diffcore-rename.c

   1 /*
   2  *
   3  * Copyright (C) 2005 Junio C Hamano
   4  */
   5 #include "cache.h"
   6 #include "diff.h"
   7 #include "diffcore.h"
   8 #include "object-store.h"
   9 #include "hashmap.h"
  10 #include "progress.h"
  11 #include "promisor-remote.h"
  12
  13 /* Table of rename/copy destinations */
  14
  15 static struct diff_rename_dst {
  16         struct diff_filespec *two;
  17         struct diff_filepair *pair;
  18 } *rename_dst;
  19 static int rename_dst_nr, rename_dst_alloc;
  20
  21 static int find_rename_dst(struct diff_filespec *two)
  22 {
  23         int first, last;
  24
  25         first = 0;
  26         last = rename_dst_nr;
  27         while (last > first) {
  28                 int next = first + ((last - first) >> 1);
  29                 struct diff_rename_dst *dst = &(rename_dst[next]);
  30                 int cmp = strcmp(two->path, dst->two->path);
  31                 if (!cmp)
  32                         return next;
  33                 if (cmp < 0) {
  34                         last = next;
  35                         continue;
  36                 }
  37                 first = next+1;
  38         }
  39         return -first - 1;
  40 }
  41
  42 static struct diff_rename_dst *locate_rename_dst(struct diff_filespec *two)
  43 {
  44         int ofs = find_rename_dst(two);
  45         return ofs < 0 ? NULL : &rename_dst[ofs];
  46 }
  47
  48 /*
  49  * Returns 0 on success, -1 if we found a duplicate.
  50  */
  51 static int add_rename_dst(struct diff_filespec *two)
  52 {
  53         int first = find_rename_dst(two);
  54
  55         if (first >= 0)
  56                 return -1;
  57         first = -first - 1;
  58
  59         /* insert to make it at "first" */
  60         ALLOC_GROW(rename_dst, rename_dst_nr + 1, rename_dst_alloc);
  61         rename_dst_nr++;
  62         if (first < rename_dst_nr)
  63                 MOVE_ARRAY(rename_dst + first + 1, rename_dst + first,
  64                            rename_dst_nr - first - 1);
  65         rename_dst[first].two = alloc_filespec(two->path);
  66         fill_filespec(rename_dst[first].two, &two->oid, two->oid_valid,
  67                       two->mode);
  68         rename_dst[first].pair = NULL;
  69         return 0;
  70 }
  71
  72 /* Table of rename/copy src files */
  73 static struct diff_rename_src {
  74         struct diff_filepair *p;
  75         unsigned short score; /* to remember the break score */
  76 } *rename_src;
  77 static int rename_src_nr, rename_src_alloc;
  78
  79 static struct diff_rename_src *register_rename_src(struct diff_filepair *p)
  80 {
  81         int first, last;
  82         struct diff_filespec *one = p->one;
  83         unsigned short score = p->score;
  84
  85         first = 0;
  86         last = rename_src_nr;
  87         while (last > first) {
  88                 int next = first + ((last - first) >> 1);
  89                 struct diff_rename_src *src = &(rename_src[next]);
  90                 int cmp = strcmp(one->path, src->p->one->path);
  91                 if (!cmp)
  92                         return src;
  93                 if (cmp < 0) {
  94                         last = next;
  95                         continue;
  96                 }
  97                 first = next+1;
  98         }
  99
 100         /* insert to make it at "first" */
 101         ALLOC_GROW(rename_src, rename_src_nr + 1, rename_src_alloc);
 102         rename_src_nr++;
 103         if (first < rename_src_nr)
 104                 MOVE_ARRAY(rename_src + first + 1, rename_src + first,
 105                            rename_src_nr - first - 1);
 106         rename_src[first].p = p;
 107         rename_src[first].score = score;
 108         return &(rename_src[first]);
 109 }
 110
 111 static int basename_same(struct diff_filespec *src, struct diff_filespec *dst)
 112 {
 113         int src_len = strlen(src->path), dst_len = strlen(dst->path);
 114         while (src_len && dst_len) {
 115                 char c1 = src->path[--src_len];
 116                 char c2 = dst->path[--dst_len];
 117                 if (c1 != c2)
 118                         return 0;
 119                 if (c1 == '/')
