detect-renamed.diff

   1 This patch adds the --detect-renamed option which makes rsync notice files
   2 that either (1) match in size & modify-time (plus the basename, if possible)
   3 or (2) match in size & checksum (when --checksum was also specified) and use
   4 each match as an alternate basis file to speed up the transfer.
   5
   6 The algorithm attempts to scan the receiving-side's files in an efficient
   7 manner.  If --delete[-before] is enabled, we'll take advantage of the
   8 pre-transfer delete pass to prepare any alternate-basis-file matches we
   9 might find.  If --delete-before is not enabled, rsync does the rename scan
  10 during the regular file-sending scan (scanning each directory right before
  11 the generator starts updating files from that dir).  In this latter mode,
  12 rsync might delay the updating of a file (if no alternate-basis match was
  13 yet found) until the full scan of the receiving side is complete, at which
  14 point any delayed files are processed.
  15
  16 I chose to hard-link the alternate-basis files into a ".~tmp~" subdir that
  17 takes advantage of rsync's pre-existing partial-dir logic.  This uses less
  18 memory than trying to keep track of the matches internally, and also allows
  19 any deletions or file-updates to occur normally without interfering with
  20 these alternate-basis discoveries.
  21
  22 To use this patch, run these commands for a successful build:
  23
  24     patch -p1 <patches/detect-renamed.diff
  25     ./configure                                 (optional if already run)
  26     make
  27
  28 TODO:
  29
  30   We need to never return a match from fattr_find() that has a basis
  31   file.  This will ensure that we don't try to give a renamed file to
  32   a file that can't use it, while missing out on giving it to a file
  33   that could use it.
  34
  35 --- old/compat.c
  36 +++ new/compat.c
  37 @@ -49,6 +49,7 @@ extern int preserve_xattrs;
  38  extern int need_messages_from_generator;
  39  extern int delete_mode, delete_before, delete_during, delete_after;
  40  extern int delete_excluded;
  41 +extern int detect_renamed;
  42  extern int make_backups;
  43  extern char *shell_cmd; /* contains VER.SUB string if client is a pre-release */
  44  extern char *backup_dir, *backup_suffix;
  45 @@ -225,7 +226,7 @@ void setup_protocol(int f_out,int f_in)
  46         } else if (protocol_version >= 30) {
  47                 if (recurse && allow_inc_recurse
  48                  && !delete_before && !delete_after && !delay_updates
  49 -                && !use_qsort && !prune_empty_dirs)
  50 +                && !use_qsort && !prune_empty_dirs && !detect_renamed)
  51                         inc_recurse = 1;
  52                 need_messages_from_generator = 1;
  53         }
  54 --- old/flist.c
  55 +++ new/flist.c
  56 @@ -61,6 +61,7 @@ extern int non_perishable_cnt;
  57  extern int prune_empty_dirs;
  58  extern int copy_links;
  59  extern int copy_unsafe_links;
  60 +extern int detect_renamed;
  61  extern int protocol_version;
  62  extern int sanitize_paths;
  63  extern struct stats stats;
  64 @@ -113,6 +114,8 @@ static int64 tmp_dev, tmp_ino;
  65  #endif
  66  static char tmp_sum[MAX_DIGEST_LEN];
  67
  68 +struct file_list the_fattr_list;
  69 +
  70  static char empty_sum[MAX_DIGEST_LEN];
  71  static int flist_count_offset; /* for --delete --progress */
  72  static int dir_count = 0;
  73 @@ -281,6 +284,45 @@ static int is_excluded(char *fname, int
  74         return 0;
  75  }
  76
  77 +static int fattr_compare(struct file_struct **file1, struct file_struct **file2)
  78 +{
  79 +       struct file_struct *f1 = *file1;
  80 +       struct file_struct *f2 = *file2;
  81 +       int64 len1 = F_LENGTH(f1), len2 = F_LENGTH(f2);
  82 +       int diff;
  83 +
  84 +       if (!f1->basename || !S_ISREG(f1->mode) || !len1) {
