Merge branch 'jn/promote-proto2-to-default'

The transport protocol version 2 becomes the default one. * jn/promote-proto2-to-default: fetch: default to protocol version 2 protocol test: let protocol.version override GIT_TEST_PROTOCOL_VERSION test: request GIT_TEST_PROTOCOL_VERSION=0 when appropriate config doc: protocol.version is not experimental fetch test: use more robust test for filtered objects