 120                         return 1;
 121         }
 122         return (!src_len || src->path[src_len - 1] == '/') &&
 123                 (!dst_len || dst->path[dst_len - 1] == '/');
 124 }
 125
 126 struct diff_score {
 127         int src; /* index in rename_src */
 128         int dst; /* index in rename_dst */
 129         unsigned short score;
 130         short name_score;
 131 };
 132
 133 struct prefetch_options {
 134         struct repository *repo;
 135         int skip_unmodified;
 136 };
 137 static void prefetch(void *prefetch_options)
 138 {
 139         struct prefetch_options *options = prefetch_options;
 140         int i;
 141         struct oid_array to_fetch = OID_ARRAY_INIT;
 142
 143         for (i = 0; i < rename_dst_nr; i++) {
 144                 if (rename_dst[i].pair)
 145                         /*
 146                          * The loop in diffcore_rename() will not need these
 147                          * blobs, so skip prefetching.
 148                          */
 149                         continue; /* already found exact match */
 150                 diff_add_if_missing(options->repo, &to_fetch,
 151                                     rename_dst[i].two);
 152         }
 153         for (i = 0; i < rename_src_nr; i++) {
 154                 if (options->skip_unmodified &&
 155                     diff_unmodified_pair(rename_src[i].p))
 156                         /*
 157                          * The loop in diffcore_rename() will not need these
 158                          * blobs, so skip prefetching.
 159                          */
 160                         continue;
 161                 diff_add_if_missing(options->repo, &to_fetch,
 162                                     rename_src[i].p->one);
 163         }
 164         promisor_remote_get_direct(options->repo, to_fetch.oid, to_fetch.nr);
 165         oid_array_clear(&to_fetch);
 166 }
 167
 168 static int estimate_similarity(struct repository *r,
 169                                struct diff_filespec *src,
 170                                struct diff_filespec *dst,
 171                                int minimum_score,
 172                                int skip_unmodified)
 173 {
 174         /* src points at a file that existed in the original tree (or
 175          * optionally a file in the destination tree) and dst points
 176          * at a newly created file.  They may be quite similar, in which
 177          * case we want to say src is renamed to dst or src is copied into
 178          * dst, and then some edit has been applied to dst.
 179          *
 180          * Compare them and return how similar they are, representing
 181          * the score as an integer between 0 and MAX_SCORE.
 182          *
 183          * When there is an exact match, it is considered a better
 184          * match than anything else; the destination does not even
 185          * call into this function in that case.
 186          */
 187         unsigned long max_size, delta_size, base_size, src_copied, literal_added;
 188         int score;
 189         struct diff_populate_filespec_options dpf_options = {
 190                 .check_size_only = 1
 191         };
 192         struct prefetch_options prefetch_options = {r, skip_unmodified};
 193
 194         if (r == the_repository && has_promisor_remote()) {
 195                 dpf_options.missing_object_cb = prefetch;
 196                 dpf_options.missing_object_data = &prefetch_options;
 197         }
 198
 199         /* We deal only with regular files.  Symlink renames are handled
 200          * only when they are exact matches --- in other words, no edits
 201          * after renaming.
 202          */
 203         if (!S_ISREG(src->mode) || !S_ISREG(dst->mode))
 204                 return 0;
 205
 206         /*
 207          * Need to check that source and destination sizes are
 208          * filled in before comparing them.
 209          *
 210          * If we already have "cnt_data" filled in, we know it's
 211          * all good (avoid checking the size for zero, as that
 212          * is a possible size - we really should have a flag to
 213          * say whether the size is valid or not!)
