path: root/net/rsync/files/extrapatch-detect-renamed.diff

This patch adds the --detect-renamed option which makes rsync notice files
that either (1) match in size & modify-time (plus the basename, if possible)
or (2) match in size & checksum (when --checksum was also specified) and use
each match as an alternate basis file to speed up the transfer.

The algorithm attempts to scan the receiving-side's files in an efficient
manner.  If --delete[-before] is enabled, we'll take advantage of the
pre-transfer delete pass to prepare any alternate-basis-file matches we
might find.  If --delete-before is not enabled, rsync does the rename scan
during the regular file-sending scan (scanning each directory right before
the generator starts updating files from that dir).  In this latter mode,
rsync might delay the updating of a file (if no alternate-basis match was
yet found) until the full scan of the receiving side is complete, at which
point any delayed files are processed.

I chose to hard-link the alternate-basis files into a ".~tmp~" subdir that
takes advantage of rsync's pre-existing partial-dir logic.  This uses less
memory than trying to keep track of the matches internally, and also allows
any deletions or file-updates to occur normally without interfering with
these alternate-basis discoveries.

To use this patch, run these commands for a successful build:

    patch -p1 <patches/detect-renamed.diff
    ./configure                                 (optional if already run)
    make

TODO:

  We need to never return a match from fattr_find() that has a basis
  file.  This will ensure that we don't try to give a renamed file to
  a file that can't use it, while missing out on giving it to a file
  that could use it.

based-on: 40afd365cc8ca968fd16e161d24df5b8a8a520cc
--- compat.c.orig   2012-04-03 10:38:42.000000000 -0400
+++ compat.c    2012-04-03 10:38:42.000000000 -0400
@@ -41,6 +41,7 @@ extern int read_batch;
 extern int delay_updates;
 extern int checksum_seed;
 extern int basis_dir_cnt;
+extern int detect_renamed;
 extern int prune_empty_dirs;
 extern int protocol_version;
 extern int protect_args;
@@ -124,6 +125,7 @@ void set_allow_inc_recurse(void)
        allow_inc_recurse = 0;
    else if (!am_sender
     && (delete_before || delete_after
+     || detect_renamed
      || delay_updates || prune_empty_dirs))
        allow_inc_recurse = 0;
    else if (am_server && !local_server
--- flist.c.orig    2012-04-03 10:38:42.000000000 -0400
+++ flist.c 2012-04-03 10:38:42.000000000 -0400
@@ -61,6 +61,7 @@ extern int non_perishable_cnt;
 extern int prune_empty_dirs;
 extern int copy_links;
 extern int copy_unsafe_links;
+extern int detect_renamed;
 extern int protocol_version;
 extern int sanitize_paths;
 extern int munge_symlinks;
@@ -121,6 +122,8 @@ static int64 tmp_dev = -1, tmp_ino;
 #endif
 static char tmp_sum[MAX_DIGEST_LEN];
 
+struct file_list the_fattr_list;
+
 static char empty_sum[MAX_DIGEST_LEN];
 static int flist_count_offset; /* for --delete --progress */
 static int dir_count = 0;
@@ -288,6 +291,45 @@ static int is_excluded(const char *fname
    return 0;
 }
 
+static int fattr_compare(struct file_struct **file1, struct file_struct **file2)
+{
+   struct file_struct *f1 = *file1;
+   struct file_struct *f2 = *file2;
+   int64 len1 = F_LENGTH(f1), len2 = F_LENGTH(f2);
+   int diff;
+
+   if (!f1->basename || !S_ISREG(f1->mode) || !len1) {
+       if (!f2->basename || !S_ISREG(f2->mode) || !len2)
+           return 0;
+       return 1;
+   }
+   if (!f2->basename || !S_ISREG(f2->mode) || !len2)
+       return -1;
+
+   /* Don't use diff for values that are longer than an int. */
+   if (len1 != len2)
+       return len1 < len2 ? -1 : 1;
+
+   if (always_checksum) {
+       diff = u_memcmp(F_SUM(f1), F_SUM(f2), checksum_len);
+       if (diff)
+           return diff;
+   } else if (f1->modtime != f2->modtime)
+       return f1->modtime < f2->modtime ? -1 : 1;
+
+   diff = u_strcmp(f1->basename, f2->basename);
+   if (diff)
+       return diff;
+
+   if (f1->dirname == f2->dirname)
+       return 0;
+   if (!f1->dirname)
+       return -1;
+   if (!f2->dirname)
+       return 1;
+   return u_strcmp(f1->dirname, f2->dirname);
+}
+
 static void send_directory(int f, struct file_list *flist,
               char *fbuf, int len, int flags);
 
