X-Git-Url: https://git.octo.it/?a=blobdiff_plain;f=diffcore-rename.c;h=dba965c0b4006251b1da04465d319c5fe9997ea4;hb=457f06d68e427bbf4f1a921877441a622a05e5c4;hp=52f09d231926e83c69a4026eba9d2ba10925d656;hpb=60896c7bfed67f1c7364595213ef9239642f83c5;p=git.git

diff --git a/diffcore-rename.c b/diffcore-rename.c
index 52f09d23..dba965c0 100644
--- a/diffcore-rename.c
+++ b/diffcore-rename.c
@@ -5,30 +5,94 @@
 #include "diff.h"
 #include "diffcore.h"
 #include "delta.h"
+#include "count-delta.h"
 
-struct diff_rename_pool {
-	struct diff_filespec **s;
-	int nr, alloc;
-};
+/* 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 void diff_rename_pool_clear(struct diff_rename_pool *pool)
+static struct diff_rename_dst *locate_rename_dst(struct diff_filespec *two,
+						 int insert_ok)
 {
-	pool->s = NULL; pool->nr = pool->alloc = 0;
+	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 = alloc_filespec(two->path);
+	fill_filespec(rename_dst[first].two, two->sha1, two->mode);
+	rename_dst[first].pair = NULL;
+	return &(rename_dst[first]);
 }
 
-static void diff_rename_pool_add(struct diff_rename_pool *pool,
-				 struct diff_filespec *s)
+/* Table of rename/copy src files */
+static struct diff_rename_src {
+	struct diff_filespec *one;
+	unsigned src_path_left : 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_path_left)
 {
-	if (S_ISDIR(s->mode))
-		return;  /* no trees, please */
+	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;
+	}
 
-	if (pool->alloc <= pool->nr) {
-		pool->alloc = alloc_nr(pool->alloc);
-		pool->s = xrealloc(pool->s,
-				   sizeof(*(pool->s)) * pool->alloc);
+	/* 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));
 	}
-	pool->s[pool->nr] = s;
-	pool->nr++;
+	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_path_left = src_path_left;
+	return &(rename_src[first]);
 }
 
 static int is_exact_match(struct diff_filespec *src, struct diff_filespec *dst)
@@ -36,8 +100,11 @@ 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) || diff_populate_filespec(dst))
-		/* this is an error but will be caught downstream */
+	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))
@@ -46,10 +113,9 @@ static int is_exact_match(struct diff_filespec *src, struct diff_filespec *dst)
 }
 
 struct diff_score {
-	struct diff_filespec *src;
-	struct diff_filespec *dst;
+	int src; /* index in rename_src */
+	int dst; /* index in rename_dst */
 	int score;
-	int rank;
 };
 
 static int estimate_similarity(struct diff_filespec *src,
@@ -63,12 +129,15 @@ static int estimate_similarity(struct diff_filespec *src,
 	 * 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 10000, except
-	 * where they match exactly it is considered better than anything
-	 * else.
+	 * 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;
+	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
@@ -85,6 +154,7 @@ static int estimate_similarity(struct diff_filespec *src,
 	/* 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.
@@ -92,17 +162,36 @@ static int estimate_similarity(struct diff_filespec *src,
 	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);
-	/*
-	 * We currently punt here, but we may later end up parsing the
-	 * delta to really assess the extent of damage.  A big consecutive
-	 * remove would produce small delta_size that affects quite a
-	 * big portion of the file.
+			   &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.
@@ -113,95 +202,31 @@ static int estimate_similarity(struct diff_filespec *src,
 	return score;
 }
 
