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