@@ -2451,6 +2493,25 @@ struct file_list *recv_file_list(int f)
 
    flist_sort_and_clean(flist, relative_paths);
 
+   if (detect_renamed) {
+       int j = flist->used;
+       the_fattr_list.used = j;
+       the_fattr_list.files = new_array(struct file_struct *, j);
+       if (!the_fattr_list.files)
+           out_of_memory("recv_file_list");
+       memcpy(the_fattr_list.files, flist->files,
+              j * sizeof (struct file_struct *));
+       qsort(the_fattr_list.files, j,
+             sizeof the_fattr_list.files[0], (int (*)())fattr_compare);
+       the_fattr_list.low = 0;
+       while (j-- > 0) {
+           struct file_struct *fp = the_fattr_list.files[j];
+           if (fp->basename && S_ISREG(fp->mode) && F_LENGTH(fp))
+               break;
+       }
+       the_fattr_list.high = j;
+   }
+
    if (protocol_version < 30) {
        /* Recv the io_error flag */
        if (ignore_errors)
--- generator.c.orig    2012-04-03 10:38:42.000000000 -0400
+++ generator.c 2012-04-03 23:16:14.000000000 -0400
@@ -79,6 +79,7 @@ extern char *basis_dir[MAX_BASIS_DIRS+1]
 extern int compare_dest;
 extern int copy_dest;
 extern int link_dest;
+extern int detect_renamed;
 extern int whole_file;
 extern int list_only;
 extern int read_batch;
@@ -97,6 +98,7 @@ extern char *backup_suffix;
 extern int backup_suffix_len;
 extern struct file_list *cur_flist, *first_flist, *dir_flist;
 extern struct filter_list_struct daemon_filter_list;
+extern struct file_list the_fattr_list;
 
 int ignore_perishable = 0;
 int non_perishable_cnt = 0;
@@ -104,6 +106,7 @@ int maybe_ATTRS_REPORT = 0;
 
 static dev_t dev_zero;
 static int deletion_count = 0; /* used to implement --max-delete */
+static int unexplored_dirs = 1;
 static int deldelay_size = 0, deldelay_cnt = 0;
 static char *deldelay_buf = NULL;
 static int deldelay_fd = -1;
@@ -114,7 +117,7 @@ static int need_retouch_dir_times;
 static int need_retouch_dir_perms;
 static const char *solo_file = NULL;
 
-/* For calling delete_item() and delete_dir_contents(). */
+/* For calling delete_item(), delete_dir_contents(), and delete_in_dir(). */
 #define DEL_NO_UID_WRITE   (1<<0) /* file/dir has our uid w/o write perm */
 #define DEL_RECURSE        (1<<1) /* if dir, delete all contents */
 #define DEL_DIR_IS_EMPTY   (1<<2) /* internal delete_FUNCTIONS use only */
@@ -123,6 +126,7 @@ static const char *solo_file = NULL;
 #define DEL_FOR_SYMLINK    (1<<5) /* making room for a replacement symlink */
 #define DEL_FOR_DEVICE     (1<<6) /* making room for a replacement device */
 #define DEL_FOR_SPECIAL    (1<<7) /* making room for a replacement special */
+#define DEL_NO_DELETIONS   (1<<9) /* just check for renames w/o deleting */
 
 #define DEL_MAKE_ROOM (DEL_FOR_FILE|DEL_FOR_DIR|DEL_FOR_SYMLINK|DEL_FOR_DEVICE|DEL_FOR_SPECIAL)
 
@@ -147,11 +151,121 @@ static int is_backup_file(char *fn)
    return k > 0 && strcmp(fn+k, backup_suffix) == 0;
 }
 
