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1/*
2 * Copyright (C) 2005 Junio C Hamano
3 */
4#include "cache.h"
5#include "diff.h"
6#include "diffcore.h"
95acf11a 7#include "promisor-remote.h"
f345b0a0 8
b78ea5fc
NTND
9static int should_break(struct repository *r,
10 struct diff_filespec *src,
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11 struct diff_filespec *dst,
12 int break_score,
13 int *merge_score_p)
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14{
15 /* dst is recorded as a modification of src. Are they so
16 * different that we are better off recording this as a pair
eeaa4603 17 * of delete and create?
f345b0a0 18 *
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19 * There are two criteria used in this algorithm. For the
20 * purposes of helping later rename/copy, we take both delete
21 * and insert into account and estimate the amount of "edit".
22 * If the edit is very large, we break this pair so that
23 * rename/copy can pick the pieces up to match with other
24 * files.
25 *
26 * On the other hand, we would want to ignore inserts for the
27 * pure "complete rewrite" detection. As long as most of the
28 * existing contents were removed from the file, it is a
29 * complete rewrite, and if sizable chunk from the original
30 * still remains in the result, it is not a rewrite. It does
31 * not matter how much or how little new material is added to
32 * the file.
33 *
34 * The score we leave for such a broken filepair uses the
35 * latter definition so that later clean-up stage can find the
36 * pieces that should not have been broken according to the
37 * latter definition after rename/copy runs, and merge the
38 * broken pair that have a score lower than given criteria
39 * back together. The break operation itself happens
40 * according to the former definition.
41 *
42 * The minimum_edit parameter tells us when to break (the
43 * amount of "edit" required for us to consider breaking the
44 * pair). We leave the amount of deletion in *merge_score_p
45 * when we return.
46 *
47 * The value we return is 1 if we want the pair to be broken,
48 * or 0 if we do not.
f345b0a0 49 */
eb3a9dd3 50 unsigned long delta_size, max_size;
6dd4b66f 51 unsigned long src_copied, literal_added, src_removed;
eeaa4603 52
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53 struct diff_populate_filespec_options options = { 0 };
54
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55 *merge_score_p = 0; /* assume no deletion --- "do not break"
56 * is the default.
57 */
f345b0a0 58
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59 if (S_ISREG(src->mode) != S_ISREG(dst->mode)) {
60 *merge_score_p = (int)MAX_SCORE;
61 return 1; /* even their types are different */
62 }
f345b0a0 63
41c9560e 64 if (src->oid_valid && dst->oid_valid &&
4a7e27e9 65 oideq(&src->oid, &dst->oid))
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66 return 0; /* they are the same */
67
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68 if (r == the_repository && has_promisor_remote()) {
69 options.missing_object_cb = diff_queued_diff_prefetch;
70 options.missing_object_data = r;
71 }
72
73 if (diff_populate_filespec(r, src, &options) ||
74 diff_populate_filespec(r, dst, &options))
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75 return 0; /* error but caught downstream */
76
6dd4b66f
LT
77 max_size = ((src->size > dst->size) ? src->size : dst->size);
78 if (max_size < MINIMUM_BREAK_SIZE)
0532a5e4 79 return 0; /* we do not break too small filepair */
f345b0a0 80
e7b00c57
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81 if (!src->size)
82 return 0; /* we do not let empty files get renamed */
83
b78ea5fc 84 if (diffcore_count_changes(r, src, dst,
8282de94 85 &src->cnt_data, &dst->cnt_data,
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86 &src_copied, &literal_added))
87 return 0;
355e76a4 88
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89 /* sanity */
90 if (src->size < src_copied)
91 src_copied = src->size;
92 if (dst->size < literal_added + src_copied) {
93 if (src_copied < dst->size)
94 literal_added = dst->size - src_copied;
95 else
96 literal_added = 0;
97 }
98 src_removed = src->size - src_copied;
99
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100 /* Compute merge-score, which is "how much is removed
101 * from the source material". The clean-up stage will
102 * merge the surviving pair together if the score is
103 * less than the minimum, after rename/copy runs.
