The fetcher made the rather bold assumption that if it fetched from the upstream,
the revisions were present and correct. These checks are fast and ensure that
really is the case. The avoids accidental network accessed and missing
branch configuration problems.
(Bitbake rev: a9112a102a89049cda597dad449e922c9e957a5d)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>