Merge branch 'km/svn-1.8-serf-only'

Subversion 1.8.0 that was recently released breaks older subversion clients coming over http/https in various ways. * km/svn-1.8-serf-only: Git.pm: revert _temp_cache use of temp_is_locked git-svn: allow git-svn fetching to work using serf Git.pm: add new temp_is_locked function