+/* Search for a regular file that matches either (1) the size & modified
+ * time (plus the basename, if possible) or (2) the size & checksum.  If
+ * we find an exact match down to the dirname, return -1 because we found
+ * an up-to-date file in the transfer, not a renamed file. */
+static int fattr_find(struct file_struct *f, char *fname)
+{
+   int low = the_fattr_list.low, high = the_fattr_list.high;
+   int mid, ok_match = -1, good_match = -1;
+   struct file_struct *fmid;
+   int diff;
+
+   while (low <= high) {
+       mid = (low + high) / 2;
+       fmid = the_fattr_list.files[mid];
+       if (F_LENGTH(fmid) != F_LENGTH(f)) {
+           if (F_LENGTH(fmid) < F_LENGTH(f))
+               low = mid + 1;
+           else
+               high = mid - 1;
+           continue;
+       }
+       if (always_checksum) {
+           /* We use the FLAG_FILE_SENT flag to indicate when we
+            * have computed the checksum for an entry. */
+           if (!(f->flags & FLAG_FILE_SENT)) {
+               if (fmid->modtime == f->modtime
+                && f_name_cmp(fmid, f) == 0)
+                   return -1; /* assume we can't help */
+               file_checksum(fname, F_SUM(f), F_LENGTH(f));
+               f->flags |= FLAG_FILE_SENT;
+           }
+           diff = u_memcmp(F_SUM(fmid), F_SUM(f), checksum_len);
+           if (diff) {
+               if (diff < 0)
+                   low = mid + 1;
+               else
+                   high = mid - 1;
+               continue;
+           }
+       } else {
+           if (fmid->modtime != f->modtime) {
+               if (fmid->modtime < f->modtime)
+                   low = mid + 1;
+               else
+                   high = mid - 1;
+               continue;
+           }
+       }
+       ok_match = mid;
+       diff = u_strcmp(fmid->basename, f->basename);
+       if (diff == 0) {
+           good_match = mid;
+           if (fmid->dirname == f->dirname)
+               return -1; /* file is up-to-date */
+           if (!fmid->dirname) {
+               low = mid + 1;
+               continue;
+           }
+           if (!f->dirname) {
+               high = mid - 1;
+               continue;
+           }
+           diff = u_strcmp(fmid->dirname, f->dirname);
+           if (diff == 0)
+               return -1; /* file is up-to-date */
+       }
+       if (diff < 0)
+           low = mid + 1;
+       else
+           high = mid - 1;
+   }
+
+   return good_match >= 0 ? good_match : ok_match;
+}
+
+static void look_for_rename(struct file_struct *file, char *fname)
+{
+   struct file_struct *fp;
+   char *partialptr, *fn;
+   STRUCT_STAT st;
+   int ndx;
+
+   if (!partial_dir || (ndx = fattr_find(file, fname)) < 0)
+       return;
+
+   fp = the_fattr_list.files[ndx];
+   fn = f_name(fp, NULL);
+   /* We don't provide an alternate-basis file if there is a basis file. */
+   if (link_stat(fn, &st, 0) == 0)
+       return;
+
+   if (!dry_run) {
+       if ((partialptr = partial_dir_fname(fn)) == NULL
+        || !handle_partial_dir(partialptr, PDIR_CREATE))
+           return;
+       /* We only use the file if we can hard-link it into our tmp dir. */
+       if (link(fname, partialptr) != 0) {
+           if (errno != EEXIST)
+               handle_partial_dir(partialptr, PDIR_DELETE);
+           return;
+       }
+   }
+
+   /* I think this falls into the -vv category with "%s is uptodate", etc. */
+   if (verbose > 1)
+       rprintf(FINFO, "found renamed: %s => %s\n", fname, fn);
+}
+
 /* Delete a file or directory.  If DEL_RECURSE is set in the flags, this will
  * delete recursively.
  *
  * Note that fbuf must point to a MAXPATHLEN buffer if the mode indicates it's
  * a directory! (The buffer is used for recursion, but returned unchanged.)
+ *
+ * Also note: --detect-rename may use this routine with DEL_NO_DELETIONS set!
  */
 static enum delret delete_item(char *fbuf, uint16 mode, uint16 flags)
 {
@@ -178,6 +292,8 @@ static enum delret delete_item(char *fbu
            goto check_ret;
        /* OK: try to delete the directory. */
    }
+   if (flags & DEL_NO_DELETIONS)
+       return DR_SUCCESS;
 