  85 +               if (!f2->basename || !S_ISREG(f2->mode) || !len2)
  86 +                       return 0;
  87 +               return 1;
  88 +       }
  89 +       if (!f2->basename || !S_ISREG(f2->mode) || !len2)
  90 +               return -1;
  91 +
  92 +       /* Don't use diff for values that are longer than an int. */
  93 +       if (len1 != len2)
  94 +               return len1 < len2 ? -1 : 1;
  95 +
  96 +       if (always_checksum) {
  97 +               diff = u_memcmp(F_SUM(f1), F_SUM(f2), checksum_len);
  98 +               if (diff)
  99 +                       return diff;
 100 +       } else if (f1->modtime != f2->modtime)
 101 +               return f1->modtime < f2->modtime ? -1 : 1;
 102 +
 103 +       diff = u_strcmp(f1->basename, f2->basename);
 104 +       if (diff)
 105 +               return diff;
 106 +
 107 +       if (f1->dirname == f2->dirname)
 108 +               return 0;
 109 +       if (!f1->dirname)
 110 +               return -1;
 111 +       if (!f2->dirname)
 112 +               return 1;
 113 +       return u_strcmp(f1->dirname, f2->dirname);
 114 +}
 115 +
 116  static void send_directory(int f, struct file_list *flist,
 117                            char *fbuf, int len, int flags);
 118
 119 @@ -1935,6 +1977,25 @@ struct file_list *send_file_list(int f,
 120         if (verbose > 2)
 121                 rprintf(FINFO, "send_file_list done\n");
 122
 123 +       if (detect_renamed) {
 124 +               int j = flist->count;
 125 +               the_fattr_list.count = j;
 126 +               the_fattr_list.files = new_array(struct file_struct *, j);
 127 +               if (!the_fattr_list.files)
 128 +                       out_of_memory("recv_file_list");
 129 +               memcpy(the_fattr_list.files, flist->files,
 130 +                      j * sizeof (struct file_struct *));
 131 +               qsort(the_fattr_list.files, j,
 132 +                     sizeof the_fattr_list.files[0], (int (*)())fattr_compare);
 133 +               the_fattr_list.low = 0;
 134 +               while (j-- > 0) {
 135 +                       struct file_struct *fp = the_fattr_list.files[j];
 136 +                       if (fp->basename && S_ISREG(fp->mode) && F_LENGTH(fp))
 137 +                               break;
 138 +               }
 139 +               the_fattr_list.high = j;
 140 +       }
 141 +
 142         if (inc_recurse) {
 143                 add_dirs_to_tree(-1, flist, dir_count);
 144                 flist_done_allocating(flist);
 145 --- old/generator.c
 146 +++ new/generator.c
 147 @@ -79,6 +79,7 @@ extern char *basis_dir[];
 148  extern int compare_dest;
 149  extern int copy_dest;
 150  extern int link_dest;
 151 +extern int detect_renamed;
 152  extern int whole_file;
 153  extern int list_only;
 154  extern int read_batch;
 155 @@ -95,6 +96,7 @@ extern char *backup_suffix;
 156  extern int backup_suffix_len;
 157  extern struct file_list *cur_flist, *first_flist, *dir_flist;
 158  extern struct filter_list_struct server_filter_list;
 159 +extern struct file_list the_fattr_list;
 160  #ifdef ICONV_OPTION
 161  extern int ic_ndx;
 162  #endif
 163 @@ -105,6 +107,7 @@ int maybe_ATTRS_REPORT = 0;
 164
 165  static dev_t dev_zero;
 166  static int deletion_count = 0; /* used to implement --max-delete */
 167 +static int unexplored_dirs = 1;
 168  static int deldelay_size = 0, deldelay_cnt = 0;
 169  static char *deldelay_buf = NULL;
 170  static int deldelay_fd = -1;
 171 @@ -114,7 +117,8 @@ static int need_retouch_dir_times;
 172  static int need_retouch_dir_perms;
 173  static const char *solo_file = NULL;
 174
 175 -/* For calling delete_item() and delete_dir_contents(). */
 176 +/* For calling delete_item(), delete_dir_contents(), and delete_in_dir(). */
 177 +#define DEL_NO_DELETIONS       (1<<0)
 178  #define DEL_RECURSE            (1<<1) /* recurse */
