[PATCH] Support alternates and http-alternates in http-fetch
[git] / 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
13 static int merge = 0;
14 static int update = 0;
15 static int index_only = 0;
16
17 static int head_idx = -1;
18 static int merge_size = 0;
19
20 static struct object_list *trees = NULL;
21
22 static struct cache_entry df_conflict_entry = { 
23 };
24
25 static struct tree_entry_list df_conflict_list = {
26         .name = NULL,
27         .next = &df_conflict_list
28 };
29
30 typedef int (*merge_fn_t)(struct cache_entry **src);
31
32 static int entcmp(char *name1, int dir1, char *name2, int dir2)
33 {
34         int len1 = strlen(name1);
35         int len2 = strlen(name2);
36         int len = len1 < len2 ? len1 : len2;
37         int ret = memcmp(name1, name2, len);
38         unsigned char c1, c2;
39         if (ret)
40                 return ret;
41         c1 = name1[len];
42         c2 = name2[len];
43         if (!c1 && dir1)
44                 c1 = '/';
45         if (!c2 && dir2)
46                 c2 = '/';
47         ret = (c1 < c2) ? -1 : (c1 > c2) ? 1 : 0;
48         if (c1 && c2 && !ret)
49                 ret = len1 - len2;
50         return ret;
51 }
52
53 static int unpack_trees_rec(struct tree_entry_list **posns, int len,
54                             const char *base, merge_fn_t fn, int *indpos)
55 {
56         int baselen = strlen(base);
57         int src_size = len + 1;
58         do {
59                 int i;
60                 char *first;
61                 int firstdir = 0;
62                 int pathlen;
63                 unsigned ce_size;
64                 struct tree_entry_list **subposns;
65                 struct cache_entry **src;
66                 int any_files = 0;
67                 int any_dirs = 0;
68                 char *cache_name;
69                 int ce_stage;
70
71                 /* Find the first name in the input. */
72
73                 first = NULL;
74                 cache_name = NULL;
75
76                 /* Check the cache */
77                 if (merge && *indpos < active_nr) {
78                         /* This is a bit tricky: */
79                         /* If the index has a subdirectory (with
80                          * contents) as the first name, it'll get a
81                          * filename like "foo/bar". But that's after
82                          * "foo", so the entry in trees will get
83                          * handled first, at which point we'll go into
84                          * "foo", and deal with "bar" from the index,
85                          * because the base will be "foo/". The only
86                          * way we can actually have "foo/bar" first of
87                          * all the things is if the trees don't
88                          * contain "foo" at all, in which case we'll
89                          * handle "foo/bar" without going into the
90                          * directory, but that's fine (and will return
91                          * an error anyway, with the added unknown
92                          * file case.
93                          */
94
95                         cache_name = active_cache[*indpos]->name;
96                         if (strlen(cache_name) > baselen &&
97                             !memcmp(cache_name, base, baselen)) {
98                                 cache_name += baselen;
99                                 first = cache_name;
100                         } else {
101                                 cache_name = NULL;
102                         }
103                 }
104
105 #if DBRT_DEBUG > 1
106                 if (first)
107                         printf("index %s\n", first);
108 #endif
109                 for (i = 0; i < len; i++) {
110                         if (!posns[i] || posns[i] == &df_conflict_list)
111                                 continue;
112 #if DBRT_DEBUG > 1
113                         printf("%d %s\n", i + 1, posns[i]->name);
114 #endif
115                         if (!first || entcmp(first, firstdir,
116                                              posns[i]->name, 
117                                              posns[i]->directory) > 0) {
118                                 first = posns[i]->name;
119                                 firstdir = posns[i]->directory;
120                         }
121                 }
122                 /* No name means we're done */
123                 if (!first)
124                         return 0;
125
126                 pathlen = strlen(first);
127                 ce_size = cache_entry_size(baselen + pathlen);
128
129                 src = xmalloc(sizeof(struct cache_entry *) * src_size);
130                 memset(src, 0, sizeof(struct cache_entry *) * src_size);
131
132                 subposns = xmalloc(sizeof(struct tree_list_entry *) * len);
133                 memset(subposns, 0, sizeof(struct tree_list_entry *) * len);
134
135                 if (cache_name && !strcmp(cache_name, first)) {
