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