Revert changeset c67920d78248.
It breaks 'hg merge && hg up -c REV' when files exist only in one of the
manifests, making hg throw a traceback like:
changeset: 0:0acdaf898367
tag: tip
user: test
date: Mon Jan 12 13:46:40 1970 +0000
summary: test
b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3 644 a
a
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 1 changesets, 1 total revisions