-static void record_rename_pair(struct diff_queue_struct *outq,
-			       struct diff_filespec *src,
-			       struct diff_filespec *dst,
-			       int rank,
-			       int score)
+static void record_rename_pair(int dst_index, int src_index, int score)
 {
-	/* The rank is used to sort the final output, because there
-	 * are certain dependencies.
-	 *
-	 *  - rank #0 depends on deleted ones.
-	 *  - rank #1 depends on kept files before they are modified.
-	 *  - rank #2 depends on kept files after they are modified;
-	 *    currently not used.
-	 *
-	 * Therefore, the final output order should be:
-	 *
-	 *  1. rank #0 rename/copy diffs.
-	 *  2. deletions in the original.
-	 *  3. rank #1 rename/copy diffs.
-	 *  4. additions and modifications in the original.
-	 *  5. rank #2 rename/copy diffs; currently not used.
-	 *
-	 * To achieve this sort order, we give xform_work the number
-	 * above.
-	 */
-	struct diff_filepair *dp = diff_queue(outq, src, dst);
-	dp->xfrm_work = (rank * 2 + 1) | (score<<RENAME_SCORE_SHIFT);
-	dst->xfrm_flags |= RENAME_DST_MATCHED;
-}
+	struct diff_filespec *one, *two, *src, *dst;
+	struct diff_filepair *dp;
 
-#if 0
-static void debug_filespec(struct diff_filespec *s, int x, const char *one)
-{
-	fprintf(stderr, "queue[%d] %s (%s) %s %06o %s\n",
-		x, one,
-		s->path,
-		DIFF_FILE_VALID(s) ? "valid" : "invalid",
-		s->mode,
-		s->sha1_valid ? sha1_to_hex(s->sha1) : "");
-	fprintf(stderr, "queue[%d] %s size %lu flags %d\n",
-		x, one,
-		s->size, s->xfrm_flags);
-}
+	if (rename_dst[dst_index].pair)
+		die("internal error: dst already matched.");
 
-static void debug_filepair(const struct diff_filepair *p, int i)
-{
-	debug_filespec(p->one, i, "one");
-	debug_filespec(p->two, i, "two");
-	fprintf(stderr, "pair flags %d, orig order %d, score %d\n",
-		(p->xfrm_work & ((1<<RENAME_SCORE_SHIFT) - 1)),
-		p->orig_order,
-		(p->xfrm_work >> RENAME_SCORE_SHIFT));
-}
+	src = rename_src[src_index].one;
+	one = alloc_filespec(src->path);
+	fill_filespec(one, src->sha1, src->mode);
 
-static void debug_queue(const char *msg, struct diff_queue_struct *q)
-{
-	int i;
-	if (msg)
-		fprintf(stderr, "%s\n", msg);
-	fprintf(stderr, "q->nr = %d\n", q->nr);
-	for (i = 0; i < q->nr; i++) {
-		struct diff_filepair *p = q->queue[i];
-		debug_filepair(p, i);
-	}
-}
-#else
-#define debug_queue(a,b) do { ; /*nothing*/ } while(0)
-#endif
+	dst = rename_dst[dst_index].two;
+	two = alloc_filespec(dst->path);
+	fill_filespec(two, dst->sha1, dst->mode);
 
-/*
- * We sort the outstanding diff entries according to the rank (see
- * comment at the beginning of record_rename_pair) and tiebreak with
- * the order in the original input.
- */
-static int rank_compare(const void *a_, const void *b_)
-{
-	const struct diff_filepair *a = *(const struct diff_filepair **)a_;
-	const struct diff_filepair *b = *(const struct diff_filepair **)b_;
-	int a_rank = a->xfrm_work & ((1<<RENAME_SCORE_SHIFT) - 1);
-	int b_rank = b->xfrm_work & ((1<<RENAME_SCORE_SHIFT) - 1);
-
-	if (a_rank != b_rank)
-		return a_rank - b_rank;
-	return a->orig_order - b->orig_order;
+	dp = diff_queue(NULL, one, two);
+	dp->score = score;
+	dp->source_stays = rename_src[src_index].src_path_left;
+	rename_dst[dst_index].pair = dp;
 }
 
 /*
  * We sort the rename similarity matrix with the score, in descending
- * order (more similar first).
+ * order (the most similar first).
  */
 static int score_compare(const void *a_, const void *b_)
 {
@@ -209,67 +234,35 @@ static int score_compare(const void *a_, const void *b_)
 	return b->score - a->score;
 }
 
