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 @@ -41,6 +41,7 @@ extern int checksum_seed;
  38  extern int basis_dir_cnt;
  39  extern int prune_empty_dirs;
  40  extern int protocol_version;
  41 +extern int detect_renamed;
  42  extern int protect_args;
  43  extern int preserve_uid;
  44  extern int preserve_gid;
  45 @@ -218,7 +219,7 @@ 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 @@ -252,6 +255,45 @@ 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 @@ -2154,6 +2196,25 @@ struct file_list *recv_file_list(int f)
 120
 121         clean_flist(flist, relative_paths);
 122
 123 +       if (detect_renamed) {
 124 +               int j = flist->used;
 125 +               the_fattr_list.used = 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 (protocol_version < 30) {
 143                 /* Recv the io_error flag */
 144                 if (ignore_errors)
 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 +140,121 @@ 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 (!partial_dir || (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 +
 276 +       if (!dry_run) {
 277 +               if ((partialptr = partial_dir_fname(fn)) == NULL
 278 +                || !handle_partial_dir(partialptr, PDIR_CREATE))
 279 +                       return;
 280 +               /* We only use the file if we can hard-link it into our tmp dir. */
 281 +               if (link(fname, partialptr) != 0) {
 282 +                       if (errno != EEXIST)
 283 +                               handle_partial_dir(partialptr, PDIR_DELETE);
 284 +                       return;
 285 +               }
 286 +       }
 287 +
 288 +       /* I think this falls into the -vv category with "%s is uptodate", etc. */
 289 +       if (verbose > 1)
 290 +               rprintf(FINFO, "found renamed: %s => %s\n", fname, fn);
 291 +}
 292 +
 293  /* Delete a file or directory.  If DEL_RECURSE is set in the flags, this will
 294   * delete recursively.
 295   *
 296   * Note that fbuf must point to a MAXPATHLEN buffer if the mode indicates it's
 297   * a directory! (The buffer is used for recursion, but returned unchanged.)
 298 + *
 299 + * Also note: --detect-rename may use this routine with DEL_NO_DELETIONS set!
 300   */
 301  static enum delret delete_item(char *fbuf, int mode, char *replace, int flags)
 302  {
 303 @@ -162,6 +276,8 @@ static enum delret delete_item(char *fbu
 304                         goto check_ret;
 305                 /* OK: try to delete the directory. */
 306         }
 307 +       if (flags & DEL_NO_DELETIONS)
 308 +               return DR_SUCCESS;
 309
 310         if (!replace && max_delete >= 0 && ++deletion_count > max_delete)
 311                 return DR_AT_LIMIT;
 312 @@ -208,6 +324,8 @@ static enum delret delete_item(char *fbu
 313   * its contents, otherwise just checks for content.  Returns DR_SUCCESS or
 314   * DR_NOT_EMPTY.  Note that fname must point to a MAXPATHLEN buffer!  (The
 315   * buffer is used for recursion, but returned unchanged.)
 316 + *
 317 + * Note: --detect-rename may use this routine with DEL_NO_DELETIONS set!
 318   */
 319  static enum delret delete_dir_contents(char *fname, int flags)
 320  {
 321 @@ -227,7 +345,9 @@ static enum delret delete_dir_contents(c
 322         save_filters = push_local_filters(fname, dlen);
 323
 324         non_perishable_cnt = 0;
 325 +       file_extra_cnt += SUM_EXTRA_CNT;
 326         dirlist = get_dirlist(fname, dlen, 0);
 327 +       file_extra_cnt -= SUM_EXTRA_CNT;
 328         ret = non_perishable_cnt ? DR_NOT_EMPTY : DR_SUCCESS;
 329
 330         if (!dirlist->used)
 331 @@ -264,6 +384,8 @@ static enum delret delete_dir_contents(c
 332                 if (S_ISDIR(fp->mode)
 333                  && delete_dir_contents(fname, flags | DEL_RECURSE) != DR_SUCCESS)
 334                         ret = DR_NOT_EMPTY;
 335 +               if (detect_renamed && S_ISREG(fp->mode))
 336 +                       look_for_rename(fp, fname);
 337                 if (delete_item(fname, fp->mode, NULL, flags) != DR_SUCCESS)
 338                         ret = DR_NOT_EMPTY;
 339         }
 340 @@ -416,13 +538,18 @@ static void do_delayed_deletions(char *d
 341   * all the --delete-WHEN options.  Note that the fbuf pointer must point to a
 342   * MAXPATHLEN buffer with the name of the directory in it (the functions we
 343   * call will append names onto the end, but the old dir value will be restored
 344 - * on exit). */
 345 -static void delete_in_dir(char *fbuf, struct file_struct *file, dev_t *fs_dev)
 346 + * on exit).
