pack-objects: fix comment of reused_chunk.difference
[git] / tree-walk.c
1 #include "cache.h"
2 #include "tree-walk.h"
3 #include "dir.h"
4 #include "object-store.h"
5 #include "tree.h"
6 #include "pathspec.h"
7 #include "json-writer.h"
8
9 static const char *get_mode(const char *str, unsigned int *modep)
10 {
11         unsigned char c;
12         unsigned int mode = 0;
13
14         if (*str == ' ')
15                 return NULL;
16
17         while ((c = *str++) != ' ') {
18                 if (c < '0' || c > '7')
19                         return NULL;
20                 mode = (mode << 3) + (c - '0');
21         }
22         *modep = mode;
23         return str;
24 }
25
26 static int decode_tree_entry(struct tree_desc *desc, const char *buf, unsigned long size, struct strbuf *err)
27 {
28         const char *path;
29         unsigned int mode, len;
30         const unsigned hashsz = the_hash_algo->rawsz;
31
32         if (size < hashsz + 3 || buf[size - (hashsz + 1)]) {
33                 strbuf_addstr(err, _("too-short tree object"));
34                 return -1;
35         }
36
37         path = get_mode(buf, &mode);
38         if (!path) {
39                 strbuf_addstr(err, _("malformed mode in tree entry"));
40                 return -1;
41         }
42         if (!*path) {
43                 strbuf_addstr(err, _("empty filename in tree entry"));
44                 return -1;
45         }
46         len = strlen(path) + 1;
47
48         /* Initialize the descriptor entry */
49         desc->entry.path = path;
50         desc->entry.mode = canon_mode(mode);
51         desc->entry.pathlen = len - 1;
52         hashcpy(desc->entry.oid.hash, (const unsigned char *)path + len);
53
54         return 0;
55 }
56
57 static int init_tree_desc_internal(struct tree_desc *desc, const void *buffer, unsigned long size, struct strbuf *err)
58 {
59         desc->buffer = buffer;
60         desc->size = size;
61         if (size)
62                 return decode_tree_entry(desc, buffer, size, err);
63         return 0;
64 }
65
66 void init_tree_desc(struct tree_desc *desc, const void *buffer, unsigned long size)
67 {
68         struct strbuf err = STRBUF_INIT;
69         if (init_tree_desc_internal(desc, buffer, size, &err))
70                 die("%s", err.buf);
71         strbuf_release(&err);
72 }
73
74 int init_tree_desc_gently(struct tree_desc *desc, const void *buffer, unsigned long size)
75 {
76         struct strbuf err = STRBUF_INIT;
77         int result = init_tree_desc_internal(desc, buffer, size, &err);
78         if (result)
79                 error("%s", err.buf);
80         strbuf_release(&err);
81         return result;
82 }
83
84 void *fill_tree_descriptor(struct repository *r,
85                            struct tree_desc *desc,
86                            const struct object_id *oid)
87 {
88         unsigned long size = 0;
89         void *buf = NULL;
90
91         if (oid) {
92                 buf = read_object_with_reference(r, oid, tree_type, &size, NULL);
93                 if (!buf)
94                         die("unable to read tree %s", oid_to_hex(oid));
95         }
96         init_tree_desc(desc, buf, size);
97         return buf;
98 }
99
100 static void entry_clear(struct name_entry *a)
101 {
102         memset(a, 0, sizeof(*a));
103 }
104
105 static void entry_extract(struct tree_desc *t, struct name_entry *a)
106 {
107         *a = t->entry;
108 }
109
110 static int update_tree_entry_internal(struct tree_desc *desc, struct strbuf *err)
111 {
112         const void *buf = desc->buffer;
113         const unsigned char *end = (const unsigned char *)desc->entry.path + desc->entry.pathlen + 1 + the_hash_algo->rawsz;
114         unsigned long size = desc->size;
115         unsigned long len = end - (const unsigned char *)buf;
116
117         if (size < len)
118                 die(_("too-short tree file"));
119         buf = end;
120         size -= len;
121         desc->buffer = buf;
122         desc->size = size;
123         if (size)
124                 return decode_tree_entry(desc, buf, size, err);
125         return 0;
126 }
127
128 void update_tree_entry(struct tree_desc *desc)
129 {
130         struct strbuf err = STRBUF_INIT;
131         if (update_tree_entry_internal(desc, &err))
132                 die("%s", err.buf);
133         strbuf_release(&err);
134 }
135
136 int update_tree_entry_gently(struct tree_desc *desc)
137 {
138         struct strbuf err = STRBUF_INIT;
139         if (update_tree_entry_internal(desc, &err)) {
140                 error("%s", err.buf);
141                 strbuf_release(&err);
142                 /* Stop processing this tree after error */
143                 desc->size = 0;
144                 return -1;
145         }
146         strbuf_release(&err);
147         return 0;
148 }
149
150 int tree_entry(struct tree_desc *desc, struct name_entry *entry)
151 {
152         if (!desc->size)
153                 return 0;
154
155         *entry = desc->entry;
156         update_tree_entry(desc);
157         return 1;
158 }
159
160 int tree_entry_gently(struct tree_desc *desc, struct name_entry *entry)
161 {
162         if (!desc->size)
163                 return 0;
164
165         *entry = desc->entry;
166         if (update_tree_entry_gently(desc))
167                 return 0;
168         return 1;
169 }
170
171 static int traverse_trees_atexit_registered;
172 static int traverse_trees_count;
173 static int traverse_trees_cur_depth;
174 static int traverse_trees_max_depth;
175
176 static void trace2_traverse_trees_statistics_atexit(void)
