Merge branch 'maint'
[git] / tree-diff.c
1 /*
2  * Helper functions for tree diff generation
3  */
4 #include "cache.h"
5 #include "diff.h"
6 #include "diffcore.h"
7 #include "tree.h"
8
9 static char *malloc_base(const char *base, int baselen, const char *path, int pathlen)
10 {
11         char *newbase = xmalloc(baselen + pathlen + 2);
12         memcpy(newbase, base, baselen);
13         memcpy(newbase + baselen, path, pathlen);
14         memcpy(newbase + baselen + pathlen, "/", 2);
15         return newbase;
16 }
17
18 static char *malloc_fullname(const char *base, int baselen, const char *path, int pathlen)
19 {
20         char *fullname = xmalloc(baselen + pathlen + 1);
21         memcpy(fullname, base, baselen);
22         memcpy(fullname + baselen, path, pathlen);
23         fullname[baselen + pathlen] = 0;
24         return fullname;
25 }
26
27 static void show_entry(struct diff_options *opt, const char *prefix, struct tree_desc *desc,
28                        const char *base, int baselen);
29
30 static int compare_tree_entry(struct tree_desc *t1, struct tree_desc *t2, const char *base, int baselen, struct diff_options *opt)
31 {
32         unsigned mode1, mode2;
33         const char *path1, *path2;
34         const unsigned char *sha1, *sha2;
35         int cmp, pathlen1, pathlen2;
36         char *fullname;
37
38         sha1 = tree_entry_extract(t1, &path1, &mode1);
39         sha2 = tree_entry_extract(t2, &path2, &mode2);
40
41         pathlen1 = tree_entry_len(path1, sha1);
42         pathlen2 = tree_entry_len(path2, sha2);
43         cmp = base_name_compare(path1, pathlen1, mode1, path2, pathlen2, mode2);
44         if (cmp < 0) {
45                 show_entry(opt, "-", t1, base, baselen);
46                 return -1;
47         }
48         if (cmp > 0) {
49                 show_entry(opt, "+", t2, base, baselen);
50                 return 1;
51         }
52         if (!DIFF_OPT_TST(opt, FIND_COPIES_HARDER) && !hashcmp(sha1, sha2) && mode1 == mode2)
53                 return 0;
54
55         /*
56          * If the filemode has changed to/from a directory from/to a regular
57          * file, we need to consider it a remove and an add.
58          */
59         if (S_ISDIR(mode1) != S_ISDIR(mode2)) {
60                 show_entry(opt, "-", t1, base, baselen);
61                 show_entry(opt, "+", t2, base, baselen);
62                 return 0;
63         }
64
65         if (DIFF_OPT_TST(opt, RECURSIVE) && S_ISDIR(mode1)) {
66                 int retval;
67                 char *newbase = malloc_base(base, baselen, path1, pathlen1);
68                 if (DIFF_OPT_TST(opt, TREE_IN_RECURSIVE)) {
69                         newbase[baselen + pathlen1] = 0;
70                         opt->change(opt, mode1, mode2,
71                                     sha1, sha2, newbase, 0, 0);
72                         newbase[baselen + pathlen1] = '/';
73                 }
74                 retval = diff_tree_sha1(sha1, sha2, newbase, opt);
75                 free(newbase);
76                 return retval;
77         }
78
79         fullname = malloc_fullname(base, baselen, path1, pathlen1);
80         opt->change(opt, mode1, mode2, sha1, sha2, fullname, 0, 0);
81         free(fullname);
82         return 0;
83 }
84
85 /*
86  * Is a tree entry interesting given the pathspec we have?
87  *
88  * Pre-condition: baselen == 0 || base[baselen-1] == '/'
89  *
90  * Return:
91  *  - 2 for "yes, and all subsequent entries will be"
92  *  - 1 for yes
93  *  - zero for no
94  *  - negative for "no, and no subsequent entries will be either"
95  */
96 static int tree_entry_interesting(struct tree_desc *desc, const char *base, int baselen, struct diff_options *opt)
97 {
98         const char *path;
99         const unsigned char *sha1;
100         unsigned mode;
101         int i;
102         int pathlen;
103         int never_interesting = -1;
104
105         if (!opt->nr_paths)
106                 return 2;
107
108         sha1 = tree_entry_extract(desc, &path, &mode);
109
110         pathlen = tree_entry_len(path, sha1);
111
112         for (i = 0; i < opt->nr_paths; i++) {
113                 const char *match = opt->paths[i];
114                 int matchlen = opt->pathlens[i];
115                 int m = -1; /* signals that we haven't called strncmp() */
116
117                 if (baselen >= matchlen) {
118                         /* If it doesn't match, move along... */
119                         if (strncmp(base, match, matchlen))
120                                 continue;
121
122                         /*
123                          * If the base is a subdirectory of a path which
124                          * was specified, all of them are interesting.
