Summary:
We have seen issues that users have outdated groups when running hg commands,
which will probably always cause issues:
- Authentication issue, unable to ssh
- Filesystem permission issue, unable to write hgcache
- Even worse with chg server since the long-running server process will keep
the wrong groups information
This extension is to address the above issues. It allows us to print a message
to let the user know they have group issues. Besides, it allows us to override
configs like `chgserver.idletimeout` so chg servers with wrong groups can have
a much smaller TTL and won't be long-running and causing issues.
Test Plan: Run the newly added test
Reviewers: #sourcecontrol, simonfar
Reviewed By: simonfar
Subscribers: simonfar, mjpieters
Differential Revision: https://phabricator.intern.facebook.com/D3896628
Signature: t1:3896628:1474454162:22785ff23e3ada75013ce5f1eead3407068ba172
