The LocalDiskRepositoryTestCase class is derived from the current
RepositoryTestCase code and is meant for application (or our own)
tests to subclass and access temporary repositories on the local
client disk.

Change-Id: Idff096cea40a7b2b56a90fb5de179ba61ea3a0eb
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>