Merge branch 'jc/waitpid' into next
[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         .name = NULL,
48         .next = &df_conflict_list
49 };
50
51 typedef int (*merge_fn_t)(struct cache_entry **src);
52
53 static struct tree_entry_list *create_tree_entry_list(struct tree *tree)
54 {
55         struct tree_desc desc;
56         struct name_entry one;
57         struct tree_entry_list *ret = NULL;
58         struct tree_entry_list **list_p = &ret;
59
60         desc.buf = tree->buffer;
61         desc.size = tree->size;
62
63         while (tree_entry(&desc, &one)) {
64                 struct tree_entry_list *entry;
65
66                 entry = xmalloc(sizeof(struct tree_entry_list));
67                 entry->name = one.path;
68                 entry->sha1 = one.sha1;
69                 entry->mode = one.mode;
70                 entry->directory = S_ISDIR(one.mode) != 0;
71                 entry->executable = (one.mode & S_IXUSR) != 0;
72                 entry->symlink = S_ISLNK(one.mode) != 0;
73                 entry->next = NULL;
74
75                 *list_p = entry;
76                 list_p = &entry->next;
77         }
78         return ret;
79 }
80
81 static int entcmp(const char *name1, int dir1, const char *name2, int dir2)
82 {
83         int len1 = strlen(name1);
84         int len2 = strlen(name2);
85         int len = len1 < len2 ? len1 : len2;
86         int ret = memcmp(name1, name2, len);
87         unsigned char c1, c2;
88         if (ret)
89                 return ret;
90         c1 = name1[len];
91         c2 = name2[len];
92         if (!c1 && dir1)
93                 c1 = '/';
94         if (!c2 && dir2)
95                 c2 = '/';
96         ret = (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
97         if (c1 && c2 && !ret)
98                 ret = len1 - len2;
99         return ret;
100 }
101
102 static int unpack_trees_rec(struct tree_entry_list **posns, int len,
103                             const char *base, merge_fn_t fn, int *indpos)
104 {
105         int baselen = strlen(base);
106         int src_size = len + 1;
107         do {
108                 int i;
109                 const char *first;
110                 int firstdir = 0;
111                 int pathlen;
112                 unsigned ce_size;
113                 struct tree_entry_list **subposns;
114                 struct cache_entry **src;
115                 int any_files = 0;
116                 int any_dirs = 0;
117                 char *cache_name;
118                 int ce_stage;
119
120                 /* Find the first name in the input. */
121
122                 first = NULL;
123                 cache_name = NULL;
124
125                 /* Check the cache */
126                 if (merge && *indpos < active_nr) {
127                         /* This is a bit tricky: */
128                         /* If the index has a subdirectory (with
129                          * contents) as the first name, it'll get a
130                          * filename like "foo/bar". But that's after
131                          * "foo", so the entry in trees will get
132                          * handled first, at which point we'll go into
133                          * "foo", and deal with "bar" from the index,
134                          * because the base will be "foo/". The only
135                          * way we can actually have "foo/bar" first of
136                          * all the things is if the trees don't
137                          * contain "foo" at all, in which case we'll
138                          * handle "foo/bar" without going into the
139                          * directory, but that's fine (and will return
140                          * an error anyway, with the added unknown
141                          * file case.
