git-svn: avoid redundant get_log calls between invocations
git-svn: avoid redundant get_log calls between invocations

Prefill .rev_db to the maximum revision we tried to fetch;
and take advantage of that so we can avoid using get_log()
on ranges we've already seen (and have deemed uninteresting).

Signed-off-by: Eric Wong <8c2951295f8292b0c03727bc4652981172298eae@yhbt.net>

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