$ git clone -n https://src.fedoraproject.org/rpms/castxml.git /var/lib/mock/f39-build-1534183-36232/root/chroot_tmpdir/scmroot/castxml
Cloning into '/var/lib/mock/f39-build-1534183-36232/root/chroot_tmpdir/scmroot/castxml'...
$ git fetch origin 1a2620fc0562085a9785e0b46d8c179839d3a9c9:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/castxml
 * [new ref]         1a2620fc0562085a9785e0b46d8c179839d3a9c9 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1a2620f Update to version 0.6.2