142                          */
143
144                         cache_name = active_cache[*indpos]->name;
145                         if (strlen(cache_name) > baselen &&
146                             !memcmp(cache_name, base, baselen)) {
147                                 cache_name += baselen;
148                                 first = cache_name;
149                         } else {
150                                 cache_name = NULL;
151                         }
152                 }
153
154 #if DBRT_DEBUG > 1
155                 if (first)
156                         printf("index %s\n", first);
157 #endif
158                 for (i = 0; i < len; i++) {
159                         if (!posns[i] || posns[i] == &df_conflict_list)
160                                 continue;
161 #if DBRT_DEBUG > 1
162                         printf("%d %s\n", i + 1, posns[i]->name);
163 #endif
164                         if (!first || entcmp(first, firstdir,
165                                              posns[i]->name, 
166                                              posns[i]->directory) > 0) {
167                                 first = posns[i]->name;
168                                 firstdir = posns[i]->directory;
169                         }
170                 }
171                 /* No name means we're done */
172                 if (!first)
173                         return 0;
174
175                 pathlen = strlen(first);
176                 ce_size = cache_entry_size(baselen + pathlen);
177
178                 src = xcalloc(src_size, sizeof(struct cache_entry *));
179
180                 subposns = xcalloc(len, sizeof(struct tree_list_entry *));
181
182                 if (cache_name && !strcmp(cache_name, first)) {
183                         any_files = 1;
184                         src[0] = active_cache[*indpos];
185                         remove_cache_entry_at(*indpos);
186                 }
187
188                 for (i = 0; i < len; i++) {
189                         struct cache_entry *ce;
190
191                         if (!posns[i] ||
192                             (posns[i] != &df_conflict_list &&
193                              strcmp(first, posns[i]->name))) {
194                                 continue;
195                         }
196
197                         if (posns[i] == &df_conflict_list) {
198                                 src[i + merge] = &df_conflict_entry;
199                                 continue;
200                         }
201
202                         if (posns[i]->directory) {
203                                 struct tree *tree = lookup_tree(posns[i]->sha1);
204                                 any_dirs = 1;
205                                 parse_tree(tree);
206                                 subposns[i] = create_tree_entry_list(tree);
207                                 posns[i] = posns[i]->next;
208                                 src[i + merge] = &df_conflict_entry;
209                                 continue;
210                         }
211
212                         if (!merge)
213                                 ce_stage = 0;
214                         else if (i + 1 < head_idx)
215                                 ce_stage = 1;
216                         else if (i + 1 > head_idx)
217                                 ce_stage = 3;
218                         else
219                                 ce_stage = 2;
220
221                         ce = xcalloc(1, ce_size);
222                         ce->ce_mode = create_ce_mode(posns[i]->mode);
223                         ce->ce_flags = create_ce_flags(baselen + pathlen,
224                                                        ce_stage);
225                         memcpy(ce->name, base, baselen);
226                         memcpy(ce->name + baselen, first, pathlen + 1);
227
228                         any_files = 1;
229
230                         memcpy(ce->sha1, posns[i]->sha1, 20);
231                         src[i + merge] = ce;
232                         subposns[i] = &df_conflict_list;
233                         posns[i] = posns[i]->next;
234                 }
235                 if (any_files) {
236                         if (merge) {
237                                 int ret;
238
239 #if DBRT_DEBUG > 1
240                                 printf("%s:\n", first);
241                                 for (i = 0; i < src_size; i++) {
242                                         printf(" %d ", i);
243                                         if (src[i])
244                                                 printf("%s\n", sha1_to_hex(src[i]->sha1));
245                                         else
246                                                 printf("\n");
247                                 }
248 #endif
249                                 ret = fn(src);
250                                 
251 #if DBRT_DEBUG > 1
252                                 printf("Added %d entries\n", ret);
253 #endif
254                                 *indpos += ret;
255                         } else {
256                                 for (i = 0; i < src_size; i++) {
257                                         if (src[i]) {
258                                                 add_cache_entry(src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
259                                         }
260                                 }
261                         }
262                 }
263                 if (any_dirs) {
264                         char *newbase = xmalloc(baselen + 2 + pathlen);
265                         memcpy(newbase, base, baselen);
266                         memcpy(newbase + baselen, first, pathlen);
267                         newbase[baselen + pathlen] = '/';
268                         newbase[baselen + pathlen + 1] = '\0';
269                         if (unpack_trees_rec(subposns, len, newbase, fn,
270                                              indpos))
271                                 return -1;
272                         free(newbase);
273                 }
274                 free(subposns);
275                 free(src);
276         } while (1);
277 }
278
279 static void reject_merge(struct cache_entry *ce)
280 {
281         die("Entry '%s' would be overwritten by merge. Cannot merge.", 
282             ce->name);
283 }
284
285 /* Unlink the last component and attempt to remove leading
286  * directories, in case this unlink is the removal of the
287  * last entry in the directory -- empty directories are removed.