136                         any_files = 1;
137                         src[0] = active_cache[*indpos];
138                         remove_cache_entry_at(*indpos);
139                 }
140
141                 for (i = 0; i < len; i++) {
142                         struct cache_entry *ce;
143
144                         if (!posns[i] ||
145                             (posns[i] != &df_conflict_list &&
146                              strcmp(first, posns[i]->name))) {
147                                 continue;
148                         }
149
150                         if (posns[i] == &df_conflict_list) {
151                                 src[i + merge] = &df_conflict_entry;
152                                 continue;
153                         }
154
155                         if (posns[i]->directory) {
156                                 any_dirs = 1;
157                                 parse_tree(posns[i]->item.tree);
158                                 subposns[i] = posns[i]->item.tree->entries;
159                                 posns[i] = posns[i]->next;
160                                 src[i + merge] = &df_conflict_entry;
161                                 continue;
162                         }
163
164                         if (!merge)
165                                 ce_stage = 0;
166                         else if (i + 1 < head_idx)
167                                 ce_stage = 1;
168                         else if (i + 1 > head_idx)
169                                 ce_stage = 3;
170                         else
171                                 ce_stage = 2;
172
173                         ce = xmalloc(ce_size);
174                         memset(ce, 0, ce_size);
175                         ce->ce_mode = create_ce_mode(posns[i]->mode);
176                         ce->ce_flags = create_ce_flags(baselen + pathlen,
177                                                        ce_stage);
178                         memcpy(ce->name, base, baselen);
179                         memcpy(ce->name + baselen, first, pathlen + 1);
180
181                         any_files = 1;
182
183                         memcpy(ce->sha1, posns[i]->item.any->sha1, 20);
184                         src[i + merge] = ce;
185                         subposns[i] = &df_conflict_list;
186                         posns[i] = posns[i]->next;
187                 }
188                 if (any_files) {
189                         if (merge) {
190                                 int ret;
191
192 #if DBRT_DEBUG > 1
193                                 printf("%s:\n", first);
194                                 for (i = 0; i < src_size; i++) {
195                                         printf(" %d ", i);
196                                         if (src[i])
197                                                 printf("%s\n", sha1_to_hex(src[i]->sha1));
198                                         else
199                                                 printf("\n");
200                                 }
201 #endif
202                                 ret = fn(src);
203                                 
204 #if DBRT_DEBUG > 1
205                                 printf("Added %d entries\n", ret);
206 #endif
207                                 *indpos += ret;
208                         } else {
209                                 for (i = 0; i < src_size; i++) {
210                                         if (src[i]) {
211                                                 add_cache_entry(src[i], ADD_CACHE_OK_TO_ADD|ADD_CACHE_SKIP_DFCHECK);
212                                         }
213                                 }
214                         }
215                 }
216                 if (any_dirs) {
217                         char *newbase = xmalloc(baselen + 2 + pathlen);
218                         memcpy(newbase, base, baselen);
219                         memcpy(newbase + baselen, first, pathlen);
220                         newbase[baselen + pathlen] = '/';
221                         newbase[baselen + pathlen + 1] = '\0';
222                         if (unpack_trees_rec(subposns, len, newbase, fn,
223                                              indpos))
224                                 return -1;
225                         free(newbase);
226                 }
227                 free(subposns);
228                 free(src);
229         } while (1);
230 }
231
232 static void reject_merge(struct cache_entry *ce)
233 {
234         die("Entry '%s' would be overwritten by merge. Cannot merge.", 
235             ce->name);
236 }
237
238 static void check_updates(struct cache_entry **src, int nr)
239 {
240         static struct checkout state = {
241                 .base_dir = "",
242                 .force = 1,
243                 .quiet = 1,
244                 .refresh_cache = 1,
245         };
246         unsigned short mask = htons(CE_UPDATE);
247         while (nr--) {
248                 struct cache_entry *ce = *src++;
249                 if (!ce->ce_mode) {
