Summary:
This diff implements some simple linkrev database classes which uses dbm to
store linkrev candidates.
Why not sqlite? sqlite's insertion seems to be much slower with index being
present, so we have to do manual buffering and do insertion in batch, not to
say parsing SQL itself can introduce overhead. If we really want sqlite for
some reason (i.e. its support for concurrent writer and reader seems to be
better), we can still implement it as a dbm engine.
Test Plan: A test will be added when there is something usable.
Reviewers: #sourcecontrol, stash
Reviewed By: stash
Subscribers: jsgf, stash, mjpieters
Differential Revision: https://phabricator.intern.facebook.com/D4143119
Signature: t1:4143119:1479131795:5f6e368ebd1798b874cec28ac05b137eb3bea86e