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/flist.c
  36 +++ new/flist.c
  37 @@ -53,6 +53,7 @@ extern int non_perishable_cnt;
  38  extern int prune_empty_dirs;
  39  extern int copy_links;
  40  extern int copy_unsafe_links;
  41 +extern int detect_renamed;
  42  extern int protocol_version;
  43  extern int sanitize_paths;
  44  extern struct stats stats;
  45 @@ -70,6 +71,8 @@ int checksum_len;
  46  dev_t filesystem_dev; /* used to implement -x */
  47  unsigned int file_struct_len;
  48
  49 +struct file_list the_fattr_list;
  50 +
  51  static char empty_sum[MD4_SUM_LENGTH];
  52  static int flist_count_offset;
  53
  54 @@ -252,6 +255,44 @@ static mode_t from_wire_mode(int mode)
  55         return mode;
  56  }
  57
  58 +static int fattr_compare(struct file_struct **file1, struct file_struct **file2)
  59 +{
  60 +       struct file_struct *f1 = *file1;
  61 +       struct file_struct *f2 = *file2;
  62 +       int diff;
  63 +
  64 +       if (!f1->basename || !S_ISREG(f1->mode) || !f1->length) {
  65 +               if (!f2->basename || !S_ISREG(f2->mode) || !f2->length)
  66 +                       return 0;
  67 +               return 1;
  68 +       }
  69 +       if (!f2->basename || !S_ISREG(f2->mode) || !f2->length)
  70 +               return -1;
  71 +
  72 +       /* Don't use diff for values that are longer than an int. */
  73 +       if (f1->length != f2->length)
  74 +               return f1->length < f2->length ? -1 : 1;
  75 +
  76 +       if (always_checksum) {
  77 +               diff = u_memcmp(f1->u.sum, f2->u.sum, checksum_len);
  78 +               if (diff)
  79 +                       return diff;
  80 +       } else if (f1->modtime != f2->modtime)
  81 +               return f1->modtime < f2->modtime ? -1 : 1;
  82 +
  83 +       diff = u_strcmp(f1->basename, f2->basename);
  84 +       if (diff)
  85 +               return diff;
  86 +
  87 +       if (f1->dirname == f2->dirname)
  88 +               return 0;
  89 +       if (!f1->dirname)
  90 +               return -1;
  91 +       if (!f2->dirname)
  92 +               return 1;
  93 +       return u_strcmp(f1->dirname, f2->dirname);
  94 +}
  95 +
  96  static void send_directory(int f, struct file_list *flist,
  97                            char *fbuf, int len);
  98
  99 @@ -1388,6 +1429,25 @@ struct file_list *recv_file_list(int f)
 100
 101         clean_flist(flist, relative_paths, 1);
 102
 103 +       if (detect_renamed) {
 104 +               int j = flist->count;
 105 +               the_fattr_list.count = j;
 106 +               the_fattr_list.files = new_array(struct file_struct *, j);
 107 +               if (!the_fattr_list.files)
 108 +                       goto oom;
 109 +               memcpy(the_fattr_list.files, flist->files,
 110 +                      j * sizeof (struct file_struct *));
 111 +               qsort(the_fattr_list.files, j,
 112 +                   sizeof the_fattr_list.files[0], (int (*)())fattr_compare);
 113 +               the_fattr_list.low = 0;
 114 +               while (j-- > 0) {
 115 +                       struct file_struct *fp = the_fattr_list.files[j];
 116 +                       if (fp->basename && S_ISREG(fp->mode) && fp->length)
 117 +                               break;
 118 +               }
 119 +               the_fattr_list.high = j;
 120 +       }
 121 +
 122         if (f >= 0) {
 123                 recv_uid_list(f, flist);
 124
 125 --- old/generator.c
 126 +++ new/generator.c
 127 @@ -76,6 +76,7 @@ extern char *basis_dir[];
 128  extern int compare_dest;
 129  extern int copy_dest;
 130  extern int link_dest;
 131 +extern int detect_renamed;
 132  extern int whole_file;
 133  extern int list_only;
 134  extern int new_root_dir;
 135 @@ -91,14 +92,17 @@ extern char *backup_dir;
 136  extern char *backup_suffix;
 137  extern int backup_suffix_len;
 138  extern struct file_list *the_file_list;
 139 +extern struct file_list the_fattr_list;
 140  extern struct filter_list_struct server_filter_list;
 141
 142  int ignore_perishable = 0;
 143  int non_perishable_cnt = 0;
 144
 145  static int deletion_count = 0; /* used to implement --max-delete */
 146 +static int unexplored_dirs = 1;
 147
 148 -/* For calling delete_item() and delete_dir_contents(). */
 149 +/* For calling delete_item(), delete_dir_contents(), and delete_in_dir(). */
 150 +#define DEL_NO_DELETIONS       (1<<0)
 151  #define DEL_RECURSE            (1<<1) /* recurse */
 152  #define DEL_DIR_IS_EMPTY       (1<<2) /* internal delete_FUNCTIONS use only */
 153
 154 @@ -120,11 +124,120 @@ static int is_backup_file(char *fn)
 155         return k > 0 && strcmp(fn+k, backup_suffix) == 0;
 156  }
 157
 158 +/* Search for a regular file that matches either (1) the size & modified
 159 + * time (plus the basename, if possible) or (2) the size & checksum.  If