 214          */
 215         if (!src->cnt_data &&
 216             diff_populate_filespec(r, src, &dpf_options))
 217                 return 0;
 218         if (!dst->cnt_data &&
 219             diff_populate_filespec(r, dst, &dpf_options))
 220                 return 0;
 221
 222         max_size = ((src->size > dst->size) ? src->size : dst->size);
 223         base_size = ((src->size < dst->size) ? src->size : dst->size);
 224         delta_size = max_size - base_size;
 225
 226         /* We would not consider edits that change the file size so
 227          * drastically.  delta_size must be smaller than
 228          * (MAX_SCORE-minimum_score)/MAX_SCORE * min(src->size, dst->size).
 229          *
 230          * Note that base_size == 0 case is handled here already
 231          * and the final score computation below would not have a
 232          * divide-by-zero issue.
 233          */
 234         if (max_size * (MAX_SCORE-minimum_score) < delta_size * MAX_SCORE)
 235                 return 0;
 236
 237         dpf_options.check_size_only = 0;
 238
 239         if (!src->cnt_data && diff_populate_filespec(r, src, &dpf_options))
 240                 return 0;
 241         if (!dst->cnt_data && diff_populate_filespec(r, dst, &dpf_options))
 242                 return 0;
 243
 244         if (diffcore_count_changes(r, src, dst,
 245                                    &src->cnt_data, &dst->cnt_data,
 246                                    &src_copied, &literal_added))
 247                 return 0;
 248
 249         /* How similar are they?
 250          * what percentage of material in dst are from source?
 251          */
 252         if (!dst->size)
 253                 score = 0; /* should not happen */
 254         else
 255                 score = (int)(src_copied * MAX_SCORE / max_size);
 256         return score;
 257 }
 258
 259 static void record_rename_pair(int dst_index, int src_index, int score)
 260 {
 261         struct diff_filespec *src, *dst;
 262         struct diff_filepair *dp;
 263
 264         if (rename_dst[dst_index].pair)
 265                 die("internal error: dst already matched.");
 266
 267         src = rename_src[src_index].p->one;
 268         src->rename_used++;
 269         src->count++;
 270
 271         dst = rename_dst[dst_index].two;
 272         dst->count++;
 273
 274         dp = diff_queue(NULL, src, dst);
 275         dp->renamed_pair = 1;
 276         if (!strcmp(src->path, dst->path))
 277                 dp->score = rename_src[src_index].score;
 278         else
 279                 dp->score = score;
 280         rename_dst[dst_index].pair = dp;
 281 }
 282
 283 /*
 284  * We sort the rename similarity matrix with the score, in descending
 285  * order (the most similar first).
 286  */
 287 static int score_compare(const void *a_, const void *b_)
 288 {
 289         const struct diff_score *a = a_, *b = b_;
 290
 291         /* sink the unused ones to the bottom */
 292         if (a->dst < 0)
 293                 return (0 <= b->dst);
 294         else if (b->dst < 0)
 295                 return -1;
 296
 297         if (a->score == b->score)
 298                 return b->name_score - a->name_score;
 299
 300         return b->score - a->score;
 301 }
 302
 303 struct file_similarity {
 304         struct hashmap_entry entry;
 305         int index;
 306         struct diff_filespec *filespec;
 307 };
 308
 309 static unsigned int hash_filespec(struct repository *r,
 310                                   struct diff_filespec *filespec)
 311 {
 312         if (!filespec->oid_valid) {
 313                 if (diff_populate_filespec(r, filespec, NULL))
 314                         return 0;
 315                 hash_object_file(r->hash_algo, filespec->data, filespec->size,
 316                                  "blob", &filespec->oid);
 317         }
 318         return oidhash(&filespec->oid);
 319 }
 320
 321 static int find_identical_files(struct hashmap *srcs,
 322                                 int dst_index,
 323                                 struct diff_options *options)
 324 {
 325         int renames = 0;
 326         struct diff_filespec *target = rename_dst[dst_index].two;
 327         struct file_similarity *p, *best = NULL;
 328         int i = 100, best_score = -1;
 329         unsigned int hash = hash_filespec(options->repo, target);
 330
 331         /*
 332          * Find the best source match for specified destination.