    if (!(flags & DEL_MAKE_ROOM) && max_delete >= 0 && ++deletion_count > max_delete)
        return DR_AT_LIMIT;
@@ -233,6 +349,8 @@ static enum delret delete_item(char *fbu
  * its contents, otherwise just checks for content.  Returns DR_SUCCESS or
  * DR_NOT_EMPTY.  Note that fname must point to a MAXPATHLEN buffer!  (The
  * buffer is used for recursion, but returned unchanged.)
+ *
+ * Note: --detect-rename may use this routine with DEL_NO_DELETIONS set!
  */
 static enum delret delete_dir_contents(char *fname, uint16 flags)
 {
@@ -252,7 +370,9 @@ static enum delret delete_dir_contents(c
    save_filters = push_local_filters(fname, dlen);
 
    non_perishable_cnt = 0;
+   file_extra_cnt += SUM_EXTRA_CNT;
    dirlist = get_dirlist(fname, dlen, 0);
+   file_extra_cnt -= SUM_EXTRA_CNT;
    ret = non_perishable_cnt ? DR_NOT_EMPTY : DR_SUCCESS;
 
    if (!dirlist->used)
@@ -292,7 +412,8 @@ static enum delret delete_dir_contents(c
        if (S_ISDIR(fp->mode)) {
            if (delete_dir_contents(fname, flags | DEL_RECURSE) != DR_SUCCESS)
                ret = DR_NOT_EMPTY;
-       }
+       } else if (detect_renamed && S_ISREG(fp->mode))
+           look_for_rename(fp, fname);
        if (delete_item(fname, fp->mode, flags) != DR_SUCCESS)
            ret = DR_NOT_EMPTY;
    }
@@ -457,13 +578,18 @@ static void do_delayed_deletions(char *d
  * all the --delete-WHEN options.  Note that the fbuf pointer must point to a
  * MAXPATHLEN buffer with the name of the directory in it (the functions we
  * call will append names onto the end, but the old dir value will be restored
- * on exit). */
-static void delete_in_dir(char *fbuf, struct file_struct *file, dev_t *fs_dev)
+ * on exit).
+ *
+ * Note:  --detect-rename may use this routine with DEL_NO_DELETIONS set!
+ */
+static void delete_in_dir(char *fbuf, struct file_struct *file, dev_t *fs_dev,
+             int del_flags)
 {
    static int already_warned = 0;
    struct file_list *dirlist;
-   char delbuf[MAXPATHLEN];
-   int dlen, i;
+   char *p, delbuf[MAXPATHLEN];
+   unsigned remainder;
+   int dlen, i, restore_dot = 0;
 
    if (!fbuf) {
        change_local_filter_dir(NULL, 0, 0);
@@ -477,17 +603,22 @@ static void delete_in_dir(char *fbuf, st
        maybe_send_keepalive();
 
    if (io_error && !ignore_errors) {
-       if (already_warned)
+       if (!already_warned) {
+           rprintf(FINFO,
+               "IO error encountered -- skipping file deletion\n");
+           already_warned = 1;
+       }
+       if (!detect_renamed)
            return;
-       rprintf(FINFO,
-           "IO error encountered -- skipping file deletion\n");
-       already_warned = 1;
-       return;
+       del_flags |= DEL_NO_DELETIONS;
    }
 
    dlen = strlen(fbuf);
    change_local_filter_dir(fbuf, dlen, F_DEPTH(file));
 
+   if (detect_renamed)
+       unexplored_dirs--;
+
    if (one_file_system) {
        if (file->flags & FLAG_TOP_DIR)
            filesystem_dev = *fs_dev;
@@ -497,6 +628,14 @@ static void delete_in_dir(char *fbuf, st
 
    dirlist = get_dirlist(fbuf, dlen, 0);
 
