1 files changed, 443 insertions, 0 deletions

diff --git a/diffcore-rename.c b/diffcore-rename.c
new file mode 100644
index 0000000000..8aa8f841c4
--- /dev/null
+++ b/diffcore-rename.c
@@ -0,0 +1,443 @@
+/*
+ * Copyright (C) 2005 Junio C Hamano
+ */
+#include "cache.h"
+#include "diff.h"
+#include "diffcore.h"
+#include "delta.h"
+
+struct diff_rename_pool {
+	struct diff_filespec **s;
+	int nr, alloc;
+};
+
+static void diff_rename_pool_clear(struct diff_rename_pool *pool)
+{
+	pool->s = NULL; pool->nr = pool->alloc = 0;
+}
+
+static void diff_rename_pool_add(struct diff_rename_pool *pool,
+				 struct diff_filespec *s)
+{
+	if (S_ISDIR(s->mode))
+		return;  /* rename/copy patch for tree does not make sense. */
+
+	if (pool->alloc <= pool->nr) {
+		pool->alloc = alloc_nr(pool->alloc);
+		pool->s = xrealloc(pool->s,
+				   sizeof(*(pool->s)) * pool->alloc);
+	}
+	pool->s[pool->nr] = s;
+	pool->nr++;
+}
+
+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 */
+		return 0;
+	if (src->size == dst->size &&
+	    !memcmp(src->data, dst->data, src->size))
+		return 1;
+	return 0;
+}
+
+struct diff_score {
+	struct diff_filespec *src;
+	struct diff_filespec *dst;
+	int score;
+	int rank;
+};
+
+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 10000, except
+	 * where they match exactly it is considered better than anything
+	 * else.
+	 */
+	void *delta;
+	unsigned long delta_size;
+	int score;
+
+	delta_size = ((src->size < dst->size) ?
+		      (dst->size - src->size) : (src->size - dst->size));
+
+	/* We would not consider rename followed by more than
+	 * minimum_score/MAX_SCORE edits; that is, delta_size must be smaller
+	 * than (src->size + dst->size)/2 * minimum_score/MAX_SCORE,
+	 * which means...
+	 */
+
+	if ((src->size+dst->size)*minimum_score < delta_size*MAX_SCORE*2)
+		return 0;
+
+	delta = diff_delta(src->data, src->size,
+			   dst->data, dst->size,
+			   &delta_size);
+	free(delta);
+
+	/* This "delta" is really xdiff with adler32 and all the
+	 * overheads but it is a quick and dirty approximation.
+	 *
+	 * Now we will give some score to it.  100% edit gets
+	 * 0 points and 0% edit gets MAX_SCORE points.  That is, every
+	 * 1/MAX_SCORE edit gets 1 point penalty.  The amount of penalty is:
+	 *
+	 * (delta_size * 2 / (src->size + dst->size)) * MAX_SCORE
+	 *
+	 */
+	score = MAX_SCORE-(MAX_SCORE*2*delta_size/(src->size+dst->size));
+	if (score < 0) return 0;
+	if (MAX_SCORE < score) return MAX_SCORE;
+	return score;
+}
+
+static void record_rename_pair(struct diff_queue_struct *outq,
+			       struct diff_filespec *src,
+			       struct diff_filespec *dst,
+			       int rank,
+			       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_file_pair *dp = diff_queue(outq, src, dst);
+	dp->xfrm_work = (rank * 2 + 1) | (score<<RENAME_SCORE_SHIFT);
+	dst->xfrm_flags |= RENAME_DST_MATCHED;
+}
+
+#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,
+		s->file_valid ? "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);
+}
+
+static void debug_filepair(const struct diff_file_pair *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));
+}
+
+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_file_pair *p = q->queue[i];
+		debug_filepair(p, i);
+	}
+}
+#else
+#define debug_queue(a,b) do { ; /*nothing*/ } while(0)
+#endif
+
+/*
+ * 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_file_pair *a = *(const struct diff_file_pair **)a_;
+	const struct diff_file_pair *b = *(const struct diff_file_pair **)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;
+}
+
+/*
+ * We sort the rename similarity matrix with the score, in descending
+ * order (more 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;
+}
+
+static int needs_to_stay(struct diff_queue_struct *q, int i,
+			 struct diff_filespec *it)
+{
+	/* 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_file_pair *p = q->queue[i++];
+		if (!p->two->file_valid)
+			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;
+	}
+	return 0;
+}
+
+void diff_detect_rename(struct diff_queue_struct *q,
+			int detect_rename,
+			int minimum_score)
+{
+	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;
+
+	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;
+
+	/* NEEDSWORK:
+	 * (1) make sure we properly ignore but pass trees.
