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