 return error("Cannot do a twoway merge of %d trees",
2284                              o->merge_size);
2285
2286         if (oldtree == o->df_conflict_entry)
2287                 oldtree = NULL;
2288         if (newtree == o->df_conflict_entry)
2289                 newtree = NULL;
2290
2291         if (current) {
2292                 if (current->ce_flags & CE_CONFLICTED) {
2293                         if (same(oldtree, newtree) || o->reset) {
2294                                 if (!newtree)
2295                                         return deleted_entry(current, current, o);
2296                                 else
2297                                         return merged_entry(newtree, current, o);
2298                         }
2299                         return reject_merge(current, o);
2300                 } else if ((!oldtree && !newtree) || /* 4 and 5 */
2301                          (!oldtree && newtree &&
2302                           same(current, newtree)) || /* 6 and 7 */
2303                          (oldtree && newtree &&
2304                           same(oldtree, newtree)) || /* 14 and 15 */
2305                          (oldtree && newtree &&
2306                           !same(oldtree, newtree) && /* 18 and 19 */
2307                           same(current, newtree))) {
2308                         return keep_entry(current, o);
2309                 } else if (oldtree && !newtree && same(current, oldtree)) {
2310                         /* 10 or 11 */
2311                         return deleted_entry(oldtree, current, o);
2312                 } else if (oldtree && newtree &&
2313                          same(current, oldtree) && !same(current, newtree)) {
2314                         /* 20 or 21 */
2315                         return merged_entry(newtree, current, o);
2316                 } else
2317                         return reject_merge(current, o);
2318         }
2319         else if (newtree) {
2320                 if (oldtree && !o->initial_checkout) {
2321                         /*
2322                          * deletion of the path was staged;
2323                          */
2324                         if (same(oldtree, newtree))
2325                                 return 1;
2326                         return reject_merge(oldtree, o);
2327                 }
2328                 return merged_entry(newtree, current, o);
2329         }
2330         return deleted_entry(oldtree, current, o);
2331 }
2332
2333 /*
2334  * Bind merge.
2335  *
2336  * Keep the index entries at stage0, collapse stage1 but make sure
2337  * stage0 does not have anything there.
2338  */
2339 int bind_merge(const struct cache_entry * const *src,
2340                struct unpack_trees_options *o)
2341 {
2342         const struct cache_entry *old = src[0];
2343         const struct cache_entry *a = src[1];
2344
2345         if (o->merge_size != 1)
2346                 return error("Cannot do a bind merge of %d trees",
2347                              o->merge_size);
2348         if (a && old)
2349                 return o->gently ? -1 :
2350                         error(ERRORMSG(o, ERROR_BIND_OVERLAP),
2351                               super_prefixed(a->name),
2352                               super_prefixed(old->name));
2353         if (!a)
2354                 return keep_entry(old, o);
2355         else
2356                 return merged_entry(a, NULL, o);
2357 }
2358
2359 /*
2360  * One-way merge.
2361  *
2362  * The rule is:
2363  * - take the stat information from stage0, take the data from stage1
2364  */
2365 int oneway_merge(const struct cache_entry * const *src,
2366                  struct unpack_trees_options *o)
2367 {
2368         const struct cache_entry *old = src[0];
2369         const struct cache_entry *a = src[1];
2370
2371         if (o->merge_size != 1)
2372                 return error("Cannot do a oneway merge of %d trees",
2373                              o->merge_size);
2374
2375         if (!a || a == o->df_conflict_entry)
2376                 return deleted_entry(old, old, o);
2377
2378         if (old && same(old, a)) {
2379                 int update = 0;
2380                 if (o->reset && o->update && !ce_uptodate(old) && !ce_skip_worktree(old)) {
2381                         struct stat st;
2382                         if (lstat(old->name, &st) ||
2383                             ie_match_stat(o->src_index, old, &st, CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE))
2384                                 update |= CE_UPDATE;
2385                 }
2386                 if (o->update && S_ISGITLINK(old->ce_mode) &&
2387                     should_update_submodules() && !verify_uptodate(old, o))
2388                         update |= CE_UPDATE;
2389                 add_entry(o, old, update, 0);
2390                 return 0;
2391         }
2392         return merged_entry(a, old, o);
2393 }