288  */
289 static void unlink_entry(char *name)
290 {
291         char *cp, *prev;
292
293         if (unlink(name))
294                 return;
295         prev = NULL;
296         while (1) {
297                 int status;
298                 cp = strrchr(name, '/');
299                 if (prev)
300                         *prev = '/';
301                 if (!cp)
302                         break;
303
304                 *cp = 0;
305                 status = rmdir(name);
306                 if (status) {
307                         *cp = '/';
308                         break;
309                 }
310                 prev = cp;
311         }
312 }
313
314 static void progress_interval(int signum)
315 {
316         progress_update = 1;
317 }
318
319 static void setup_progress_signal(void)
320 {
321         struct sigaction sa;
322         struct itimerval v;
323
324         memset(&sa, 0, sizeof(sa));
325         sa.sa_handler = progress_interval;
326         sigemptyset(&sa.sa_mask);
327         sa.sa_flags = SA_RESTART;
328         sigaction(SIGALRM, &sa, NULL);
329
330         v.it_interval.tv_sec = 1;
331         v.it_interval.tv_usec = 0;
332         v.it_value = v.it_interval;
333         setitimer(ITIMER_REAL, &v, NULL);
334 }
335
336 static void check_updates(struct cache_entry **src, int nr)
337 {
338         static struct checkout state = {
339                 .base_dir = "",
340                 .force = 1,
341                 .quiet = 1,
342                 .refresh_cache = 1,
343         };
344         unsigned short mask = htons(CE_UPDATE);
345         unsigned last_percent = 200, cnt = 0, total = 0;
346
347         if (update && verbose_update) {
348                 for (total = cnt = 0; cnt < nr; cnt++) {
349                         struct cache_entry *ce = src[cnt];
350                         if (!ce->ce_mode || ce->ce_flags & mask)
351                                 total++;
352                 }
353
354                 /* Don't bother doing this for very small updates */
355                 if (total < 250)
356                         total = 0;
357
358                 if (total) {
359                         fprintf(stderr, "Checking files out...\n");
360                         setup_progress_signal();
361                         progress_update = 1;
362                 }
363                 cnt = 0;
364         }
365
366         while (nr--) {
367                 struct cache_entry *ce = *src++;
368
369                 if (total) {
370                         if (!ce->ce_mode || ce->ce_flags & mask) {
371                                 unsigned percent;
372                                 cnt++;
373                                 percent = (cnt * 100) / total;
374                                 if (percent != last_percent ||
375                                     progress_update) {
376                                         fprintf(stderr, "%4u%% (%u/%u) done\r",
377                                                 percent, cnt, total);
378                                         last_percent = percent;
379                                         progress_update = 0;
380                                 }
381                         }
382                 }
383                 if (!ce->ce_mode) {
384                         if (update)
385                                 unlink_entry(ce->name);
386                         continue;
387                 }
388                 if (ce->ce_flags & mask) {
389                         ce->ce_flags &= ~mask;
390                         if (update)
391                                 checkout_entry(ce, &state, NULL);
392                 }
393         }
394         if (total) {
395                 signal(SIGALRM, SIG_IGN);
396                 fputc('\n', stderr);
397         }
398 }
399
400 static int unpack_trees(merge_fn_t fn)
401 {
402         int indpos = 0;
403         unsigned len = object_list_length(trees);
404         struct tree_entry_list **posns;
405         int i;
406         struct object_list *posn = trees;
407         merge_size = len;
408
409         if (len) {
410                 posns = xmalloc(len * sizeof(struct tree_entry_list *));
411                 for (i = 0; i < len; i++) {
412                         posns[i] = create_tree_entry_list((struct tree *) posn->item);
413                         posn = posn->next;
414                 }
415                 if (unpack_trees_rec(posns, len, prefix ? prefix : "",
