summaryrefslogtreecommitdiff
path: root/diffcore-rename.c
blob: 6a52699f732c76540d71ce1500bd8d838ee8a265 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
/*
 * Copyright (C) 2005 Junio C Hamano
 */
#include "cache.h"
#include "diff.h"
#include "diffcore.h"
#include "delta.h"
#include "count-delta.h"

/* Table of rename/copy destinations */

static struct diff_rename_dst {
	struct diff_filespec *two;
	struct diff_filepair *pair;
} *rename_dst;
static int rename_dst_nr, rename_dst_alloc;

static struct diff_rename_dst *locate_rename_dst(struct diff_filespec *two,
						 int insert_ok)
{
	int first, last;

	first = 0;
	last = rename_dst_nr;
	while (last > first) {
		int next = (last + first) >> 1;
		struct diff_rename_dst *dst = &(rename_dst[next]);
		int cmp = strcmp(two->path, dst->two->path);
		if (!cmp)
			return dst;
		if (cmp < 0) {
			last = next;
			continue;
		}
		first = next+1;
	}
	/* not found */
	if (!insert_ok)
		return NULL;
	/* insert to make it at "first" */
	if (rename_dst_alloc <= rename_dst_nr) {
		rename_dst_alloc = alloc_nr(rename_dst_alloc);
		rename_dst = xrealloc(rename_dst,
				      rename_dst_alloc * sizeof(*rename_dst));
	}
	rename_dst_nr++;
	if (first < rename_dst_nr)
		memmove(rename_dst + first + 1, rename_dst + first,
			(rename_dst_nr - first - 1) * sizeof(*rename_dst));
	rename_dst[first].two = two;
	rename_dst[first].pair = NULL;
	return &(rename_dst[first]);
}

/* Table of rename/copy src files */
static struct diff_rename_src {
	struct diff_filespec *one;
	unsigned src_stays : 1;
} *rename_src;
static int rename_src_nr, rename_src_alloc;

static struct diff_rename_src *register_rename_src(struct diff_filespec *one,
						   int src_stays)
{
	int first, last;

	first = 0;
	last = rename_src_nr;
	while (last > first) {
		int next = (last + first) >> 1;
		struct diff_rename_src *src = &(rename_src[next]);
		int cmp = strcmp(one->path, src->one->path);
		if (!cmp)
			return src;
		if (cmp < 0) {
			last = next;
			continue;
		}
		first = next+1;
	}

	/* insert to make it at "first" */
	if (rename_src_alloc <= rename_src_nr) {
		rename_src_alloc = alloc_nr(rename_src_alloc);
		rename_src = xrealloc(rename_src,
				      rename_src_alloc * sizeof(*rename_src));
	}
	rename_src_nr++;
	if (first < rename_src_nr)
		memmove(rename_src + first + 1, rename_src + first,
			(rename_src_nr - first - 1) * sizeof(*rename_src));
	rename_src[first].one = one;
	rename_src[first].src_stays = src_stays;
	return &(rename_src[first]);
}

static int is_exact_match(struct diff_filespec *src, struct diff_filespec *dst)
{
	if (src->sha1_valid && dst->sha1_valid &&
	    !memcmp(src->sha1, dst->sha1, 20))
		return 1;
	if (diff_populate_filespec(src, 1) || diff_populate_filespec(dst, 1))
		return 0;
	if (src->size != dst->size)
		return 0;
	if (diff_populate_filespec(src, 0) || diff_populate_filespec(dst, 0))
		return 0;
	if (src->size == dst->size &&
	    !memcmp(src->data, dst->data, src->size))
		return 1;
	return 0;
}

struct diff_score {
	int src; /* index in rename_src */
	int dst; /* index in rename_dst */
	int score;
};

static int estimate_similarity(struct diff_filespec *src,
			       struct diff_filespec *dst,
			       int minimum_score)
{
	/* src points at a file that existed in the original tree (or
	 * optionally a file in the destination tree) and dst points
	 * at a newly created file.  They may be quite similar, in which
	 * case we want to say src is renamed to dst or src is copied into
	 * dst, and then some edit has been applied to dst.
	 *
	 * Compare them and return how similar they are, representing
	 * the score as an integer between 0 and MAX_SCORE.
	 *
	 * When there is an exact match, it is considered a better
	 * match than anything else; the destination does not even
	 * call into this function in that case.
	 */
	void *delta;
	unsigned long delta_size, base_size, src_copied, literal_added;
	unsigned long delta_limit;
	int score;