+   p = fbuf + dlen;
+   if (dlen == 1 && *fbuf == '.') {
+       restore_dot = 1;
+       p = fbuf;
+   } else if (dlen != 1 || *fbuf != '/')
+       *p++ = '/';
+   remainder = MAXPATHLEN - (p - fbuf);
+
    /* If an item in dirlist is not found in flist, delete it
     * from the filesystem. */
    for (i = dirlist->used; i--; ) {
@@ -509,6 +648,10 @@ static void delete_in_dir(char *fbuf, st
                    f_name(fp, NULL));
            continue;
        }
+       if (detect_renamed && S_ISREG(fp->mode)) {
+           strlcpy(p, fp->basename, remainder);
+           look_for_rename(fp, fbuf);
+       }
        /* Here we want to match regardless of file type.  Replacement
         * of a file with one of another type is handled separately by
         * a delete_item call with a DEL_MAKE_ROOM flag. */
@@ -517,14 +660,19 @@ static void delete_in_dir(char *fbuf, st
            if (!(fp->mode & S_IWUSR) && !am_root && fp->flags & FLAG_OWNED_BY_US)
                flags |= DEL_NO_UID_WRITE;
            f_name(fp, delbuf);
-           if (delete_during == 2) {
-               if (!remember_delete(fp, delbuf, flags))
+           if (delete_during == 2 && !(del_flags & DEL_NO_DELETIONS)) {
+               if (!remember_delete(fp, delbuf, del_flags | flags))
                    break;
            } else
-               delete_item(delbuf, fp->mode, flags);
-       }
+               delete_item(delbuf, fp->mode, del_flags | flags);
+       } else if (detect_renamed && S_ISDIR(fp->mode))
+           unexplored_dirs++;
    }
 
+   if (restore_dot)
+       fbuf[0] = '.';
+   fbuf[dlen] = '\0';
+
    flist_free(dirlist);
 }
 
@@ -557,9 +705,9 @@ static void do_delete_pass(void)
         || !S_ISDIR(st.st_mode))
            continue;
 
-       delete_in_dir(fbuf, file, &st.st_dev);
+       delete_in_dir(fbuf, file, &st.st_dev, 0);
    }
-   delete_in_dir(NULL, NULL, &dev_zero);
+   delete_in_dir(NULL, NULL, &dev_zero, 0);
 
    if (do_progress && !am_server)
        rprintf(FINFO, "                    \r");
@@ -1278,6 +1426,7 @@ static void list_file_entry(struct file_
    }
 }
 
+static struct bitbag *delayed_bits = NULL;
 static int phase = 0;
 static int dflt_perms;
 
@@ -1567,9 +1716,12 @@ static void recv_generator(char *fname, 
        }
        else if (delete_during && f_out != -1 && !phase
            && !(file->flags & FLAG_MISSING_DIR)) {
-           if (file->flags & FLAG_CONTENT_DIR)
-               delete_in_dir(fname, file, &real_sx.st.st_dev);
-           else
+           if (file->flags & FLAG_CONTENT_DIR) {
+               if (detect_renamed && real_ret != 0)
+                   unexplored_dirs++;
+               delete_in_dir(fname, file, &real_sx.st.st_dev,
+                         delete_during < 0 ? DEL_NO_DELETIONS : 0);
+           } else
                change_local_filter_dir(fname, strlen(fname), F_DEPTH(file));
        }
        goto cleanup;
@@ -1853,8 +2005,14 @@ static void recv_generator(char *fname, 
            goto cleanup;
        }
 #endif
-       if (stat_errno == ENOENT)
+       if (stat_errno == ENOENT) {
+           if (detect_renamed && unexplored_dirs > 0
+            && F_LENGTH(file)) {
+               bitbag_set_bit(delayed_bits, ndx);
+               return;
+           }
            goto notify_others;
+       }
        rsyserr(FERROR_XFER, stat_errno, "recv_generator: failed to stat %s",
            full_fname(fname));
        goto cleanup;
@@ -2263,6 +2421,12 @@ void generate_files(int f_out, const cha
    if (verbose > 2)
        rprintf(FINFO, "generator starting pid=%ld\n", (long)getpid());
 
+   if (detect_renamed) {
+       delayed_bits = bitbag_create(cur_flist->used);
+       if (!delete_before && !delete_during)
+           delete_during = -1;
+   }
+
    if (delete_before && !solo_file && cur_flist->used > 0)
        do_delete_pass();
    if (delete_during == 2) {
@@ -2273,7 +2437,7 @@ void generate_files(int f_out, const cha
    }
    do_progress = 0;
 
