$ git clone -n https://src.fedoraproject.org/rpms/rubygem-excon.git /var/lib/mock/f40-build-2053424-49093/root/chroot_tmpdir/scmroot/rubygem-excon
Cloning into '/var/lib/mock/f40-build-2053424-49093/root/chroot_tmpdir/scmroot/rubygem-excon'...
$ git fetch origin 66c1b4f01cdfa9d6eaf9998b9a9880d0296186c0:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-excon
 * [new ref]         66c1b4f01cdfa9d6eaf9998b9a9880d0296186c0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 66c1b4f Update to Excon 0.100.0.