 347 + *
 348 + * Note:  --detect-rename may use this routine with DEL_NO_DELETIONS set!
 349 + */
 350 +static void delete_in_dir(char *fbuf, struct file_struct *file, dev_t *fs_dev,
 351 +                         int flags)
 352  {
 353         static int already_warned = 0;
 354         struct file_list *dirlist;
 355 -       char delbuf[MAXPATHLEN];
 356 -       int dlen, i;
 357 +       char *p, delbuf[MAXPATHLEN];
 358 +       unsigned remainder;
 359 +       int dlen, i, restore_dot = 0;
 360
 361         if (!fbuf) {
 362                 change_local_filter_dir(NULL, 0, 0);
 363 @@ -432,21 +559,28 @@ static void delete_in_dir(char *fbuf, st
 364         if (verbose > 2)
 365                 rprintf(FINFO, "delete_in_dir(%s)\n", fbuf);
 366
 367 +       flags |= DEL_RECURSE;
 368 +
 369         if (allowed_lull)
 370                 maybe_send_keepalive();
 371
 372         if (io_error && !ignore_errors) {
 373 -               if (already_warned)
 374 +               if (!already_warned) {
 375 +                       rprintf(FINFO,
 376 +                           "IO error encountered -- skipping file deletion\n");
 377 +                       already_warned = 1;
 378 +               }
 379 +               if (!detect_renamed)
 380                         return;
 381 -               rprintf(FINFO,
 382 -                       "IO error encountered -- skipping file deletion\n");
 383 -               already_warned = 1;
 384 -               return;
 385 +               flags |= DEL_NO_DELETIONS;
 386         }
 387
 388         dlen = strlen(fbuf);
 389         change_local_filter_dir(fbuf, dlen, F_DEPTH(file));
 390
 391 +       if (detect_renamed)
 392 +               unexplored_dirs--;
 393 +
 394         if (one_file_system) {
 395                 if (file->flags & FLAG_TOP_DIR)
 396                         filesystem_dev = *fs_dev;
 397 @@ -456,6 +590,14 @@ static void delete_in_dir(char *fbuf, st
 398
 399         dirlist = get_dirlist(fbuf, dlen, 0);
 400
 401 +       p = fbuf + dlen;
 402 +       if (dlen == 1 && *fbuf == '.') {
 403 +               restore_dot = 1;
 404 +               p = fbuf;
 405 +       } else if (dlen != 1 || *fbuf != '/')
 406 +               *p++ = '/';
 407 +       remainder = MAXPATHLEN - (p - fbuf);
 408 +
 409         /* If an item in dirlist is not found in flist, delete it
 410          * from the filesystem. */
 411         for (i = dirlist->used; i--; ) {
 412 @@ -468,16 +610,25 @@ static void delete_in_dir(char *fbuf, st
 413                                         f_name(fp, NULL));
 414                         continue;
 415                 }
 416 +               if (detect_renamed && S_ISREG(fp->mode)) {
 417 +                       strlcpy(p, fp->basename, remainder);
 418 +                       look_for_rename(fp, fbuf);
 419 +               }
 420                 if (flist_find(cur_flist, fp) < 0) {
 421                         f_name(fp, delbuf);
 422 -                       if (delete_during == 2) {
 423 +                       if (delete_during == 2 && !(flags & DEL_NO_DELETIONS)) {
 424                                 if (!remember_delete(fp, delbuf))
 425                                         break;
 426                         } else
 427 -                               delete_item(delbuf, fp->mode, NULL, DEL_RECURSE);
 428 -               }
 429 +                               delete_item(delbuf, fp->mode, NULL, flags);
 430 +               } else if (detect_renamed && S_ISDIR(fp->mode))
 431 +                       unexplored_dirs++;
 432         }
 433
 434 +       if (restore_dot)
 435 +               fbuf[0] = '.';
 436 +       fbuf[dlen] = '\0';