177 {
178         struct json_writer jw = JSON_WRITER_INIT;
179
180         jw_object_begin(&jw, 0);
181         jw_object_intmax(&jw, "traverse_trees_count", traverse_trees_count);
182         jw_object_intmax(&jw, "traverse_trees_max_depth", traverse_trees_max_depth);
183         jw_end(&jw);
184
185         trace2_data_json("traverse_trees", the_repository, "statistics", &jw);
186
187         jw_release(&jw);
188 }
189
190 void setup_traverse_info(struct traverse_info *info, const char *base)
191 {
192         size_t pathlen = strlen(base);
193         static struct traverse_info dummy;
194
195         memset(info, 0, sizeof(*info));
196         if (pathlen && base[pathlen-1] == '/')
197                 pathlen--;
198         info->pathlen = pathlen ? pathlen + 1 : 0;
199         info->name = base;
200         info->namelen = pathlen;
201         if (pathlen)
202                 info->prev = &dummy;
203
204         if (trace2_is_enabled() && !traverse_trees_atexit_registered) {
205                 atexit(trace2_traverse_trees_statistics_atexit);
206                 traverse_trees_atexit_registered = 1;
207         }
208 }
209
210 char *make_traverse_path(char *path, size_t pathlen,
211                          const struct traverse_info *info,
212                          const char *name, size_t namelen)
213 {
214         /* Always points to the end of the name we're about to add */
215         size_t pos = st_add(info->pathlen, namelen);
216
217         if (pos >= pathlen)
218                 BUG("too small buffer passed to make_traverse_path");
219
220         path[pos] = 0;
221         for (;;) {
222                 if (pos < namelen)
223                         BUG("traverse_info pathlen does not match strings");
224                 pos -= namelen;
225                 memcpy(path + pos, name, namelen);
226
227                 if (!pos)
228                         break;
229                 path[--pos] = '/';
230
231                 if (!info)
232                         BUG("traverse_info ran out of list items");
233                 name = info->name;
234                 namelen = info->namelen;
235                 info = info->prev;
236         }
237         return path;
238 }
239
240 void strbuf_make_traverse_path(struct strbuf *out,
241                                const struct traverse_info *info,
242                                const char *name, size_t namelen)
243 {
244         size_t len = traverse_path_len(info, namelen);
245
246         strbuf_grow(out, len);
247         make_traverse_path(out->buf + out->len, out->alloc - out->len,
248                            info, name, namelen);
249         strbuf_setlen(out, out->len + len);
250 }
251
252 struct tree_desc_skip {
253         struct tree_desc_skip *prev;
254         const void *ptr;
255 };
256
257 struct tree_desc_x {
258         struct tree_desc d;
259         struct tree_desc_skip *skip;
260 };
261
262 static int check_entry_match(const char *a, int a_len, const char *b, int b_len)
263 {
264         /*
265          * The caller wants to pick *a* from a tree or nothing.
266          * We are looking at *b* in a tree.
267          *
268          * (0) If a and b are the same name, we are trivially happy.
269          *
270          * There are three possibilities where *a* could be hiding
271          * behind *b*.
272          *
273          * (1) *a* == "t",   *b* == "ab"  i.e. *b* sorts earlier than *a* no
274          *                                matter what.
275          * (2) *a* == "t",   *b* == "t-2" and "t" is a subtree in the tree;
276          * (3) *a* == "t-2", *b* == "t"   and "t-2" is a blob in the tree.
277          *
278          * Otherwise we know *a* won't appear in the tree without
279          * scanning further.
280          */
281
282         int cmp = name_compare(a, a_len, b, b_len);
283
284         /* Most common case first -- reading sync'd trees */
285         if (!cmp)
286                 return cmp;
287
288         if (0 < cmp) {
289                 /* a comes after b; it does not matter if it is case (3)
290                 if (b_len < a_len && !memcmp(a, b, b_len) && a[b_len] < '/')
291                         return 1;
292                 */
293                 return 1; /* keep looking */
294         }
295
296         /* b comes after a; are we looking at case (2)? */
297         if (a_len < b_len && !memcmp(a, b, a_len) && b[a_len] < '/')
298                 return 1; /* keep looking */
299
300         return -1; /* a cannot appear in the tree */
301 }
302
303 /*
304  * From the extended tree_desc, extract the first name entry, while
305  * paying attention to the candidate "first" name.  Most importantly,
306  * when looking for an entry, if there are entries that sorts earlier
307  * in the tree object representation than that name, skip them and
308  * process the named entry first.  We will remember that we haven't
309  * processed the first entry yet, and in the later call skip the
310  * entry we processed early when update_extended_entry() is called.
311  *
312  * E.g. if the underlying tree object has these entries:
313  *
314  *    blob    "t-1"
315  *    blob    "t-2"
316  *    tree    "t"
317  *    blob    "t=1"
318  *
319  * and the "first" asks for "t", remember that we still need to
320  * process "t-1" and "t-2" but extract "t".  After processing the
321  * entry "t" from this call, the caller will let us know by calling
322  * update_extended_entry() that we can remember "t" has been processed
323  * already.
