Merge branch 'jc/capabilities' into maint

Merge branch 'jc/capabilities' into maint

* jc/capabilities:
  fetch-pack: mention server version with verbose output
  parse_feature_request: make it easier to see feature values
  fetch-pack: do not ask for unadvertised capabilities
  do not send client agent unless server does first
  send-pack: fix capability-sending logic
  include agent identifier in capability string