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100644 370 lines (331 sloc) 8.9 kb
68faf689 » Junio C Hamano
2007-02-15 A new merge stragety 'subtree'.
1 #include "cache.h"
2 #include "tree.h"
3 #include "tree-walk.h"
4
5 static int score_missing(unsigned mode, const char *path)
6 {
7 int score;
8
9 if (S_ISDIR(mode))
10 score = -1000;
11 else if (S_ISLNK(mode))
12 score = -500;
13 else
14 score = -50;
15 return score;
16 }
17
18 static int score_differs(unsigned mode1, unsigned mode2, const char *path)
19 {
20 int score;
21
22 if (S_ISDIR(mode1) != S_ISDIR(mode2))
23 score = -100;
24 else if (S_ISLNK(mode1) != S_ISLNK(mode2))
25 score = -50;
26 else
27 score = -5;
28 return score;
29 }
30
31 static int score_matches(unsigned mode1, unsigned mode2, const char *path)
32 {
33 int score;
34
35 /* Heh, we found SHA-1 collisions between different kind of objects */
36 if (S_ISDIR(mode1) != S_ISDIR(mode2))
37 score = -100;
38 else if (S_ISLNK(mode1) != S_ISLNK(mode2))
39 score = -50;
40
41 else if (S_ISDIR(mode1))
42 score = 1000;
43 else if (S_ISLNK(mode1))
44 score = 500;
45 else
46 score = 250;
47 return score;
48 }
49
50 /*
51 * Inspect two trees, and give a score that tells how similar they are.
52 */
53 static int score_trees(const unsigned char *hash1, const unsigned char *hash2)
54 {
55 struct tree_desc one;
56 struct tree_desc two;
57 void *one_buf, *two_buf;
58 int score = 0;
59 enum object_type type;
60 unsigned long size;
61
62 one_buf = read_sha1_file(hash1, &type, &size);
63 if (!one_buf)
64 die("unable to read tree (%s)", sha1_to_hex(hash1));
65 if (type != OBJ_TREE)
66 die("%s is not a tree", sha1_to_hex(hash1));
67 init_tree_desc(&one, one_buf, size);
68 two_buf = read_sha1_file(hash2, &type, &size);
69 if (!two_buf)
70 die("unable to read tree (%s)", sha1_to_hex(hash2));
71 if (type != OBJ_TREE)
72 die("%s is not a tree", sha1_to_hex(hash2));
73 init_tree_desc(&two, two_buf, size);
74 while (one.size | two.size) {
75 const unsigned char *elem1 = elem1;
76 const unsigned char *elem2 = elem2;
77 const char *path1 = path1;
78 const char *path2 = path2;
79 unsigned mode1 = mode1;
80 unsigned mode2 = mode2;
81 int cmp;
82
83 if (one.size)
84 elem1 = tree_entry_extract(&one, &path1, &mode1);
85 if (two.size)
86 elem2 = tree_entry_extract(&two, &path2, &mode2);
87
88 if (!one.size) {
89 /* two has more entries */
90 score += score_missing(mode2, path2);
91 update_tree_entry(&two);
92 continue;
93 }
94 if (!two.size) {
95 /* two lacks this entry */
96 score += score_missing(mode1, path1);
97 update_tree_entry(&one);
98 continue;
99 }
100 cmp = base_name_compare(path1, strlen(path1), mode1,
101 path2, strlen(path2), mode2);
102 if (cmp < 0) {
103 /* path1 does not appear in two */
104 score += score_missing(mode1, path1);
105 update_tree_entry(&one);
106 continue;
107 }
108 else if (cmp > 0) {
109 /* path2 does not appear in one */
110 score += score_missing(mode2, path2);
111 update_tree_entry(&two);
112 continue;
113 }
114 else if (hashcmp(elem1, elem2))
115 /* they are different */
116 score += score_differs(mode1, mode2, path1);
117 else
118 /* same subtree or blob */
119 score += score_matches(mode1, mode2, path1);
120 update_tree_entry(&one);
121 update_tree_entry(&two);
122 }
123 free(one_buf);
124 free(two_buf);
125 return score;
126 }
127
128 /*
129 * Match one itself and its subtrees with two and pick the best match.