324  */
325
326 static void extended_entry_extract(struct tree_desc_x *t,
327                                    struct name_entry *a,
328                                    const char *first,
329                                    int first_len)
330 {
331         const char *path;
332         int len;
333         struct tree_desc probe;
334         struct tree_desc_skip *skip;
335
336         /*
337          * Extract the first entry from the tree_desc, but skip the
338          * ones that we already returned in earlier rounds.
339          */
340         while (1) {
341                 if (!t->d.size) {
342                         entry_clear(a);
343                         break; /* not found */
344                 }
345                 entry_extract(&t->d, a);
346                 for (skip = t->skip; skip; skip = skip->prev)
347                         if (a->path == skip->ptr)
348                                 break; /* found */
349                 if (!skip)
350                         break;
351                 /* We have processed this entry already. */
352                 update_tree_entry(&t->d);
353         }
354
355         if (!first || !a->path)
356                 return;
357
358         /*
359          * The caller wants "first" from this tree, or nothing.
360          */
361         path = a->path;
362         len = tree_entry_len(a);
363         switch (check_entry_match(first, first_len, path, len)) {
364         case -1:
365                 entry_clear(a);
366         case 0:
367                 return;
368         default:
369                 break;
370         }
371
372         /*
373          * We need to look-ahead -- we suspect that a subtree whose
374          * name is "first" may be hiding behind the current entry "path".
375          */
376         probe = t->d;
377         while (probe.size) {
378                 entry_extract(&probe, a);
379                 path = a->path;
380                 len = tree_entry_len(a);
381                 switch (check_entry_match(first, first_len, path, len)) {
382                 case -1:
383                         entry_clear(a);
384                 case 0:
385                         return;
386                 default:
387                         update_tree_entry(&probe);
388                         break;
389                 }
390                 /* keep looking */
391         }
392         entry_clear(a);
393 }
394
395 static void update_extended_entry(struct tree_desc_x *t, struct name_entry *a)
396 {
397         if (t->d.entry.path == a->path) {
398                 update_tree_entry(&t->d);
399         } else {
400                 /* we have returned this entry early */
401                 struct tree_desc_skip *skip = xmalloc(sizeof(*skip));
402                 skip->ptr = a->path;
403                 skip->prev = t->skip;
404                 t->skip = skip;
405         }
406 }
407
408 static void free_extended_entry(struct tree_desc_x *t)
409 {
410         struct tree_desc_skip *p, *s;
411
412         for (s = t->skip; s; s = p) {
413                 p = s->prev;
414                 free(s);
415         }
416 }
417
418 static inline int prune_traversal(struct index_state *istate,
419                                   struct name_entry *e,
420                                   struct traverse_info *info,
421                                   struct strbuf *base,
422                                   int still_interesting)
423 {
424         if (!info->pathspec || still_interesting == 2)
425                 return 2;
426         if (still_interesting < 0)
427                 return still_interesting;
428         return tree_entry_interesting(istate, e, base,
429                                       0, info->pathspec);
430 }
431
432 int traverse_trees(struct index_state *istate,
433                    int n, struct tree_desc *t,
434                    struct traverse_info *info)
435 {
436         int error = 0;
437         struct name_entry entry[MAX_TRAVERSE_TREES];
438         int i;
439         struct tree_desc_x tx[ARRAY_SIZE(entry)];
440         struct strbuf base = STRBUF_INIT;
441         int interesting = 1;
442         char *traverse_path;
443
444         traverse_trees_count++;
445         traverse_trees_cur_depth++;
446
447         if (traverse_trees_cur_depth > traverse_trees_max_depth)
448                 traverse_trees_max_depth = traverse_trees_cur_depth;
449
450         if (n >= ARRAY_SIZE(entry))
451                 BUG("traverse_trees() called with too many trees (%d)", n);
452
453         for (i = 0; i < n; i++) {
454                 tx[i].d = t[i];
455                 tx[i].skip = NULL;
456         }
457
458         if (info->prev) {
459                 strbuf_make_traverse_path(&base, info->prev,
460                                           info->name, info->namelen);
461                 strbuf_addch(&base, '/');
462                 traverse_path = xstrndup(base.buf, base.len);
463         } else {
464                 traverse_path = xstrndup(info->name, info->pathlen);
465         }
466         info->traverse_path = traverse_path;
467         for (;;) {
468                 int trees_used;
469                 unsigned long mask, dirmask;
470                 const char *first = NULL;
471                 int first_len = 0;
472                 struct name_entry *e = NULL;
473                 int len;
474
475                 for (i = 0; i < n; i++) {
476                         e = entry + i;
477                         extended_entry_extract(tx + i, e, NULL, 0);
478                 }
479
480                 /*
481                  * A tree may have "t-2" at the current location even
482                  * though it may have "t" that is a subtree behind it,
483                  * and another tree may return "t".  We want to grab
484                  * all "t" from all trees to match in such a case.
