GIT 1.4.2
[git] / builtin-read-tree.c
1 /*
2  * GIT - The information manager from hell
3  *
4  * Copyright (C) Linus Torvalds, 2005
5  */
6 #define DBRT_DEBUG 1
7
8 #include "cache.h"
9
10 #include "object.h"
11 #include "tree.h"
12 #include "tree-walk.h"
13 #include "cache-tree.h"
14 #include <sys/time.h>
15 #include <signal.h>
16 #include "builtin.h"
17
18 static int reset = 0;
19 static int merge = 0;
20 static int update = 0;
21 static int index_only = 0;
22 static int nontrivial_merge = 0;
23 static int trivial_merges_only = 0;
24 static int aggressive = 0;
25 static int verbose_update = 0;
26 static volatile int progress_update = 0;
27 static const char *prefix = NULL;
28
29 static int head_idx = -1;
30 static int merge_size = 0;
31
32 static struct object_list *trees = NULL;
33
34 static struct cache_entry df_conflict_entry;
35
36 struct tree_entry_list {
37         struct tree_entry_list *next;
38         unsigned directory : 1;
39         unsigned executable : 1;
40         unsigned symlink : 1;
41         unsigned int mode;
42         const char *name;
43         const unsigned char *sha1;
44 };
45
46 static struct tree_entry_list df_conflict_list;
47
48 typedef int (*merge_fn_t)(struct cache_entry **src);
49
50 static struct tree_entry_list *create_tree_entry_list(struct tree *tree)
51 {
52         struct tree_desc desc;
53         struct name_entry one;
54         struct tree_entry_list *ret = NULL;
55         struct tree_entry_list **list_p = &ret;
56
57         desc.buf = tree->buffer;
58         desc.size = tree->size;
59
60         while (tree_entry(&desc, &one)) {
61                 struct tree_entry_list *entry;
62
63                 entry = xmalloc(sizeof(struct tree_entry_list));
64                 entry->name = one.path;
65                 entry->sha1 = one.sha1;
66                 entry->mode = one.mode;
67                 entry->directory = S_ISDIR(one.mode) != 0;
68                 entry->executable = (one.mode & S_IXUSR) != 0;
69                 entry->symlink = S_ISLNK(one.mode) != 0;
70                 entry->next = NULL;
71
72                 *list_p = entry;
73                 list_p = &entry->next;
74         }
75         return ret;
76 }
77
78 static int entcmp(const char *name1, int dir1, const char *name2, int dir2)
79 {
80         int len1 = strlen(name1);
81         int len2 = strlen(name2);
82         int len = len1 < len2 ? len1 : len2;
83         int ret = memcmp(name1, name2, len);
84         unsigned char c1, c2;
85         if (ret)
86                 return ret;
87         c1 = name1[len];
88         c2 = name2[len];
89         if (!c1 && dir1)
90                 c1 = '/';
91         if (!c2 && dir2)
92                 c2 = '/';
93         ret = (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
94         if (c1 && c2 && !ret)
95                 ret = len1 - len2;
96         return ret;
97 }
98
99 static int unpack_trees_rec(struct tree_entry_list **posns, int len,
100                             const char *base, merge_fn_t fn, int *indpos)
101 {
102         int baselen = strlen(base);
103         int src_size = len + 1;
104         do {
105                 int i;
106                 const char *first;
107                 int firstdir = 0;
108                 int pathlen;
109                 unsigned ce_size;
110                 struct tree_entry_list **subposns;
111                 struct cache_entry **src;
112                 int any_files = 0;
113                 int any_dirs = 0;
114                 char *cache_name;
115                 int ce_stage;
116
117                 /* Find the first name in the input. */
118
119                 first = NULL;
120                 cache_name = NULL;
121
122                 /* Check the cache */
123                 if (merge && *indpos < active_nr) {
124                         /* This is a bit tricky: */
125                         /* If the index has a subdirectory (with
126                          * contents) as the first name, it'll get a
127                          * filename like "foo/bar". But that's after
128                          * "foo", so the entry in trees will get
129                          * handled first, at which point we'll go into
130                          * "foo", and deal with "bar" from the index,
131                          * because the base will be "foo/". The only
132                          * way we can actually have "foo/bar" first of
133                          * all the things is if the trees don't
134                          * contain "foo" at all, in which case we'll
135                          * handle "foo/bar" without going into the
136                          * directory, but that's fine (and will return
137                          * an error anyway, with the added unknown
138                          * file case.