+	 *
+	 * (2) make sure we do right thing on the same path deleted
+	 *     and created in the same patch.
+	 */
+
+	for (i = 0; i < q->nr; i++) {
+		struct diff_file_pair *p = q->queue[i];
+		if (!p->one->file_valid)
+			if (!p->two->file_valid)
+				continue; /* ignore nonsense */
+			else
+				diff_rename_pool_add(&created, p->two);
+		else if (!p->two->file_valid)
+			diff_rename_pool_add(&deleted, p->one);
+		else if (1 < detect_rename) /* find copy, too */
+			diff_rename_pool_add(&stay, p->one);
+	}
+	if (created.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.
+	 *
+	 * 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 */
+			}
+		}
+	}
+	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;
+
+	num_create = (created.nr - outq.nr);
+	num_src = deleted.nr + stay.nr;
+	mx = xmalloc(sizeof(*mx) * num_create * num_src);
+	for (dst_cnt = i = 0; i < created.nr; i++) {
+		int base = dst_cnt * num_src;
+		if (created.s[i]->xfrm_flags & RENAME_DST_MATCHED)
+			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;
+			}
+		}
+		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. */
+		if (mx[i].score < minimum_score)
+			continue;
+		record_rename_pair(&outq,
+				  mx[i].src, mx[i].dst, mx[i].rank,
+				  mx[i].score);
+	}
+	free(mx);
+	debug_queue("done detecting fuzzy", &outq);
+
+ flush_rest:
+	/* 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_file_pair with any comment
+	 * so there is nothing other than p to free.
+	 */
+	for (i = 0; i < q->nr; i++) {
+		struct diff_file_pair *dp, *p = q->queue[i];
+		if (!p->one->file_valid) {
+			if (p->two->file_valid) {
+				/* creation */
+				dp = diff_queue(&outq, p->one, p->two);
+				dp->xfrm_work = 4;
+			}
+			/* otherwise it is a nonsense; just ignore it */
+		}
+		else if (!p->two->file_valid) {
+			/* 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_file_pair *p = outq.queue[i];
+		if (!p->one->file_valid) {
+			/* created */
+			if (p->two->xfrm_flags & RENAME_DST_MATCHED)
+				; /* rename/copy created it already */
+			else
+				diff_queue(q, p->one, p->two);
+		}
+		else if (!p->two->file_valid) {
+			/* deleted */
+			if (p->one->xfrm_flags & RENAME_SRC_GONE)
+				; /* rename/copy deleted it already */
+			else
+				diff_queue(q, p->one, p->two);
+		}
+		else if (strcmp(p->one->path, p->two->path)) {
+			/* rename or copy */
+			struct diff_file_pair *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.
+			 */
+			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);
+			}
+			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);
+			}
+		}
+		else
+			/* otherwise it is a modified (or stayed) entry */
+			diff_queue(q, p->one, p->two);
+		free(p);
+	}
+
+	free(outq.queue);
+	debug_queue("done collapsing", q);
+
+ cleanup:
+	free(created.s);
+	free(deleted.s);
+	free(stay.s);
+	return;
+}