485                  */
486                 for (i = 0; i < n; i++) {
487                         e = entry + i;
488                         if (!e->path)
489                                 continue;
490                         len = tree_entry_len(e);
491                         if (!first) {
492                                 first = e->path;
493                                 first_len = len;
494                                 continue;
495                         }
496                         if (name_compare(e->path, len, first, first_len) < 0) {
497                                 first = e->path;
498                                 first_len = len;
499                         }
500                 }
501
502                 if (first) {
503                         for (i = 0; i < n; i++) {
504                                 e = entry + i;
505                                 extended_entry_extract(tx + i, e, first, first_len);
506                                 /* Cull the ones that are not the earliest */
507                                 if (!e->path)
508                                         continue;
509                                 len = tree_entry_len(e);
510                                 if (name_compare(e->path, len, first, first_len))
511                                         entry_clear(e);
512                         }
513                 }
514
515                 /* Now we have in entry[i] the earliest name from the trees */
516                 mask = 0;
517                 dirmask = 0;
518                 for (i = 0; i < n; i++) {
519                         if (!entry[i].path)
520                                 continue;
521                         mask |= 1ul << i;
522                         if (S_ISDIR(entry[i].mode))
523                                 dirmask |= 1ul << i;
524                         e = &entry[i];
525                 }
526                 if (!mask)
527                         break;
528                 interesting = prune_traversal(istate, e, info, &base, interesting);
529                 if (interesting < 0)
530                         break;
531                 if (interesting) {
532                         trees_used = info->fn(n, mask, dirmask, entry, info);
533                         if (trees_used < 0) {
534                                 error = trees_used;
535                                 if (!info->show_all_errors)
536                                         break;
537                         }
538                         mask &= trees_used;
539                 }
540                 for (i = 0; i < n; i++)
541                         if (mask & (1ul << i))
542                                 update_extended_entry(tx + i, entry + i);
543         }
544         for (i = 0; i < n; i++)
545                 free_extended_entry(tx + i);
546         free(traverse_path);
547         info->traverse_path = NULL;
548         strbuf_release(&base);
549
550         traverse_trees_cur_depth--;
551         return error;
552 }
553
554 struct dir_state {
555         void *tree;
556         unsigned long size;
557         struct object_id oid;
558 };
559
560 static int find_tree_entry(struct repository *r, struct tree_desc *t,
561                            const char *name, struct object_id *result,
562                            unsigned short *mode)
563 {
564         int namelen = strlen(name);
565         while (t->size) {
566                 const char *entry;
567                 struct object_id oid;
568                 int entrylen, cmp;
569
570                 oidcpy(&oid, tree_entry_extract(t, &entry, mode));
571                 entrylen = tree_entry_len(&t->entry);
572                 update_tree_entry(t);
573                 if (entrylen > namelen)
574                         continue;
575                 cmp = memcmp(name, entry, entrylen);
576                 if (cmp > 0)
577                         continue;
578                 if (cmp < 0)
579                         break;
580                 if (entrylen == namelen) {
581                         oidcpy(result, &oid);
582                         return 0;
583                 }
584                 if (name[entrylen] != '/')
585                         continue;
586                 if (!S_ISDIR(*mode))
587                         break;
588                 if (++entrylen == namelen) {
589                         oidcpy(result, &oid);
590                         return 0;
591                 }
592                 return get_tree_entry(r, &oid, name + entrylen, result, mode);
593         }
594         return -1;
595 }
596
597 int get_tree_entry(struct repository *r,
598                    const struct object_id *tree_oid,
599                    const char *name,
600                    struct object_id *oid,
601                    unsigned short *mode)
602 {
603         int retval;
604         void *tree;
605         unsigned long size;
606         struct object_id root;
607
608         tree = read_object_with_reference(r, tree_oid, tree_type, &size, &root);
609         if (!tree)
610                 return -1;
611
612         if (name[0] == '\0') {
613                 oidcpy(oid, &root);
614                 free(tree);
615                 return 0;
616         }
617
618         if (!size) {
619                 retval = -1;
620         } else {
621                 struct tree_desc t;
622                 init_tree_desc(&t, tree, size);
623                 retval = find_tree_entry(r, &t, name, oid, mode);
624         }
625         free(tree);
626         return retval;
627 }
628
629 /*
630  * This is Linux's built-in max for the number of symlinks to follow.
631  * That limit, of course, does not affect git, but it's a reasonable
632  * choice.
633  */
634 #define GET_TREE_ENTRY_FOLLOW_SYMLINKS_MAX_LINKS 40
635
636 /**
637  * Find a tree entry by following symlinks in tree_sha (which is
638  * assumed to be the root of the repository).  In the event that a
639  * symlink points outside the repository (e.g. a link to /foo or a
640  * root-level link to ../foo), the portion of the link which is
641  * outside the repository will be returned in result_path, and *mode
642  * will be set to 0.  It is assumed that result_path is uninitialized.
643  * If there are no symlinks, or the end result of the symlink chain
644  * points to an object inside the repository, result will be filled in
645  * with the sha1 of the found object, and *mode will hold the mode of
646  * the object.
647  *
648  * See the code for enum get_oid_result for a description of
649  * the return values.
