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68faf689 JH |
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, | |
135 | char *base, | |
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, | |
188 | char *prefix, | |
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 | ||
267 | add_score = del_score = score_trees(hash1, hash2); | |
268 | add_prefix = xcalloc(1, 1); | |
269 | del_prefix = xcalloc(1, 1); | |
270 | ||
271 | /* | |
272 | * See if one's subtree resembles two; if so we need to prefix | |
273 | * two with a few fake trees to match the prefix. | |
274 | */ | |
275 | match_trees(hash1, hash2, &add_score, &add_prefix, "", depth_limit); | |
276 | ||
277 | /* | |
278 | * See if two's subtree resembles one; if so we need to | |
279 | * pick only subtree of two. | |
280 | */ | |
281 | match_trees(hash2, hash1, &del_score, &del_prefix, "", depth_limit); | |
282 | ||
283 | /* Assume we do not have to do any shifting */ | |
284 | hashcpy(shifted, hash2); | |
285 | ||
286 | if (add_score < del_score) { | |
287 | /* We need to pick a subtree of two */ | |
288 | unsigned mode; | |
289 | ||
290 | if (!*del_prefix) | |
291 | return; | |
292 | ||
293 | if (get_tree_entry(hash2, del_prefix, shifted, &mode)) | |
294 | die("cannot find path %s in tree %s", | |
295 | del_prefix, sha1_to_hex(hash2)); | |
296 | return; | |
297 | } | |
298 | ||
299 | if (!*add_prefix) | |
300 | return; | |
301 | ||
302 | splice_tree(hash1, add_prefix, hash2, shifted); | |
303 | } | |
304 |