139                          */
140
141                         cache_name = active_cache[*indpos]->name;
142                         if (strlen(cache_name) > baselen &&
143                             !memcmp(cache_name, base, baselen)) {
144                                 cache_name += baselen;
145                                 first = cache_name;
146                         } else {
147                                 cache_name = NULL;
148                         }
149                 }
150
151 #if DBRT_DEBUG > 1
152                 if (first)
153                         printf("index %s\n", first);
154 #endif
155                 for (i = 0; i < len; i++) {
156                         if (!posns[i] || posns[i] == &df_conflict_list)
157                                 continue;
158 #if DBRT_DEBUG > 1
159                         printf("%d %s\n", i + 1, posns[i]->name);
160 #endif
161                         if (!first || entcmp(first, firstdir,
162                                              posns[i]->name, 
163                                              posns[i]->directory) > 0) {
164                                 first = posns[i]->name;
165                                 firstdir = posns[i]->directory;
166                         }
167                 }
168                 /* No name means we're done */
169                 if (!first)
170                         return 0;
171
172                 pathlen = strlen(first);
173                 ce_size = cache_entry_size(baselen + pathlen);
174
175                 src = xcalloc(src_size, sizeof(struct cache_entry *));
176
177                 subposns = xcalloc(len, sizeof(struct tree_list_entry *));
178
179                 if (cache_name && !strcmp(cache_name, first)) {
180                         any_files = 1;
181                         src[0] = active_cache[*indpos];
182                         remove_cache_entry_at(*indpos);
183                 }
184
185                 for (i = 0; i < len; i++) {
186                         struct cache_entry *ce;
187
188                         if (!posns[i] ||
189                             (posns[i] != &df_conflict_list &&
190                              strcmp(first, posns[i]->name))) {
191                                 continue;
192                         }
193
194                         if (posns[i] == &df_conflict_list) {
195                                 src[i + merge] = &df_conflict_entry;
196                                 continue;
197                         }
198
199                         if (posns[i]->directory) {
200                                 struct tree *tree = lookup_tree(posns[i]->sha1);
201                                 any_dirs = 1;
202                                 parse_tree(tree);
203                                 subposns[i] = create_tree_entry_list(tree);
204                                 posns[i] = posns[i]->next;
205                                 src[i + merge] = &df_conflict_entry;
206                                 continue;
207                         }
208
209                         if (!merge)
210                                 ce_stage = 0;
211                         else if (i + 1 < head_idx)
212                                 ce_stage = 1;
213                         else if (i + 1 > head_idx)
214                                 ce_stage = 3;
215                         else
216                                 ce_stage = 2;
217
218                         ce = xcalloc(1, ce_size);
219                         ce->ce_mode = create_ce_mode(posns[i]->mode);
220                         ce->ce_flags = create_ce_flags(baselen + pathlen,
221                                                        ce_stage);
222                         memcpy(ce->name, base, baselen);
223                         memcpy(ce->name + baselen, first, pathlen + 1);
224
225                         any_files = 1;
226
227                         memcpy(ce->sha1, posns[i]->sha1, 20);
228                         src[i + merge] = ce;
229                         subposns[i] = &df_conflict_list;
230                         posns[i] = posns[i]->next;
231                 }
232                 if (any_files) {
233                         if (merge) {
234                                 int ret;
235
236 #if DBRT_DEBUG > 1
237                                 printf("%s:\n", first);
238                                 for (i = 0; i < src_size; i++) {
239                                         printf(" %d ", i);