650  */
651 enum get_oid_result get_tree_entry_follow_symlinks(struct repository *r,
652                 struct object_id *tree_oid, const char *name,
653                 struct object_id *result, struct strbuf *result_path,
654                 unsigned short *mode)
655 {
656         int retval = MISSING_OBJECT;
657         struct dir_state *parents = NULL;
658         size_t parents_alloc = 0;
659         size_t i, parents_nr = 0;
660         struct object_id current_tree_oid;
661         struct strbuf namebuf = STRBUF_INIT;
662         struct tree_desc t;
663         int follows_remaining = GET_TREE_ENTRY_FOLLOW_SYMLINKS_MAX_LINKS;
664
665         init_tree_desc(&t, NULL, 0UL);
666         strbuf_addstr(&namebuf, name);
667         oidcpy(&current_tree_oid, tree_oid);
668
669         while (1) {
670                 int find_result;
671                 char *first_slash;
672                 char *remainder = NULL;
673
674                 if (!t.buffer) {
675                         void *tree;
676                         struct object_id root;
677                         unsigned long size;
678                         tree = read_object_with_reference(r,
679                                                           &current_tree_oid,
680                                                           tree_type, &size,
681                                                           &root);
682                         if (!tree)
683                                 goto done;
684
685                         ALLOC_GROW(parents, parents_nr + 1, parents_alloc);
686                         parents[parents_nr].tree = tree;
687                         parents[parents_nr].size = size;
688                         oidcpy(&parents[parents_nr].oid, &root);
689                         parents_nr++;
690
691                         if (namebuf.buf[0] == '\0') {
692                                 oidcpy(result, &root);
693                                 retval = FOUND;
694                                 goto done;
695                         }
696
697                         if (!size)
698                                 goto done;
699
700                         /* descend */
701                         init_tree_desc(&t, tree, size);
702                 }
703
704                 /* Handle symlinks to e.g. a//b by removing leading slashes */
705                 while (namebuf.buf[0] == '/') {
706                         strbuf_remove(&namebuf, 0, 1);
707                 }
708
709                 /* Split namebuf into a first component and a remainder */
710                 if ((first_slash = strchr(namebuf.buf, '/'))) {
711                         *first_slash = 0;
712                         remainder = first_slash + 1;
713                 }
714
715                 if (!strcmp(namebuf.buf, "..")) {
716                         struct dir_state *parent;
717                         /*
718                          * We could end up with .. in the namebuf if it
719                          * appears in a symlink.
720                          */
721
722                         if (parents_nr == 1) {
723                                 if (remainder)
724                                         *first_slash = '/';
725                                 strbuf_add(result_path, namebuf.buf,
726                                            namebuf.len);
727                                 *mode = 0;
728                                 retval = FOUND;
729                                 goto done;
730                         }
731                         parent = &parents[parents_nr - 1];
732                         free(parent->tree);
733                         parents_nr--;
734                         parent = &parents[parents_nr - 1];
735                         init_tree_desc(&t, parent->tree, parent->size);
736                         strbuf_remove(&namebuf, 0, remainder ? 3 : 2);
737                         continue;
738                 }
739
740                 /* We could end up here via a symlink to dir/.. */
741                 if (namebuf.buf[0] == '\0') {
742                         oidcpy(result, &parents[parents_nr - 1].oid);
743                         retval = FOUND;
744                         goto done;
745                 }
746
747                 /* Look up the first (or only) path component in the tree. */
748                 find_result = find_tree_entry(r, &t, namebuf.buf,
749                                               &current_tree_oid, mode);
750                 if (find_result) {
751                         goto done;
752                 }
753
754                 if (S_ISDIR(*mode)) {
755                         if (!remainder) {
756                                 oidcpy(result, &current_tree_oid);
757                                 retval = FOUND;
758                                 goto done;
759                         }
760                         /* Descend the tree */
761                         t.buffer = NULL;
762                         strbuf_remove(&namebuf, 0,
763                                       1 + first_slash - namebuf.buf);
764                 } else if (S_ISREG(*mode)) {
765                         if (!remainder) {
766                                 oidcpy(result, &current_tree_oid);
767                                 retval = FOUND;
768                         } else {
769                                 retval = NOT_DIR;
770                         }
771                         goto done;
772                 } else if (S_ISLNK(*mode)) {
773                         /* Follow a symlink */
774                         unsigned long link_len;
775                         size_t len;
776                         char *contents, *contents_start;
777                         struct dir_state *parent;
778                         enum object_type type;
779
780                         if (follows_remaining-- == 0) {
781                                 /* Too many symlinks followed */
782                                 retval = SYMLINK_LOOP;
783                                 goto done;
784                         }
785
786                         /*
787                          * At this point, we have followed at a least
788                          * one symlink, so on error we need to report this.
789                          */
790                         retval = DANGLING_SYMLINK;
791
792                         contents = repo_read_object_file(r,
793                                                     &current_tree_oid, &type,
794                                                     &link_len);
795
796                         if (!contents)
797                                 goto done;
798
799                         if (contents[0] == '/') {
800                                 strbuf_addstr(result_path, contents);
801                                 free(contents);
802                                 *mode = 0;
803                                 retval = FOUND;
804                                 goto done;
805                         }
806
807                         if (remainder)
808                                 len = first_slash - namebuf.buf;
809                         else
810                                 len = namebuf.len;
811
812                         contents_start = contents;
813
814                         parent = &parents[parents_nr - 1];
815                         init_tree_desc(&t, parent->tree, parent->size);
816                         strbuf_splice(&namebuf, 0, len,
817                                       contents_start, link_len);
818                         if (remainder)
819                                 namebuf.buf[link_len] = '/';
820                         free(contents);
821                 }
822         }
823 done:
824         for (i = 0; i < parents_nr; i++)
825                 free(parents[i].tree);
826         free(parents);
827
828         strbuf_release(&namebuf);
829         return retval;
830 }
831
832 static int match_entry(const struct pathspec_item *item,
833                        const struct name_entry *entry, int pathlen,
834                        const char *match, int matchlen,
835                        enum interesting *never_interesting)
836 {
837         int m = -1; /* signals that we haven't called strncmp() */
838
839         if (item->magic & PATHSPEC_ICASE)
840                 /*
841                  * "Never interesting" trick requires exact
842                  * matching. We could do something clever with inexact
843                  * matching, but it's trickier (and not to forget that
844                  * strcasecmp is locale-dependent, at least in
845                  * glibc). Just disable it for now. It can't be worse
846                  * than the wildcard's codepath of '[Tt][Hi][Is][Ss]'
847                  * pattern.
