Merge branch 'jt/test-protocol-version' into jt/fetch-no-update-shallow-in-proto-v2

* 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

diff --cc t/README
Simple merge

diff --cc t/t5551-http-fetch-smart.sh
Simple merge