t9001: refactor sendmail aliases test infrastructure
t9001: refactor sendmail aliases test infrastructure

Several new tests of sendmail aliases parsing will be added in a
subsequent patch, so factor out functionality common to all of them
into a new helper function.

Signed-off-by: Eric Sunshine <8d6e34f987851aa599257d3831a1af040886842f@sunshineco.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git