	/* We deal only with regular files.  Symlink renames are handled
	 * only when they are exact matches --- in other words, no edits
	 * after renaming.
	 */
	if (!S_ISREG(src->mode) || !S_ISREG(dst->mode))
		return 0;

	delta_size = ((src->size < dst->size) ?
		      (dst->size - src->size) : (src->size - dst->size));
	base_size = ((src->size < dst->size) ? src->size : dst->size);

	/* We would not consider edits that change the file size so
	 * drastically.  delta_size must be smaller than
	 * (MAX_SCORE-minimum_score)/MAX_SCORE * min(src->size, dst->size).
	 *
	 * Note that base_size == 0 case is handled here already
	 * and the final score computation below would not have a
	 * divide-by-zero issue.
	 */
	if (base_size * (MAX_SCORE-minimum_score) < delta_size * MAX_SCORE)
		return 0;

	if (diff_populate_filespec(src, 0) || diff_populate_filespec(dst, 0))
		return 0; /* error but caught downstream */

	delta_limit = base_size * (MAX_SCORE-minimum_score) / MAX_SCORE;
	delta = diff_delta(src->data, src->size,
			   dst->data, dst->size,
			   &delta_size, delta_limit);
	if (!delta)
		/* If delta_limit is exceeded, we have too much differences */
		return 0;

	/* A delta that has a lot of literal additions would have
	 * big delta_size no matter what else it does.
	 */
	if (base_size * (MAX_SCORE-minimum_score) < delta_size * MAX_SCORE)
		return 0;

	/* Estimate the edit size by interpreting delta. */
	if (count_delta(delta, delta_size, &src_copied, &literal_added)) {
		free(delta);
		return 0;
	}
	free(delta);

	/* Extent of damage */
	if (src->size + literal_added < src_copied)
		delta_size = 0;
	else
		delta_size = (src->size - src_copied) + literal_added;

	/*
	 * Now we will give some score to it.  100% edit gets 0 points
	 * and 0% edit gets MAX_SCORE points.
	 */
	score = MAX_SCORE - (MAX_SCORE * delta_size / base_size); 
	if (score < 0) return 0;
	if (MAX_SCORE < score) return MAX_SCORE;
	return score;
}

static void record_rename_pair(struct diff_queue_struct *renq,
			       int dst_index, int src_index, int score)
{
	struct diff_filespec *one, *two, *src, *dst;
	struct diff_filepair *dp;

	if (rename_dst[dst_index].pair)
		die("internal error: dst already matched.");

	src = rename_src[src_index].one;
	one = alloc_filespec(src->path);
	fill_filespec(one, src->sha1, src->mode);

	dst = rename_dst[dst_index].two;
	two = alloc_filespec(dst->path);
	fill_filespec(two, dst->sha1, dst->mode);

	dp = diff_queue(renq, one, two);
	dp->score = score;
	dp->source_stays = rename_src[src_index].src_stays;
	rename_dst[dst_index].pair = dp;
}

/*
 * We sort the rename similarity matrix with the score, in descending
 * order (the most similar first).
 */
static int score_compare(const void *a_, const void *b_)
{
	const struct diff_score *a = a_, *b = b_;
	return b->score - a->score;
}

void diffcore_rename(int detect_rename, int minimum_score)
{
	struct diff_queue_struct *q = &diff_queued_diff;
	struct diff_queue_struct renq, outq;
	struct diff_score *mx;
	int i, j;
	int num_create, num_src, dst_cnt;

	if (!minimum_score)
		minimum_score = DEFAULT_RENAME_SCORE;
	renq.queue = NULL;
	renq.nr = renq.alloc = 0;

	for (i = 0; i < q->nr; i++) {
		struct diff_filepair *p = q->queue[i];
		if (!DIFF_FILE_VALID(p->one))
			if (!DIFF_FILE_VALID(p->two))
				continue; /* unmerged */
			else
				locate_rename_dst(p->two, 1);
		else if (!DIFF_FILE_VALID(p->two)) {
			/* If the source is a broken "delete", and
			 * they did not really want to get broken,
			 * that means the source actually stays.
			 */
			int stays = (p->broken_pair && !p->score);
			register_rename_src(p->one, stays);
		}
		else if (detect_rename == DIFF_DETECT_COPY)
			register_rename_src(p->one, 1);
	}
	if (rename_dst_nr == 0)
		goto cleanup; /* nothing to do */