125                          */
126                         if (!matchlen ||
127                             base[matchlen] == '/' ||
128                             match[matchlen - 1] == '/')
129                                 return 2;
130
131                         /* Just a random prefix match */
132                         continue;
133                 }
134
135                 /* Does the base match? */
136                 if (strncmp(base, match, baselen))
137                         continue;
138
139                 match += baselen;
140                 matchlen -= baselen;
141
142                 if (never_interesting) {
143                         /*
144                          * We have not seen any match that sorts later
145                          * than the current path.
146                          */
147
148                         /*
149                          * Does match sort strictly earlier than path
150                          * with their common parts?
151                          */
152                         m = strncmp(match, path,
153                                     (matchlen < pathlen) ? matchlen : pathlen);
154                         if (m < 0)
155                                 continue;
156
157                         /*
158                          * If we come here even once, that means there is at
159                          * least one pathspec that would sort equal to or
160                          * later than the path we are currently looking at.
161                          * In other words, if we have never reached this point
162                          * after iterating all pathspecs, it means all
163                          * pathspecs are either outside of base, or inside the
164                          * base but sorts strictly earlier than the current
165                          * one.  In either case, they will never match the
166                          * subsequent entries.  In such a case, we initialized
167                          * the variable to -1 and that is what will be
168                          * returned, allowing the caller to terminate early.
169                          */
170                         never_interesting = 0;
171                 }
172
173                 if (pathlen > matchlen)
174                         continue;
175
176                 if (matchlen > pathlen) {
177                         if (match[pathlen] != '/')
178                                 continue;
179                         if (!S_ISDIR(mode))
180                                 continue;
181                 }
182
183                 if (m == -1)
184                         /*
185                          * we cheated and did not do strncmp(), so we do
186                          * that here.
187                          */
188                         m = strncmp(match, path, pathlen);
189
190                 /*
191                  * If common part matched earlier then it is a hit,
192                  * because we rejected the case where path is not a
193                  * leading directory and is shorter than match.
194                  */
195                 if (!m)
196                         return 1;
197         }
198         return never_interesting; /* No matches */
199 }
200
201 /* A whole sub-tree went away or appeared */
202 static void show_tree(struct diff_options *opt, const char *prefix, struct tree_desc *desc, const char *base, int baselen)
203 {
204         int all_interesting = 0;
205         while (desc->size) {
206                 int show;
207
208                 if (all_interesting)
209                         show = 1;
210                 else {
211                         show = tree_entry_interesting(desc, base, baselen,
212                                                       opt);
213                         if (show == 2)
214                                 all_interesting = 1;
215                 }
216                 if (show < 0)
217                         break;
218                 if (show)
219                         show_entry(opt, prefix, desc, base, baselen);
220                 update_tree_entry(desc);
221         }
222 }
223
224 /* A file entry went away or appeared */
225 static void show_entry(struct diff_options *opt, const char *prefix, struct tree_desc *desc,
226                        const char *base, int baselen)
227 {
228         unsigned mode;
229         const char *path;
230         const unsigned char *sha1 = tree_entry_extract(desc, &path, &mode);
231         int pathlen = tree_entry_len(path, sha1);
232
233         if (DIFF_OPT_TST(opt, RECURSIVE) && S_ISDIR(mode)) {
234                 enum object_type type;
235                 char *newbase = malloc_base(base, baselen, path, pathlen);
236                 struct tree_desc inner;
237                 void *tree;
238                 unsigned long size;
239
240                 tree = read_sha1_file(sha1, &type, &size);
241                 if (!tree || type != OBJ_TREE)
242                         die("corrupt tree sha %s", sha1_to_hex(sha1));
243
244                 if (DIFF_OPT_TST(opt, TREE_IN_RECURSIVE)) {
