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