-static int needs_to_stay(struct diff_queue_struct *q, int i,
-			 struct diff_filespec *it)
+static int compute_stays(struct diff_queue_struct *q,
+			 struct diff_filespec *one)
 {
-	/* If it will be used in later entry (either stay or used
-	 * as the source of rename/copy), we need to copy, not rename.
-	 */
-	while (i < q->nr) {
-		struct diff_filepair *p = q->queue[i++];
-		if (!DIFF_FILE_VALID(p->two))
-			continue; /* removed is fine */
-		if (strcmp(p->one->path, it->path))
-			continue; /* not relevant */
-
-		/* p has its src set to *it and it is not a delete;
-		 * it will be used for in-place change or rename/copy,
-		 * so we cannot rename it out.
-		 */
-		return 1;
+	int i;
+	for (i = 0; i < q->nr; i++) {
+		struct diff_filepair *p = q->queue[i];
+		if (strcmp(one->path, p->two->path))
+			continue;
+		if (DIFF_PAIR_RENAME(p)) {
+			return 0; /* something else is renamed into this */
+		}
 	}
-	return 0;
+	return 1;
 }
 
-int diff_scoreopt_parse(const char *opt)
-{
-	int diglen, num, scale, i;
-	if (opt[0] != '-' || (opt[1] != 'M' && opt[1] != 'C'))
-		return -1; /* that is not a -M nor -C option */
-	diglen = strspn(opt+2, "0123456789");
-	if (diglen == 0 || strlen(opt+2) != diglen)
-		return 0; /* use default */
-	sscanf(opt+2, "%d", &num);
-	for (i = 0, scale = 1; i < diglen; i++)
-		scale *= 10;
-
-	/* user says num divided by scale and we say internally that
-	 * is MAX_SCORE * num / scale.
-	 */
-	return MAX_SCORE * num / scale;
-}
-
-void diffcore_rename(int detect_rename, int minimum_score)
+void diffcore_rename(struct diff_options *options)
 {
+	int detect_rename = options->detect_rename;
+	int minimum_score = options->rename_score;
+	int rename_limit = options->rename_limit;
 	struct diff_queue_struct *q = &diff_queued_diff;
 	struct diff_queue_struct outq;
-	struct diff_rename_pool created, deleted, stay;
-	struct diff_rename_pool *(srcs[2]);
 	struct diff_score *mx;
-	int h, i, j;
-	int num_create, num_src, dst_cnt, src_cnt;
+	int i, j, rename_count;
+	int num_create, num_src, dst_cnt;
 
 	if (!minimum_score)
-		minimum_score = DEFAULT_MINIMUM_SCORE;
-	outq.queue = NULL;
-	outq.nr = outq.alloc = 0;
-
-	diff_rename_pool_clear(&created);
-	diff_rename_pool_clear(&deleted);
-	diff_rename_pool_clear(&stay);
-
-	srcs[0] = &deleted;
-	srcs[1] = &stay;
+		minimum_score = DEFAULT_RENAME_SCORE;
+	rename_count = 0;
 
 	for (i = 0; i < q->nr; i++) {
 		struct diff_filepair *p = q->queue[i];
@@ -277,185 +270,194 @@ void diffcore_rename(int detect_rename, int minimum_score)
 			if (!DIFF_FILE_VALID(p->two))
 				continue; /* unmerged */
 			else
-				diff_rename_pool_add(&created, p->two);
-		else if (!DIFF_FILE_VALID(p->two))
-			diff_rename_pool_add(&deleted, p->one);
-		else if (1 < detect_rename) /* find copy, too */
-			diff_rename_pool_add(&stay, p->one);
+				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 (created.nr == 0)
+	if (rename_dst_nr == 0 ||
+	    (0 < rename_limit && rename_limit < rename_dst_nr))
 		goto cleanup; /* nothing to do */
 