 160 + * we find an exact match down to the dirname, return -1 because we found
 161 + * an up-to-date file in the transfer, not a renamed file. */
 162 +static int fattr_find(struct file_struct *f, char *fname, alloc_pool_t pool)
 163 +{
 164 +       int low = the_fattr_list.low, high = the_fattr_list.high;
 165 +       int mid, ok_match = -1, good_match = -1;
 166 +       struct file_struct *fmid;
 167 +       int diff;
 168 +
 169 +       while (low <= high) {
 170 +               mid = (low + high) / 2;
 171 +               fmid = the_fattr_list.files[mid];
 172 +               if (fmid->length != f->length) {
 173 +                       if (fmid->length < f->length)
 174 +                               low = mid + 1;
 175 +                       else
 176 +                               high = mid - 1;
 177 +                       continue;
 178 +               }
 179 +               if (always_checksum) {
 180 +                       if (!f->u.sum) {
 181 +                               if (fmid->modtime == f->modtime
 182 +                                && f_name_cmp(fmid, f) == 0)
 183 +                                       return -1; /* assume we can't help */
 184 +                               f->u.sum = pool_alloc(pool, MD4_SUM_LENGTH,
 185 +                                                     "fattr_find");
 186 +                               file_checksum(fname, f->u.sum, f->length);
 187 +                       }
 188 +                       diff = u_memcmp(fmid->u.sum, f->u.sum, checksum_len);
 189 +                       if (diff) {
 190 +                               if (diff < 0)
 191 +                                       low = mid + 1;
 192 +                               else
 193 +                                       high = mid - 1;
 194 +                               continue;
 195 +                       }
 196 +               } else {
 197 +                       if (fmid->modtime != f->modtime) {
 198 +                               if (fmid->modtime < f->modtime)
 199 +                                       low = mid + 1;
 200 +                               else
 201 +                                       high = mid - 1;
 202 +                               continue;
 203 +                       }
 204 +               }
 205 +               ok_match = mid;
 206 +               diff = u_strcmp(fmid->basename, f->basename);
 207 +               if (diff == 0) {
 208 +                       good_match = mid;
 209 +                       if (fmid->dirname == f->dirname)
 210 +                               return -1; /* file is up-to-date */
 211 +                       if (!fmid->dirname) {
 212 +                               low = mid + 1;
 213 +                               continue;
 214 +                       }
 215 +                       if (!f->dirname) {
 216 +                               high = mid - 1;
 217 +                               continue;
 218 +                       }
 219 +                       diff = u_strcmp(fmid->dirname, f->dirname);
 220 +                       if (diff == 0)
 221 +                               return -1; /* file is up-to-date */
 222 +               }
 223 +               if (diff < 0)
 224 +                       low = mid + 1;
 225 +               else
 226 +                       high = mid - 1;
 227 +       }
 228 +
 229 +       return good_match >= 0 ? good_match : ok_match;
 230 +}
 231 +
 232 +static void look_for_rename(struct file_struct *file, char *fname,
 233 +                           alloc_pool_t pool)
 234 +{
 235 +       struct file_struct *fp;
 236 +       char *partialptr, *fn;
 237 +       STRUCT_STAT st;
 238 +       int ndx;
 239 +
 240 +       if ((ndx = fattr_find(file, fname, pool)) < 0)
 241 +               return;
 242 +
 243 +       fp = the_fattr_list.files[ndx];
 244 +       fn = f_name(fp, NULL);
 245 +       /* We don't provide an alternate-basis file if there is a basis file. */
 246 +       if (link_stat(fn, &st, 0) == 0)
 247 +               return;
 248 +       if ((partialptr = partial_dir_fname(fn)) == NULL
 249 +        || !handle_partial_dir(partialptr, PDIR_CREATE))
 250 +               return;
 251 +
 252 +       /* We only use the file if we can hard-link it into our tmp dir. */
 253 +       if (link(fname, partialptr) == 0) {
 254 +               if (verbose > 2) {
 255 +                       rprintf(FINFO, "found renamed: %s => %s\n",
 256 +                               fname, partialptr);
 257 +               }
 258 +               return;
 259 +       }
 260 +
 261 +       if (errno != EEXIST)
 262 +               handle_partial_dir(partialptr, PDIR_DELETE);
 263 +}
 264 +
 265  /* Delete a file or directory.  If DEL_RECURSE is set in the flags, this will
 266   * delete recursively.