 179  #define DEL_DIR_IS_EMPTY       (1<<2) /* internal delete_FUNCTIONS use only */
 180
 181 @@ -136,11 +140,120 @@ static int is_backup_file(char *fn)
 182         return k > 0 && strcmp(fn+k, backup_suffix) == 0;
 183  }
 184
 185 +/* Search for a regular file that matches either (1) the size & modified
 186 + * time (plus the basename, if possible) or (2) the size & checksum.  If
 187 + * we find an exact match down to the dirname, return -1 because we found
 188 + * an up-to-date file in the transfer, not a renamed file. */
 189 +static int fattr_find(struct file_struct *f, char *fname)
 190 +{
 191 +       int low = the_fattr_list.low, high = the_fattr_list.high;
 192 +       int mid, ok_match = -1, good_match = -1;
 193 +       struct file_struct *fmid;
 194 +       int diff;
 195 +
 196 +       while (low <= high) {
 197 +               mid = (low + high) / 2;
 198 +               fmid = the_fattr_list.files[mid];
 199 +               if (F_LENGTH(fmid) != F_LENGTH(f)) {
 200 +                       if (F_LENGTH(fmid) < F_LENGTH(f))
 201 +                               low = mid + 1;
 202 +                       else
 203 +                               high = mid - 1;
 204 +                       continue;
 205 +               }
 206 +               if (always_checksum) {
 207 +                       /* We use the FLAG_FILE_SENT flag to indicate when we
 208 +                        * have computed the checksum for an entry. */
 209 +                       if (!(f->flags & FLAG_FILE_SENT)) {
 210 +                               if (fmid->modtime == f->modtime
 211 +                                && f_name_cmp(fmid, f) == 0)
 212 +                                       return -1; /* assume we can't help */
 213 +                               file_checksum(fname, F_SUM(f), F_LENGTH(f));
 214 +                               f->flags |= FLAG_FILE_SENT;
 215 +                       }
 216 +                       diff = u_memcmp(F_SUM(fmid), F_SUM(f), checksum_len);
 217 +                       if (diff) {
 218 +                               if (diff < 0)
 219 +                                       low = mid + 1;
 220 +                               else
 221 +                                       high = mid - 1;
 222 +                               continue;
 223 +                       }
 224 +               } else {
 225 +                       if (fmid->modtime != f->modtime) {
 226 +                               if (fmid->modtime < f->modtime)
 227 +                                       low = mid + 1;
 228 +                               else
 229 +                                       high = mid - 1;
 230 +                               continue;
 231 +                       }
 232 +               }
 233 +               ok_match = mid;
 234 +               diff = u_strcmp(fmid->basename, f->basename);
 235 +               if (diff == 0) {
 236 +                       good_match = mid;
 237 +                       if (fmid->dirname == f->dirname)
 238 +                               return -1; /* file is up-to-date */
 239 +                       if (!fmid->dirname) {
 240 +                               low = mid + 1;
 241 +                               continue;
 242 +                       }
 243 +                       if (!f->dirname) {
 244 +                               high = mid - 1;
 245 +                               continue;
 246 +                       }
 247 +                       diff = u_strcmp(fmid->dirname, f->dirname);
 248 +                       if (diff == 0)
 249 +                               return -1; /* file is up-to-date */
 250 +               }
 251 +               if (diff < 0)
 252 +                       low = mid + 1;
 253 +               else
 254 +                       high = mid - 1;
 255 +       }
 256 +
 257 +       return good_match >= 0 ? good_match : ok_match;
 258 +}
 259 +
