$ git clone -n https://src.fedoraproject.org/rpms/swift-lang.git /var/lib/mock/f38-build-side-42-init-devel-1121460-30242/root/chroot_tmpdir/scmroot/swift-lang
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-1121460-30242/root/chroot_tmpdir/scmroot/swift-lang'...
$ git fetch origin ed1e815a8872624ab0966d8eb46b5259b2369795:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/swift-lang
 * [new ref]         ed1e815a8872624ab0966d8eb46b5259b2369795 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at ed1e815 Updated to Swift 5.8-RELEASE