416                                      fn, &indpos))
417                         return -1;
418         }
419
420         if (trivial_merges_only && nontrivial_merge)
421                 die("Merge requires file-level merging");
422
423         check_updates(active_cache, active_nr);
424         return 0;
425 }
426
427 static int list_tree(unsigned char *sha1)
428 {
429         struct tree *tree = parse_tree_indirect(sha1);
430         if (!tree)
431                 return -1;
432         object_list_append(&tree->object, &trees);
433         return 0;
434 }
435
436 static int same(struct cache_entry *a, struct cache_entry *b)
437 {
438         if (!!a != !!b)
439                 return 0;
440         if (!a && !b)
441                 return 1;
442         return a->ce_mode == b->ce_mode && 
443                 !memcmp(a->sha1, b->sha1, 20);
444 }
445
446
447 /*
448  * When a CE gets turned into an unmerged entry, we
449  * want it to be up-to-date
450  */
451 static void verify_uptodate(struct cache_entry *ce)
452 {
453         struct stat st;
454
455         if (index_only || reset)
456                 return;
457
458         if (!lstat(ce->name, &st)) {
459                 unsigned changed = ce_match_stat(ce, &st, 1);
460                 if (!changed)
461                         return;
462                 errno = 0;
463         }
464         if (reset) {
465                 ce->ce_flags |= htons(CE_UPDATE);
466                 return;
467         }
468         if (errno == ENOENT)
469                 return;
470         die("Entry '%s' not uptodate. Cannot merge.", ce->name);
471 }
472
473 static void invalidate_ce_path(struct cache_entry *ce)
474 {
475         if (ce)
476                 cache_tree_invalidate_path(active_cache_tree, ce->name);
477 }
478
479 /*
480  * We do not want to remove or overwrite a working tree file that
481  * is not tracked.
482  */
483 static void verify_absent(const char *path, const char *action)
484 {
485         struct stat st;
486
487         if (index_only || reset || !update)
488                 return;
489         if (!lstat(path, &st))
490                 die("Untracked working tree file '%s' "
491                     "would be %s by merge.", path, action);
492 }
493
494 static int merged_entry(struct cache_entry *merge, struct cache_entry *old)
495 {
496         merge->ce_flags |= htons(CE_UPDATE);
497         if (old) {
498                 /*
499                  * See if we can re-use the old CE directly?
500                  * That way we get the uptodate stat info.
501                  *
502                  * This also removes the UPDATE flag on
503                  * a match.
504                  */
505                 if (same(old, merge)) {
506                         *merge = *old;
507                 } else {
508                         verify_uptodate(old);
509                         invalidate_ce_path(old);
510                 }
511         }
512         else {
513                 verify_absent(merge->name, "overwritten");
514                 invalidate_ce_path(merge);
515         }
516
517         merge->ce_flags &= ~htons(CE_STAGEMASK);
518         add_cache_entry(merge, ADD_CACHE_OK_TO_ADD);
519         return 1;
520 }
521
522 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old)
523 {
524         if (old)
525                 verify_uptodate(old);
526         else
527                 verify_absent(ce->name, "removed");
528         ce->ce_mode = 0;
529         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
530         invalidate_ce_path(ce);
531         return 1;
532 }
533
534 static int keep_entry(struct cache_entry *ce)
535 {
536         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
537         return 1;
538 }
539
540 #if DBRT_DEBUG
541 static void show_stage_entry(FILE *o,
542                              const char *label, const struct cache_entry *ce)
543 {
544         if (!ce)
545                 fprintf(o, "%s (missing)\n", label);
546         else
547                 fprintf(o, "%s%06o %s %d\t%s\n",
548                         label,
549                         ntohl(ce->ce_mode),
550                         sha1_to_hex(ce->sha1),
551                         ce_stage(ce),
552                         ce->name);
553 }
554 #endif
555
556 static int threeway_merge(struct cache_entry **stages)
557 {
558         struct cache_entry *index;
559         struct cache_entry *head; 
