git-remote-mediawiki: make mediafiles export optional
git-remote-mediawiki: make mediafiles export optional

It is possible to use git-remote-mediawiki on a tree with both .mw files
and other files. Before git-remote-mediawiki learnt how to export
mediafiles, such mixed trees allowed the user to maintain both the wiki
and other files for the same project in the same repository. With the
newly added support for exporting mediafiles, pushing such mixed trees
would upload unrelated files as mediafiles, which may not be desired.

Signed-off-by: Matthieu Moy <d4d2cc2a6ec7b2aa587d4887cc5ed200f9b685a1@imag.fr>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git