 267   *
 268   * Note that fname must point to a MAXPATHLEN buffer if the mode indicates it's
 269   * a directory! (The buffer is used for recursion, but returned unchanged.)
 270 + *
 271 + * Also note: --detect-rename may use this routine with DEL_NO_DELETIONS set!
 272   */
 273  static enum delret delete_item(char *fname, int mode, char *replace, int flags)
 274  {
 275 @@ -146,6 +259,8 @@ static enum delret delete_item(char *fna
 276                         goto check_ret;
 277                 /* OK: try to delete the directory. */
 278         }
 279 +       if (flags & DEL_NO_DELETIONS)
 280 +               return DR_SUCCESS;
 281
 282         if (!replace && max_delete >= 0 && ++deletion_count > max_delete)
 283                 return DR_AT_LIMIT;
 284 @@ -192,6 +307,8 @@ static enum delret delete_item(char *fna
 285   * its contents, otherwise just checks for content.  Returns DR_SUCCESS or
 286   * DR_NOT_EMPTY.  Note that fname must point to a MAXPATHLEN buffer!  (The
 287   * buffer is used for recursion, but returned unchanged.)
 288 + *
 289 + * Note: --detect-rename may use this routine with DEL_NO_DELETIONS set!
 290   */
 291  static enum delret delete_dir_contents(char *fname, int flags)
 292  {
 293 @@ -248,6 +365,8 @@ static enum delret delete_dir_contents(c
 294                 if (S_ISDIR(fp->mode)
 295                  && delete_dir_contents(fname, flags | DEL_RECURSE) != DR_SUCCESS)
 296                         ret = DR_NOT_EMPTY;
 297 +               if (detect_renamed && S_ISREG(fp->mode))
 298 +                       look_for_rename(fp, fname, dirlist->file_pool);
 299                 if (delete_item(fname, fp->mode, NULL, flags) != DR_SUCCESS)
 300                         ret = DR_NOT_EMPTY;
 301         }
 302 @@ -270,15 +389,19 @@ static enum delret delete_dir_contents(c
 303   * all the --delete-WHEN options.  Note that the fbuf pointer must point to a
 304   * MAXPATHLEN buffer with the name of the directory in it (the functions we
 305   * call will append names onto the end, but the old dir value will be restored
 306 - * on exit). */
 307 + * on exit).
 308 + *
 309 + * Note:  --detect-rename may use this routine with DEL_NO_DELETIONS set!