	/* We really want to cull the candidates list early
	 * with cheap tests in order to avoid doing deltas.
	 */
	for (i = 0; i < rename_dst_nr; i++) {
		struct diff_filespec *two = rename_dst[i].two;
		for (j = 0; j < rename_src_nr; j++) {
			struct diff_filespec *one = rename_src[j].one;
			if (!is_exact_match(one, two))
				continue;
			record_rename_pair(&renq, i, j, MAX_SCORE);
			break; /* we are done with this entry */
		}
	}
	diff_debug_queue("done detecting exact", &renq);

	/* Have we run out the created file pool?  If so we can avoid
	 * doing the delta matrix altogether.
	 */
	if (renq.nr == rename_dst_nr)
		goto cleanup;

	num_create = (rename_dst_nr - renq.nr);
	num_src = rename_src_nr;
	mx = xmalloc(sizeof(*mx) * num_create * num_src);
	for (dst_cnt = i = 0; i < rename_dst_nr; i++) {
		int base = dst_cnt * num_src;
		struct diff_filespec *two = rename_dst[i].two;
		if (rename_dst[i].pair)
			continue; /* dealt with exact match already. */
		for (j = 0; j < rename_src_nr; j++) {
			struct diff_filespec *one = rename_src[j].one;
			struct diff_score *m = &mx[base+j];
			m->src = j;
			m->dst = i;
			m->score = estimate_similarity(one, two,
						       minimum_score);
		}
		dst_cnt++;
	}
	/* cost matrix sorted by most to least similar pair */
	qsort(mx, num_create * num_src, sizeof(*mx), score_compare);
	for (i = 0; i < num_create * num_src; i++) {
		struct diff_rename_dst *dst = &rename_dst[mx[i].dst];
		if (dst->pair)
			continue; /* already done, either exact or fuzzy. */
		if (mx[i].score < minimum_score)
			break; /* there is no more usable pair. */
		record_rename_pair(&renq, mx[i].dst, mx[i].src, mx[i].score);
	}
	free(mx);
	diff_debug_queue("done detecting fuzzy", &renq);

 cleanup:
	/* At this point, we have found some renames and copies and they
	 * are kept in renq.  The original list is still in *q.
	 */
	outq.queue = NULL;
	outq.nr = outq.alloc = 0;
	for (i = 0; i < q->nr; i++) {
		struct diff_filepair *p = q->queue[i];
		struct diff_filepair *pair_to_free = NULL;

		if (!DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two)) {
			/*
			 * Creation
			 *
			 * We would output this create record if it has
			 * not been turned into a rename/copy already.
			 */
			struct diff_rename_dst *dst =
				locate_rename_dst(p->two, 0);
			if (dst && dst->pair) {
				diff_q(&outq, dst->pair);
				pair_to_free = p;
			}
			else
				/* no matching rename/copy source, so
				 * record this as a creation.
				 */
				diff_q(&outq, p);
		}
		else if (DIFF_FILE_VALID(p->one) && !DIFF_FILE_VALID(p->two)) {
			/*
			 * Deletion
			 *
			 * We would output this delete record if:
			 *
			 * (1) this is a broken delete and the counterpart
			 *     broken create remains in the output; or
			 * (2) this is not a broken delete, and renq does
			 *     not have a rename/copy to move p->one->path
			 *     out.
			 *
			 * Otherwise, the counterpart broken create
			 * has been turned into a rename-edit; or
			 * delete did not have a matching create to
			 * begin with.
			 */
			if (DIFF_PAIR_BROKEN(p)) {
				/* broken delete */
				struct diff_rename_dst *dst =
					locate_rename_dst(p->one, 0);
				if (dst && dst->pair)
					/* counterpart is now rename/copy */
					pair_to_free = p;
			}
			else {
				for (j = 0; j < renq.nr; j++)
					if (!strcmp(renq.queue[j]->one->path,
						    p->one->path))
						break;
				if (j < renq.nr)
					/* this path remains */
					pair_to_free = p;
			}

			if (pair_to_free)
				;
			else
				diff_q(&outq, p);
		}
		else if (!diff_unmodified_pair(p))
			/* all the usual ones need to be kept */
			diff_q(&outq, p);
		else
			/* no need to keep unmodified pairs */
			pair_to_free = p;

		if (pair_to_free)
			diff_free_filepair(pair_to_free);
	}
	diff_debug_queue("done copying original", &outq);

	free(renq.queue);
	free(q->queue);
	*q = outq;
	diff_debug_queue("done collapsing", q);

	free(rename_dst);
	rename_dst = NULL;
	rename_dst_nr = rename_dst_alloc = 0;
	free(rename_src);
	rename_src = NULL;
	rename_src_nr = rename_src_alloc = 0;
	return;
}