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f345b0a0 JH |
1 | /* |
2 | * Copyright (C) 2005 Junio C Hamano | |
3 | */ | |
4 | #include "cache.h" | |
5 | #include "diff.h" | |
6 | #include "diffcore.h" | |
f345b0a0 | 7 | |
eeaa4603 JH |
8 | static int should_break(struct diff_filespec *src, |
9 | struct diff_filespec *dst, | |
10 | int break_score, | |
11 | int *merge_score_p) | |
f345b0a0 JH |
12 | { |
13 | /* dst is recorded as a modification of src. Are they so | |
14 | * different that we are better off recording this as a pair | |
eeaa4603 | 15 | * of delete and create? |
f345b0a0 | 16 | * |
eeaa4603 JH |
17 | * There are two criteria used in this algorithm. For the |
18 | * purposes of helping later rename/copy, we take both delete | |
19 | * and insert into account and estimate the amount of "edit". | |
20 | * If the edit is very large, we break this pair so that | |
21 | * rename/copy can pick the pieces up to match with other | |
22 | * files. | |
23 | * | |
24 | * On the other hand, we would want to ignore inserts for the | |
25 | * pure "complete rewrite" detection. As long as most of the | |
26 | * existing contents were removed from the file, it is a | |
27 | * complete rewrite, and if sizable chunk from the original | |
28 | * still remains in the result, it is not a rewrite. It does | |
29 | * not matter how much or how little new material is added to | |
30 | * the file. | |
31 | * | |
32 | * The score we leave for such a broken filepair uses the | |
33 | * latter definition so that later clean-up stage can find the | |
34 | * pieces that should not have been broken according to the | |
35 | * latter definition after rename/copy runs, and merge the | |
36 | * broken pair that have a score lower than given criteria | |
37 | * back together. The break operation itself happens | |
38 | * according to the former definition. | |
39 | * | |
40 | * The minimum_edit parameter tells us when to break (the | |
41 | * amount of "edit" required for us to consider breaking the | |
42 | * pair). We leave the amount of deletion in *merge_score_p | |
43 | * when we return. | |
44 | * | |
45 | * The value we return is 1 if we want the pair to be broken, | |
46 | * or 0 if we do not. | |
f345b0a0 | 47 | */ |
355e76a4 | 48 | unsigned long delta_size, base_size, src_copied, literal_added; |
eeaa4603 JH |
49 | int to_break = 0; |
50 | ||
51 | *merge_score_p = 0; /* assume no deletion --- "do not break" | |
52 | * is the default. | |
53 | */ | |
f345b0a0 JH |
54 | |
55 | if (!S_ISREG(src->mode) || !S_ISREG(dst->mode)) | |
56 | return 0; /* leave symlink rename alone */ | |
57 | ||
aeecd23a JH |
58 | if (src->sha1_valid && dst->sha1_valid && |
59 | !memcmp(src->sha1, dst->sha1, 20)) | |
60 | return 0; /* they are the same */ | |
61 | ||
eeaa4603 | 62 | if (diff_populate_filespec(src, 0) || diff_populate_filespec(dst, 0)) |
f345b0a0 JH |
63 | return 0; /* error but caught downstream */ |
64 | ||
f78c79c5 | 65 | base_size = ((src->size < dst->size) ? src->size : dst->size); |
0532a5e4 JH |
66 | if (base_size < MINIMUM_BREAK_SIZE) |
67 | return 0; /* we do not break too small filepair */ | |
f345b0a0 | 68 | |
65416758 JH |
69 | if (diffcore_count_changes(src->data, src->size, |
70 | dst->data, dst->size, | |
71 | 0, | |
72 | &src_copied, &literal_added)) | |
73 | return 0; | |
355e76a4 | 74 | |
eeaa4603 JH |
75 | /* Compute merge-score, which is "how much is removed |
76 | * from the source material". The clean-up stage will | |
77 | * merge the surviving pair together if the score is | |
78 | * less than the minimum, after rename/copy runs. | |
79 | */ | |
80 | if (src->size <= src_copied) | |
f78c79c5 JH |
81 | ; /* all copied, nothing removed */ |
