t5607: avoid using prerequisites to select algorithm
In this test, we currently use the SHA1 prerequisite to specify the
algorithm we're using to test, since SHA-256 bundles are always v3,
whereas SHA-1 bundles default to v2, and as a result the default output
differs.
However, this causes a problem if we run with GIT_TEST_FAIL_PREREQS set,
since that means that we'll unexpectedly fail the SHA1 prerequisite,
resulting in incorrect expected output. Let's fix this by checking
against the built-in data called "algo", which tells us which algorithm
is in use. This should work in any situation, making our test a little
more robust.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>