-   if (append_mode > 0 || whole_file < 0)
+   if (append_mode > 0 || detect_renamed || whole_file < 0)
        whole_file = 0;
    if (verbose >= 2) {
        rprintf(FINFO, "delta-transmission %s\n",
@@ -2315,7 +2479,7 @@ void generate_files(int f_out, const cha
                        dirdev = MAKEDEV(DEV_MAJOR(devp), DEV_MINOR(devp));
                    } else
                        dirdev = MAKEDEV(0, 0);
-                   delete_in_dir(fbuf, fp, &dirdev);
+                   delete_in_dir(fbuf, fp, &dirdev, 0);
                } else
                    change_local_filter_dir(fbuf, strlen(fbuf), F_DEPTH(fp));
            }
@@ -2362,7 +2526,21 @@ void generate_files(int f_out, const cha
    } while ((cur_flist = cur_flist->next) != NULL);
 
    if (delete_during)
-       delete_in_dir(NULL, NULL, &dev_zero);
+       delete_in_dir(NULL, NULL, &dev_zero, 0);
+   if (detect_renamed) {
+       if (delete_during < 0)
+           delete_during = 0;
+       detect_renamed = 0;
+
+       for (i = -1; (i = bitbag_next_bit(delayed_bits, i)) >= 0; ) {
+           struct file_struct *file = cur_flist->files[i];
+           if (local_name)
+               strlcpy(fbuf, local_name, sizeof fbuf);
+           else
+               f_name(file, fbuf);
+           recv_generator(fbuf, file, i, itemizing, code, f_out);
+       }
+   }
    phase++;
    if (verbose > 2)
        rprintf(FINFO, "generate_files phase=%d\n", phase);
--- options.c.orig  2012-04-03 10:38:42.000000000 -0400
+++ options.c   2012-04-03 10:38:42.000000000 -0400
@@ -82,6 +82,7 @@ int am_sender = 0;
 int am_starting_up = 1;
 int relative_paths = -1;
 int implied_dirs = 1;
+int detect_renamed = 0;
 int numeric_ids = 0;
 int allow_8bit_chars = 0;
 int force_delete = 0;
@@ -392,6 +393,7 @@ void usage(enum logcode F)
   rprintf(F,"     --modify-window=NUM     compare mod-times with reduced accuracy\n");
   rprintf(F," -T, --temp-dir=DIR          create temporary files in directory DIR\n");
   rprintf(F," -y, --fuzzy                 find similar file for basis if no dest file\n");
+  rprintf(F,"     --detect-renamed        try to find renamed files to speed up the transfer\n");
   rprintf(F,"     --compare-dest=DIR      also compare destination files relative to DIR\n");
   rprintf(F,"     --copy-dest=DIR         ... and include copies of unchanged files\n");
   rprintf(F,"     --link-dest=DIR         hardlink to files in DIR when unchanged\n");
@@ -582,6 +584,7 @@ static struct poptOption long_options[] 
   {"compare-dest",     0,  POPT_ARG_STRING, 0, OPT_COMPARE_DEST, 0, 0 },
   {"copy-dest",        0,  POPT_ARG_STRING, 0, OPT_COPY_DEST, 0, 0 },
   {"link-dest",        0,  POPT_ARG_STRING, 0, OPT_LINK_DEST, 0, 0 },
+  {"detect-renamed",   0,  POPT_ARG_NONE,   &detect_renamed, 0, 0, 0 },
   {"fuzzy",           'y', POPT_ARG_VAL,    &fuzzy_basis, 1, 0, 0 },
   {"no-fuzzy",         0,  POPT_ARG_VAL,    &fuzzy_basis, 0, 0, 0 },
   {"no-y",             0,  POPT_ARG_VAL,    &fuzzy_basis, 0, 0, 0 },
@@ -1606,7 +1609,7 @@ int parse_arguments(int *argc_p, const c
        inplace = 1;
    }
 