 437 +
 438         flist_free(dirlist);
 439  }
 440
 441 @@ -507,9 +658,9 @@ static void do_delete_pass(void)
 442                  || !S_ISDIR(st.st_mode))
 443                         continue;
 444
 445 -               delete_in_dir(fbuf, file, &st.st_dev);
 446 +               delete_in_dir(fbuf, file, &st.st_dev, 0);
 447         }
 448 -       delete_in_dir(NULL, NULL, &dev_zero);
 449 +       delete_in_dir(NULL, NULL, &dev_zero, 0);
 450
 451         if (do_progress && !am_server)
 452                 rprintf(FINFO, "                    \r");
 453 @@ -1101,6 +1252,7 @@ static void list_file_entry(struct file_
 454         }
 455  }
 456
 457 +static struct bitbag *delayed_bits = NULL;
 458  static int phase = 0;
 459  static int dflt_perms;
 460
 461 @@ -1345,8 +1497,12 @@ static void recv_generator(char *fname,
 462                         }
 463                 }
 464                 else if (delete_during && f_out != -1 && !phase && dry_run < 2
 465 -                   && (file->flags & FLAG_CONTENT_DIR))
 466 -                       delete_in_dir(fname, file, &real_sx.st.st_dev);
 467 +                   && (file->flags & FLAG_CONTENT_DIR)) {
 468 +                       if (detect_renamed && real_ret != 0)
 469 +                               unexplored_dirs++;
 470 +                       delete_in_dir(fname, file, &real_sx.st.st_dev,
 471 +                                     delete_during < 0 ? DEL_NO_DELETIONS : 0);
 472 +               }
 473                 goto cleanup;
 474         }
 475
 476 @@ -1624,8 +1780,14 @@ static void recv_generator(char *fname,
 477                         goto cleanup;
 478                 }
 479  #endif
 480 -               if (stat_errno == ENOENT)
 481 +               if (stat_errno == ENOENT) {
 482 +                       if (detect_renamed && unexplored_dirs > 0
 483 +                        && F_LENGTH(file)) {
 484 +                               bitbag_set_bit(delayed_bits, ndx);
 485 +                               return;
 486 +                       }
 487                         goto notify_others;
 488 +               }
 489                 rsyserr(FERROR, stat_errno, "recv_generator: failed to stat %s",
 490                         full_fname(fname));
 491                 goto cleanup;
 492 @@ -1961,6 +2123,12 @@ void generate_files(int f_out, const cha
 493         if (verbose > 2)
 494                 rprintf(FINFO, "generator starting pid=%ld\n", (long)getpid());
 495
 496 +       if (detect_renamed) {
 497 +               delayed_bits = bitbag_create(cur_flist->used);
 498 +               if (!delete_before && !delete_during)
 499 +                       delete_during = -1;
 500 +       }
 501 +
 502         if (delete_before && !solo_file && cur_flist->used > 0)
 503                 do_delete_pass();
 504         if (delete_during == 2) {
 505 @@ -1971,7 +2139,7 @@ void generate_files(int f_out, const cha
 506         }
 507         do_progress = 0;
 508
 509 -       if (append_mode > 0 || whole_file < 0)
 510 +       if (append_mode > 0 || detect_renamed || whole_file < 0)
 511                 whole_file = 0;
 512         if (verbose >= 2) {
 513                 rprintf(FINFO, "delta-transmission %s\n",
 514 @@ -2009,7 +2177,7 @@ void generate_files(int f_out, const cha
 515                                                 dirdev = MAKEDEV(DEV_MAJOR(devp), DEV_MINOR(devp));
 516                                         } else
 517                                                 dirdev = MAKEDEV(0, 0);
 518 -                                       delete_in_dir(f_name(fp, fbuf), fp, &dirdev);