560         struct cache_entry *remote = stages[head_idx + 1];
561         int count;
562         int head_match = 0;
563         int remote_match = 0;
564         const char *path = NULL;
565
566         int df_conflict_head = 0;
567         int df_conflict_remote = 0;
568
569         int any_anc_missing = 0;
570         int no_anc_exists = 1;
571         int i;
572
573         for (i = 1; i < head_idx; i++) {
574                 if (!stages[i])
575                         any_anc_missing = 1;
576                 else {
577                         if (!path)
578                                 path = stages[i]->name;
579                         no_anc_exists = 0;
580                 }
581         }
582
583         index = stages[0];
584         head = stages[head_idx];
585
586         if (head == &df_conflict_entry) {
587                 df_conflict_head = 1;
588                 head = NULL;
589         }
590
591         if (remote == &df_conflict_entry) {
592                 df_conflict_remote = 1;
593                 remote = NULL;
594         }
595
596         if (!path && index)
597                 path = index->name;
598         if (!path && head)
599                 path = head->name;
600         if (!path && remote)
601                 path = remote->name;
602
603         /* First, if there's a #16 situation, note that to prevent #13
604          * and #14.
605          */
606         if (!same(remote, head)) {
607                 for (i = 1; i < head_idx; i++) {
608                         if (same(stages[i], head)) {
609                                 head_match = i;
610                         }
611                         if (same(stages[i], remote)) {
612                                 remote_match = i;
613                         }
614                 }
615         }
616
617         /* We start with cases where the index is allowed to match
618          * something other than the head: #14(ALT) and #2ALT, where it
619          * is permitted to match the result instead.
620          */
621         /* #14, #14ALT, #2ALT */
622         if (remote && !df_conflict_head && head_match && !remote_match) {
623                 if (index && !same(index, remote) && !same(index, head))
624                         reject_merge(index);
625                 return merged_entry(remote, index);
626         }
627         /*
628          * If we have an entry in the index cache, then we want to
629          * make sure that it matches head.
630          */
631         if (index && !same(index, head)) {
632                 reject_merge(index);
633         }
634
635         if (head) {
636                 /* #5ALT, #15 */
637                 if (same(head, remote))
638                         return merged_entry(head, index);
639                 /* #13, #3ALT */
640                 if (!df_conflict_remote && remote_match && !head_match)
641                         return merged_entry(head, index);
642         }
643
644         /* #1 */
645         if (!head && !remote && any_anc_missing)
646                 return 0;
647
648         /* Under the new "aggressive" rule, we resolve mostly trivial
649          * cases that we historically had git-merge-one-file resolve.
650          */
651         if (aggressive) {
652                 int head_deleted = !head && !df_conflict_head;
653                 int remote_deleted = !remote && !df_conflict_remote;
654                 /*
655                  * Deleted in both.
656                  * Deleted in one and unchanged in the other.
657                  */
658                 if ((head_deleted && remote_deleted) ||
659                     (head_deleted && remote && remote_match) ||
660                     (remote_deleted && head && head_match)) {
661                         if (index)
662                                 return deleted_entry(index, index);
663                         else if (path)
664                                 verify_absent(path, "removed");
665                         return 0;
666                 }
667                 /*
668                  * Added in both, identically.
669                  */
670                 if (no_anc_exists && head && remote && same(head, remote))
671                         return merged_entry(head, index);
672
673         }
674
675         /* Below are "no merge" cases, which require that the index be
676          * up-to-date to avoid the files getting overwritten with
677          * conflict resolution files. 
