$ git clone -n https://src.fedoraproject.org/rpms/libxmlb.git /var/lib/mock/f45-build-17363-498/root/chroot_tmpdir/scmroot/libxmlb
Cloning into '/var/lib/mock/f45-build-17363-498/root/chroot_tmpdir/scmroot/libxmlb'...
$ git fetch origin 4ff6f75dbf69f6878ebb8cbf35db6857ed926e78:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/libxmlb
 * [new ref]         4ff6f75dbf69f6878ebb8cbf35db6857ed926e78 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 4ff6f75 New upstream release