250                         if (update)
251                                 unlink(ce->name);
252                         continue;
253                 }
254                 if (ce->ce_flags & mask) {
255                         ce->ce_flags &= ~mask;
256                         if (update)
257                                 checkout_entry(ce, &state);
258                 }
259         }
260 }
261
262 static int unpack_trees(merge_fn_t fn)
263 {
264         int indpos = 0;
265         unsigned len = object_list_length(trees);
266         struct tree_entry_list **posns = 
267                 xmalloc(len * sizeof(struct tree_entry_list *));
268         int i;
269         struct object_list *posn = trees;
270         merge_size = len;
271         for (i = 0; i < len; i++) {
272                 posns[i] = ((struct tree *) posn->item)->entries;
273                 posn = posn->next;
274         }
275         if (unpack_trees_rec(posns, len, "", fn, &indpos))
276                 return -1;
277
278         check_updates(active_cache, active_nr);
279         return 0;
280 }
281
282 static int list_tree(unsigned char *sha1)
283 {
284         struct tree *tree = parse_tree_indirect(sha1);
285         if (!tree)
286                 return -1;
287         object_list_append(&tree->object, &trees);
288         return 0;
289 }
290
291 static int same(struct cache_entry *a, struct cache_entry *b)
292 {
293         if (!!a != !!b)
294                 return 0;
295         if (!a && !b)
296                 return 1;
297         return a->ce_mode == b->ce_mode && 
298                 !memcmp(a->sha1, b->sha1, 20);
299 }
300
301
302 /*
303  * When a CE gets turned into an unmerged entry, we
304  * want it to be up-to-date
305  */
306 static void verify_uptodate(struct cache_entry *ce)
307 {
308         struct stat st;
309
310         if (index_only)
311                 return;
312
313         if (!lstat(ce->name, &st)) {
314                 unsigned changed = ce_match_stat(ce, &st);
315                 if (!changed)
316                         return;
317                 errno = 0;
318         }
319         if (errno == ENOENT)
320                 return;
321         die("Entry '%s' not uptodate. Cannot merge.", ce->name);
322 }
323
324 static int merged_entry(struct cache_entry *merge, struct cache_entry *old)
325 {
326         merge->ce_flags |= htons(CE_UPDATE);
327         if (old) {
328                 /*
329                  * See if we can re-use the old CE directly?
330                  * That way we get the uptodate stat info.
331                  *
332                  * This also removes the UPDATE flag on
333                  * a match.
334                  */
335                 if (same(old, merge)) {
336                         *merge = *old;
337                 } else {
338                         verify_uptodate(old);
339                 }
340         }
341         merge->ce_flags &= ~htons(CE_STAGEMASK);
342         add_cache_entry(merge, ADD_CACHE_OK_TO_ADD);
343         return 1;
344 }
345
346 static int deleted_entry(struct cache_entry *ce, struct cache_entry *old)
347 {
348         if (old)
349                 verify_uptodate(old);
350         ce->ce_mode = 0;
351         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
352         return 1;
353 }
354
355 static int keep_entry(struct cache_entry *ce)
356 {
357         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD);
358         return 1;
359 }
360
361 #if DBRT_DEBUG
362 static void show_stage_entry(FILE *o,
363                              const char *label, const struct cache_entry *ce)
364 {
365         if (!ce)
366                 fprintf(o, "%s (missing)\n", label);
367         else
368                 fprintf(o, "%s%06o %s %d\t%s\n",
369                         label,
370                         ntohl(ce->ce_mode),
371                         sha1_to_hex(ce->sha1),
372                         ce_stage(ce),
373                         ce->name);
374 }
375 #endif
376
377 static int threeway_merge(struct cache_entry **stages)
378 {
379         struct cache_entry *index;
380         struct cache_entry *head; 
381         struct cache_entry *remote = stages[head_idx + 1];
382         int count;
383         int head_match = 0;
384         int remote_match = 0;
385
386         int df_conflict_head = 0;
387         int df_conflict_remote = 0;
388
389         int any_anc_missing = 0;
390         int i;
391
392         for (i = 1; i < head_idx; i++) {
393                 if (!stages[i])
394                         any_anc_missing = 1;
395         }
396
397         index = stages[0];
398         head = stages[head_idx];
399
400         if (head == &df_conflict_entry) {
401                 df_conflict_head = 1;
402                 head = NULL;
403         }
404
405         if (remote == &df_conflict_entry) {
406                 df_conflict_remote = 1;
407                 remote = NULL;
408         }
409
410         /* First, if there's a #16 situation, note that to prevent #13
411          * and #14. 
