$ git clone -n https://src.fedoraproject.org/rpms/guile-reader.git /var/lib/mock/f41-build-857971-168280/root/chroot_tmpdir/scmroot/guile-reader
Cloning into '/var/lib/mock/f41-build-857971-168280/root/chroot_tmpdir/scmroot/guile-reader'...
$ git fetch origin 1fc5da6313247c311a517dc71f0db52939c518bc:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/guile-reader
 * [new ref]         1fc5da6313247c311a517dc71f0db52939c518bc -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1fc5da6 Build using Guile 3