240                                         if (src[i])
241                                                 printf("%s\n", sha1_to_hex(src[i]->sha1));
242                                         else
243                                                 printf("\n");
244                                 }
245 #endif
246                                 ret = fn(src);
247                                 
248 #if DBRT_DEBUG > 1
249                                 printf("Added %d entries\n", ret);
250 #endif
251                                 *indpos += ret;
252                         } else {
253                                 for (i = 0; i < src_size; i++) {
254                                         if (src[i]) {
255                                                 add_cache_entry(src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
256                                         }
257                                 }
258                         }
259                 }
260                 if (any_dirs) {
261                         char *newbase = xmalloc(baselen + 2 + pathlen);
262                         memcpy(newbase, base, baselen);
263                         memcpy(newbase + baselen, first, pathlen);
264                         newbase[baselen + pathlen] = '/';
265                         newbase[baselen + pathlen + 1] = '\0';
266                         if (unpack_trees_rec(subposns, len, newbase, fn,
267                                              indpos))
268                                 return -1;
269                         free(newbase);
270                 }
271                 free(subposns);
272                 free(src);
273         } while (1);
274 }
275
276 static void reject_merge(struct cache_entry *ce)
277 {
278         die("Entry '%s' would be overwritten by merge. Cannot merge.", 
279             ce->name);
280 }
281
282 /* Unlink the last component and attempt to remove leading
283  * directories, in case this unlink is the removal of the
284  * last entry in the directory -- empty directories are removed.
285  */
286 static void unlink_entry(char *name)
287 {
288         char *cp, *prev;
289
290         if (unlink(name))
291                 return;
292         prev = NULL;
293         while (1) {
294                 int status;
295                 cp = strrchr(name, '/');
296                 if (prev)
297                         *prev = '/';
298                 if (!cp)
299                         break;
300
301                 *cp = 0;
302                 status = rmdir(name);
303                 if (status) {
304                         *cp = '/';
305                         break;
306                 }
307                 prev = cp;
308         }
309 }
310
311 static void progress_interval(int signum)
312 {
313         progress_update = 1;
314 }
315
316 static void setup_progress_signal(void)
317 {
318         struct sigaction sa;
319         struct itimerval v;
320
321         memset(&sa, 0, sizeof(sa));
322         sa.sa_handler = progress_interval;
323         sigemptyset(&sa.sa_mask);
324         sa.sa_flags = SA_RESTART;
325         sigaction(SIGALRM, &sa, NULL);
326
327         v.it_interval.tv_sec = 1;
328         v.it_interval.tv_usec = 0;
329         v.it_value = v.it_interval;
330         setitimer(ITIMER_REAL, &v, NULL);
331 }
332
333 static struct checkout state;
334 static void check_updates(struct cache_entry **src, int nr)
335 {
336         unsigned short mask = htons(CE_UPDATE);
337         unsigned last_percent = 200, cnt = 0, total = 0;
338
339         if (update && verbose_update) {
340                 for (total = cnt = 0; cnt < nr; cnt++) {
341                         struct cache_entry *ce = src[cnt];
342                         if (!ce->ce_mode || ce->ce_flags & mask)
343                                 total++;
344                 }
345
346                 /* Don't bother doing this for very small updates */
347                 if (total < 250)
348                         total = 0;
349
350                 if (total) {
351                         fprintf(stderr, "Checking files out...\n");
352                         setup_progress_signal();
353                         progress_update = 1;
354                 }
355                 cnt = 0;
356         }
357
358         while (nr--) {
359                 struct cache_entry *ce = *src++;
360
361                 if (total) {
362                         if (!ce->ce_mode || ce->ce_flags & mask) {
363                                 unsigned percent;
