* test/lisp/vc/vc-git-tests.el
(vc-git-test-dir-track-local-branch): Remove in favor of new
test.
(vc-git-test--start-branch): New helper to get a repository
going.
(vc-git-test--dir-headers): New helper to get a list of headers
in the current vc-dir buffer.
(vc-git-test-dir-branch-headers): New test, exercising the
original bug recipe plus more common scenarios.