When we delete stable branches a commit may not appear to be on a
named branch, so validation for old releases may fail even though the
commit is still in the repository. This change uses 'git show' instead
of 'git branch --contains' to separate the tests for existence and
branch membership.
Change-Id: I58213b29bb37c7c428017204a4bdd5235a5816ca
Signed-off-by: Doug Hellmann <doug@doughellmann.com>
68fadcd1d7