364                                 cnt++;
365                                 percent = (cnt * 100) / total;
366                                 if (percent != last_percent ||
367                                     progress_update) {
368                                         fprintf(stderr, "%4u%% (%u/%u) done\r",
369                                                 percent, cnt, total);
370                                         last_percent = percent;
371                                         progress_update = 0;
372                                 }
373                         }
374                 }
375                 if (!ce->ce_mode) {
376                         if (update)
377                                 unlink_entry(ce->name);
378                         continue;
379                 }
380                 if (ce->ce_flags & mask) {
381                         ce->ce_flags &= ~mask;
382                         if (update)
383                                 checkout_entry(ce, &state, NULL);
384                 }
385         }
386         if (total) {
387                 signal(SIGALRM, SIG_IGN);
388                 fputc('\n', stderr);
389         }
390 }
391
392 static int unpack_trees(merge_fn_t fn)
393 {
394         int indpos = 0;
395         unsigned len = object_list_length(trees);
396         struct tree_entry_list **posns;
397         int i;
398         struct object_list *posn = trees;
399         merge_size = len;
400
401         if (len) {
402                 posns = xmalloc(len * sizeof(struct tree_entry_list *));
403                 for (i = 0; i < len; i++) {
404                         posns[i] = create_tree_entry_list((struct tree *) posn->item);
405                         posn = posn->next;
406                 }
407                 if (unpack_trees_rec(posns, len, prefix ? prefix : "",
408                                      fn, &indpos))
409                         return -1;
410         }
411
412         if (trivial_merges_only && nontrivial_merge)
413                 die("Merge requires file-level merging");
414
415         check_updates(active_cache, active_nr);
416         return 0;
417 }
418
419 static int list_tree(unsigned char *sha1)
420 {
421         struct tree *tree = parse_tree_indirect(sha1);
422         if (!tree)
423                 return -1;
424         object_list_append(&tree->object, &trees);
425         return 0;
426 }
427
428 static int same(struct cache_entry *a, struct cache_entry *b)
429 {
430         if (!!a != !!b)
431                 return 0;
432         if (!a && !b)
433                 return 1;
434         return a->ce_mode == b->ce_mode && 
435                 !memcmp(a->sha1, b->sha1, 20);
436 }
437
438
439 /*
440  * When a CE gets turned into an unmerged entry, we
441  * want it to be up-to-date
442  */
443 static void verify_uptodate(struct cache_entry *ce)
444 {
445         struct stat st;
446
447         if (index_only || reset)
448                 return;
449
450         if (!lstat(ce->name, &st)) {
451                 unsigned changed = ce_match_stat(ce, &st, 1);
452                 if (!changed)
453                         return;
454                 errno = 0;
455         }
456         if (reset) {
457                 ce->ce_flags |= htons(CE_UPDATE);
458                 return;
459         }
460         if (errno == ENOENT)
461                 return;
462         die("Entry '%s' not uptodate. Cannot merge.", ce->name);
463 }
464
465 static void invalidate_ce_path(struct cache_entry *ce)
466 {
467         if (ce)
468                 cache_tree_invalidate_path(active_cache_tree, ce->name);
469 }
470
471 /*
472  * We do not want to remove or overwrite a working tree file that
473  * is not tracked.
474  */
475 static void verify_absent(const char *path, const char *action)
476 {
477         struct stat st;
478
479         if (index_only || reset || !update)
480                 return;
481         if (!lstat(path, &st))
482                 die("Untracked working tree file '%s' "
483                     "would be %s by merge.", path, action);
484 }
485
486 static int merged_entry(struct cache_entry *merge, struct cache_entry *old)
487 {
488         merge->ce_flags |= htons(CE_UPDATE);
489         if (old) {
490                 /*
491                  * See if we can re-use the old CE directly?
492                  * That way we get the uptodate stat info.
493                  *
494                  * This also removes the UPDATE flag on
495                  * a match.