 333          */
 334         p = hashmap_get_entry_from_hash(srcs, hash, NULL,
 335                                         struct file_similarity, entry);
 336         hashmap_for_each_entry_from(srcs, p, entry) {
 337                 int score;
 338                 struct diff_filespec *source = p->filespec;
 339
 340                 /* False hash collision? */
 341                 if (!oideq(&source->oid, &target->oid))
 342                         continue;
 343                 /* Non-regular files? If so, the modes must match! */
 344                 if (!S_ISREG(source->mode) || !S_ISREG(target->mode)) {
 345                         if (source->mode != target->mode)
 346                                 continue;
 347                 }
 348                 /* Give higher scores to sources that haven't been used already */
 349                 score = !source->rename_used;
 350                 if (source->rename_used && options->detect_rename != DIFF_DETECT_COPY)
 351                         continue;
 352                 score += basename_same(source, target);
 353                 if (score > best_score) {
 354                         best = p;
 355                         best_score = score;
 356                         if (score == 2)
 357                                 break;
 358                 }
 359
 360                 /* Too many identical alternatives? Pick one */
 361                 if (!--i)
 362                         break;
 363         }
 364         if (best) {
 365                 record_rename_pair(dst_index, best->index, MAX_SCORE);
 366                 renames++;
 367         }
 368         return renames;
 369 }
 370
 371 static void insert_file_table(struct repository *r,
 372                               struct hashmap *table, int index,
 373                               struct diff_filespec *filespec)
 374 {
 375         struct file_similarity *entry = xmalloc(sizeof(*entry));
 376
 377         entry->index = index;
 378         entry->filespec = filespec;
 379
 380         hashmap_entry_init(&entry->entry, hash_filespec(r, filespec));
 381         hashmap_add(table, &entry->entry);
 382 }
 383
 384 /*
 385  * Find exact renames first.
 386  *
 387  * The first round matches up the up-to-date entries,
 388  * and then during the second round we try to match
 389  * cache-dirty entries as well.
 390  */
 391 static int find_exact_renames(struct diff_options *options)
 392 {
 393         int i, renames = 0;
 394         struct hashmap file_table;
 395
 396         /* Add all sources to the hash table in reverse order, because
 397          * later on they will be retrieved in LIFO order.
 398          */
 399         hashmap_init(&file_table, NULL, NULL, rename_src_nr);
 400         for (i = rename_src_nr-1; i >= 0; i--)
 401                 insert_file_table(options->repo,
 402                                   &file_table, i,
 403                                   rename_src[i].p->one);
 404
 405         /* Walk the destinations and find best source match */
 406         for (i = 0; i < rename_dst_nr; i++)
 407                 renames += find_identical_files(&file_table, i, options);
 408
 409         /* Free the hash data structure and entries */
 410         hashmap_clear_and_free(&file_table, struct file_similarity, entry);
 411
 412         return renames;
 413 }
 414
 415 #define NUM_CANDIDATE_PER_DST 4
 416 static void record_if_better(struct diff_score m[], struct diff_score *o)
 417 {
 418         int i, worst;
 419
 420         /* find the worst one */
 421         worst = 0;
 422         for (i = 1; i < NUM_CANDIDATE_PER_DST; i++)
 423                 if (score_compare(&m[i], &m[worst]) > 0)
 424                         worst = i;
 425
 426         /* is it better than the worst one? */
 427         if (score_compare(&m[worst], o) > 0)
 428                 m[worst] = *o;
 429 }
 430
 431 /*
 432  * Returns:
 433  * 0 if we are under the limit;
 434  * 1 if we need to disable inexact rename detection;
 435  * 2 if we would be under the limit if we were given -C instead of -C -C.
