log: slowpath: only walk specified revision range during preparation
Even with --removed, it does not make sense to examine changesets outside
of the revision range that was specified by the user: the last phase only
yields a subset of (revs), preparation phase hence only has to examine
(revs) to fill correctly fncache.
adding foo
% no signatures
% hg sign 0
Signing 0:e63c23eaa88a
% hg sigs
hgtest 0:e63c23eaa88ae77967edcf4ea194d31167c478b0
% hg sigcheck 0
e63c23eaa88a is signed by:
hgtest