Merge branch 'jt/test-protocol-version'

Help developers by making it easier to run most of the tests under different versions of over-the-wire protocols. * jt/test-protocol-version: t5552: compensate for v2 filtering ref adv. tests: fix protocol version for overspecifications t5700: only run with protocol version 1 t5512: compensate for v0 only sending HEAD symrefs t5503: fix overspecification of trace expectation tests: always test fetch of unreachable with v0 t5601: check ssh command only with protocol v0 tests: define GIT_TEST_PROTOCOL_VERSION