$ git clone -n https://src.fedoraproject.org/rpms/swift-lang.git /var/lib/mock/f41-build-850496-165462/root/chroot_tmpdir/scmroot/swift-lang
Cloning into '/var/lib/mock/f41-build-850496-165462/root/chroot_tmpdir/scmroot/swift-lang'...
$ git fetch origin dc57945df0778d12437c93103036297e350c6349:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/swift-lang
 * [new ref]         dc57945df0778d12437c93103036297e350c6349 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at dc57945 Export Swift development tool libraries to libdir