130 */
131 static void match_trees(const unsigned char *hash1,
132 const unsigned char *hash2,
133 int *best_score,
134 char **best_match,
538dfe73 » spearce
2007-10-21 Improved const correctness for strings
135 const char *base,
68faf689 » Junio C Hamano
2007-02-15 A new merge stragety 'subtree'.
136 int recurse_limit)
137 {
138 struct tree_desc one;
139 void *one_buf;
140 enum object_type type;
141 unsigned long size;
142
143 one_buf = read_sha1_file(hash1, &type, &size);
144 if (!one_buf)
145 die("unable to read tree (%s)", sha1_to_hex(hash1));
146 if (type != OBJ_TREE)
147 die("%s is not a tree", sha1_to_hex(hash1));
148 init_tree_desc(&one, one_buf, size);
149
150 while (one.size) {
151 const char *path;
152 const unsigned char *elem;
153 unsigned mode;
154 int score;
155
156 elem = tree_entry_extract(&one, &path, &mode);
157 if (!S_ISDIR(mode))
158 goto next;
159 score = score_trees(elem, hash2);
160 if (*best_score < score) {
161 char *newpath;
162 newpath = xmalloc(strlen(base) + strlen(path) + 1);
163 sprintf(newpath, "%s%s", base, path);
164 free(*best_match);
165 *best_match = newpath;
166 *best_score = score;
167 }
168 if (recurse_limit) {
169 char *newbase;
170 newbase = xmalloc(strlen(base) + strlen(path) + 2);
171 sprintf(newbase, "%s%s/", base, path);
172 match_trees(elem, hash2, best_score, best_match,
173 newbase, recurse_limit - 1);
174 free(newbase);
175 }
176
177 next:
178 update_tree_entry(&one);
179 }
180 free(one_buf);
181 }
182
183 /*
184 * A tree "hash1" has a subdirectory at "prefix". Come up with a
185 * tree object by replacing it with another tree "hash2".
186 */
187 static int splice_tree(const unsigned char *hash1,
85e51b78 »
2008-06-30 Make "subtree" part more orthogonal to the rest of merge-recursive.
188 const char *prefix,
68faf689 » Junio C Hamano
2007-02-15 A new merge stragety 'subtree'.
189 const unsigned char *hash2,
190 unsigned char *result)
191 {
192 char *subpath;
193 int toplen;
194 char *buf;
195 unsigned long sz;
196 struct tree_desc desc;
197 unsigned char *rewrite_here;
198 const unsigned char *rewrite_with;
199 unsigned char subtree[20];
200 enum object_type type;
201 int status;
202
203 subpath = strchr(prefix, '/');
204 if (!subpath)
205 toplen = strlen(prefix);
206 else {
207 toplen = subpath - prefix;
208 subpath++;
209 }
210
211 buf = read_sha1_file(hash1, &type, &sz);
212 if (!buf)
213 die("cannot read tree %s", sha1_to_hex(hash1));
214 init_tree_desc(&desc, buf, sz);
215
216 rewrite_here = NULL;
217 while (desc.size) {
218 const char *name;
219 unsigned mode;
220 const unsigned char *sha1;
221
222 sha1 = tree_entry_extract(&desc, &name, &mode);
223 if (strlen(name) == toplen &&
224 !memcmp(name, prefix, toplen)) {
225 if (!S_ISDIR(mode))
226 die("entry %s in tree %s is not a tree",
227 name, sha1_to_hex(hash1));
228 rewrite_here = (unsigned char *) sha1;
229 break;
230 }
231 update_tree_entry(&desc);
232 }
233 if (!rewrite_here)
234 die("entry %.*s not found in tree %s",
235 toplen, prefix, sha1_to_hex(hash1));
236 if (subpath) {
237 status = splice_tree(rewrite_here, subpath, hash2, subtree);
238 if (status)
239 return status;
240 rewrite_with = subtree;
241 }
242 else
243 rewrite_with = hash2;
244 hashcpy(rewrite_here, rewrite_with);
245 status = write_sha1_file(buf, sz, tree_type, result);
246 free(buf);
247 return status;
248 }
249
250 /*
251 * We are trying to come up with a merge between one and two that
252 * results in a tree shape similar to one. The tree two might
253 * correspond to a subtree of one, in which case it needs to be
254 * shifted down by prefixing otherwise empty directories. On the
255 * other hand, it could cover tree one and we might need to pick a
256 * subtree of it.