 260 +static void look_for_rename(struct file_struct *file, char *fname)
 261 +{
 262 +       struct file_struct *fp;
 263 +       char *partialptr, *fn;
 264 +       STRUCT_STAT st;
 265 +       int ndx;
 266 +
 267 +       if ((ndx = fattr_find(file, fname)) < 0)
 268 +               return;
 269 +
 270 +       fp = the_fattr_list.files[ndx];
 271 +       fn = f_name(fp, NULL);
 272 +       /* We don't provide an alternate-basis file if there is a basis file. */
 273 +       if (link_stat(fn, &st, 0) == 0)
 274 +               return;
 275 +       if ((partialptr = partial_dir_fname(fn)) == NULL
 276 +        || !handle_partial_dir(partialptr, PDIR_CREATE))
 277 +               return;
 278 +
 279 +       /* We only use the file if we can hard-link it into our tmp dir. */
 280 +       if (link(fname, partialptr) == 0) {
 281 +               if (verbose > 2) {
 282 +                       rprintf(FINFO, "found renamed: %s => %s\n",
 283 +                               fname, partialptr);
 284 +               }
 285 +               return;
 286 +       }
 287 +
 288 +       if (errno != EEXIST)
 289 +               handle_partial_dir(partialptr, PDIR_DELETE);
 290 +}
 291 +
 292  /* Delete a file or directory.  If DEL_RECURSE is set in the flags, this will
 293   * delete recursively.
 294   *
 295   * Note that fbuf must point to a MAXPATHLEN buffer if the mode indicates it's
 296   * a directory! (The buffer is used for recursion, but returned unchanged.)
 297 + *
 298 + * Also note: --detect-rename may use this routine with DEL_NO_DELETIONS set!
 299   */
 300  static enum delret delete_item(char *fbuf, int mode, char *replace, int flags)
 301  {
 302 @@ -162,6 +275,8 @@ static enum delret delete_item(char *fbu
 303                         goto check_ret;
 304                 /* OK: try to delete the directory. */
 305         }
 306 +       if (flags & DEL_NO_DELETIONS)
 307 +               return DR_SUCCESS;
 308
 309         if (!replace && max_delete >= 0 && ++deletion_count > max_delete)
 310                 return DR_AT_LIMIT;
 311 @@ -208,6 +323,8 @@ static enum delret delete_item(char *fbu
 312   * its contents, otherwise just checks for content.  Returns DR_SUCCESS or
 313   * DR_NOT_EMPTY.  Note that fname must point to a MAXPATHLEN buffer!  (The
 314   * buffer is used for recursion, but returned unchanged.)
 315 + *
 316 + * Note: --detect-rename may use this routine with DEL_NO_DELETIONS set!
 317   */
 318  static enum delret delete_dir_contents(char *fname, int flags)
 319  {
 320 @@ -227,7 +344,9 @@ static enum delret delete_dir_contents(c
 321         save_filters = push_local_filters(fname, dlen);
 322
 323         non_perishable_cnt = 0;
 324 +       file_extra_cnt += SUM_EXTRA_CNT;
 325         dirlist = get_dirlist(fname, dlen, 0);
 326 +       file_extra_cnt -= SUM_EXTRA_CNT;
 327         ret = non_perishable_cnt ? DR_NOT_EMPTY : DR_SUCCESS;
 328
 329         if (!dirlist->used)
 330 @@ -264,6 +383,8 @@ static enum delret delete_dir_contents(c
 331                 if (S_ISDIR(fp->mode)
 332                  && delete_dir_contents(fname, flags | DEL_RECURSE) != DR_SUCCESS)
 333                         ret = DR_NOT_EMPTY;
 334 +               if (detect_renamed && S_ISREG(fp->mode))
 335 +                       look_for_rename(fp, fname);
 336                 if (delete_item(fname, fp->mode, NULL, flags) != DR_SUCCESS)
 337                         ret = DR_NOT_EMPTY;
 338         }
 339 @@ -416,12 +537,17 @@ static void do_delayed_deletions(char *d
 340   * all the --delete-WHEN options.  Note that the fbuf pointer must point to a
 341   * MAXPATHLEN buffer with the name of the directory in it (the functions we
 342   * call will append names onto the end, but the old dir value will be restored
 343 - * on exit). */
 344 -static void delete_in_dir(char *fbuf, struct file_struct *file, dev_t *fs_dev)
 345 + * on exit).