 519 +                                       delete_in_dir(f_name(fp, fbuf), fp, &dirdev, 0);
 520                                 }
 521                         }
 522                 }
 523 @@ -2054,7 +2222,21 @@ void generate_files(int f_out, const cha
 524         } while ((cur_flist = cur_flist->next) != NULL);
 525
 526         if (delete_during)
 527 -               delete_in_dir(NULL, NULL, &dev_zero);
 528 +               delete_in_dir(NULL, NULL, &dev_zero, 0);
 529 +       if (detect_renamed) {
 530 +               if (delete_during < 0)
 531 +                       delete_during = 0;
 532 +               detect_renamed = 0;
 533 +
 534 +               for (i = -1; (i = bitbag_next_bit(delayed_bits, i)) >= 0; ) {
 535 +                       struct file_struct *file = cur_flist->files[i];
 536 +                       if (local_name)
 537 +                               strlcpy(fbuf, local_name, sizeof fbuf);
 538 +                       else
 539 +                               f_name(file, fbuf);
 540 +                       recv_generator(fbuf, file, i, itemizing, code, f_out);
 541 +               }
 542 +       }
 543         phase++;
 544         if (verbose > 2)
 545                 rprintf(FINFO, "generate_files phase=%d\n", phase);
 546 --- old/options.c
 547 +++ new/options.c
 548 @@ -80,6 +80,7 @@ int am_generator = 0;
 549  int am_starting_up = 1;
 550  int relative_paths = -1;
 551  int implied_dirs = 1;
 552 +int detect_renamed = 0;
 553  int numeric_ids = 0;
 554  int allow_8bit_chars = 0;
 555  int force_delete = 0;
 556 @@ -383,6 +384,7 @@ void usage(enum logcode F)
 557    rprintf(F,"     --modify-window=NUM     compare mod-times with reduced accuracy\n");
 558    rprintf(F," -T, --temp-dir=DIR          create temporary files in directory DIR\n");
 559    rprintf(F," -y, --fuzzy                 find similar file for basis if no dest file\n");
 560 +  rprintf(F,"     --detect-renamed        try to find renamed files to speed up the transfer\n");
 561    rprintf(F,"     --compare-dest=DIR      also compare destination files relative to DIR\n");
 562    rprintf(F,"     --copy-dest=DIR         ... and include copies of unchanged files\n");
 563    rprintf(F,"     --link-dest=DIR         hardlink to files in DIR when unchanged\n");
 564 @@ -561,6 +563,7 @@ static struct poptOption long_options[]
 565    {"compare-dest",     0,  POPT_ARG_STRING, 0, OPT_COMPARE_DEST, 0, 0 },
 566    {"copy-dest",        0,  POPT_ARG_STRING, 0, OPT_COPY_DEST, 0, 0 },
 567    {"link-dest",        0,  POPT_ARG_STRING, 0, OPT_LINK_DEST, 0, 0 },
 568 +  {"detect-renamed",   0,  POPT_ARG_NONE,   &detect_renamed, 0, 0, 0 },
 569    {"fuzzy",           'y', POPT_ARG_NONE,   &fuzzy_basis, 0, 0, 0 },
 570    {"compress",        'z', POPT_ARG_NONE,   0, 'z', 0, 0 },
 571    {"no-compress",      0,  POPT_ARG_VAL,    &do_compression, 0, 0, 0 },
 572 @@ -1532,7 +1535,7 @@ int parse_arguments(int *argc_p, const c
 573                 inplace = 1;
 574         }
 575
 576 -       if (delay_updates && !partial_dir)
 577 +       if ((delay_updates || detect_renamed) && !partial_dir)
 578                 partial_dir = tmp_partialdir;
 579
 580         if (inplace) {
 581 @@ -1541,6 +1544,7 @@ int parse_arguments(int *argc_p, const c
 582                         snprintf(err_buf, sizeof err_buf,
 583                                  "--%s cannot be used with --%s\n",
 584                                  append_mode ? "append" : "inplace",
 585 +                                detect_renamed ? "detect-renamed" :
 586                                  delay_updates ? "delay-updates" : "partial-dir");
 587                         return 0;
 588                 }