257 */
258 void shift_tree(const unsigned char *hash1,
259 const unsigned char *hash2,
260 unsigned char *shifted,
261 int depth_limit)
262 {
263 char *add_prefix;
264 char *del_prefix;
265 int add_score, del_score;
266
85e51b78 »
2008-06-30 Make "subtree" part more orthogonal to the rest of merge-recursive.
267 /*
268 * NEEDSWORK: this limits the recursion depth to hardcoded
269 * value '2' to avoid excessive overhead.
270 */
271 if (!depth_limit)
272 depth_limit = 2;
273
68faf689 » Junio C Hamano
2007-02-15 A new merge stragety 'subtree'.
274 add_score = del_score = score_trees(hash1, hash2);
275 add_prefix = xcalloc(1, 1);
276 del_prefix = xcalloc(1, 1);
277
278 /*
279 * See if one's subtree resembles two; if so we need to prefix
280 * two with a few fake trees to match the prefix.
281 */
282 match_trees(hash1, hash2, &add_score, &add_prefix, "", depth_limit);
283
284 /*
285 * See if two's subtree resembles one; if so we need to
286 * pick only subtree of two.
287 */
288 match_trees(hash2, hash1, &del_score, &del_prefix, "", depth_limit);
289
290 /* Assume we do not have to do any shifting */
291 hashcpy(shifted, hash2);
292
293 if (add_score < del_score) {
294 /* We need to pick a subtree of two */
295 unsigned mode;
296
297 if (!*del_prefix)
298 return;
299
300 if (get_tree_entry(hash2, del_prefix, shifted, &mode))
301 die("cannot find path %s in tree %s",
302 del_prefix, sha1_to_hex(hash2));
303 return;
304 }
305
306 if (!*add_prefix)
307 return;
308
309 splice_tree(hash1, add_prefix, hash2, shifted);
310 }
85e51b78 »
2008-06-30 Make "subtree" part more orthogonal to the rest of merge-recursive.
311
312 /*
313 * The user says the trees will be shifted by this much.
314 * Unfortunately we cannot fundamentally tell which one to
315 * be prefixed, as recursive merge can work in either direction.
316 */
317 void shift_tree_by(const unsigned char *hash1,
318 const unsigned char *hash2,
319 unsigned char *shifted,
320 const char *shift_prefix)
321 {
322 unsigned char sub1[20], sub2[20];
323 unsigned mode1, mode2;
324 unsigned candidate = 0;
325
326 /* Can hash2 be a tree at shift_prefix in tree hash1? */
327 if (!get_tree_entry(hash1, shift_prefix, sub1, &mode1) &&
328 S_ISDIR(mode1))
329 candidate |= 1;
330
331 /* Can hash1 be a tree at shift_prefix in tree hash2? */
332 if (!get_tree_entry(hash2, shift_prefix, sub2, &mode2) &&
333 S_ISDIR(mode2))
334 candidate |= 2;
335
336 if (candidate == 3) {
337 /* Both are plausible -- we need to evaluate the score */
338 int best_score = score_trees(hash1, hash2);
339 int score;
340
341 candidate = 0;
342 score = score_trees(sub1, hash2);
343 if (score > best_score) {
344 candidate = 1;
345 best_score = score;
346 }
347 score = score_trees(sub2, hash1);
348 if (score > best_score)
349 candidate = 2;
350 }
351
352 if (!candidate) {
353 /* Neither is plausible -- do not shift */
354 hashcpy(shifted, hash2);
355 return;
356 }
357
358 if (candidate == 1)
359 /*
360 * shift tree2 down by adding shift_prefix above it
361 * to match tree1.
362 */
363 splice_tree(hash1, shift_prefix, hash2, shifted);
364 else
365 /*
366 * shift tree2 up by removing shift_prefix from it
367 * to match tree1.
368 */
369 hashcpy(shifted, sub2);
370 }
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