848                  */
849                 *never_interesting = entry_not_interesting;
850         else if (*never_interesting != entry_not_interesting) {
851                 /*
852                  * We have not seen any match that sorts later
853                  * than the current path.
854                  */
855
856                 /*
857                  * Does match sort strictly earlier than path
858                  * with their common parts?
859                  */
860                 m = strncmp(match, entry->path,
861                             (matchlen < pathlen) ? matchlen : pathlen);
862                 if (m < 0)
863                         return 0;
864
865                 /*
866                  * If we come here even once, that means there is at
867                  * least one pathspec that would sort equal to or
868                  * later than the path we are currently looking at.
869                  * In other words, if we have never reached this point
870                  * after iterating all pathspecs, it means all
871                  * pathspecs are either outside of base, or inside the
872                  * base but sorts strictly earlier than the current
873                  * one.  In either case, they will never match the
874                  * subsequent entries.  In such a case, we initialized
875                  * the variable to -1 and that is what will be
876                  * returned, allowing the caller to terminate early.
877                  */
878                 *never_interesting = entry_not_interesting;
879         }
880
881         if (pathlen > matchlen)
882                 return 0;
883
884         if (matchlen > pathlen) {
885                 if (match[pathlen] != '/')
886                         return 0;
887                 /*
888                  * Reject non-directories as partial pathnames, except
889                  * when match is a submodule with a trailing slash and
890                  * nothing else (to handle 'submod/' and 'submod'
891                  * uniformly).
892                  */
893                 if (!S_ISDIR(entry->mode) &&
894                     (!S_ISGITLINK(entry->mode) || matchlen > pathlen + 1))
895                         return 0;
896         }
897
898         if (m == -1)
899                 /*
900                  * we cheated and did not do strncmp(), so we do
901                  * that here.
902                  */
903                 m = ps_strncmp(item, match, entry->path, pathlen);
904
905         /*
906          * If common part matched earlier then it is a hit,
907          * because we rejected the case where path is not a
908          * leading directory and is shorter than match.
909          */
910         if (!m)
911                 /*
912                  * match_entry does not check if the prefix part is
913                  * matched case-sensitively. If the entry is a
914                  * directory and part of prefix, it'll be rematched
915                  * eventually by basecmp with special treatment for
916                  * the prefix.
917                  */
918                 return 1;
919
920         return 0;
921 }
922
923 /* :(icase)-aware string compare */
924 static int basecmp(const struct pathspec_item *item,
925                    const char *base, const char *match, int len)
926 {
927         if (item->magic & PATHSPEC_ICASE) {
928                 int ret, n = len > item->prefix ? item->prefix : len;
929                 ret = strncmp(base, match, n);
930                 if (ret)
931                         return ret;
932                 base += n;
933                 match += n;
934                 len -= n;
935         }
936         return ps_strncmp(item, base, match, len);
937 }
938
939 static int match_dir_prefix(const struct pathspec_item *item,
940                             const char *base,
941                             const char *match, int matchlen)
942 {
943         if (basecmp(item, base, match, matchlen))
944                 return 0;
945
946         /*
947          * If the base is a subdirectory of a path which
948          * was specified, all of them are interesting.
949          */
950         if (!matchlen ||
951             base[matchlen] == '/' ||
952             match[matchlen - 1] == '/')
953                 return 1;
954
955         /* Just a random prefix match */
956         return 0;
957 }
958
959 /*
960  * Perform matching on the leading non-wildcard part of
961  * pathspec. item->nowildcard_len must be greater than zero. Return
962  * non-zero if base is matched.
963  */
964 static int match_wildcard_base(const struct pathspec_item *item,
965                                const char *base, int baselen,
966                                int *matched)
967 {
968         const char *match = item->match;
969         /* the wildcard part is not considered in this function */
970         int matchlen = item->nowildcard_len;
971
972         if (baselen) {
973                 int dirlen;
974                 /*
975                  * Return early if base is longer than the
976                  * non-wildcard part but it does not match.
977                  */
978                 if (baselen >= matchlen) {
979                         *matched = matchlen;
980                         return !basecmp(item, base, match, matchlen);
981                 }
982
983                 dirlen = matchlen;
984                 while (dirlen && match[dirlen - 1] != '/')
985                         dirlen--;
986
987                 /*
988                  * Return early if base is shorter than the
989                  * non-wildcard part but it does not match. Note that
990                  * base ends with '/' so we are sure it really matches
991                  * directory
992                  */
993                 if (basecmp(item, base, match, baselen))
994                         return 0;
995                 *matched = baselen;
996         } else
997                 *matched = 0;
998         /*
999          * we could have checked entry against the non-wildcard part
1000          * that is not in base and does similar never_interesting
1001          * optimization as in match_entry. For now just be happy with
1002          * base comparison.
1003          */
1004         return entry_interesting;
1005 }
1006
1007 /*
1008  * Is a tree entry interesting given the pathspec we have?
1009  *
1010  * Pre-condition: either baselen == base_offset (i.e. empty path)
1011  * or base[baselen-1] == '/' (i.e. with trailing slash).