82 | else { | |
eeaa4603 | 83 | delta_size = src->size - src_copied; |
f78c79c5 JH |
84 | *merge_score_p = delta_size * MAX_SCORE / src->size; |
85 | } | |
eeaa4603 JH |
86 | |
87 | /* Extent of damage, which counts both inserts and | |
88 | * deletes. | |
89 | */ | |
90 | if (src->size + literal_added <= src_copied) | |
91 | delta_size = 0; /* avoid wrapping around */ | |
355e76a4 JH |
92 | else |
93 | delta_size = (src->size - src_copied) + literal_added; | |
eeaa4603 JH |
94 | |
95 | /* We break if the edit exceeds the minimum. | |
96 | * i.e. (break_score / MAX_SCORE < delta_size / base_size) | |
97 | */ | |
98 | if (break_score * base_size < delta_size * MAX_SCORE) | |
99 | to_break = 1; | |
f345b0a0 | 100 | |
eeaa4603 | 101 | return to_break; |
f345b0a0 JH |
102 | } |
103 | ||
eeaa4603 | 104 | void diffcore_break(int break_score) |
f345b0a0 JH |
105 | { |
106 | struct diff_queue_struct *q = &diff_queued_diff; | |
107 | struct diff_queue_struct outq; | |
eeaa4603 JH |
108 | |
109 | /* When the filepair has this much edit (insert and delete), | |
110 | * it is first considered to be a rewrite and broken into a | |
111 | * create and delete filepair. This is to help breaking a | |
112 | * file that had too much new stuff added, possibly from | |
113 | * moving contents from another file, so that rename/copy can | |
114 | * match it with the other file. | |
115 | * | |
116 | * int break_score; we reuse incoming parameter for this. | |
117 | */ | |
118 | ||
119 | /* After a pair is broken according to break_score and | |
120 | * subjected to rename/copy, both of them may survive intact, | |
121 | * due to lack of suitable rename/copy peer. Or, the caller | |
122 | * may be calling us without using rename/copy. When that | |
123 | * happens, we merge the broken pieces back into one | |
124 | * modification together if the pair did not have more than | |
125 | * this much delete. For this computation, we do not take | |
126 | * insert into account at all. If you start from a 100-line | |
127 | * file and delete 97 lines of it, it does not matter if you | |
128 | * add 27 lines to it to make a new 30-line file or if you add | |
129 | * 997 lines to it to make a 1000-line file. Either way what | |
130 | * you did was a rewrite of 97%. On the other hand, if you | |
131 | * delete 3 lines, keeping 97 lines intact, it does not matter | |
132 | * if you add 3 lines to it to make a new 100-line file or if | |
133 | * you add 903 lines to it to make a new 1000-line file. | |
134 | * Either way you did a lot of additions and not a rewrite. | |
135 | * This merge happens to catch the latter case. A merge_score | |
136 | * of 80% would be a good default value (a broken pair that | |
137 | * has score lower than merge_score will be merged back | |
138 | * together). | |
139 | */ | |
140 | int merge_score; | |
f345b0a0 JH |
141 | int i; |
142 | ||
eeaa4603 JH |
143 | /* See comment on DEFAULT_BREAK_SCORE and |
144 | * DEFAULT_MERGE_SCORE in diffcore.h | |
145 | */ | |
146 | merge_score = (break_score >> 16) & 0xFFFF; | |
147 | break_score = (break_score & 0xFFFF); | |
148 | ||
149 | if (!break_score) | |
150 | break_score = DEFAULT_BREAK_SCORE; | |
151 | if (!merge_score) | |
152 | merge_score = DEFAULT_MERGE_SCORE; | |
f345b0a0 JH |
153 | |
154 | outq.nr = outq.alloc = 0; | |
155 | outq.queue = NULL; | |
156 | ||
157 | for (i = 0; i < q->nr; i++) { | |
158 | struct diff_filepair *p = q->queue[i]; | |
159 | int score; | |
160 | ||
161 | /* We deal only with in-place edit of non directory. | |
162 | * We do not break anything else. | |
163 | */ | |
164 | if (DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two) && | |
165 | !S_ISDIR(p->one->mode) && !S_ISDIR(p->two->mode) && | |