496                  */
497                 if (same(old, merge)) {
498                         *merge = *old;
499                 } else {
500                         verify_uptodate(old);
501                         invalidate_ce_path(old);
502                 }
503         }
504         else {
505                 verify_absent(merge->name, "overwritten");
506                 invalidate_ce_path(merge);
507         }
508
509         merge->ce_flags &= ~htons(CE_STAGEMASK);
510         add_cache_entry(merge, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
511         return 1;
512 }
513
514 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old)
515 {
516         if (old)
517                 verify_uptodate(old);
518         else
519                 verify_absent(ce->name, "removed");
520         ce->ce_mode = 0;
521         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
522         invalidate_ce_path(ce);
523         return 1;
524 }
525
526 static int keep_entry(struct cache_entry *ce)
527 {
528         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
529         return 1;
530 }
531
532 #if DBRT_DEBUG
533 static void show_stage_entry(FILE *o,
534                              const char *label, const struct cache_entry *ce)
535 {
536         if (!ce)
537                 fprintf(o, "%s (missing)\n", label);
538         else
539                 fprintf(o, "%s%06o %s %d\t%s\n",
540                         label,
541                         ntohl(ce->ce_mode),
542                         sha1_to_hex(ce->sha1),
543                         ce_stage(ce),
544                         ce->name);
545 }
546 #endif
547
548 static int threeway_merge(struct cache_entry **stages)
549 {
550         struct cache_entry *index;
551         struct cache_entry *head; 
552         struct cache_entry *remote = stages[head_idx + 1];
553         int count;
554         int head_match = 0;
555         int remote_match = 0;
556         const char *path = NULL;
557
558         int df_conflict_head = 0;
559         int df_conflict_remote = 0;
560
561         int any_anc_missing = 0;
562         int no_anc_exists = 1;
563         int i;
564
565         for (i = 1; i < head_idx; i++) {
566                 if (!stages[i])
567                         any_anc_missing = 1;
568                 else {
569                         if (!path)
570                                 path = stages[i]->name;
571                         no_anc_exists = 0;
572                 }
573         }
574
575         index = stages[0];
576         head = stages[head_idx];
577
578         if (head == &df_conflict_entry) {
579                 df_conflict_head = 1;
580                 head = NULL;
581         }
582
583         if (remote == &df_conflict_entry) {
584                 df_conflict_remote = 1;
585                 remote = NULL;
586         }
587
588         if (!path && index)
589                 path = index->name;
590         if (!path && head)
591                 path = head->name;
592         if (!path && remote)
593                 path = remote->name;
594
595         /* First, if there's a #16 situation, note that to prevent #13
596          * and #14.
597          */
598         if (!same(remote, head)) {
599                 for (i = 1; i < head_idx; i++) {
600                         if (same(stages[i], head)) {
601                                 head_match = i;
602                         }
603                         if (same(stages[i], remote)) {
604                                 remote_match = i;
605                         }
606                 }
607         }
608
609         /* We start with cases where the index is allowed to match
610          * something other than the head: #14(ALT) and #2ALT, where it
611          * is permitted to match the result instead.
612          */
613         /* #14, #14ALT, #2ALT */
614         if (remote && !df_conflict_head && head_match && !remote_match) {
615                 if (index && !same(index, remote) && !same(index, head))
616                         reject_merge(index);
617                 return merged_entry(remote, index);
618         }
619         /*
620          * If we have an entry in the index cache, then we want to
621          * make sure that it matches head.
622          */
623         if (index && !same(index, head)) {
624                 reject_merge(index);
625         }
626
627         if (head) {
628                 /* #5ALT, #15 */
629                 if (same(head, remote))
630                         return merged_entry(head, index);
631                 /* #13, #3ALT */
632                 if (!df_conflict_remote && remote_match && !head_match)
633                         return merged_entry(head, index);
634         }
635
636         /* #1 */
637         if (!head && !remote && any_anc_missing)
638                 return 0;
639
640         /* Under the new "aggressive" rule, we resolve mostly trivial
641          * cases that we historically had git-merge-one-file resolve.
642          */
643         if (aggressive) {
644                 int head_deleted = !head && !df_conflict_head;
645                 int remote_deleted = !remote && !df_conflict_remote;
646                 /*
647                  * Deleted in both.
648                  * Deleted in one and unchanged in the other.
649                  */
650                 if ((head_deleted && remote_deleted) ||
651                     (head_deleted && remote && remote_match) ||
652                     (remote_deleted && head && head_match)) {
653                         if (index)
654                                 return deleted_entry(index, index);
655                         else if (path)
656                                 verify_absent(path, "removed");
657                         return 0;
658                 }
659                 /*
660                  * Added in both, identically.