 436  */
 437 static int too_many_rename_candidates(int num_create,
 438                                       struct diff_options *options)
 439 {
 440         int rename_limit = options->rename_limit;
 441         int num_src = rename_src_nr;
 442         int i;
 443
 444         options->needed_rename_limit = 0;
 445
 446         /*
 447          * This basically does a test for the rename matrix not
 448          * growing larger than a "rename_limit" square matrix, ie:
 449          *
 450          *    num_create * num_src > rename_limit * rename_limit
 451          */
 452         if (rename_limit <= 0)
 453                 rename_limit = 32767;
 454         if ((num_create <= rename_limit || num_src <= rename_limit) &&
 455             ((uint64_t)num_create * (uint64_t)num_src
 456              <= (uint64_t)rename_limit * (uint64_t)rename_limit))
 457                 return 0;
 458
 459         options->needed_rename_limit =
 460                 num_src > num_create ? num_src : num_create;
 461
 462         /* Are we running under -C -C? */
 463         if (!options->flags.find_copies_harder)
 464                 return 1;
 465
 466         /* Would we bust the limit if we were running under -C? */
 467         for (num_src = i = 0; i < rename_src_nr; i++) {
 468                 if (diff_unmodified_pair(rename_src[i].p))
 469                         continue;
 470                 num_src++;
 471         }
 472         if ((num_create <= rename_limit || num_src <= rename_limit) &&
 473             ((uint64_t)num_create * (uint64_t)num_src
 474              <= (uint64_t)rename_limit * (uint64_t)rename_limit))
 475                 return 2;
 476         return 1;
 477 }
 478
 479 static int find_renames(struct diff_score *mx, int dst_cnt, int minimum_score, int copies)
 480 {
 481         int count = 0, i;
 482
 483         for (i = 0; i < dst_cnt * NUM_CANDIDATE_PER_DST; i++) {
 484                 struct diff_rename_dst *dst;
 485
 486                 if ((mx[i].dst < 0) ||
 487                     (mx[i].score < minimum_score))
 488                         break; /* there is no more usable pair. */
 489                 dst = &rename_dst[mx[i].dst];
 490                 if (dst->pair)
 491                         continue; /* already done, either exact or fuzzy. */
 492                 if (!copies && rename_src[mx[i].src].p->one->rename_used)
 493                         continue;
 494                 record_rename_pair(mx[i].dst, mx[i].src, mx[i].score);
 495                 count++;
 496         }
 497         return count;
 498 }
 499
 500 void diffcore_rename(struct diff_options *options)
 501 {
 502         int detect_rename = options->detect_rename;
 503         int minimum_score = options->rename_score;
 504         struct diff_queue_struct *q = &diff_queued_diff;
 505         struct diff_queue_struct outq;
 506         struct diff_score *mx;
 507         int i, j, rename_count, skip_unmodified = 0;
 508         int num_create, dst_cnt;
 509         struct progress *progress = NULL;
 510
 511         if (!minimum_score)
 512                 minimum_score = DEFAULT_RENAME_SCORE;
 513
 514         for (i = 0; i < q->nr; i++) {
 515                 struct diff_filepair *p = q->queue[i];
 516                 if (!DIFF_FILE_VALID(p->one)) {
 517                         if (!DIFF_FILE_VALID(p->two))
 518                                 continue; /* unmerged */
 519                         else if (options->single_follow &&
 520                                  strcmp(options->single_follow, p->two->path))
 521                                 continue; /* not interested */
 522                         else if (!options->flags.rename_empty &&
 523                                  is_empty_blob_oid(&p->two->oid))
 524                                 continue;
 525                         else if (add_rename_dst(p->two) < 0) {
 526                                 warning("skipping rename detection, detected"
 527                                         " duplicate destination '%s'",
 528                                         p->two->path);
 529                                 goto cleanup;
 530                         }
 531                 }
 532                 else if (!options->flags.rename_empty &&
 533                          is_empty_blob_oid(&p->one->oid))
 534                         continue;
 535                 else if (!DIFF_PAIR_UNMERGED(p) && !DIFF_FILE_VALID(p->two)) {
 536                         /*
 537                          * If the source is a broken "delete", and
 538                          * they did not really want to get broken,
 539                          * that means the source actually stays.
