pack-objects: turn off bitmaps when we split packs
[git.git] / match-trees.c
blobe80b4af354f87caa7a5130660e9c9c530246b8be
1 #include "cache.h"
2 #include "tree.h"
3 #include "tree-walk.h"
5 static int score_missing(unsigned mode, const char *path)
7 int score;
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;
18 static int score_differs(unsigned mode1, unsigned mode2, const char *path)
20 int score;
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;
31 static int score_matches(unsigned mode1, unsigned mode2, const char *path)
33 int score;
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;
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;
50 static void *fill_tree_desc_strict(struct tree_desc *desc,
51 const unsigned char *hash)
53 void *buffer;
54 enum object_type type;
55 unsigned long size;
57 buffer = read_sha1_file(hash, &type, &size);
58 if (!buffer)
59 die("unable to read tree (%s)", sha1_to_hex(hash));
60 if (type != OBJ_TREE)
61 die("%s is not a tree", sha1_to_hex(hash));
62 init_tree_desc(desc, buffer, size);
63 return buffer;
66 static int base_name_entries_compare(const struct name_entry *a,
67 const struct name_entry *b)
69 return base_name_compare(a->path, tree_entry_len(a), a->mode,
70 b->path, tree_entry_len(b), b->mode);
74 * Inspect two trees, and give a score that tells how similar they are.
76 static int score_trees(const unsigned char *hash1, const unsigned char *hash2)
78 struct tree_desc one;
79 struct tree_desc two;
80 void *one_buf = fill_tree_desc_strict(&one, hash1);
81 void *two_buf = fill_tree_desc_strict(&two, hash2);
82 int score = 0;
84 for (;;) {
85 struct name_entry e1, e2;
86 int got_entry_from_one = tree_entry(&one, &e1);
87 int got_entry_from_two = tree_entry(&two, &e2);
88 int cmp;
90 if (got_entry_from_one && got_entry_from_two)
91 cmp = base_name_entries_compare(&e1, &e2);
92 else if (got_entry_from_one)
93 /* two lacks this entry */
94 cmp = -1;
95 else if (got_entry_from_two)
96 /* two has more entries */
97 cmp = 1;
98 else
99 break;
101 if (cmp < 0)
102 /* path1 does not appear in two */
103 score += score_missing(e1.mode, e1.path);
104 else if (cmp > 0)
105 /* path2 does not appear in one */
106 score += score_missing(e2.mode, e2.path);
107 else if (hashcmp(e1.sha1, e2.sha1))
108 /* they are different */
109 score += score_differs(e1.mode, e2.mode, e1.path);
110 else
111 /* same subtree or blob */
112 score += score_matches(e1.mode, e2.mode, e1.path);
114 free(one_buf);
115 free(two_buf);
116 return score;
120 * Match one itself and its subtrees with two and pick the best match.
122 static void match_trees(const unsigned char *hash1,
123 const unsigned char *hash2,
124 int *best_score,
125 char **best_match,
126 const char *base,
127 int recurse_limit)
129 struct tree_desc one;
130 void *one_buf = fill_tree_desc_strict(&one, hash1);
132 while (one.size) {
133 const char *path;
134 const unsigned char *elem;
135 unsigned mode;
136 int score;
138 elem = tree_entry_extract(&one, &path, &mode);
139 if (!S_ISDIR(mode))
140 goto next;
141 score = score_trees(elem, hash2);
142 if (*best_score < score) {
143 char *newpath;
144 newpath = xmalloc(strlen(base) + strlen(path) + 1);
145 sprintf(newpath, "%s%s", base, path);
146 free(*best_match);
147 *best_match = newpath;
148 *best_score = score;
150 if (recurse_limit) {
151 char *newbase;
152 newbase = xmalloc(strlen(base) + strlen(path) + 2);
153 sprintf(newbase, "%s%s/", base, path);
154 match_trees(elem, hash2, best_score, best_match,
155 newbase, recurse_limit - 1);
156 free(newbase);
159 next:
160 update_tree_entry(&one);
162 free(one_buf);
166 * A tree "hash1" has a subdirectory at "prefix". Come up with a
167 * tree object by replacing it with another tree "hash2".