 589 @@ -1890,6 +1894,9 @@ void server_options(char **args, int *ar
 590                         args[ac++] = arg;
 591                 }
 592         }
 593 +       /* Both sides need to know in case this disables incremental recursion. */
 594 +       if (detect_renamed)
 595 +               args[ac++] = "--detect-renamed";
 596
 597         if (modify_window_set) {
 598                 if (asprintf(&arg, "--modify-window=%d", modify_window) < 0)
 599 --- old/rsync.yo
 600 +++ new/rsync.yo
 601 @@ -384,6 +384,7 @@ to the detailed description below for a
 602       --modify-window=NUM     compare mod-times with reduced accuracy
 603   -T, --temp-dir=DIR          create temporary files in directory DIR
 604   -y, --fuzzy                 find similar file for basis if no dest file
 605 +     --detect-renamed        try to find renamed files to speed the xfer
 606       --compare-dest=DIR      also compare received files relative to DIR
 607       --copy-dest=DIR         ... and include copies of unchanged files
 608       --link-dest=DIR         hardlink to files in DIR when unchanged
 609 @@ -1424,6 +1425,21 @@ Note that the use of the bf(--delete) op
 610  fuzzy-match files, so either use bf(--delete-after) or specify some
 611  filename exclusions if you need to prevent this.
 612
 613 +dit(bf(--detect-renamed)) With this option, for each new source file
 614 +(call it em(src/S)), rsync looks for a file em(dest/D) anywhere in the
 615 +destination that passes the quick check with em(src/S).  If such a em(dest/D)
 616 +is found, rsync uses it as an alternate basis for transferring em(S).  The
 617 +idea is that if em(src/S) was renamed from em(src/D) (as opposed to em(src/S)
 618 +passing the quick check with em(dest/D) by coincidence), the delta-transfer
 619 +algorithm will find that all the data matches between em(src/S) and em(dest/D),
 620 +and the transfer will be really fast.
 621 +
 622 +By default, alternate-basis files are hard-linked into a directory named
 623 +".~tmp~" in each file's destination directory, but if you've specified
 624 +the bf(--partial-dir) option, that directory will be used instead.  These
 625 +potential alternate-basis files will be removed as the transfer progresses.
 626 +This option conflicts with bf(--inplace) and bf(--append).
 627 +
 628  dit(bf(--compare-dest=DIR)) This option instructs rsync to use em(DIR) on
 629  the destination machine as an additional hierarchy to compare destination
 630  files against doing transfers (if the files are missing in the destination
 631 --- old/util.c
 632 +++ new/util.c
 633 @@ -1030,6 +1030,32 @@ int handle_partial_dir(const char *fname
 634         return 1;
 635  }
 636
 637 +/* We need to supply our own strcmp function for file list comparisons
 638 + * to ensure that signed/unsigned usage is consistent between machines. */
 639 +int u_strcmp(const char *p1, const char *p2)
 640 +{
 641 +        for ( ; *p1; p1++, p2++) {
 642 +               if (*p1 != *p2)
 643 +                       break;
 644 +       }
 645 +
 646 +       return (int)*(uchar*)p1 - (int)*(uchar*)p2;
 647 +}
 648 +
 649 +/* We need a memcmp function compares unsigned-byte values. */
 650 +int u_memcmp(const void *p1, const void *p2, size_t len)
 651 +{
 652 +       const uchar *u1 = p1;
 653 +       const uchar *u2 = p2;
 654 +
 655 +       while (len--) {
 656 +               if (*u1 != *u2)
 657 +                       return (int)*u1 - (int)*u2;
 658 +       }
 659 +
 660 +       return 0;
 661 +}
 662 +
 663  /**
 664   * Determine if a symlink points outside the current directory tree.
 665   * This is considered "unsafe" because e.g. when mirroring somebody