245                         newbase[baselen + pathlen] = 0;
246                         opt->add_remove(opt, *prefix, mode, sha1, newbase, 0);
247                         newbase[baselen + pathlen] = '/';
248                 }
249
250                 init_tree_desc(&inner, tree, size);
251                 show_tree(opt, prefix, &inner, newbase, baselen + 1 + pathlen);
252
253                 free(tree);
254                 free(newbase);
255         } else {
256                 char *fullname = malloc_fullname(base, baselen, path, pathlen);
257                 opt->add_remove(opt, prefix[0], mode, sha1, fullname, 0);
258                 free(fullname);
259         }
260 }
261
262 static void skip_uninteresting(struct tree_desc *t, const char *base, int baselen, struct diff_options *opt, int *all_interesting)
263 {
264         while (t->size) {
265                 int show = tree_entry_interesting(t, base, baselen, opt);
266                 if (show == 2)
267                         *all_interesting = 1;
268                 if (!show) {
269                         update_tree_entry(t);
270                         continue;
271                 }
272                 /* Skip it all? */
273                 if (show < 0)
274                         t->size = 0;
275                 return;
276         }
277 }
278
279 int diff_tree(struct tree_desc *t1, struct tree_desc *t2, const char *base, struct diff_options *opt)
280 {
281         int baselen = strlen(base);
282         int all_t1_interesting = 0;
283         int all_t2_interesting = 0;
284
285         for (;;) {
286                 if (DIFF_OPT_TST(opt, QUICK) &&
287                     DIFF_OPT_TST(opt, HAS_CHANGES))
288                         break;
289                 if (opt->nr_paths) {
290                         if (!all_t1_interesting)
291                                 skip_uninteresting(t1, base, baselen, opt,
292                                                    &all_t1_interesting);
293                         if (!all_t2_interesting)
294                                 skip_uninteresting(t2, base, baselen, opt,
295                                                    &all_t2_interesting);
296                 }
297                 if (!t1->size) {
298                         if (!t2->size)
299                                 break;
300                         show_entry(opt, "+", t2, base, baselen);
301                         update_tree_entry(t2);
302                         continue;
303                 }
304                 if (!t2->size) {
305                         show_entry(opt, "-", t1, base, baselen);
306                         update_tree_entry(t1);
307                         continue;
308                 }
309                 switch (compare_tree_entry(t1, t2, base, baselen, opt)) {
310                 case -1:
311                         update_tree_entry(t1);
312                         continue;
313                 case 0:
314                         update_tree_entry(t1);
315                         /* Fallthrough */
316                 case 1:
317                         update_tree_entry(t2);
318                         continue;
319                 }
320                 die("git diff-tree: internal error");
321         }
322         return 0;
323 }
324
325 /*
326  * Does it look like the resulting diff might be due to a rename?
327  *  - single entry
328  *  - not a valid previous file
329  */
330 static inline int diff_might_be_rename(void)
331 {
332         return diff_queued_diff.nr == 1 &&
333                 !DIFF_FILE_VALID(diff_queued_diff.queue[0]->one);
334 }
335
336 static void try_to_follow_renames(struct tree_desc *t1, struct tree_desc *t2, const char *base, struct diff_options *opt)
337 {
338         struct diff_options diff_opts;
339         struct diff_queue_struct *q = &diff_queued_diff;
340         struct diff_filepair *choice;
341         const char *paths[1];
342         int i;
343
344         /* Remove the file creation entry from the diff queue, and remember it */
345         choice = q->queue[0];
346         q->nr = 0;
347
348         diff_setup(&diff_opts);
349         DIFF_OPT_SET(&diff_opts, RECURSIVE);
350         DIFF_OPT_SET(&diff_opts, FIND_COPIES_HARDER);
351         diff_opts.output_format = DIFF_FORMAT_NO_OUTPUT;
352         diff_opts.single_follow = opt->paths[0];
353         diff_opts.break_opt = opt->break_opt;
354         paths[0] = NULL;
355         diff_tree_setup_paths(paths, &diff_opts);
356         if (diff_setup_done(&diff_opts) < 0)
357                 die("unable to set up diff options to follow renames");
358         diff_tree(t1, t2, base, &diff_opts);
359         diffcore_std(&diff_opts);
360         diff_tree_release_paths(&diff_opts);
361
362         /* Go through the new set of filepairing, and see if we find a more interesting one */
363         opt->found_follow = 0;
364         for (i = 0; i < q->nr; i++) {
365                 struct diff_filepair *p = q->queue[i];
366
367                 /*
368                  * Found a source? Not only do we use that for the new
369                  * diff_queued_diff, we will also use that as the path in
370                  * the future!