1012  */
1013 static enum interesting do_match(struct index_state *istate,
1014                                  const struct name_entry *entry,
1015                                  struct strbuf *base, int base_offset,
1016                                  const struct pathspec *ps,
1017                                  int exclude)
1018 {
1019         int i;
1020         int pathlen, baselen = base->len - base_offset;
1021         enum interesting never_interesting = ps->has_wildcard ?
1022                 entry_not_interesting : all_entries_not_interesting;
1023
1024         GUARD_PATHSPEC(ps,
1025                        PATHSPEC_FROMTOP |
1026                        PATHSPEC_MAXDEPTH |
1027                        PATHSPEC_LITERAL |
1028                        PATHSPEC_GLOB |
1029                        PATHSPEC_ICASE |
1030                        PATHSPEC_EXCLUDE |
1031                        PATHSPEC_ATTR);
1032
1033         if (!ps->nr) {
1034                 if (!ps->recursive ||
1035                     !(ps->magic & PATHSPEC_MAXDEPTH) ||
1036                     ps->max_depth == -1)
1037                         return all_entries_interesting;
1038                 return within_depth(base->buf + base_offset, baselen,
1039                                     !!S_ISDIR(entry->mode),
1040                                     ps->max_depth) ?
1041                         entry_interesting : entry_not_interesting;
1042         }
1043
1044         pathlen = tree_entry_len(entry);
1045
1046         for (i = ps->nr - 1; i >= 0; i--) {
1047                 const struct pathspec_item *item = ps->items+i;
1048                 const char *match = item->match;
1049                 const char *base_str = base->buf + base_offset;
1050                 int matchlen = item->len, matched = 0;
1051
1052                 if ((!exclude &&   item->magic & PATHSPEC_EXCLUDE) ||
1053                     ( exclude && !(item->magic & PATHSPEC_EXCLUDE)))
1054                         continue;
1055
1056                 if (baselen >= matchlen) {
1057                         /* If it doesn't match, move along... */
1058                         if (!match_dir_prefix(item, base_str, match, matchlen))
1059                                 goto match_wildcards;
1060
1061                         if (!ps->recursive ||
1062                             !(ps->magic & PATHSPEC_MAXDEPTH) ||
1063                             ps->max_depth == -1) {
1064                                 if (!item->attr_match_nr)
1065                                         return all_entries_interesting;
1066                                 else
1067                                         goto interesting;
1068                         }
1069
1070                         if (within_depth(base_str + matchlen + 1,
1071                                          baselen - matchlen - 1,
1072                                          !!S_ISDIR(entry->mode),
1073                                          ps->max_depth))
1074                                 goto interesting;
1075                         else
1076                                 return entry_not_interesting;
1077                 }
1078
1079                 /* Either there must be no base, or the base must match. */
1080                 if (baselen == 0 || !basecmp(item, base_str, match, baselen)) {
1081                         if (match_entry(item, entry, pathlen,
1082                                         match + baselen, matchlen - baselen,
1083                                         &never_interesting))
1084                                 goto interesting;
1085
1086                         if (item->nowildcard_len < item->len) {
1087                                 if (!git_fnmatch(item, match + baselen, entry->path,
1088                                                  item->nowildcard_len - baselen))
1089                                         goto interesting;
1090
1091                                 /*
1092                                  * Match all directories. We'll try to
1093                                  * match files later on.
1094                                  */
1095                                 if (ps->recursive && S_ISDIR(entry->mode))
1096                                         return entry_interesting;
1097
1098                                 /*
1099                                  * When matching against submodules with
1100                                  * wildcard characters, ensure that the entry
1101                                  * at least matches up to the first wild
1102                                  * character.  More accurate matching can then
1103                                  * be performed in the submodule itself.
1104                                  */
1105                                 if (ps->recurse_submodules &&
1106                                     S_ISGITLINK(entry->mode) &&
1107                                     !ps_strncmp(item, match + baselen,
1108                                                 entry->path,
1109                                                 item->nowildcard_len - baselen))
1110                                         goto interesting;
1111                         }
1112
1113                         continue;
1114                 }
1115
1116 match_wildcards:
1117                 if (item->nowildcard_len == item->len)
1118                         continue;
1119
1120                 if (item->nowildcard_len &&
1121                     !match_wildcard_base(item, base_str, baselen, &matched))
1122                         continue;
1123
1124                 /*
1125                  * Concatenate base and entry->path into one and do
1126                  * fnmatch() on it.
1127                  *
1128                  * While we could avoid concatenation in certain cases
1129                  * [1], which saves a memcpy and potentially a
1130                  * realloc, it turns out not worth it. Measurement on
1131                  * linux-2.6 does not show any clear improvements,
1132                  * partly because of the nowildcard_len optimization
1133                  * in git_fnmatch(). Avoid micro-optimizations here.
1134                  *
1135                  * [1] if match_wildcard_base() says the base
1136                  * directory is already matched, we only need to match
1137                  * the rest, which is shorter so _in theory_ faster.
1138                  */
1139
1140                 strbuf_add(base, entry->path, pathlen);
1141
1142                 if (!git_fnmatch(item, match, base->buf + base_offset,
1143                                  item->nowildcard_len)) {
1144                         strbuf_setlen(base, base_offset + baselen);
1145                         goto interesting;
1146                 }
1147
1148                 /*
1149                  * When matching against submodules with
1150                  * wildcard characters, ensure that the entry
1151                  * at least matches up to the first wild
1152                  * character.  More accurate matching can then
1153                  * be performed in the submodule itself.