661                  */
662                 if (no_anc_exists && head && remote && same(head, remote))
663                         return merged_entry(head, index);
664
665         }
666
667         /* Below are "no merge" cases, which require that the index be
668          * up-to-date to avoid the files getting overwritten with
669          * conflict resolution files. 
670          */
671         if (index) {
672                 verify_uptodate(index);
673         }
674         else if (path)
675                 verify_absent(path, "overwritten");
676
677         nontrivial_merge = 1;
678
679         /* #2, #3, #4, #6, #7, #9, #11. */
680         count = 0;
681         if (!head_match || !remote_match) {
682                 for (i = 1; i < head_idx; i++) {
683                         if (stages[i]) {
684                                 keep_entry(stages[i]);
685                                 count++;
686                                 break;
687                         }
688                 }
689         }
690 #if DBRT_DEBUG
691         else {
692                 fprintf(stderr, "read-tree: warning #16 detected\n");
693                 show_stage_entry(stderr, "head   ", stages[head_match]);
694                 show_stage_entry(stderr, "remote ", stages[remote_match]);
695         }
696 #endif
697         if (head) { count += keep_entry(head); }
698         if (remote) { count += keep_entry(remote); }
699         return count;
700 }
701
702 /*
703  * Two-way merge.
704  *
705  * The rule is to "carry forward" what is in the index without losing
706  * information across a "fast forward", favoring a successful merge
707  * over a merge failure when it makes sense.  For details of the
708  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
709  *
710  */
711 static int twoway_merge(struct cache_entry **src)
712 {
713         struct cache_entry *current = src[0];
714         struct cache_entry *oldtree = src[1], *newtree = src[2];
715
716         if (merge_size != 2)
717                 return error("Cannot do a twoway merge of %d trees",
718                              merge_size);
719
720         if (current) {
721                 if ((!oldtree && !newtree) || /* 4 and 5 */
722                     (!oldtree && newtree &&
723                      same(current, newtree)) || /* 6 and 7 */
724                     (oldtree && newtree &&
725                      same(oldtree, newtree)) || /* 14 and 15 */
726                     (oldtree && newtree &&
727                      !same(oldtree, newtree) && /* 18 and 19*/
728                      same(current, newtree))) {
729                         return keep_entry(current);
730                 }
731                 else if (oldtree && !newtree && same(current, oldtree)) {
732                         /* 10 or 11 */
733                         return deleted_entry(oldtree, current);
734                 }
735                 else if (oldtree && newtree &&
736                          same(current, oldtree) && !same(current, newtree)) {
737                         /* 20 or 21 */
738                         return merged_entry(newtree, current);
739                 }
740                 else {
741                         /* all other failures */
742                         if (oldtree)
743                                 reject_merge(oldtree);
744                         if (current)
745                                 reject_merge(current);
746                         if (newtree)
747                                 reject_merge(newtree);
748                         return -1;
749                 }
750         }
751         else if (newtree)
752                 return merged_entry(newtree, current);
753         else
754                 return deleted_entry(oldtree, current);
755 }
756
757 /*
758  * Bind merge.
759  *
760  * Keep the index entries at stage0, collapse stage1 but make sure
761  * stage0 does not have anything there.
762  */
763 static int bind_merge(struct cache_entry **src)
764 {
765         struct cache_entry *old = src[0];
766         struct cache_entry *a = src[1];
767
768         if (merge_size != 1)
769                 return error("Cannot do a bind merge of %d trees\n",
770                              merge_size);
771         if (a && old)
772                 die("Entry '%s' overlaps.  Cannot bind.", a->name);
773         if (!a)
774                 return keep_entry(old);
775         else
776                 return merged_entry(a, NULL);
777 }
778
779 /*
780  * One-way merge.