104 */
dc49cd76 105 *merge_score_p = (int)(src_removed * MAX_SCORE / src->size);
6dd4b66f
LT
106 if (*merge_score_p > break_score)
107 return 1;
4d0f39ce 108
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109 /* Extent of damage, which counts both inserts and
110 * deletes.
111 */
4d0f39ce 112 delta_size = src_removed + literal_added;
6dd4b66f 113 if (delta_size * MAX_SCORE / max_size < break_score)
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114 return 0;
115
116 /* If you removed a lot without adding new material, that is
117 * not really a rewrite.
eeaa4603 118 */
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119 if ((src->size * break_score < src_removed * MAX_SCORE) &&
120 (literal_added * 20 < src_removed) &&
121 (literal_added * 20 < src_copied))
122 return 0;
f345b0a0 123
4d0f39ce 124 return 1;
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125}
126
b78ea5fc 127void diffcore_break(struct repository *r, int break_score)
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128{
129 struct diff_queue_struct *q = &diff_queued_diff;
130 struct diff_queue_struct outq;
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131
132 /* When the filepair has this much edit (insert and delete),
133 * it is first considered to be a rewrite and broken into a
134 * create and delete filepair. This is to help breaking a
135 * file that had too much new stuff added, possibly from
136 * moving contents from another file, so that rename/copy can
137 * match it with the other file.
138 *
139 * int break_score; we reuse incoming parameter for this.
140 */
141
142 /* After a pair is broken according to break_score and
143 * subjected to rename/copy, both of them may survive intact,
144 * due to lack of suitable rename/copy peer. Or, the caller
145 * may be calling us without using rename/copy. When that
146 * happens, we merge the broken pieces back into one
147 * modification together if the pair did not have more than
148 * this much delete. For this computation, we do not take
149 * insert into account at all. If you start from a 100-line
150 * file and delete 97 lines of it, it does not matter if you
151 * add 27 lines to it to make a new 30-line file or if you add
152 * 997 lines to it to make a 1000-line file. Either way what
153 * you did was a rewrite of 97%. On the other hand, if you
154 * delete 3 lines, keeping 97 lines intact, it does not matter
155 * if you add 3 lines to it to make a new 100-line file or if
156 * you add 903 lines to it to make a new 1000-line file.
157 * Either way you did a lot of additions and not a rewrite.
158 * This merge happens to catch the latter case. A merge_score
159 * of 80% would be a good default value (a broken pair that
160 * has score lower than merge_score will be merged back
161 * together).
162 */
163 int merge_score;
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164 int i;
165
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166 /* See comment on DEFAULT_BREAK_SCORE and
167 * DEFAULT_MERGE_SCORE in diffcore.h
168 */
169 merge_score = (break_score >> 16) & 0xFFFF;
170 break_score = (break_score & 0xFFFF);
171
172 if (!break_score)
173 break_score = DEFAULT_BREAK_SCORE;
174 if (!merge_score)
175 merge_score = DEFAULT_MERGE_SCORE;
f345b0a0 176
9ca5df90 177 DIFF_QUEUE_CLEAR(&outq);
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178
179 for (i = 0; i < q->nr; i++) {
180 struct diff_filepair *p = q->queue[i];
181 int score;
182
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183 /*
184 * We deal only with in-place edit of blobs.
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185 * We do not break anything else.
186 */
187 if (DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two) &&
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188 object_type(p->one->mode) == OBJ_BLOB &&
189 object_type(p->two->mode) == OBJ_BLOB &&
f345b0a0 190 !strcmp(p->one->path, p->two->path)) {
b78ea5fc 191 if (should_break(r, p->one, p->two,
0532a5e4 192 break_score, &score)) {
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193 /* Split this into delete and create */
194 struct diff_filespec *null_one, *null_two;
195 struct diff_filepair *dp;
196
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197 /* Set score to 0 for the pair that
198 * needs to be merged back together
199 * should they survive rename/copy.