-   if (delay_updates && !partial_dir)
+   if ((delay_updates || detect_renamed) && !partial_dir)
        partial_dir = tmp_partialdir;
 
    if (inplace) {
@@ -1615,6 +1618,7 @@ int parse_arguments(int *argc_p, const c
            snprintf(err_buf, sizeof err_buf,
                 "--%s cannot be used with --%s\n",
                 append_mode ? "append" : "inplace",
+                detect_renamed ? "detect-renamed" :
                 delay_updates ? "delay-updates" : "partial-dir");
            return 0;
        }
@@ -1979,6 +1983,8 @@ void server_options(char **args, int *ar
            args[ac++] = "--super";
        if (size_only)
            args[ac++] = "--size-only";
+       if (detect_renamed)
+           args[ac++] = "--detect-renamed";
    } else {
        if (skip_compress) {
            if (asprintf(&arg, "--skip-compress=%s", skip_compress) < 0)
--- rsync.yo.orig   2012-04-03 10:38:42.000000000 -0400
+++ rsync.yo    2012-04-03 10:38:42.000000000 -0400
@@ -403,6 +403,7 @@ to the detailed description below for a 
      --modify-window=NUM     compare mod-times with reduced accuracy
  -T, --temp-dir=DIR          create temporary files in directory DIR
  -y, --fuzzy                 find similar file for basis if no dest file
+     --detect-renamed        try to find renamed files to speed the xfer
      --compare-dest=DIR      also compare received files relative to DIR
      --copy-dest=DIR         ... and include copies of unchanged files
      --link-dest=DIR         hardlink to files in DIR when unchanged
@@ -1597,6 +1598,21 @@ Note that the use of the bf(--delete) op
 fuzzy-match files, so either use bf(--delete-after) or specify some
 filename exclusions if you need to prevent this.
 
+dit(bf(--detect-renamed)) With this option, for each new source file
+(call it em(src/S)), rsync looks for a file em(dest/D) anywhere in the
+destination that passes the quick check with em(src/S).  If such a em(dest/D)
+is found, rsync uses it as an alternate basis for transferring em(S).  The
+idea is that if em(src/S) was renamed from em(src/D) (as opposed to em(src/S)
+passing the quick check with em(dest/D) by coincidence), the delta-transfer
+algorithm will find that all the data matches between em(src/S) and em(dest/D),
+and the transfer will be really fast.
+
+By default, alternate-basis files are hard-linked into a directory named
+".~tmp~" in each file's destination directory, but if you've specified
+the bf(--partial-dir) option, that directory will be used instead.  These
+potential alternate-basis files will be removed as the transfer progresses.
+This option conflicts with bf(--inplace) and bf(--append).
+
 dit(bf(--compare-dest=DIR)) This option instructs rsync to use em(DIR) on
 the destination machine as an additional hierarchy to compare destination
 files against doing transfers (if the files are missing in the destination
--- syscall.c.orig  2011-02-21 14:32:51.000000000 -0500
+++ syscall.c   2012-04-04 11:01:33.000000000 -0400
@@ -217,6 +217,22 @@ void trim_trailing_slashes(char *name)
    }
 }
 
+int do_mkdir_path(char *fname, mode_t mode)
+{
+   char fnametmp[MAXPATHLEN], *fnametmpptr;
+   STRUCT_STAT st;
+
+   if (fname) {
+       strcpy(fnametmp, fname);
+       if ((fnametmpptr = strrchr(fnametmp, '/')) != NULL) {
+           *fnametmpptr = '\0';
+           if (do_stat(fnametmp, &st) < 0)
+               do_mkdir_path(fnametmp, mode);
+       }
+   }
+   return do_mkdir(fname, mode);
+}
+
 int do_mkdir(char *fname, mode_t mode)
 {
    if (dry_run) return 0;
--- util.c.orig 2012-04-03 10:38:42.000000000 -0400
+++ util.c  2012-04-03 23:15:12.000000000 -0400
@@ -1172,7 +1172,7 @@ int handle_partial_dir(const char *fname
            }
            statret = -1;
        }
-       if (statret < 0 && do_mkdir(dir, 0700) < 0) {
+       if (statret < 0 && do_mkdir_path(dir, 0700) < 0) {
            *fn = '/';
            return 0;
        }
@@ -1183,6 +1183,32 @@ int handle_partial_dir(const char *fname
    return 1;
 }
 