 310 + */
 311  static void delete_in_dir(struct file_list *flist, char *fbuf,
 312 -                         struct file_struct *file, STRUCT_STAT *stp)
 313 +                         struct file_struct *file, STRUCT_STAT *stp, int flags)
 314  {
 315         static int min_depth = MAXPATHLEN, cur_depth = -1;
 316         static void *filt_array[MAXPATHLEN/2+1];
 317         static int already_warned = 0;
 318         struct file_list *dirlist;
 319 -       char delbuf[MAXPATHLEN];
 320 +       char *p, delbuf[MAXPATHLEN];
 321 +       unsigned remainder;
 322         int dlen, i;
 323
 324         if (!flist) {
 325 @@ -292,6 +415,8 @@ static void delete_in_dir(struct file_li
 326         if (verbose > 2)
 327                 rprintf(FINFO, "delete_in_dir(%s)\n", fbuf);
 328
 329 +       flags |= DEL_RECURSE;
 330 +
 331         if (allowed_lull)
 332                 maybe_send_keepalive();
 333
 334 @@ -299,12 +424,14 @@ static void delete_in_dir(struct file_li
 335                 return; /* Impossible... */
 336
 337         if (io_error && !(lp_ignore_errors(module_id) || ignore_errors)) {
 338 -               if (already_warned)
 339 +               if (!already_warned) {
 340 +                       rprintf(FINFO,
 341 +                           "IO error encountered -- skipping file deletion\n");
 342 +                       already_warned = 1;
 343 +               }
 344 +               if (!detect_renamed)
 345                         return;
 346 -               rprintf(FINFO,
 347 -                       "IO error encountered -- skipping file deletion\n");
 348 -               already_warned = 1;
 349 -               return;
 350 +               flags |= DEL_NO_DELETIONS;
 351         }
 352
 353         while (cur_depth >= file->dir.depth && cur_depth >= min_depth)
 354 @@ -315,6 +442,9 @@ static void delete_in_dir(struct file_li
 355         dlen = strlen(fbuf);
 356         filt_array[cur_depth] = push_local_filters(fbuf, dlen);
 357
 358 +       if (detect_renamed)
 359 +               unexplored_dirs--;
 360 +
 361         if (one_file_system) {
 362                 if (file->flags & FLAG_TOP_DIR)
 363                         filesystem_dev = stp->st_dev;
 364 @@ -324,6 +454,11 @@ static void delete_in_dir(struct file_li
 365
 366         dirlist = get_dirlist(fbuf, dlen, 0);
 367
 368 +       p = fbuf + dlen;
 369 +       if (dlen != 1 || *fbuf != '/')
 370 +               *p++ = '/';
 371 +       remainder = MAXPATHLEN - (p - fbuf);
 372 +
 373         /* If an item in dirlist is not found in flist, delete it
 374          * from the filesystem. */
 375         for (i = dirlist->count; i--; ) {
 376 @@ -336,12 +471,19 @@ static void delete_in_dir(struct file_li
 377                                         f_name(fp, NULL));
 378                         continue;
 379                 }
 380 +               if (detect_renamed && S_ISREG(fp->mode)) {
 381 +                       strlcpy(p, fp->basename, remainder);
 382 +                       look_for_rename(fp, fbuf, dirlist->file_pool);
 383 +               }
 384                 if (flist_find(flist, fp) < 0) {
 385                         f_name(fp, delbuf);
 386 -                       delete_item(delbuf, fp->mode, NULL, DEL_RECURSE);
 387 -               }
 388 +                       delete_item(delbuf, fp->mode, NULL, flags);
 389 +               } else if (detect_renamed && S_ISDIR(fp->mode))
 390 +                       unexplored_dirs++;
 391         }
 392
 393 +       fbuf[dlen] = '\0';
 394 +
 395         flist_free(dirlist);
 396  }
 397
 398 @@ -371,9 +513,9 @@ static void do_delete_pass(struct file_l
 399                  || !S_ISDIR(st.st_mode))
 400                         continue;
 401
 402 -               delete_in_dir(flist, fbuf, file, &st);
 403 +               delete_in_dir(flist, fbuf, file, &st, 0);
 404         }
 405 -       delete_in_dir(NULL, NULL, NULL, NULL);
 406 +       delete_in_dir(NULL, NULL, NULL, NULL, 0);
 407
 408         if (do_progress && !am_server)
 409                 rprintf(FINFO, "                    \r");
 410 @@ -902,6 +1044,7 @@ static int try_dests_non(struct file_str
 411         return j;
 412  }
 413
 414 +static struct bitbag *delayed_bits = NULL;
 415  static int phase = 0;
 416
 417  /* Acts on the_file_list->file's ndx'th item, whose name is fname.  If a dir,
 418 @@ -1087,8 +1230,12 @@ static void recv_generator(char *fname,
 419                 if (real_ret != 0 && one_file_system)