 540                          * So we increment the "rename_used" score
 541                          * by one, to indicate ourselves as a user
 542                          */
 543                         if (p->broken_pair && !p->score)
 544                                 p->one->rename_used++;
 545                         register_rename_src(p);
 546                 }
 547                 else if (detect_rename == DIFF_DETECT_COPY) {
 548                         /*
 549                          * Increment the "rename_used" score by
 550                          * one, to indicate ourselves as a user.
 551                          */
 552                         p->one->rename_used++;
 553                         register_rename_src(p);
 554                 }
 555         }
 556         if (rename_dst_nr == 0 || rename_src_nr == 0)
 557                 goto cleanup; /* nothing to do */
 558
 559         /*
 560          * We really want to cull the candidates list early
 561          * with cheap tests in order to avoid doing deltas.
 562          */
 563         rename_count = find_exact_renames(options);
 564
 565         /* Did we only want exact renames? */
 566         if (minimum_score == MAX_SCORE)
 567                 goto cleanup;
 568
 569         /*
 570          * Calculate how many renames are left (but all the source
 571          * files still remain as options for rename/copies!)
 572          */
 573         num_create = (rename_dst_nr - rename_count);
 574
 575         /* All done? */
 576         if (!num_create)
 577                 goto cleanup;
 578
 579         switch (too_many_rename_candidates(num_create, options)) {
 580         case 1:
 581                 goto cleanup;
 582         case 2:
 583                 options->degraded_cc_to_c = 1;
 584                 skip_unmodified = 1;
 585                 break;
 586         default:
 587                 break;
 588         }
 589
 590         if (options->show_rename_progress) {
 591                 progress = start_delayed_progress(
 592                                 _("Performing inexact rename detection"),
 593                                 (uint64_t)rename_dst_nr * (uint64_t)rename_src_nr);
 594         }
 595
 596         mx = xcalloc(st_mult(NUM_CANDIDATE_PER_DST, num_create), sizeof(*mx));
 597         for (dst_cnt = i = 0; i < rename_dst_nr; i++) {
 598                 struct diff_filespec *two = rename_dst[i].two;
 599                 struct diff_score *m;
 600
 601                 if (rename_dst[i].pair)
 602                         continue; /* dealt with exact match already. */
 603
 604                 m = &mx[dst_cnt * NUM_CANDIDATE_PER_DST];
 605                 for (j = 0; j < NUM_CANDIDATE_PER_DST; j++)
 606                         m[j].dst = -1;
 607
 608                 for (j = 0; j < rename_src_nr; j++) {
 609                         struct diff_filespec *one = rename_src[j].p->one;
 610                         struct diff_score this_src;
 611
 612                         if (skip_unmodified &&
 613                             diff_unmodified_pair(rename_src[j].p))
 614                                 continue;
 615
 616                         this_src.score = estimate_similarity(options->repo,
 617                                                              one, two,
 618                                                              minimum_score,
 619                                                              skip_unmodified);
 620                         this_src.name_score = basename_same(one, two);
 621                         this_src.dst = i;
 622                         this_src.src = j;
 623                         record_if_better(m, &this_src);
 624                         /*
 625                          * Once we run estimate_similarity,
 626                          * We do not need the text anymore.