 	/* We really want to cull the candidates list early
 	 * with cheap tests in order to avoid doing deltas.
-	 *
-	 * With the current callers, we should not have already
-	 * matched entries at this point, but it is nonetheless
-	 * checked for sanity.
 	 */
-	for (i = 0; i < created.nr; i++) {
-		if (created.s[i]->xfrm_flags & RENAME_DST_MATCHED)
-			continue; /* we have matched exactly already */
-		for (h = 0; h < sizeof(srcs)/sizeof(srcs[0]); h++) {
-			struct diff_rename_pool *p = srcs[h];
-			for (j = 0; j < p->nr; j++) {
-				if (!is_exact_match(p->s[j], created.s[i]))
-					continue;
-				record_rename_pair(&outq,
-						   p->s[j], created.s[i], h,
-						   MAX_SCORE);
-				break; /* we are done with this entry */
-			}
+	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(i, j, MAX_SCORE);
+			rename_count++;
+			break; /* we are done with this entry */
 		}
 	}
-	debug_queue("done detecting exact", &outq);
 
 	/* Have we run out the created file pool?  If so we can avoid
 	 * doing the delta matrix altogether.
 	 */
-	if (outq.nr == created.nr)
-		goto flush_rest;
+	if (rename_count == rename_dst_nr)
+		goto cleanup;
 
-	num_create = (created.nr - outq.nr);
-	num_src = deleted.nr + stay.nr;
+	if (minimum_score == MAX_SCORE)
+		goto cleanup;
+
+	num_create = (rename_dst_nr - rename_count);
+	num_src = rename_src_nr;
 	mx = xmalloc(sizeof(*mx) * num_create * num_src);
-	for (dst_cnt = i = 0; i < created.nr; i++) {
+	for (dst_cnt = i = 0; i < rename_dst_nr; i++) {
 		int base = dst_cnt * num_src;
-		if (created.s[i]->xfrm_flags & RENAME_DST_MATCHED)
+		struct diff_filespec *two = rename_dst[i].two;
+		if (rename_dst[i].pair)
 			continue; /* dealt with exact match already. */
-		for (src_cnt = h = 0; h < sizeof(srcs)/sizeof(srcs[0]); h++) {
-			struct diff_rename_pool *p = srcs[h];
-			for (j = 0; j < p->nr; j++, src_cnt++) {
-				struct diff_score *m = &mx[base + src_cnt];
-				m->src = p->s[j];
-				m->dst = created.s[i];
-				m->score = estimate_similarity(m->src, m->dst,
-							       minimum_score);
-				m->rank = h;
-			}
+		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++) {
-		if (mx[i].dst->xfrm_flags & RENAME_DST_MATCHED)
-			continue; /* alreayd done, either exact or fuzzy. */
+		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 not any more diffs applicable. */
-		record_rename_pair(&outq,
-				  mx[i].src, mx[i].dst, mx[i].rank,
-				  mx[i].score);
+			break; /* there is no more usable pair. */
+		record_rename_pair(mx[i].dst, mx[i].src, mx[i].score);
+		rename_count++;
 	}
 	free(mx);
-	debug_queue("done detecting fuzzy", &outq);
 