 346 + *
 347 + * Note:  --detect-rename may use this routine with DEL_NO_DELETIONS set!
 348 + */
 349 +static void delete_in_dir(char *fbuf, struct file_struct *file, dev_t *fs_dev,
 350 +                         int flags)
 351  {
 352         static int already_warned = 0;
 353         struct file_list *dirlist;
 354 -       char delbuf[MAXPATHLEN];
 355 +       char *p, delbuf[MAXPATHLEN];
 356 +       unsigned remainder;
 357         int dlen, i;
 358
 359         if (!fbuf) {
 360 @@ -432,21 +558,28 @@ static void delete_in_dir(char *fbuf, st
 361         if (verbose > 2)
 362                 rprintf(FINFO, "delete_in_dir(%s)\n", fbuf);
 363
 364 +       flags |= DEL_RECURSE;
 365 +
 366         if (allowed_lull)
 367                 maybe_send_keepalive();
 368
 369         if (io_error && !ignore_errors) {
 370 -               if (already_warned)
 371 +               if (!already_warned) {
 372 +                       rprintf(FINFO,
 373 +                           "IO error encountered -- skipping file deletion\n");
 374 +                       already_warned = 1;
 375 +               }
 376 +               if (!detect_renamed)
 377                         return;
 378 -               rprintf(FINFO,
 379 -                       "IO error encountered -- skipping file deletion\n");
 380 -               already_warned = 1;
 381 -               return;
 382 +               flags |= DEL_NO_DELETIONS;
 383         }
 384
 385         dlen = strlen(fbuf);
 386         change_local_filter_dir(fbuf, dlen, F_DEPTH(file));
 387
 388 +       if (detect_renamed)
 389 +               unexplored_dirs--;
 390 +
 391         if (one_file_system) {
 392                 if (file->flags & FLAG_TOP_DIR)
 393                         filesystem_dev = *fs_dev;
 394 @@ -456,6 +589,11 @@ static void delete_in_dir(char *fbuf, st
 395
 396         dirlist = get_dirlist(fbuf, dlen, 0);
 397
 398 +       p = fbuf + dlen;
 399 +       if (dlen != 1 || *fbuf != '/')
 400 +               *p++ = '/';
 401 +       remainder = MAXPATHLEN - (p - fbuf);
 402 +
 403         /* If an item in dirlist is not found in flist, delete it
 404          * from the filesystem. */
 405         for (i = dirlist->used; i--; ) {
 406 @@ -468,16 +606,23 @@ static void delete_in_dir(char *fbuf, st
 407                                         f_name(fp, NULL));
 408                         continue;
 409                 }
 410 +               if (detect_renamed && S_ISREG(fp->mode)) {
 411 +                       strlcpy(p, fp->basename, remainder);
 412 +                       look_for_rename(fp, fbuf);
 413 +               }
 414                 if (flist_find(cur_flist, fp) < 0) {
 415                         f_name(fp, delbuf);
 416 -                       if (delete_during == 2) {
 417 +                       if (delete_during == 2 && !(flags & DEL_NO_DELETIONS)) {
 418                                 if (!remember_delete(fp, delbuf))
 419                                         break;
 420                         } else
 421 -                               delete_item(delbuf, fp->mode, NULL, DEL_RECURSE);
 422 -               }
 423 +                               delete_item(delbuf, fp->mode, NULL, flags);
 424 +               } else if (detect_renamed && S_ISDIR(fp->mode))
 425 +                       unexplored_dirs++;
 426         }
 427
 428 +       fbuf[dlen] = '\0';
 429 +
 430         flist_free(dirlist);
 431  }
 432
 433 @@ -507,9 +652,9 @@ static void do_delete_pass(void)