781  *
782  * The rule is:
783  * - take the stat information from stage0, take the data from stage1
784  */
785 static int oneway_merge(struct cache_entry **src)
786 {
787         struct cache_entry *old = src[0];
788         struct cache_entry *a = src[1];
789
790         if (merge_size != 1)
791                 return error("Cannot do a oneway merge of %d trees",
792                              merge_size);
793
794         if (!a)
795                 return deleted_entry(old, old);
796         if (old && same(old, a)) {
797                 if (reset) {
798                         struct stat st;
799                         if (lstat(old->name, &st) ||
800                             ce_match_stat(old, &st, 1))
801                                 old->ce_flags |= htons(CE_UPDATE);
802                 }
803                 return keep_entry(old);
804         }
805         return merged_entry(a, old);
806 }
807
808 static int read_cache_unmerged(void)
809 {
810         int i;
811         struct cache_entry **dst;
812         struct cache_entry *last = NULL;
813
814         read_cache();
815         dst = active_cache;
816         for (i = 0; i < active_nr; i++) {
817                 struct cache_entry *ce = active_cache[i];
818                 if (ce_stage(ce)) {
819                         if (last && !strcmp(ce->name, last->name))
820                                 continue;
821                         invalidate_ce_path(ce);
822                         last = ce;
823                         ce->ce_mode = 0;
824                         ce->ce_flags &= ~htons(CE_STAGEMASK);
825                 }
826                 *dst++ = ce;
827         }
828         active_nr = dst - active_cache;
829         return !!last;
830 }
831
832 static void prime_cache_tree_rec(struct cache_tree *it, struct tree *tree)
833 {
834         struct tree_desc desc;
835         struct name_entry entry;
836         int cnt;
837
838         memcpy(it->sha1, tree->object.sha1, 20);
839         desc.buf = tree->buffer;
840         desc.size = tree->size;
841         cnt = 0;
842         while (tree_entry(&desc, &entry)) {
843                 if (!S_ISDIR(entry.mode))
844                         cnt++;
845                 else {
846                         struct cache_tree_sub *sub;
847                         struct tree *subtree = lookup_tree(entry.sha1);
848                         if (!subtree->object.parsed)
849                                 parse_tree(subtree);
850                         sub = cache_tree_sub(it, entry.path);
851                         sub->cache_tree = cache_tree();
852                         prime_cache_tree_rec(sub->cache_tree, subtree);
853                         cnt += sub->cache_tree->entry_count;
854                 }
855         }
856         it->entry_count = cnt;
857 }
858
859 static void prime_cache_tree(void)
860 {
861         struct tree *tree = (struct tree *)trees->item;
862         if (!tree)
863                 return;
864         active_cache_tree = cache_tree();
865         prime_cache_tree_rec(active_cache_tree, tree);
866
867 }
868
869 static const char read_tree_usage[] = "git-read-tree (<sha> | [[-m [--aggressive] | --reset | --prefix=<prefix>] [-u | -i]] <sha1> [<sha2> [<sha3>]])";
870
871 static struct lock_file lock_file;
872
873 int cmd_read_tree(int argc, const char **argv, const char *unused_prefix)
874 {
875         int i, newfd, stage = 0;
876         unsigned char sha1[20];
877         merge_fn_t fn = NULL;
878
879         df_conflict_list.next = &df_conflict_list;
880         state.base_dir = "";
881         state.force = 1;
882         state.quiet = 1;
883         state.refresh_cache = 1;
884
885         git_config(git_default_config);
886
887         newfd = hold_lock_file_for_update(&lock_file, get_index_file(), 1);
888
889         git_config(git_default_config);
890
891         merge = 0;
892         reset = 0;
893         for (i = 1; i < argc; i++) {
894                 const char *arg = argv[i];
895
896                 /* "-u" means "update", meaning that a merge will update
897                  * the working tree.
898                  */
899                 if (!strcmp(arg, "-u")) {
900                         update = 1;
901                         continue;
902                 }
903
904                 if (!strcmp(arg, "-v")) {
905                         verbose_update = 1;
906                         continue;
907                 }
908
909                 /* "-i" means "index only", meaning that a merge will
910                  * not even look at the working tree.
911                  */
912                 if (!strcmp(arg, "-i")) {
913                         index_only = 1;
914                         continue;
915                 }
916
917                 /* "--prefix=<subdirectory>/" means keep the current index
918                  *  entries and put the entries from the tree under the
919                  * given subdirectory.