- flush_rest:
+ cleanup:
 	/* At this point, we have found some renames and copies and they
-	 * are kept in outq.  The original list is still in *q.
-	 *
-	 * Scan the original list and move them into the outq; we will sort
-	 * outq and swap it into the queue supplied to pass that to
-	 * downstream, so we assign the sort keys in this loop.
-	 *
-	 * See comments at the top of record_rename_pair for numbers used
-	 * to assign xfrm_work.
-	 *
-	 * Note that we have not annotated the diff_filepair with any comment
-	 * so there is nothing other than p to free.
+	 * are recorded in rename_dst.  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 *dp, *p = q->queue[i];
-		if (!DIFF_FILE_VALID(p->one)) {
-			/* creation or unmerged entries */
-			dp = diff_queue(&outq, p->one, p->two);
-			dp->xfrm_work = 4;
-		}
-		else if (!DIFF_FILE_VALID(p->two)) {
-			/* deletion */
-			dp = diff_queue(&outq, p->one, p->two);
-			dp->xfrm_work = 2;
-		}
-		else {
-			/* modification, or stay as is */
-			dp = diff_queue(&outq, p->one, p->two);
-			dp->xfrm_work = 4;
-		}
-		free(p);
-	}
-	debug_queue("done copying original", &outq);
-
-	/* Sort outq */
-	qsort(outq.queue, outq.nr, sizeof(outq.queue[0]), rank_compare);
-
-	debug_queue("done sorting", &outq);
-
-	free(q->queue);
-	q->nr = q->alloc = 0;
-	q->queue = NULL;
-
-	/* Copy it out to q, removing duplicates. */
-	for (i = 0; i < outq.nr; i++) {
-		struct diff_filepair *p = outq.queue[i];
-		if (!DIFF_FILE_VALID(p->one)) {
-			/* created or unmerged */
-			if (p->two->xfrm_flags & RENAME_DST_MATCHED)
-				; /* rename/copy created it already */
-			else
-				diff_queue(q, p->one, p->two);
-		}
-		else if (!DIFF_FILE_VALID(p->two)) {
-			/* deleted */
-			if (p->one->xfrm_flags & RENAME_SRC_GONE)
-				; /* rename/copy deleted it already */
+		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
-				diff_queue(q, p->one, p->two);
+				/* no matching rename/copy source, so
+				 * record this as a creation.
+				 */
+				diff_q(&outq, p);
 		}
-		else if (strcmp(p->one->path, p->two->path)) {
-			/* rename or copy */
-			struct diff_filepair *dp =
-				diff_queue(q, p->one, p->two);
-			int msglen = (strlen(p->one->path) +
-				      strlen(p->two->path) + 100);
-			int score = (p->xfrm_work >> RENAME_SCORE_SHIFT);
-			dp->xfrm_msg = xmalloc(msglen);
-
-			/* if we have a later entry that is a rename/copy
-			 * that depends on p->one, then we copy here.
-			 * otherwise we rename it.
+		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 rename_dst
+			 *     does not have a rename/copy to move p->one->path
+			 *     out of existence.
+			 *
+			 * Otherwise, the counterpart broken create
+			 * has been turned into a rename-edit; or
+			 * delete did not have a matching create to
+			 * begin with.
 			 */
-			if (needs_to_stay(&outq, i+1, p->one)) {
-				/* copy it */
-				sprintf(dp->xfrm_msg,
-					"similarity index %d%%\n"
-					"copy from %s\n"
-					"copy to %s\n",
-					(int)(0.5 + score * 100 / MAX_SCORE),
-					p->one->path, p->two->path);
+			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 {
-				/* rename it, and mark it as gone. */
-				p->one->xfrm_flags |= RENAME_SRC_GONE;
-				sprintf(dp->xfrm_msg,
-					"similarity index %d%%\n"
-					"rename old %s\n"
-					"rename new %s\n",
-					(int)(0.5 + score * 100 / MAX_SCORE),
-					p->one->path, p->two->path);
+				for (j = 0; j < rename_dst_nr; j++) {
+					if (!rename_dst[j].pair)
+						continue;
+					if (strcmp(rename_dst[j].pair->
+						   one->path,
+						   p->one->path))
+						continue;
+					break;
+				}
+				if (j < rename_dst_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
-			/* otherwise it is a modified (or stayed) entry */
-			diff_queue(q, p->one, p->two);
-		diff_free_filepair(p);
+			/* 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(q->queue);
+	*q = outq;
+	diff_debug_queue("done collapsing", q);
+
+	/* We need to see which rename source really stays here;
+	 * earlier we only checked if the path is left in the result,
+	 * but even if a path remains in the result, if that is coming
+	 * from copying something else on top of it, then the original
+	 * source is lost and does not stay.
+	 */
+	for (i = 0; i < q->nr; i++) {
+		struct diff_filepair *p = q->queue[i];
+		if (DIFF_PAIR_RENAME(p) && p->source_stays) {
+			/* If one appears as the target of a rename-copy,
+			 * then mark p->source_stays = 0; otherwise
+			 * leave it as is.
+			 */
+			p->source_stays = compute_stays(q, p->one);
+		}
 	}
 
-	free(outq.queue);
-	debug_queue("done collapsing", q);
+	for (i = 0; i < rename_dst_nr; i++) {
+		diff_free_filespec_data(rename_dst[i].two);
+		free(rename_dst[i].two);
+	}
 
- cleanup:
-	free(created.s);
-	free(deleted.s);
-	free(stay.s);
+	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;
 }