 434                  || !S_ISDIR(st.st_mode))
 435                         continue;
 436
 437 -               delete_in_dir(fbuf, file, &st.st_dev);
 438 +               delete_in_dir(fbuf, file, &st.st_dev, 0);
 439         }
 440 -       delete_in_dir(NULL, NULL, &dev_zero);
 441 +       delete_in_dir(NULL, NULL, &dev_zero, 0);
 442
 443         if (do_progress && !am_server)
 444                 rprintf(FINFO, "                    \r");
 445 @@ -1072,6 +1217,7 @@ static int try_dests_non(struct file_str
 446         return j;
 447  }
 448
 449 +static struct bitbag *delayed_bits = NULL;
 450  static int phase = 0;
 451  static int dflt_perms;
 452
 453 @@ -1308,8 +1454,12 @@ static void recv_generator(char *fname,
 454                         }
 455                 }
 456                 else if (delete_during && f_out != -1 && !phase && dry_run < 2
 457 -                   && (file->flags & FLAG_XFER_DIR))
 458 -                       delete_in_dir(fname, file, &real_sx.st.st_dev);
 459 +                   && (file->flags & FLAG_XFER_DIR)) {
 460 +                       if (detect_renamed && real_ret != 0)
 461 +                               unexplored_dirs++;
 462 +                       delete_in_dir(fname, file, &real_sx.st.st_dev,
 463 +                                     delete_during < 0 ? DEL_NO_DELETIONS : 0);
 464 +               }
 465                 goto cleanup;
 466         }
 467
 468 @@ -1587,8 +1737,14 @@ static void recv_generator(char *fname,
 469                         goto cleanup;
 470                 }
 471  #endif
 472 -               if (stat_errno == ENOENT)
 473 +               if (stat_errno == ENOENT) {
 474 +                       if (detect_renamed && unexplored_dirs > 0
 475 +                        && F_LENGTH(file)) {
 476 +                               bitbag_set_bit(delayed_bits, ndx);
 477 +                               return;
 478 +                       }
 479                         goto notify_others;
 480 +               }
 481                 rsyserr(FERROR, stat_errno, "recv_generator: failed to stat %s",
 482                         full_fname(fname));
 483                 goto cleanup;
 484 @@ -1910,6 +2066,12 @@ void generate_files(int f_out, const cha
 485         if (verbose > 2)
 486                 rprintf(FINFO, "generator starting pid=%ld\n", (long)getpid());
 487
 488 +       if (detect_renamed) {
 489 +               delayed_bits = bitbag_create(cur_flist->count);
 490 +               if (!delete_before && !delete_during)
 491 +                       delete_during = -1;
 492 +       }
 493 +
 494         if (delete_before && !solo_file && cur_flist->used > 0)
 495                 do_delete_pass();
 496         if (delete_during == 2) {
 497 @@ -1920,7 +2082,7 @@ void generate_files(int f_out, const cha
 498         }
 499         do_progress = 0;
 500
 501 -       if (append_mode > 0 || whole_file < 0)
 502 +       if (append_mode > 0 || detect_renamed || whole_file < 0)
 503                 whole_file = 0;
 504         if (verbose >= 2) {
 505                 rprintf(FINFO, "delta-transmission %s\n",
 506 @@ -1958,7 +2120,7 @@ void generate_files(int f_out, const cha
 507                                                 dirdev = MAKEDEV(DEV_MAJOR(devp), DEV_MINOR(devp));
 508                                         } else
 509                                                 dirdev = MAKEDEV(0, 0);
 510 -                                       delete_in_dir(f_name(fp, fbuf), fp, &dirdev);