412          */
413         if (!same(remote, head)) {
414                 for (i = 1; i < head_idx; i++) {
415                         if (same(stages[i], head)) {
416                                 head_match = i;
417                         }
418                         if (same(stages[i], remote)) {
419                                 remote_match = i;
420                         }
421                 }
422         }
423
424         /* We start with cases where the index is allowed to match
425          * something other than the head: #14(ALT) and #2ALT, where it
426          * is permitted to match the result instead.
427          */
428         /* #14, #14ALT, #2ALT */
429         if (remote && !df_conflict_head && head_match && !remote_match) {
430                 if (index && !same(index, remote) && !same(index, head))
431                         reject_merge(index);
432                 return merged_entry(remote, index);
433         }
434         /*
435          * If we have an entry in the index cache, then we want to
436          * make sure that it matches head.
437          */
438         if (index && !same(index, head)) {
439                 reject_merge(index);
440         }
441
442         if (head) {
443                 /* #5ALT, #15 */
444                 if (same(head, remote))
445                         return merged_entry(head, index);
446                 /* #13, #3ALT */
447                 if (!df_conflict_remote && remote_match && !head_match)
448                         return merged_entry(head, index);
449         }
450
451         /* #1 */
452         if (!head && !remote && any_anc_missing)
453                 return 0;
454
455         /* Below are "no merge" cases, which require that the index be
456          * up-to-date to avoid the files getting overwritten with
457          * conflict resolution files. 
458          */
459         if (index) {
460                 verify_uptodate(index);
461         }
462
463         /* #2, #3, #4, #6, #7, #9, #11. */
464         count = 0;
465         if (!head_match || !remote_match) {
466                 for (i = 1; i < head_idx; i++) {
467                         if (stages[i]) {
468                                 keep_entry(stages[i]);
469                                 count++;
470                                 break;
471                         }
472                 }
473         }
474 #if DBRT_DEBUG
475         else {
476                 fprintf(stderr, "read-tree: warning #16 detected\n");
477                 show_stage_entry(stderr, "head   ", stages[head_match]);
478                 show_stage_entry(stderr, "remote ", stages[remote_match]);
479         }
480 #endif
481         if (head) { count += keep_entry(head); }
482         if (remote) { count += keep_entry(remote); }
483         return count;
484 }
485
486 /*
487  * Two-way merge.
488  *
489  * The rule is to "carry forward" what is in the index without losing
490  * information across a "fast forward", favoring a successful merge
491  * over a merge failure when it makes sense.  For details of the
492  * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
493  *
494  */
495 static int twoway_merge(struct cache_entry **src)
496 {
497         struct cache_entry *current = src[0];
498         struct cache_entry *oldtree = src[1], *newtree = src[2];
499
500         if (merge_size != 2)
501                 return error("Cannot do a twoway merge of %d trees\n",
502                              merge_size);
503
504         if (current) {
505                 if ((!oldtree && !newtree) || /* 4 and 5 */
506                     (!oldtree && newtree &&
507                      same(current, newtree)) || /* 6 and 7 */
508                     (oldtree && newtree &&
509                      same(oldtree, newtree)) || /* 14 and 15 */
510                     (oldtree && newtree &&
511                      !same(oldtree, newtree) && /* 18 and 19*/
512                      same(current, newtree))) {
513                         return keep_entry(current);
514                 }
515                 else if (oldtree && !newtree && same(current, oldtree)) {
516                         /* 10 or 11 */
517                         return deleted_entry(oldtree, current);
518                 }
519                 else if (oldtree && newtree &&
520                          same(current, oldtree) && !same(current, newtree)) {
521                         /* 20 or 21 */
522                         return merged_entry(newtree, current);
523                 }
524                 else {
525                         /* all other failures */
526                         if (oldtree)
527                                 reject_merge(oldtree);
528                         if (current)
529                                 reject_merge(current);
530                         if (newtree)
531                                 reject_merge(newtree);
532                         return -1;
533                 }
534         }
535         else if (newtree)
536                 return merged_entry(newtree, current);
537         else
538                 return deleted_entry(oldtree, current);
539 }
540
541 /*
542  * One-way merge.