166 | !strcmp(p->one->path, p->two->path)) { | |
eeaa4603 | 167 | if (should_break(p->one, p->two, |
0532a5e4 | 168 | break_score, &score)) { |
f345b0a0 JH |
169 | /* Split this into delete and create */ |
170 | struct diff_filespec *null_one, *null_two; | |
171 | struct diff_filepair *dp; | |
172 | ||
eeaa4603 JH |
173 | /* Set score to 0 for the pair that |
174 | * needs to be merged back together | |
175 | * should they survive rename/copy. | |
176 | * Also we do not want to break very | |
177 | * small files. | |
178 | */ | |
f78c79c5 | 179 | if (score < merge_score) |
eeaa4603 JH |
180 | score = 0; |
181 | ||
f345b0a0 JH |
182 | /* deletion of one */ |
183 | null_one = alloc_filespec(p->one->path); | |
184 | dp = diff_queue(&outq, p->one, null_one); | |
185 | dp->score = score; | |
186 | dp->broken_pair = 1; | |
187 | ||
188 | /* creation of two */ | |
189 | null_two = alloc_filespec(p->two->path); | |
190 | dp = diff_queue(&outq, null_two, p->two); | |
191 | dp->score = score; | |
192 | dp->broken_pair = 1; | |
193 | ||
194 | free(p); /* not diff_free_filepair(), we are | |
195 | * reusing one and two here. | |
196 | */ | |
197 | continue; | |
198 | } | |
199 | } | |
200 | diff_q(&outq, p); | |
201 | } | |
202 | free(q->queue); | |
203 | *q = outq; | |
204 | ||
205 | return; | |
206 | } | |
eeaa4603 JH |
207 | |
208 | static void merge_broken(struct diff_filepair *p, | |
209 | struct diff_filepair *pp, | |
210 | struct diff_queue_struct *outq) | |
211 | { | |
212 | /* p and pp are broken pairs we want to merge */ | |
366175ef | 213 | struct diff_filepair *c = p, *d = pp, *dp; |
eeaa4603 JH |
214 | if (DIFF_FILE_VALID(p->one)) { |
215 | /* this must be a delete half */ | |
216 | d = p; c = pp; | |
217 | } | |
218 | /* Sanity check */ | |
219 | if (!DIFF_FILE_VALID(d->one)) | |
220 | die("internal error in merge #1"); | |
221 | if (DIFF_FILE_VALID(d->two)) | |
222 | die("internal error in merge #2"); | |
223 | if (DIFF_FILE_VALID(c->one)) | |
224 | die("internal error in merge #3"); | |
225 | if (!DIFF_FILE_VALID(c->two)) | |
226 | die("internal error in merge #4"); | |
227 | ||
366175ef JH |
228 | dp = diff_queue(outq, d->one, c->two); |
229 | dp->score = p->score; | |
19397b45 JH |
230 | diff_free_filespec_data(d->two); |
231 | diff_free_filespec_data(c->one); | |
eeaa4603 JH |
232 | free(d); |
233 | free(c); | |
234 | } | |
235 | ||
236 | void diffcore_merge_broken(void) | |
237 | { | |
238 | struct diff_queue_struct *q = &diff_queued_diff; | |
239 | struct diff_queue_struct outq; | |
240 | int i, j; | |
241 | ||
242 | outq.nr = outq.alloc = 0; | |
243 | outq.queue = NULL; | |
244 | ||
245 | for (i = 0; i < q->nr; i++) { | |
246 | struct diff_filepair *p = q->queue[i]; | |
247 | if (!p) | |
248 | /* we already merged this with its peer */ | |
249 | continue; | |
250 | else if (p->broken_pair && | |
eeaa4603 JH |
251 | !strcmp(p->one->path, p->two->path)) { |
252 | /* If the peer also survived rename/copy, then | |
253 | * we merge them back together. | |
254 | */ | |
255 | for (j = i + 1; j < q->nr; j++) { | |
256 | struct diff_filepair *pp = q->queue[j]; | |
257 | if (pp->broken_pair && | |
eeaa4603 JH |
258 | !strcmp(pp->one->path, pp->two->path) && |
259 | !strcmp(p->one->path, pp->two->path)) { | |
260 | /* Peer survived. Merge them */ | |
261 | merge_broken(p, pp, &outq); | |
262 | q->queue[j] = NULL; | |
263 | break; | |
264 | } | |
265 | } | |
266 | if (q->nr <= j) | |
267 | /* The peer did not survive, so we keep | |
268 | * it in the output. | |
269 | */ | |
270 | diff_q(&outq, p); | |
271 | } | |
272 | else | |
273 | diff_q(&outq, p); | |
274 | } | |
275 | free(q->queue); | |
276 | *q = outq; | |
277 | ||
278 | return; | |
279 | } |