git-remote-mediawiki: more efficient 'pull' in the best case

git-remote-mediawiki: more efficient 'pull' in the best case

The only way to fetch new revisions from a wiki before this patch was to
query each page for new revisions. This is good when tracking a small set
of pages on a large wiki, but very inefficient when tracking many pages
on a wiki with little activity.

Implement a new strategy that queries the wiki for its last global
revision, queries each new revision, and filter out pages that are not
tracked.

Signed-off-by: Simon Perrat <simon.perrat@ensimag.imag.fr>
Signed-off-by: Simon CATHEBRAS <Simon.Cathebras@ensimag.imag.fr>
Signed-off-by: Julien KHAYAT <Julien.Khayat@ensimag.imag.fr>
Signed-off-by: Charles ROUSSEL <Charles.Roussel@ensimag.imag.fr>
Signed-off-by: Guillaume SASDY <Guillaume.Sasdy@ensimag.imag.fr>
Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>