A patch from Stefan Müller to add the --downdate option, which works
in the opposite manner as --update.

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

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

based-on: a01e3b490eb36ccf9e704840e1b6683dab867550
diff --git a/generator.c b/generator.c
--- a/generator.c
+++ b/generator.c
@@ -56,6 +56,7 @@ extern int ignore_errors;
 extern int remove_source_files;
 extern int delay_updates;
 extern int update_only;
+extern int downdate_only;
 extern int human_readable;
 extern int ignore_existing;
 extern int ignore_non_existing;
@@ -1529,6 +1530,13 @@ static void recv_generator(char *fname, struct file_struct *file, int ndx,
 		goto cleanup;
 	}
 
+	if (downdate_only && statret == 0
+	    && cmp_time(sx.st.st_mtime, file->modtime) < 0) {
+		if (INFO_GTE(SKIP, 1))
+			rprintf(FINFO, "%s is older\n", fname);
+		return;
+	}
+
 	fnamecmp = fname;
 	fnamecmp_type = FNAMECMP_FNAME;
 
@@ -1962,6 +1970,7 @@ void check_for_finished_files(int itemizing, enum logcode code, int check_redo)
 			ignore_existing = -ignore_existing;
 			ignore_non_existing = -ignore_non_existing;
 			update_only = -update_only;
+			downdate_only = -downdate_only;
 			always_checksum = -always_checksum;
 			size_only = -size_only;
 			append_mode = -append_mode;
@@ -1987,6 +1996,7 @@ void check_for_finished_files(int itemizing, enum logcode code, int check_redo)
 			ignore_existing = -ignore_existing;
 			ignore_non_existing = -ignore_non_existing;
 			update_only = -update_only;
+			downdate_only = -downdate_only;
 			always_checksum = -always_checksum;
 			size_only = -size_only;
 			append_mode = -append_mode;
diff --git a/options.c b/options.c
--- a/options.c
+++ b/options.c
@@ -60,6 +60,7 @@ int preserve_uid = 0;
 int preserve_gid = 0;
 int preserve_times = 0;
 int update_only = 0;
+int downdate_only = 0;
 int cvs_exclude = 0;
 int dry_run = 0;
 int do_xfers = 1;
@@ -671,6 +672,7 @@ void usage(enum logcode F)
   rprintf(F,"     --backup-dir=DIR        make backups into hierarchy based in DIR\n");
   rprintf(F,"     --suffix=SUFFIX         set backup suffix (default %s w/o --backup-dir)\n",BACKUP_SUFFIX);
   rprintf(F," -u, --update                skip files that are newer on the receiver\n");
+  rprintf(F," -w, --downdate              skip files that are older on the receiver\n");
   rprintf(F,"     --inplace               update destination files in-place (SEE MAN PAGE)\n");
   rprintf(F,"     --append                append data onto shorter files\n");
   rprintf(F,"     --append-verify         like --append, but with old data in file checksum\n");
@@ -892,6 +894,7 @@ static struct poptOption long_options[] = {
   {"no-one-file-system",'x',POPT_ARG_VAL,   &one_file_system, 0, 0, 0 },
   {"no-x",            'x', POPT_ARG_VAL,    &one_file_system, 0, 0, 0 },
   {"update",          'u', POPT_ARG_NONE,   &update_only, 0, 0, 0 },
+  {"downdate",        'w', POPT_ARG_NONE,   &downdate_only, 0, 0, 0 },
   {"existing",         0,  POPT_ARG_NONE,   &ignore_non_existing, 0, 0, 0 },
   {"ignore-non-existing",0,POPT_ARG_NONE,   &ignore_non_existing, 0, 0, 0 },
   {"ignore-existing",  0,  POPT_ARG_NONE,   &ignore_existing, 0, 0, 0 },