This is used to get the page creation time for a file from the RCS, by looking
it up in the history.
-It's ok if this is not implemented, and throws an error.
-
If the RCS cannot determine a ctime for the file, return 0.
#### `rcs_getmtime($)`
so `rcs_commit_staged` will complete it. It should return undef on _success_
and an error message on failure.
+This hook and `rcs_preprevert` are optional, if not implemented, no revert
+web interface will be available.
+
### PageSpec plugins
It's also possible to write plugins that add new functions to