678          */
679         if (index) {
680                 verify_uptodate(index);
681         }
682         else if (path)
683                 verify_absent(path, "overwritten");
684
685         nontrivial_merge = 1;
686
687         /* #2, #3, #4, #6, #7, #9, #11. */
688         count = 0;
689         if (!head_match || !remote_match) {
690                 for (i = 1; i < head_idx; i++) {
691                         if (stages[i]) {
692                                 keep_entry(stages[i]);
693                                 count++;
694                                 break;
695                         }
696                 }
697         }
698 #if DBRT_DEBUG
699         else {
700                 fprintf(stderr, "read-tree: warning #16 detected\n");
701                 show_stage_entry(stderr, "head   ", stages[head_match]);
702                 show_stage_entry(stderr, "remote ", stages[remote_match]);
703         }
704 #endif
705         if (head) { count += keep_entry(head); }
706         if (remote) { count += keep_entry(remote); }
707         return count;
708 }
709
710 /*
711  * Two-way merge.
712  *
713  * The rule is to "carry forward" what is in the index without losing
714  * information across a "fast forward", favoring a successful merge
715  * over a merge failure when it makes sense.  For details of the
716  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
717  *
718  */
719 static int twoway_merge(struct cache_entry **src)
720 {
721         struct cache_entry *current = src[0];
722         struct cache_entry *oldtree = src[1], *newtree = src[2];
723
724         if (merge_size != 2)
725                 return error("Cannot do a twoway merge of %d trees",
726                              merge_size);
727
728         if (current) {
729                 if ((!oldtree && !newtree) || /* 4 and 5 */
730                     (!oldtree && newtree &&
731                      same(current, newtree)) || /* 6 and 7 */
732                     (oldtree && newtree &&
733                      same(oldtree, newtree)) || /* 14 and 15 */
734                     (oldtree && newtree &&
735                      !same(oldtree, newtree) && /* 18 and 19*/
736                      same(current, newtree))) {
737                         return keep_entry(current);
738                 }
739                 else if (oldtree && !newtree && same(current, oldtree)) {
740                         /* 10 or 11 */
741                         return deleted_entry(oldtree, current);
742                 }
743                 else if (oldtree && newtree &&
744                          same(current, oldtree) && !same(current, newtree)) {
745                         /* 20 or 21 */
746                         return merged_entry(newtree, current);
747                 }
748                 else {
749                         /* all other failures */
750                         if (oldtree)
751                                 reject_merge(oldtree);
752                         if (current)
753                                 reject_merge(current);
754                         if (newtree)
755                                 reject_merge(newtree);
756                         return -1;
757                 }
758         }
759         else if (newtree)
760                 return merged_entry(newtree, current);
761         else
762                 return deleted_entry(oldtree, current);
763 }
764
765 /*
766  * Bind merge.
767  *
768  * Keep the index entries at stage0, collapse stage1 but make sure
769  * stage0 does not have anything there.
770  */
771 static int bind_merge(struct cache_entry **src)
772 {
773         struct cache_entry *old = src[0];
774         struct cache_entry *a = src[1];
775
776         if (merge_size != 1)
777                 return error("Cannot do a bind merge of %d trees\n",
778                              merge_size);
779         if (a && old)
780                 die("Entry '%s' overlaps.  Cannot bind.", a->name);
781         if (!a)
782                 return keep_entry(old);
783         else
784                 return merged_entry(a, NULL);
785 }
786
787 /*
788  * One-way merge.
