revlog: drop cache after use to save memory footprint
If we reconstruct back to back large versions, we need to drop the cache first to avoid doubling memory usage.
adding a
abort: abandoned transaction found - run hg recover!
rolling back interrupted transaction
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 1 changesets, 1 total revisions
% check that zero-size journals are correctly aborted
adding changesets
abort: Permission denied