1154                  */
1155                 if (ps->recurse_submodules && S_ISGITLINK(entry->mode) &&
1156                     !ps_strncmp(item, match, base->buf + base_offset,
1157                                 item->nowildcard_len)) {
1158                         strbuf_setlen(base, base_offset + baselen);
1159                         goto interesting;
1160                 }
1161
1162                 strbuf_setlen(base, base_offset + baselen);
1163
1164                 /*
1165                  * Match all directories. We'll try to match files
1166                  * later on.
1167                  * max_depth is ignored but we may consider support it
1168                  * in future, see
1169                  * https://lore.kernel.org/git/7vmxo5l2g4.fsf@alter.siamese.dyndns.org/
1170                  */
1171                 if (ps->recursive && S_ISDIR(entry->mode))
1172                         return entry_interesting;
1173                 continue;
1174 interesting:
1175                 if (item->attr_match_nr) {
1176                         int ret;
1177
1178                         /*
1179                          * Must not return all_entries_not_interesting
1180                          * prematurely. We do not know if all entries do not
1181                          * match some attributes with current attr API.
1182                          */
1183                         never_interesting = entry_not_interesting;
1184
1185                         /*
1186                          * Consider all directories interesting (because some
1187                          * of those files inside may match some attributes
1188                          * even though the parent dir does not)
1189                          *
1190                          * FIXME: attributes _can_ match directories and we
1191                          * can probably return all_entries_interesting or
1192                          * all_entries_not_interesting here if matched.
1193                          */
1194                         if (S_ISDIR(entry->mode))
1195                                 return entry_interesting;
1196
1197                         strbuf_add(base, entry->path, pathlen);
1198                         ret = match_pathspec_attrs(istate, base->buf + base_offset,
1199                                                    base->len - base_offset, item);
1200                         strbuf_setlen(base, base_offset + baselen);
1201                         if (!ret)
1202                                 continue;
1203                 }
1204                 return entry_interesting;
1205         }
1206         return never_interesting; /* No matches */
1207 }
1208
1209 /*
1210  * Is a tree entry interesting given the pathspec we have?
1211  *
1212  * Pre-condition: either baselen == base_offset (i.e. empty path)
1213  * or base[baselen-1] == '/' (i.e. with trailing slash).
1214  */
1215 enum interesting tree_entry_interesting(struct index_state *istate,
1216                                         const struct name_entry *entry,
1217                                         struct strbuf *base, int base_offset,
1218                                         const struct pathspec *ps)
1219 {
1220         enum interesting positive, negative;
1221         positive = do_match(istate, entry, base, base_offset, ps, 0);
1222
1223         /*
1224          * case | entry | positive | negative | result
1225          * -----+-------+----------+----------+-------
1226          *   1  |  file |   -1     |  -1..2   |  -1
1227          *   2  |  file |    0     |  -1..2   |   0
1228          *   3  |  file |    1     |   -1     |   1
1229          *   4  |  file |    1     |    0     |   1
1230          *   5  |  file |    1     |    1     |   0
1231          *   6  |  file |    1     |    2     |   0
1232          *   7  |  file |    2     |   -1     |   2
1233          *   8  |  file |    2     |    0     |   1
1234          *   9  |  file |    2     |    1     |   0
1235          *  10  |  file |    2     |    2     |  -1
1236          * -----+-------+----------+----------+-------
1237          *  11  |  dir  |   -1     |  -1..2   |  -1
1238          *  12  |  dir  |    0     |  -1..2   |   0
1239          *  13  |  dir  |    1     |   -1     |   1
1240          *  14  |  dir  |    1     |    0     |   1
1241          *  15  |  dir  |    1     |    1     |   1 (*)
1242          *  16  |  dir  |    1     |    2     |   0
1243          *  17  |  dir  |    2     |   -1     |   2
1244          *  18  |  dir  |    2     |    0     |   1
1245          *  19  |  dir  |    2     |    1     |   1 (*)
1246          *  20  |  dir  |    2     |    2     |  -1
1247          *
1248          * (*) An exclude pattern interested in a directory does not
1249          * necessarily mean it will exclude all of the directory. In
1250          * wildcard case, it can't decide until looking at individual
1251          * files inside. So don't write such directories off yet.
1252          */
1253
1254         if (!(ps->magic & PATHSPEC_EXCLUDE) ||
1255             positive <= entry_not_interesting) /* #1, #2, #11, #12 */
1256                 return positive;
1257
1258         negative = do_match(istate, entry, base, base_offset, ps, 1);
1259
1260         /* #8, #18 */
1261         if (positive == all_entries_interesting &&
1262             negative == entry_not_interesting)
1263                 return entry_interesting;
1264
1265         /* #3, #4, #7, #13, #14, #17 */
1266         if (negative <= entry_not_interesting)
1267                 return positive;
1268
1269         /* #15, #19 */
1270         if (S_ISDIR(entry->mode) &&
1271             positive >= entry_interesting &&
1272             negative == entry_interesting)
1273                 return entry_interesting;
1274
1275         if ((positive == entry_interesting &&
1276              negative >= entry_interesting) || /* #5, #6, #16 */
1277             (positive == all_entries_interesting &&
1278              negative == entry_interesting)) /* #9 */
1279                 return entry_not_interesting;
1280
1281         return all_entries_not_interesting; /* #10, #20 */
1282 }