789  *
790  * The rule is:
791  * - take the stat information from stage0, take the data from stage1
792  */
793 static int oneway_merge(struct cache_entry **src)
794 {
795         struct cache_entry *old = src[0];
796         struct cache_entry *a = src[1];
797
798         if (merge_size != 1)
799                 return error("Cannot do a oneway merge of %d trees",
800                              merge_size);
801
802         if (!a)
803                 return deleted_entry(old, old);
804         if (old && same(old, a)) {
805                 if (reset) {
806                         struct stat st;
807                         if (lstat(old->name, &st) ||
808                             ce_match_stat(old, &st, 1))
809                                 old->ce_flags |= htons(CE_UPDATE);
810                 }
811                 return keep_entry(old);
812         }
813         return merged_entry(a, old);
814 }
815
816 static int read_cache_unmerged(void)
817 {
818         int i;
819         struct cache_entry **dst;
820         struct cache_entry *last = NULL;
821
822         read_cache();
823         dst = active_cache;
824         for (i = 0; i < active_nr; i++) {
825                 struct cache_entry *ce = active_cache[i];
826                 if (ce_stage(ce)) {
827                         if (last && !strcmp(ce->name, last->name))
828                                 continue;
829                         invalidate_ce_path(ce);
830                         last = ce;
831                         ce->ce_mode = 0;
832                         ce->ce_flags &= ~htons(CE_STAGEMASK);
833                 }
834                 *dst++ = ce;
835         }
836         active_nr = dst - active_cache;
837         return !!last;
838 }
839
840 static void prime_cache_tree_rec(struct cache_tree *it, struct tree *tree)
841 {
842         struct tree_desc desc;
843         struct name_entry entry;
844         int cnt;
845
846         memcpy(it->sha1, tree->object.sha1, 20);
847         desc.buf = tree->buffer;
848         desc.size = tree->size;
849         cnt = 0;
850         while (tree_entry(&desc, &entry)) {
851                 if (!S_ISDIR(entry.mode))
852                         cnt++;
853                 else {
854                         struct cache_tree_sub *sub;
855                         struct tree *subtree = lookup_tree(entry.sha1);
856                         if (!subtree->object.parsed)
857                                 parse_tree(subtree);
858                         sub = cache_tree_sub(it, entry.path);
859                         sub->cache_tree = cache_tree();
860                         prime_cache_tree_rec(sub->cache_tree, subtree);
861                         cnt += sub->cache_tree->entry_count;
862                 }
863         }
864         it->entry_count = cnt;
865 }
866
867 static void prime_cache_tree(void)
868 {
869         struct tree *tree = (struct tree *)trees->item;
870         if (!tree)
871                 return;
872         active_cache_tree = cache_tree();
873         prime_cache_tree_rec(active_cache_tree, tree);
874
875 }
876
877 static const char read_tree_usage[] = "git-read-tree (<sha> | [[-m [--aggressive] | --reset | --prefix=<prefix>] [-u | -i]] <sha1> [<sha2> [<sha3>]])";
878
879 static struct lock_file lock_file;
880
881 int cmd_read_tree(int argc, const char **argv, char **envp)
882 {
883         int i, newfd, stage = 0;
884         unsigned char sha1[20];
885         merge_fn_t fn = NULL;
886
887         setup_git_directory();
888         git_config(git_default_config);
889
890         newfd = hold_lock_file_for_update(&lock_file, get_index_file());
891         if (newfd < 0)
892                 die("unable to create new index file");
893
894         git_config(git_default_config);
895
896         merge = 0;
897         reset = 0;
898         for (i = 1; i < argc; i++) {
899                 const char *arg = argv[i];
900
901                 /* "-u" means "update", meaning that a merge will update
902                  * the working tree.
903                  */
904                 if (!strcmp(arg, "-u")) {
905                         update = 1;
906                         continue;
907                 }
908
909                 if (!strcmp(arg, "-v")) {
910                         verbose_update = 1;
911                         continue;
912                 }
913
914                 /* "-i" means "index only", meaning that a merge will
915                  * not even look at the working tree.
916                  */
917                 if (!strcmp(arg, "-i")) {
918                         index_only = 1;
919                         continue;
920                 }
921
922                 /* "--prefix=<subdirectory>/" means keep the current index
923                  *  entries and put the entries from the tree under the
924                  * given subdirectory.