 420                         real_st.st_dev = filesystem_dev;
 421                 if (delete_during && f_out != -1 && !phase && dry_run < 2
 422 -                   && (file->flags & FLAG_DEL_HERE))
 423 -                       delete_in_dir(the_file_list, fname, file, &real_st);
 424 +                   && (file->flags & FLAG_DEL_HERE)) {
 425 +                       if (detect_renamed && real_ret != 0)
 426 +                               unexplored_dirs++;
 427 +                       delete_in_dir(the_file_list, fname, file, &real_st,
 428 +                                     delete_during < 0 ? DEL_NO_DELETIONS : 0);
 429 +               }
 430                 return;
 431         }
 432
 433 @@ -1340,8 +1487,14 @@ static void recv_generator(char *fname,
 434                     && hard_link_check(file, ndx, fname, statret, &st,
 435                                        itemizing, code, HL_SKIP))
 436                         return;
 437 -               if (stat_errno == ENOENT)
 438 +               if (stat_errno == ENOENT) {
 439 +                       if (detect_renamed && unexplored_dirs > 0
 440 +                        && file->length) {
 441 +                               bitbag_set_bit(delayed_bits, ndx);
 442 +                               return;
 443 +                       }
 444                         goto notify_others;
 445 +               }
 446                 rsyserr(FERROR, stat_errno, "recv_generator: failed to stat %s",
 447                         full_fname(fname));
 448                 return;
 449 @@ -1527,11 +1680,17 @@ void generate_files(int f_out, struct fi
 450                         (long)getpid(), flist->count);
 451         }
 452
 453 +       if (detect_renamed) {
 454 +               delayed_bits = bitbag_create(flist->count);
 455 +               if (!delete_before && !delete_during)
 456 +                       delete_during = -1;
 457 +       }
 458 +
 459         if (delete_before && !local_name && flist->count > 0)
 460                 do_delete_pass(flist);
 461         do_progress = 0;
 462
 463 -       if (append_mode || whole_file < 0)
 464 +       if (append_mode || detect_renamed || whole_file < 0)
 465                 whole_file = 0;
 466         if (verbose >= 2) {
 467                 rprintf(FINFO, "delta-transmission %s\n",
 468 @@ -1586,7 +1745,23 @@ void generate_files(int f_out, struct fi
 469         }
 470         recv_generator(NULL, NULL, 0, 0, 0, code, -1);
 471         if (delete_during)
 472 -               delete_in_dir(NULL, NULL, NULL, NULL);
 473 +               delete_in_dir(NULL, NULL, NULL, NULL, 0);
 474 +
 475 +       if (detect_renamed) {
 476 +               if (delete_during < 0)
 477 +                       delete_during = 0;
 478 +               detect_renamed = 0;
 479 +
 480 +               for (i = -1; (i = bitbag_next_bit(delayed_bits, i)) >= 0; ) {
 481 +                       struct file_struct *file = flist->files[i];
 482 +                       if (local_name)
 483 +                               strlcpy(fbuf, local_name, sizeof fbuf);
 484 +                       else
 485 +                               f_name(file, fbuf);
 486 +                       recv_generator(fbuf, file, i, itemizing,
 487 +                                      maybe_ATTRS_REPORT, code, f_out);
 488 +               }
 489 +       }
 490
 491         phase++;
 492         csum_length = SUM_LENGTH;
 493 --- old/options.c
 494 +++ new/options.c
 495 @@ -78,6 +78,7 @@ int am_generator = 0;
 496  int am_starting_up = 1;
 497  int relative_paths = -1;
 498  int implied_dirs = 1;
 499 +int detect_renamed = 0;
 500  int numeric_ids = 0;
 501  int allow_8bit_chars = 0;
 502  int force_delete = 0;
 503 @@ -346,6 +347,7 @@ void usage(enum logcode F)
 504    rprintf(F,"     --modify-window=NUM     compare mod-times with reduced accuracy\n");
 505    rprintf(F," -T, --temp-dir=DIR          create temporary files in directory DIR\n");
 506    rprintf(F," -y, --fuzzy                 find similar file for basis if no dest file\n");
 507 +  rprintf(F,"     --detect-renamed        try to find renamed files to speed up the transfer\n");
 508    rprintf(F,"     --compare-dest=DIR      also compare destination files relative to DIR\n");
 509    rprintf(F,"     --copy-dest=DIR         ... and include copies of unchanged files\n");
 510    rprintf(F,"     --link-dest=DIR         hardlink to files in DIR when unchanged\n");
 511 @@ -499,6 +501,7 @@ static struct poptOption long_options[]