 511 +                                       delete_in_dir(f_name(fp, fbuf), fp, &dirdev, 0);
 512                                 }
 513                         }
 514                 }
 515 @@ -2003,7 +2165,21 @@ void generate_files(int f_out, const cha
 516         } while ((cur_flist = cur_flist->next) != NULL);
 517
 518         if (delete_during)
 519 -               delete_in_dir(NULL, NULL, &dev_zero);
 520 +               delete_in_dir(NULL, NULL, &dev_zero, 0);
 521 +       if (detect_renamed) {
 522 +               if (delete_during < 0)
 523 +                       delete_during = 0;
 524 +               detect_renamed = 0;
 525 +
 526 +               for (i = -1; (i = bitbag_next_bit(delayed_bits, i)) >= 0; ) {
 527 +                       struct file_struct *file = cur_flist->files[i];
 528 +                       if (local_name)
 529 +                               strlcpy(fbuf, local_name, sizeof fbuf);
 530 +                       else
 531 +                               f_name(file, fbuf);
 532 +                       recv_generator(fbuf, file, i, itemizing, code, f_out);
 533 +               }
 534 +       }
 535         phase++;
 536         if (verbose > 2)
 537                 rprintf(FINFO, "generate_files phase=%d\n", phase);
 538 --- old/options.c
 539 +++ new/options.c
 540 @@ -79,6 +79,7 @@ int am_generator = 0;
 541  int am_starting_up = 1;
 542  int relative_paths = -1;
 543  int implied_dirs = 1;
 544 +int detect_renamed = 0;
 545  int numeric_ids = 0;
 546  int allow_8bit_chars = 0;
 547  int force_delete = 0;
 548 @@ -382,6 +383,7 @@ void usage(enum logcode F)
 549    rprintf(F,"     --modify-window=NUM     compare mod-times with reduced accuracy\n");
 550    rprintf(F," -T, --temp-dir=DIR          create temporary files in directory DIR\n");
 551    rprintf(F," -y, --fuzzy                 find similar file for basis if no dest file\n");
 552 +  rprintf(F,"     --detect-renamed        try to find renamed files to speed up the transfer\n");
 553    rprintf(F,"     --compare-dest=DIR      also compare destination files relative to DIR\n");
 554    rprintf(F,"     --copy-dest=DIR         ... and include copies of unchanged files\n");
 555    rprintf(F,"     --link-dest=DIR         hardlink to files in DIR when unchanged\n");
 556 @@ -561,6 +563,7 @@ static struct poptOption long_options[]
 557    {"compare-dest",     0,  POPT_ARG_STRING, 0, OPT_COMPARE_DEST, 0, 0 },
 558    {"copy-dest",        0,  POPT_ARG_STRING, 0, OPT_COPY_DEST, 0, 0 },
 559    {"link-dest",        0,  POPT_ARG_STRING, 0, OPT_LINK_DEST, 0, 0 },
 560 +  {"detect-renamed",   0,  POPT_ARG_NONE,   &detect_renamed, 0, 0, 0 },
 561    {"fuzzy",           'y', POPT_ARG_NONE,   &fuzzy_basis, 0, 0, 0 },
 562    {"compress",        'z', POPT_ARG_NONE,   0, 'z', 0, 0 },
 563    {"no-compress",      0,  POPT_ARG_VAL,    &do_compression, 0, 0, 0 },
 564 @@ -1531,7 +1534,7 @@ int parse_arguments(int *argc_p, const c
 565                 inplace = 1;
 566         }
 567
 568 -       if (delay_updates && !partial_dir)
 569 +       if ((delay_updates || detect_renamed) && !partial_dir)
 570                 partial_dir = tmp_partialdir;
 571
 572         if (inplace) {
 573 @@ -1540,6 +1543,7 @@ int parse_arguments(int *argc_p, const c
 574                         snprintf(err_buf, sizeof err_buf,
 575                                  "--%s cannot be used with --%s\n",
 576                                  append_mode ? "append" : "inplace",