200 * Also we do not want to break very
201 * small files.
202 */
f78c79c5 203 if (score < merge_score)
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204 score = 0;
205
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206 /* deletion of one */
207 null_one = alloc_filespec(p->one->path);
208 dp = diff_queue(&outq, p->one, null_one);
209 dp->score = score;
210 dp->broken_pair = 1;
211
212 /* creation of two */
213 null_two = alloc_filespec(p->two->path);
214 dp = diff_queue(&outq, null_two, p->two);
215 dp->score = score;
216 dp->broken_pair = 1;
217
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218 diff_free_filespec_blob(p->one);
219 diff_free_filespec_blob(p->two);
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220 free(p); /* not diff_free_filepair(), we are
221 * reusing one and two here.
222 */
223 continue;
224 }
225 }
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226 diff_free_filespec_data(p->one);
227 diff_free_filespec_data(p->two);
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228 diff_q(&outq, p);
229 }
230 free(q->queue);
231 *q = outq;
232
233 return;
234}
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235
236static void merge_broken(struct diff_filepair *p,
237 struct diff_filepair *pp,
238 struct diff_queue_struct *outq)
239{
240 /* p and pp are broken pairs we want to merge */
366175ef 241 struct diff_filepair *c = p, *d = pp, *dp;
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242 if (DIFF_FILE_VALID(p->one)) {
243 /* this must be a delete half */
244 d = p; c = pp;
245 }
246 /* Sanity check */
247 if (!DIFF_FILE_VALID(d->one))
248 die("internal error in merge #1");
249 if (DIFF_FILE_VALID(d->two))
250 die("internal error in merge #2");
251 if (DIFF_FILE_VALID(c->one))
252 die("internal error in merge #3");
253 if (!DIFF_FILE_VALID(c->two))
254 die("internal error in merge #4");
255
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256 dp = diff_queue(outq, d->one, c->two);
257 dp->score = p->score;
6936b585
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258 /*
259 * We will be one extra user of the same src side of the
260 * broken pair, if it was used as the rename source for other
261 * paths elsewhere. Increment to mark that the path stays
262 * in the resulting tree.
263 */
264 d->one->rename_used++;
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265 diff_free_filespec_data(d->two);
266 diff_free_filespec_data(c->one);
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267 free(d);
268 free(c);
269}
270
271void diffcore_merge_broken(void)
272{
273 struct diff_queue_struct *q = &diff_queued_diff;
274 struct diff_queue_struct outq;
275 int i, j;
276
9ca5df90 277 DIFF_QUEUE_CLEAR(&outq);
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278
279 for (i = 0; i < q->nr; i++) {
280 struct diff_filepair *p = q->queue[i];
281 if (!p)
282 /* we already merged this with its peer */
283 continue;
284 else if (p->broken_pair &&
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285 !strcmp(p->one->path, p->two->path)) {
286 /* If the peer also survived rename/copy, then
287 * we merge them back together.
288 */
289 for (j = i + 1; j < q->nr; j++) {
290 struct diff_filepair *pp = q->queue[j];
291 if (pp->broken_pair &&
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292 !strcmp(pp->one->path, pp->two->path) &&
293 !strcmp(p->one->path, pp->two->path)) {
294 /* Peer survived. Merge them */
295 merge_broken(p, pp, &outq);
296 q->queue[j] = NULL;
baed6bbb 297 goto next;
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298 }
299 }
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AH
300 /* The peer did not survive, so we keep
301 * it in the output.
302 */
303 diff_q(&outq, p);
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304 }
305 else
306 diff_q(&outq, p);
baed6bbb 307next:;
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308 }
309 free(q->queue);
310 *q = outq;
311
312 return;
313}