sample update-hook: sanely handle a new branch head.
[gitweb.git] / diffcore-rename.c
index 28b1de25de4d8444bdf369506f04126b6aede665..39d9126cb9d397df06d41495a3402123fa4ba46b 100644 (file)
@@ -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;  /* rename/copy patch for tree does not make sense. */
+       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,
@@ -63,39 +129,69 @@ 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
+        * 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
-        * minimum_score/MAX_SCORE * min(src->size, dst->size).
+        * (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 * minimum_score < delta_size * MAX_SCORE)
+       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.
@@ -106,95 +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_)
 {
@@ -202,237 +234,230 @@ 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;
 }
 
-void diff_detect_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;
-
-       outq.queue = NULL;
-       outq.nr = outq.alloc = 0;
+       int i, j, rename_count;
+       int num_create, num_src, dst_cnt;
 
-       diff_rename_pool_clear(&created);
-       diff_rename_pool_clear(&deleted);
-       diff_rename_pool_clear(&stay);
-
-       srcs[0] = &deleted;
-       srcs[1] = &stay;
+       if (!minimum_score)
+               minimum_score = DEFAULT_RENAME_SCORE;
+       rename_count = 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; /* ignore nonsense */
+                               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 || rename_src_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)) {
-                       if (DIFF_FILE_VALID(p->two)) {
-                               /* creation */
-                               dp = diff_queue(&outq, p->one, p->two);
-                               dp->xfrm_work = 4;
+               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;
                        }
-                       /* otherwise it is a nonsense; just ignore it */
-               }
-               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 */
-                       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 */
                        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);
-               free(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(outq.queue);
-       debug_queue("done collapsing", q);
+       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);
+               }
+       }
 
- cleanup:
-       free(created.s);
-       free(deleted.s);
-       free(stay.s);
+       for (i = 0; i < rename_dst_nr; i++) {
+               diff_free_filespec_data(rename_dst[i].two);
+               free(rename_dst[i].two);
+       }
+
+       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;
 }