169 static int splice_tree(const unsigned char *hash1,
170 const char *prefix,
171 const unsigned char *hash2,
172 unsigned char *result)
174 char *subpath;
175 int toplen;
176 char *buf;
177 unsigned long sz;
178 struct tree_desc desc;
179 unsigned char *rewrite_here;
180 const unsigned char *rewrite_with;
181 unsigned char subtree[20];
182 enum object_type type;
183 int status;
185 subpath = strchrnul(prefix, '/');
186 toplen = subpath - prefix;
187 if (*subpath)
188 subpath++;
190 buf = read_sha1_file(hash1, &type, &sz);
191 if (!buf)
192 die("cannot read tree %s", sha1_to_hex(hash1));
193 init_tree_desc(&desc, buf, sz);
195 rewrite_here = NULL;
196 while (desc.size) {
197 const char *name;
198 unsigned mode;
199 const unsigned char *sha1;
201 sha1 = tree_entry_extract(&desc, &name, &mode);
202 if (strlen(name) == toplen &&
203 !memcmp(name, prefix, toplen)) {
204 if (!S_ISDIR(mode))
205 die("entry %s in tree %s is not a tree",
206 name, sha1_to_hex(hash1));
207 rewrite_here = (unsigned char *) sha1;
208 break;
210 update_tree_entry(&desc);
212 if (!rewrite_here)
213 die("entry %.*s not found in tree %s",
214 toplen, prefix, sha1_to_hex(hash1));
215 if (*subpath) {
216 status = splice_tree(rewrite_here, subpath, hash2, subtree);
217 if (status)
218 return status;
219 rewrite_with = subtree;
221 else
222 rewrite_with = hash2;
223 hashcpy(rewrite_here, rewrite_with);
224 status = write_sha1_file(buf, sz, tree_type, result);
225 free(buf);
226 return status;
230 * We are trying to come up with a merge between one and two that
231 * results in a tree shape similar to one. The tree two might
232 * correspond to a subtree of one, in which case it needs to be
233 * shifted down by prefixing otherwise empty directories. On the
234 * other hand, it could cover tree one and we might need to pick a
235 * subtree of it.
237 void shift_tree(const unsigned char *hash1,
238 const unsigned char *hash2,
239 unsigned char *shifted,
240 int depth_limit)
242 char *add_prefix;
243 char *del_prefix;
244 int add_score, del_score;
247 * NEEDSWORK: this limits the recursion depth to hardcoded
248 * value '2' to avoid excessive overhead.
250 if (!depth_limit)
251 depth_limit = 2;
253 add_score = del_score = score_trees(hash1, hash2);
254 add_prefix = xcalloc(1, 1);
255 del_prefix = xcalloc(1, 1);
258 * See if one's subtree resembles two; if so we need to prefix
259 * two with a few fake trees to match the prefix.
261 match_trees(hash1, hash2, &add_score, &add_prefix, "", depth_limit);
264 * See if two's subtree resembles one; if so we need to
265 * pick only subtree of two.
267 match_trees(hash2, hash1, &del_score, &del_prefix, "", depth_limit);
269 /* Assume we do not have to do any shifting */
270 hashcpy(shifted, hash2);
272 if (add_score < del_score) {
273 /* We need to pick a subtree of two */
274 unsigned mode;
276 if (!*del_prefix)
277 return;
279 if (get_tree_entry(hash2, del_prefix, shifted, &mode))
280 die("cannot find path %s in tree %s",
281 del_prefix, sha1_to_hex(hash2));
282 return;
285 if (!*add_prefix)
286 return;
288 splice_tree(hash1, add_prefix, hash2, shifted);
292 * The user says the trees will be shifted by this much.
293 * Unfortunately we cannot fundamentally tell which one to
294 * be prefixed, as recursive merge can work in either direction.
296 void shift_tree_by(const unsigned char *hash1,
297 const unsigned char *hash2,
298 unsigned char *shifted,
299 const char *shift_prefix)
301 unsigned char sub1[20], sub2[20];
302 unsigned mode1, mode2;
303 unsigned candidate = 0;
305 /* Can hash2 be a tree at shift_prefix in tree hash1? */
306 if (!get_tree_entry(hash1, shift_prefix, sub1, &mode1) &&
307 S_ISDIR(mode1))
308 candidate |= 1;
310 /* Can hash1 be a tree at shift_prefix in tree hash2? */
311 if (!get_tree_entry(hash2, shift_prefix, sub2, &mode2) &&
312 S_ISDIR(mode2))
313 candidate |= 2;
315 if (candidate == 3) {
316 /* Both are plausible -- we need to evaluate the score */
317 int best_score = score_trees(hash1, hash2);
318 int score;
320 candidate = 0;
321 score = score_trees(sub1, hash2);
322 if (score > best_score) {
323 candidate = 1;
324 best_score = score;
326 score = score_trees(sub2, hash1);
327 if (score > best_score)
328 candidate = 2;
331 if (!candidate) {
332 /* Neither is plausible -- do not shift */
333 hashcpy(shifted, hash2);
334 return;
337 if (candidate == 1)
339 * shift tree2 down by adding shift_prefix above it
340 * to match tree1.
342 splice_tree(hash1, shift_prefix, hash2, shifted);
343 else
345 * shift tree2 up by removing shift_prefix from it
346 * to match tree1.
348 hashcpy(shifted, sub2);