543  *
544  * The rule is:
545  * - take the stat information from stage0, take the data from stage1
546  */
547 static int oneway_merge(struct cache_entry **src)
548 {
549         struct cache_entry *old = src[0];
550         struct cache_entry *a = src[1];
551
552         if (merge_size != 1)
553                 return error("Cannot do a oneway merge of %d trees\n",
554                              merge_size);
555
556         if (!a)
557                 return 0;
558         if (old && same(old, a)) {
559                 return keep_entry(old);
560         }
561         return merged_entry(a, NULL);
562 }
563
564 static int read_cache_unmerged(void)
565 {
566         int i, deleted;
567         struct cache_entry **dst;
568
569         read_cache();
570         dst = active_cache;
571         deleted = 0;
572         for (i = 0; i < active_nr; i++) {
573                 struct cache_entry *ce = active_cache[i];
574                 if (ce_stage(ce)) {
575                         deleted++;
576                         continue;
577                 }
578                 if (deleted)
579                         *dst = ce;
580                 dst++;
581         }
582         active_nr -= deleted;
583         return deleted;
584 }
585
586 static const char read_tree_usage[] = "git-read-tree (<sha> | -m [-u | -i] <sha1> [<sha2> [<sha3>]])";
587
588 static struct cache_file cache_file;
589
590 int main(int argc, char **argv)
591 {
592         int i, newfd, reset, stage = 0;
593         unsigned char sha1[20];
594         merge_fn_t fn = NULL;
595
596         newfd = hold_index_file_for_update(&cache_file, get_index_file());
597         if (newfd < 0)
598                 die("unable to create new cachefile");
599
600         merge = 0;
601         reset = 0;
602         for (i = 1; i < argc; i++) {
603                 const char *arg = argv[i];
604
605                 /* "-u" means "update", meaning that a merge will update
606                  * the working tree.
607                  */
608                 if (!strcmp(arg, "-u")) {
609                         update = 1;
610                         continue;
611                 }
612
613                 /* "-i" means "index only", meaning that a merge will
614                  * not even look at the working tree.
615                  */
616                 if (!strcmp(arg, "-i")) {
617                         index_only = 1;
618                         continue;
619                 }
620
621                 /* This differs from "-m" in that we'll silently ignore unmerged entries */
622                 if (!strcmp(arg, "--reset")) {
623                         if (stage || merge)
624                                 usage(read_tree_usage);
625                         reset = 1;
626                         merge = 1;
627                         stage = 1;
628                         read_cache_unmerged();
629                         continue;
630                 }
631
632                 if (!strcmp(arg, "--head")) {
633                         head_idx = stage - 1;
634                         fn = threeway_merge;
635                 }
636
637                 /* "-m" stands for "merge", meaning we start in stage 1 */
638                 if (!strcmp(arg, "-m")) {
639                         if (stage || merge)
640                                 usage(read_tree_usage);
641                         if (read_cache_unmerged())
642                                 die("you need to resolve your current index first");
643                         stage = 1;
644                         merge = 1;
645                         continue;
646                 }
647
648                 /* using -u and -i at the same time makes no sense */
649                 if (1 < index_only + update)
650                         usage(read_tree_usage);
651
652                 if (get_sha1(arg, sha1) < 0)
653                         usage(read_tree_usage);
654                 if (list_tree(sha1) < 0)
655                         die("failed to unpack tree object %s", arg);
656                 stage++;
657         }
658         if (update && !merge)
659                 usage(read_tree_usage);
660         if (merge && !fn) {
661                 if (stage < 2)
662                         die("just how do you expect me to merge %d trees?", stage-1);
663                 switch (stage - 1) {
664                 case 1:
665                         fn = oneway_merge;
666                         break;
667                 case 2:
668                         fn = twoway_merge;
669                         break;
670                 case 3:
671                         fn = threeway_merge;
672                         break;
673                 default:
674                         fn = threeway_merge;
675                         break;
676                 }
677         }
678
679         if (head_idx < 0) {
680                 if (stage - 1 >= 3)
681                         head_idx = stage - 2;
682                 else
683                         head_idx = 1;
684         }
685
686         unpack_trees(fn);
687         if (write_cache(newfd, active_cache, active_nr) ||
688             commit_index_file(&cache_file))
689                 die("unable to write new index file");
690         return 0;
691 }