Don't do that. Synchronizing back is a very difficult task, and you
will
find yourself in deep trouble very soon. If you don't do proper replication conflict resolution, you'll have either junk on your side
or
on the Wikipedia side. In the later case, you'll probably get blocked rather soon, in the other case your users will get frustrated because their edits don't get through.
Regards,
jens
At one wiki site (not a Wikipedia) an improved version of Special:Ancientpages is used to manually synchrolize between localhost and webhost clone wiki sites. This version of Special:Ancientpages allows to select another exportable namespaces besides NS_MAIN and optionally submits these to Special:Export. By default, the functionality of Special:Export is very limited (at least it was last time I was cheking it).
A better approach probably would be introducing an --date option to maintenance/dumpBackup.php.
The important problem though is, that during XML import not all hooks are called and extension-specific data is not saved/restored correctly :-( I think it's major problem that these hooks doesn't allow to pass their own XML tags into the dumps. Dmitriy