925                  */
926                 if (!strncmp(arg, "--prefix=", 9)) {
927                         if (stage || merge || prefix)
928                                 usage(read_tree_usage);
929                         prefix = arg + 9;
930                         merge = 1;
931                         stage = 1;
932                         if (read_cache_unmerged())
933                                 die("you need to resolve your current index first");
934                         continue;
935                 }
936
937                 /* This differs from "-m" in that we'll silently ignore
938                  * unmerged entries and overwrite working tree files that
939                  * correspond to them.
940                  */
941                 if (!strcmp(arg, "--reset")) {
942                         if (stage || merge || prefix)
943                                 usage(read_tree_usage);
944                         reset = 1;
945                         merge = 1;
946                         stage = 1;
947                         read_cache_unmerged();
948                         continue;
949                 }
950
951                 if (!strcmp(arg, "--trivial")) {
952                         trivial_merges_only = 1;
953                         continue;
954                 }
955
956                 if (!strcmp(arg, "--aggressive")) {
957                         aggressive = 1;
958                         continue;
959                 }
960
961                 /* "-m" stands for "merge", meaning we start in stage 1 */
962                 if (!strcmp(arg, "-m")) {
963                         if (stage || merge || prefix)
964                                 usage(read_tree_usage);
965                         if (read_cache_unmerged())
966                                 die("you need to resolve your current index first");
967                         stage = 1;
968                         merge = 1;
969                         continue;
970                 }
971
972                 /* using -u and -i at the same time makes no sense */
973                 if (1 < index_only + update)
974                         usage(read_tree_usage);
975
976                 if (get_sha1(arg, sha1))
977                         die("Not a valid object name %s", arg);
978                 if (list_tree(sha1) < 0)
979                         die("failed to unpack tree object %s", arg);
980                 stage++;
981         }
982         if ((update||index_only) && !merge)
983                 usage(read_tree_usage);
984
985         if (prefix) {
986                 int pfxlen = strlen(prefix);
987                 int pos;
988                 if (prefix[pfxlen-1] != '/')
989                         die("prefix must end with /");
990                 if (stage != 2)
991                         die("binding merge takes only one tree");
992                 pos = cache_name_pos(prefix, pfxlen);
993                 if (0 <= pos)
994                         die("corrupt index file");
995                 pos = -pos-1;
996                 if (pos < active_nr &&
997                     !strncmp(active_cache[pos]->name, prefix, pfxlen))
998                         die("subdirectory '%s' already exists.", prefix);
999                 pos = cache_name_pos(prefix, pfxlen-1);
1000                 if (0 <= pos)
1001                         die("file '%.*s' already exists.", pfxlen-1, prefix);
1002         }
1003
1004         if (merge) {
1005                 if (stage < 2)
1006                         die("just how do you expect me to merge %d trees?", stage-1);
1007                 switch (stage - 1) {
1008                 case 1:
1009                         fn = prefix ? bind_merge : oneway_merge;
1010                         break;
1011                 case 2:
1012                         fn = twoway_merge;
1013                         break;
1014                 case 3:
1015                 default:
1016                         fn = threeway_merge;
1017                         cache_tree_free(&active_cache_tree);
1018                         break;
1019                 }
1020
1021                 if (stage - 1 >= 3)
1022                         head_idx = stage - 2;
1023                 else
1024                         head_idx = 1;
1025         }
1026
1027         unpack_trees(fn);
1028
1029         /*
1030          * When reading only one tree (either the most basic form,
1031          * "-m ent" or "--reset ent" form), we can obtain a fully
1032          * valid cache-tree because the index must match exactly
1033          * what came from the tree.
1034          */
1035         if (trees && trees->item && !prefix && (!merge || (stage == 2))) {
1036                 cache_tree_free(&active_cache_tree);
1037                 prime_cache_tree();
1038         }
1039
1040         if (write_cache(newfd, active_cache, active_nr) ||
1041             commit_lock_file(&lock_file))
1042                 die("unable to write new index file");
1043         return 0;
1044 }