+/* We need to supply our own strcmp function for file list comparisons
+ * to ensure that signed/unsigned usage is consistent between machines. */
+int u_strcmp(const char *p1, const char *p2)
+{
+        for ( ; *p1; p1++, p2++) {
+       if (*p1 != *p2)
+           break;
+   }
+
+   return (int)*(uchar*)p1 - (int)*(uchar*)p2;
+}
+
+/* We need a memcmp function compares unsigned-byte values. */
+int u_memcmp(const void *p1, const void *p2, size_t len)
+{
+   const uchar *u1 = p1;
+   const uchar *u2 = p2;
+
+   while (len--) {
+       if (*u1 != *u2)
+           return (int)*u1 - (int)*u2;
+   }
+
+   return 0;
+}
+
 /* Determine if a symlink points outside the current directory tree.
  * This is considered "unsafe" because e.g. when mirroring somebody
  * else's machine it might allow them to establish a symlink to
--- proto.h.orig    2012-04-03 10:38:42.000000000 -0400
+++ proto.h 2012-04-03 23:29:23.000000000 -0400
@@ -305,6 +305,7 @@ int do_chmod(const char *path, mode_t mo
 int do_rename(const char *fname1, const char *fname2);
 int do_ftruncate(int fd, OFF_T size);
 void trim_trailing_slashes(char *name);
+int do_mkdir_path(char *fname, mode_t mode);
 int do_mkdir(char *fname, mode_t mode);
 int do_mkstemp(char *template, mode_t perms);
 int do_stat(const char *fname, STRUCT_STAT *st);
@@ -362,6 +363,8 @@ char *normalize_path(char *path, BOOL fo
 char *full_fname(const char *fn);
 char *partial_dir_fname(const char *fname);
 int handle_partial_dir(const char *fname, int create);
+int u_strcmp(const char *p1, const char *p2);
+int u_memcmp(const void *p1, const void *p2, size_t len);
 int unsafe_symlink(const char *dest, const char *src);
 char *human_num(int64 num);
 char *human_dnum(double dnum, int decimal_digits);
--- rsync.1.orig    2012-04-03 10:38:42.000000000 -0400
+++ rsync.1 2012-04-03 21:48:49.000000000 -0400
@@ -479,6 +479,7 @@ to the detailed description below for a 
      \-\-modify\-window=NUM     compare mod\-times with reduced accuracy
  \-T, \-\-temp\-dir=DIR          create temporary files in directory DIR
  \-y, \-\-fuzzy                 find similar file for basis if no dest file
+     \-\-detect\-renamed        try to find renamed files to speed the xfer
      \-\-compare\-dest=DIR      also compare received files relative to DIR
      \-\-copy\-dest=DIR         ... and include copies of unchanged files
      \-\-link\-dest=DIR         hardlink to files in DIR when unchanged
@@ -1828,6 +1829,22 @@ Note that the use of the \fB\-\-delete\f
 fuzzy\-match files, so either use \fB\-\-delete\-after\fP or specify some
 filename exclusions if you need to prevent this.
 .IP 
+.IP "\fB\-\-detect\-renamed\fP"
+With this option, for each new source file
+(call it \fIsrc/S\fP), rsync looks for a file \fIdest/D\fP anywhere in the
+destination that passes the quick check with \fIsrc/S\fP.  If such a \fIdest/D\fP
+is found, rsync uses it as an alternate basis for transferring \fIS\fP.  The
+idea is that if \fIsrc/S\fP was renamed from \fIsrc/D\fP (as opposed to \fIsrc/S\fP
+passing the quick check with \fIdest/D\fP by coincidence), the delta\-transfer
+algorithm will find that all the data matches between \fIsrc/S\fP and \fIdest/D\fP,
+and the transfer will be really fast.
+.IP 
+By default, alternate\-basis files are hard\-linked into a directory named
+\(dq\&.~tmp~\(dq\& in each file\(cq\&s destination directory, but if you\(cq\&ve specified
+the \fB\-\-partial\-dir\fP option, that directory will be used instead.  These
+potential alternate\-basis files will be removed as the transfer progresses.
+This option conflicts with \fB\-\-inplace\fP and \fB\-\-append\fP.
+.IP 
 .IP "\fB\-\-compare\-dest=DIR\fP"
 This option instructs rsync to use \fIDIR\fP on
 the destination machine as an additional hierarchy to compare destination