 577 +                                detect_renamed ? "detect-renamed" :
 578                                  delay_updates ? "delay-updates" : "partial-dir");
 579                         return 0;
 580                 }
 581 @@ -1887,6 +1891,8 @@ void server_options(char **args, int *ar
 582                         args[ac++] = "--super";
 583                 if (size_only)
 584                         args[ac++] = "--size-only";
 585 +               if (detect_renamed)
 586 +                       args[ac++] = "--detect-renamed";
 587         } else {
 588                 if (skip_compress) {
 589                         if (asprintf(&arg, "--skip-compress=%s", skip_compress) < 0)
 590 --- old/rsync.yo
 591 +++ new/rsync.yo
 592 @@ -389,6 +389,7 @@ to the detailed description below for a
 593       --modify-window=NUM     compare mod-times with reduced accuracy
 594   -T, --temp-dir=DIR          create temporary files in directory DIR
 595   -y, --fuzzy                 find similar file for basis if no dest file
 596 +     --detect-renamed        try to find renamed files to speed the xfer
 597       --compare-dest=DIR      also compare received files relative to DIR
 598       --copy-dest=DIR         ... and include copies of unchanged files
 599       --link-dest=DIR         hardlink to files in DIR when unchanged
 600 @@ -1394,6 +1395,15 @@ Note that the use of the bf(--delete) op
 601  fuzzy-match files, so either use bf(--delete-after) or specify some
 602  filename exclusions if you need to prevent this.
 603
 604 +dit(bf(--detect-renamed)) This option tells rsync to scan the receiving
 605 +side for files that have been renamed, and to use any that are found as
 606 +alternate basis files to help speed up the transfer.
 607 +By default, alternate-basis files are hard-linked into a directory named
 608 +".~tmp~" in each file's destination directory, but if you've specified
 609 +the bf(--partial-dir) option, that directory will be used instead.  These
 610 +potential alternate-basis files will be removed as the transfer progresses.
 611 +This option conflicts with bf(--inplace) and bf(--append).
 612 +
 613  dit(bf(--compare-dest=DIR)) This option instructs rsync to use em(DIR) on
 614  the destination machine as an additional hierarchy to compare destination
 615  files against doing transfers (if the files are missing in the destination
 616 --- old/util.c
 617 +++ new/util.c
 618 @@ -1029,6 +1029,32 @@ int handle_partial_dir(const char *fname
 619         return 1;
 620  }
 621
 622 +/* We need to supply our own strcmp function for file list comparisons
 623 + * to ensure that signed/unsigned usage is consistent between machines. */
 624 +int u_strcmp(const char *p1, const char *p2)
 625 +{
 626 +        for ( ; *p1; p1++, p2++) {
 627 +               if (*p1 != *p2)
 628 +                       break;
 629 +       }
 630 +
 631 +       return (int)*(uchar*)p1 - (int)*(uchar*)p2;
 632 +}
 633 +
 634 +/* We need a memcmp function compares unsigned-byte values. */
 635 +int u_memcmp(const void *p1, const void *p2, size_t len)
 636 +{
 637 +       const uchar *u1 = p1;
 638 +       const uchar *u2 = p2;
 639 +
 640 +       while (len--) {
 641 +               if (*u1 != *u2)
 642 +                       return (int)*u1 - (int)*u2;
 643 +       }
 644 +
 645 +       return 0;
 646 +}
 647 +
 648  /**
 649   * Determine if a symlink points outside the current directory tree.
 650   * This is considered "unsafe" because e.g. when mirroring somebody