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.
% prepare repo
adding a
% import patch
applying patch from stdin
patching file a
Hunk #1 succeeded at 43 (offset 34 lines).
Hunk #2 succeeded at 87 (offset 34 lines).
Hunk #3 succeeded at 109 (offset 34 lines).
a
% compare imported changes against reference file