371                  */
372                 if ((p->status == 'R' || p->status == 'C') && !strcmp(p->two->path, opt->paths[0])) {
373                         /* Switch the file-pairs around */
374                         q->queue[i] = choice;
375                         choice = p;
376
377                         /* Update the path we use from now on.. */
378                         diff_tree_release_paths(opt);
379                         opt->paths[0] = xstrdup(p->one->path);
380                         diff_tree_setup_paths(opt->paths, opt);
381
382                         /*
383                          * The caller expects us to return a set of vanilla
384                          * filepairs to let a later call to diffcore_std()
385                          * it makes to sort the renames out (among other
386                          * things), but we already have found renames
387                          * ourselves; signal diffcore_std() not to muck with
388                          * rename information.
389                          */
390                         opt->found_follow = 1;
391                         break;
392                 }
393         }
394
395         /*
396          * Then, discard all the non-relevant file pairs...
397          */
398         for (i = 0; i < q->nr; i++) {
399                 struct diff_filepair *p = q->queue[i];
400                 diff_free_filepair(p);
401         }
402
403         /*
404          * .. and re-instate the one we want (which might be either the
405          * original one, or the rename/copy we found)
406          */
407         q->queue[0] = choice;
408         q->nr = 1;
409 }
410
411 int diff_tree_sha1(const unsigned char *old, const unsigned char *new, const char *base, struct diff_options *opt)
412 {
413         void *tree1, *tree2;
414         struct tree_desc t1, t2;
415         unsigned long size1, size2;
416         int retval;
417
418         tree1 = read_object_with_reference(old, tree_type, &size1, NULL);
419         if (!tree1)
420                 die("unable to read source tree (%s)", sha1_to_hex(old));
421         tree2 = read_object_with_reference(new, tree_type, &size2, NULL);
422         if (!tree2)
423                 die("unable to read destination tree (%s)", sha1_to_hex(new));
424         init_tree_desc(&t1, tree1, size1);
425         init_tree_desc(&t2, tree2, size2);
426         retval = diff_tree(&t1, &t2, base, opt);
427         if (!*base && DIFF_OPT_TST(opt, FOLLOW_RENAMES) && diff_might_be_rename()) {
428                 init_tree_desc(&t1, tree1, size1);
429                 init_tree_desc(&t2, tree2, size2);
430                 try_to_follow_renames(&t1, &t2, base, opt);
431         }
432         free(tree1);
433         free(tree2);
434         return retval;
435 }
436
437 int diff_root_tree_sha1(const unsigned char *new, const char *base, struct diff_options *opt)
438 {
439         int retval;
440         void *tree;
441         unsigned long size;
442         struct tree_desc empty, real;
443
444         tree = read_object_with_reference(new, tree_type, &size, NULL);
445         if (!tree)
446                 die("unable to read root tree (%s)", sha1_to_hex(new));
447         init_tree_desc(&real, tree, size);
448
449         init_tree_desc(&empty, "", 0);
450         retval = diff_tree(&empty, &real, base, opt);
451         free(tree);
452         return retval;
453 }
454
455 static int count_paths(const char **paths)
456 {
457         int i = 0;
458         while (*paths++)
459                 i++;
460         return i;
461 }
462
463 void diff_tree_release_paths(struct diff_options *opt)
464 {
465         free(opt->pathlens);
466 }
467
468 void diff_tree_setup_paths(const char **p, struct diff_options *opt)
469 {
470         opt->nr_paths = 0;
471         opt->pathlens = NULL;
472         opt->paths = NULL;
473
474         if (p) {
475                 int i;
476
477                 opt->paths = p;
478                 opt->nr_paths = count_paths(p);
479                 if (opt->nr_paths == 0) {
480                         opt->pathlens = NULL;
481                         return;
482                 }
483                 opt->pathlens = xmalloc(opt->nr_paths * sizeof(int));
484                 for (i=0; i < opt->nr_paths; i++)
485                         opt->pathlens[i] = strlen(p[i]);
486         }
487 }