 627                          */
 628                         diff_free_filespec_blob(one);
 629                         diff_free_filespec_blob(two);
 630                 }
 631                 dst_cnt++;
 632                 display_progress(progress, (uint64_t)(i+1)*(uint64_t)rename_src_nr);
 633         }
 634         stop_progress(&progress);
 635
 636         /* cost matrix sorted by most to least similar pair */
 637         STABLE_QSORT(mx, dst_cnt * NUM_CANDIDATE_PER_DST, score_compare);
 638
 639         rename_count += find_renames(mx, dst_cnt, minimum_score, 0);
 640         if (detect_rename == DIFF_DETECT_COPY)
 641                 rename_count += find_renames(mx, dst_cnt, minimum_score, 1);
 642         free(mx);
 643
 644  cleanup:
 645         /* At this point, we have found some renames and copies and they
 646          * are recorded in rename_dst.  The original list is still in *q.
 647          */
 648         DIFF_QUEUE_CLEAR(&outq);
 649         for (i = 0; i < q->nr; i++) {
 650                 struct diff_filepair *p = q->queue[i];
 651                 struct diff_filepair *pair_to_free = NULL;
 652
 653                 if (DIFF_PAIR_UNMERGED(p)) {
 654                         diff_q(&outq, p);
 655                 }
 656                 else if (!DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two)) {
 657                         /*
 658                          * Creation
 659                          *
 660                          * We would output this create record if it has
 661                          * not been turned into a rename/copy already.
 662                          */
 663                         struct diff_rename_dst *dst = locate_rename_dst(p->two);
 664                         if (dst && dst->pair) {
 665                                 diff_q(&outq, dst->pair);
 666                                 pair_to_free = p;
 667                         }
 668                         else
 669                                 /* no matching rename/copy source, so
 670                                  * record this as a creation.
 671                                  */
 672                                 diff_q(&outq, p);
 673                 }
 674                 else if (DIFF_FILE_VALID(p->one) && !DIFF_FILE_VALID(p->two)) {
 675                         /*
 676                          * Deletion
 677                          *
 678                          * We would output this delete record if:
 679                          *
 680                          * (1) this is a broken delete and the counterpart
 681                          *     broken create remains in the output; or
 682                          * (2) this is not a broken delete, and rename_dst
 683                          *     does not have a rename/copy to move p->one->path
 684                          *     out of existence.
 685                          *
 686                          * Otherwise, the counterpart broken create
 687                          * has been turned into a rename-edit; or
 688                          * delete did not have a matching create to
 689                          * begin with.
 690                          */
 691                         if (DIFF_PAIR_BROKEN(p)) {
 692                                 /* broken delete */
 693                                 struct diff_rename_dst *dst = locate_rename_dst(p->one);
 694                                 if (dst && dst->pair)
 695                                         /* counterpart is now rename/copy */
 696                                         pair_to_free = p;
 697                         }
 698                         else {
 699                                 if (p->one->rename_used)
 700                                         /* this path remains */
 701                                         pair_to_free = p;
 702                         }
 703
 704                         if (pair_to_free)
 705                                 ;
 706                         else
 707                                 diff_q(&outq, p);
 708                 }
 709                 else if (!diff_unmodified_pair(p))
 710                         /* all the usual ones need to be kept */
 711                         diff_q(&outq, p);
 712                 else
 713                         /* no need to keep unmodified pairs */
 714                         pair_to_free = p;
 715
 716                 if (pair_to_free)
 717                         diff_free_filepair(pair_to_free);
 718         }
 719         diff_debug_queue("done copying original", &outq);
 720
 721         free(q->queue);
 722         *q = outq;
 723         diff_debug_queue("done collapsing", q);
 724
 725         for (i = 0; i < rename_dst_nr; i++)
 726                 free_filespec(rename_dst[i].two);
 727
 728         FREE_AND_NULL(rename_dst);
 729         rename_dst_nr = rename_dst_alloc = 0;
 730         FREE_AND_NULL(rename_src);
 731         rename_src_nr = rename_src_alloc = 0;
 732         return;
 733 }