$ git clone -n https://src.fedoraproject.org/rpms/golang-github-siddontang.git /var/lib/mock/f40-build-2236564-53513/root/chroot_tmpdir/scmroot/golang-github-siddontang
Cloning into '/var/lib/mock/f40-build-2236564-53513/root/chroot_tmpdir/scmroot/golang-github-siddontang'...
$ git fetch origin fa7c75a7074cd0f57e369c5bc9f87c242b094101:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/golang-github-siddontang
 * [new ref]         fa7c75a7074cd0f57e369c5bc9f87c242b094101 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fa7c75a Remove deprecated %patchN syntax