Greetings, and thanks for all of your work on the wonderful rsync!

I recently had the need to transfer files only with different mod
dates (and to *not* transfer them based on file size differences).
This is because I'm backing up files remotely on an untrusted machine,
so I'm encrypting them with gpg before transfer.  I discovered that
rsync didn't already have a --date-only flag, so I added one and am
enclosing the diffs in case you (as I hope) decide to include this
option in future releases.

Again, thanks!

Best Regards,
Jeremy Bornstein

[Patched update to have context and apply to latest CVS source.]

--- generator.c	18 May 2004 08:50:17 -0000	1.85
+++ generator.c	18 May 2004 09:31:22 -0000
@@ -51,6 +51,7 @@ extern int list_only;
 extern int only_existing;
 extern int orig_umask;
 extern int safe_symlinks;
+extern int date_only;
 
 extern struct exclude_list_struct server_exclude_list;
 
@@ -58,6 +59,8 @@ extern struct exclude_list_struct server
 /* choose whether to skip a particular file */
 static int skip_file(char *fname, struct file_struct *file, STRUCT_STAT *st)
 {
+	if (date_only)
+		return cmp_modtime(st->st_mtime,file->modtime) == 0;
 	if (st->st_size != file->length) {
 		return 0;
 	}
--- options.c	6 May 2004 21:08:01 -0000	1.148
+++ options.c	18 May 2004 09:31:23 -0000
@@ -82,6 +82,7 @@ int keep_partial = 0;
 int safe_symlinks = 0;
 int copy_unsafe_links = 0;
 int size_only = 0;
+int date_only = 0;
 int bwlimit = 0;
 int delete_after = 0;
 int only_existing = 0;
@@ -262,6 +263,7 @@ void usage(enum logcode F)
   rprintf(F,"     --timeout=TIME          set I/O timeout in seconds\n");
   rprintf(F," -I, --ignore-times          turn off mod time & file size quick check\n");
   rprintf(F,"     --size-only             ignore mod time for quick check (use size)\n");
+  rprintf(F,"     --date-only             ignore size for quick check (use mod time)\n");
   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,"     --compare-dest=DIR      also compare destination files relative to DIR\n");
@@ -316,6 +318,7 @@ static struct poptOption long_options[] 
   {"password-file",    0,  POPT_ARG_STRING, &password_file, 0, 0, 0 },
   {"ignore-times",    'I', POPT_ARG_NONE,   &ignore_times, 0, 0, 0 },
   {"size-only",        0,  POPT_ARG_NONE,   &size_only, 0, 0, 0 },
+  {"date-only",        0,  POPT_ARG_NONE,   &date_only, 0, 0, 0 },
   {"modify-window",    0,  POPT_ARG_INT,    &modify_window, OPT_MODIFY_WINDOW, 0, 0 },
   {"one-file-system", 'x', POPT_ARG_NONE,   &one_file_system, 0, 0, 0 },
   {"delete",           0,  POPT_ARG_NONE,   &delete_mode, 0, 0, 0 },
@@ -905,6 +908,9 @@ void server_options(char **args,int *arg
 
 	if (size_only)
 		args[ac++] = "--size-only";
+
+	if (date_only)
+		args[ac++] = "--date-only";
 
 	if (modify_window_set) {
 		if (asprintf(&arg, "--modify-window=%d", modify_window) < 0)
--- rsync.yo	7 May 2004 00:18:37 -0000	1.169
+++ rsync.yo	18 May 2004 09:31:23 -0000
@@ -320,6 +320,7 @@ verb(
      --timeout=TIME          set I/O timeout in seconds
  -I, --ignore-times          turn off mod time & file size quick check
      --size-only             ignore mod time for quick check (use size)
+     --date-only             ignore size for quick check (use mod time)
      --modify-window=NUM     compare mod times with reduced accuracy
  -T  --temp-dir=DIR          create temporary files in directory DIR
      --compare-dest=DIR      also compare received files relative to DIR
@@ -392,6 +393,12 @@ already the same size and have the same 
 regardless of timestamp. This is useful when starting to use rsync
 after using another mirroring system which may not preserve timestamps
 exactly.
+
+dit(bf(--date-only)) Normally rsync will skip any files that are
+already the same size and have the same modification time-stamp. With the
+--date-only option, files will be skipped if they have the same
+timestamp, regardless of size. This may be useful when the remote
+files have passed through a size-changing filter, e.g. for encryption.
 
 dit(bf(--modify-window)) When comparing two timestamps rsync treats
 the timestamps as being equal if they are within the value of