 512    {"compare-dest",     0,  POPT_ARG_STRING, 0, OPT_COMPARE_DEST, 0, 0 },
 513    {"copy-dest",        0,  POPT_ARG_STRING, 0, OPT_COPY_DEST, 0, 0 },
 514    {"link-dest",        0,  POPT_ARG_STRING, 0, OPT_LINK_DEST, 0, 0 },
 515 +  {"detect-renamed",   0,  POPT_ARG_NONE,   &detect_renamed, 0, 0, 0 },
 516    {"fuzzy",           'y', POPT_ARG_NONE,   &fuzzy_basis, 0, 0, 0 },
 517    {"compress",        'z', POPT_ARG_NONE,   0, 'z', 0, 0 },
 518    {"compress-level",   0,  POPT_ARG_INT,    &def_compress_level, 'z', 0, 0 },
 519 @@ -1362,7 +1365,7 @@ int parse_arguments(int *argc, const cha
 520                 inplace = 1;
 521         }
 522
 523 -       if (delay_updates && !partial_dir)
 524 +       if ((delay_updates || detect_renamed) && !partial_dir)
 525                 partial_dir = tmp_partialdir;
 526
 527         if (inplace) {
 528 @@ -1371,6 +1374,7 @@ int parse_arguments(int *argc, const cha
 529                         snprintf(err_buf, sizeof err_buf,
 530                                  "--%s cannot be used with --%s\n",
 531                                  append_mode ? "append" : "inplace",
 532 +                                detect_renamed ? "detect-renamed" :
 533                                  delay_updates ? "delay-updates" : "partial-dir");
 534                         return 0;
 535                 }
 536 @@ -1674,6 +1678,8 @@ void server_options(char **args,int *arg
 537                         args[ac++] = "--super";
 538                 if (size_only)
 539                         args[ac++] = "--size-only";
 540 +               if (detect_renamed)
 541 +                       args[ac++] = "--detect-renamed";
 542         }
 543
 544         if (modify_window_set) {
 545 --- old/rsync.yo
 546 +++ new/rsync.yo
 547 @@ -363,6 +363,7 @@ to the detailed description below for a
 548       --modify-window=NUM     compare mod-times with reduced accuracy
 549   -T, --temp-dir=DIR          create temporary files in directory DIR
 550   -y, --fuzzy                 find similar file for basis if no dest file
 551 +     --detect-renamed        try to find renamed files to speed the xfer
 552       --compare-dest=DIR      also compare received files relative to DIR
 553       --copy-dest=DIR         ... and include copies of unchanged files
 554       --link-dest=DIR         hardlink to files in DIR when unchanged
 555 @@ -1265,6 +1266,15 @@ Note that the use of the bf(--delete) op
 556  fuzzy-match files, so either use bf(--delete-after) or specify some
 557  filename exclusions if you need to prevent this.
 558
 559 +dit(bf(--detect-renamed)) This option tells rsync to scan the receiving
 560 +side for files that have been renamed, and to use any that are found as
 561 +alternate basis files to help speed up the transfer.
 562 +By default, alternate-basis files are hard-linked into a directory named
 563 +".~tmp~" in each file's destination directory, but if you've specified
 564 +the bf(--partial-dir) option, that directory will be used instead.  These
 565 +potential alternate-basis files will be removed as the transfer progresses.
 566 +This option conflicts with bf(--inplace) and bf(--append).
 567 +
 568  dit(bf(--compare-dest=DIR)) This option instructs rsync to use em(DIR) on
 569  the destination machine as an additional hierarchy to compare destination
 570  files against doing transfers (if the files are missing in the destination
 571 --- old/util.c
 572 +++ new/util.c
 573 @@ -1025,6 +1025,32 @@ int handle_partial_dir(const char *fname
 574         return 1;
 575  }
 576
 577 +/* We need to supply our own strcmp function for file list comparisons
 578 + * to ensure that signed/unsigned usage is consistent between machines. */
 579 +int u_strcmp(const char *p1, const char *p2)
 580 +{
 581 +        for ( ; *p1; p1++, p2++) {
 582 +               if (*p1 != *p2)
 583 +                       break;
 584 +       }
 585 +
 586 +       return (int)*(uchar*)p1 - (int)*(uchar*)p2;
 587 +}
 588 +
 589 +/* We need a memcmp function compares unsigned-byte values. */
 590 +int u_memcmp(const void *p1, const void *p2, size_t len)
 591 +{
 592 +       const uchar *u1 = p1;
 593 +       const uchar *u2 = p2;
 594 +
 595 +       while (len--) {
 596 +               if (*u1 != *u2)
 597 +                       return (int)*u1 - (int)*u2;
 598 +       }
 599 +
 600 +       return 0;
 601 +}
 602 +
 603  /**
 604   * Determine if a symlink points outside the current directory tree.
 605   * This is considered "unsafe" because e.g. when mirroring somebody