920                  */
921                 if (!strncmp(arg, "--prefix=", 9)) {
922                         if (stage || merge || prefix)
923                                 usage(read_tree_usage);
924                         prefix = arg + 9;
925                         merge = 1;
926                         stage = 1;
927                         if (read_cache_unmerged())
928                                 die("you need to resolve your current index first");
929                         continue;
930                 }
931
932                 /* This differs from "-m" in that we'll silently ignore
933                  * unmerged entries and overwrite working tree files that
934                  * correspond to them.
935                  */
936                 if (!strcmp(arg, "--reset")) {
937                         if (stage || merge || prefix)
938                                 usage(read_tree_usage);
939                         reset = 1;
940                         merge = 1;
941                         stage = 1;
942                         read_cache_unmerged();
943                         continue;
944                 }
945
946                 if (!strcmp(arg, "--trivial")) {
947                         trivial_merges_only = 1;
948                         continue;
949                 }
950
951                 if (!strcmp(arg, "--aggressive")) {
952                         aggressive = 1;
953                         continue;
954                 }
955
956                 /* "-m" stands for "merge", meaning we start in stage 1 */
957                 if (!strcmp(arg, "-m")) {
958                         if (stage || merge || prefix)
959                                 usage(read_tree_usage);
960                         if (read_cache_unmerged())
961                                 die("you need to resolve your current index first");
962                         stage = 1;
963                         merge = 1;
964                         continue;
965                 }
966
967                 /* using -u and -i at the same time makes no sense */
968                 if (1 < index_only + update)
969                         usage(read_tree_usage);
970
971                 if (get_sha1(arg, sha1))
972                         die("Not a valid object name %s", arg);
973                 if (list_tree(sha1) < 0)
974                         die("failed to unpack tree object %s", arg);
975                 stage++;
976         }
977         if ((update||index_only) && !merge)
978                 usage(read_tree_usage);
979
980         if (prefix) {
981                 int pfxlen = strlen(prefix);
982                 int pos;
983                 if (prefix[pfxlen-1] != '/')
984                         die("prefix must end with /");
985                 if (stage != 2)
986                         die("binding merge takes only one tree");
987                 pos = cache_name_pos(prefix, pfxlen);
988                 if (0 <= pos)
989                         die("corrupt index file");
990                 pos = -pos-1;
991                 if (pos < active_nr &&
992                     !strncmp(active_cache[pos]->name, prefix, pfxlen))
993                         die("subdirectory '%s' already exists.", prefix);
994                 pos = cache_name_pos(prefix, pfxlen-1);
995                 if (0 <= pos)
996                         die("file '%.*s' already exists.", pfxlen-1, prefix);
997         }
998
999         if (merge) {
1000                 if (stage < 2)
1001                         die("just how do you expect me to merge %d trees?", stage-1);
1002                 switch (stage - 1) {
1003                 case 1:
1004                         fn = prefix ? bind_merge : oneway_merge;
1005                         break;
1006                 case 2:
1007                         fn = twoway_merge;
1008                         break;
1009                 case 3:
1010                 default:
1011                         fn = threeway_merge;
1012                         cache_tree_free(&active_cache_tree);
1013                         break;
1014                 }
1015
1016                 if (stage - 1 >= 3)
1017                         head_idx = stage - 2;
1018                 else
1019                         head_idx = 1;
1020         }
1021
1022         unpack_trees(fn);
1023
1024         /*
1025          * When reading only one tree (either the most basic form,
1026          * "-m ent" or "--reset ent" form), we can obtain a fully
1027          * valid cache-tree because the index must match exactly
1028          * what came from the tree.
1029          */
1030         if (trees && trees->item && !prefix && (!merge || (stage == 2))) {
1031                 cache_tree_free(&active_cache_tree);
1032                 prime_cache_tree();
1033         }
1034
1035         if (write_cache(newfd, active_cache, active_nr) ||
1036             close(newfd) || commit_lock_file(&lock_file))
1037                 die("unable to write new index file");
1038         return 0;
1039 }