$ git clone -n https://github.com/xcp-ng-rpms/libidn2.git /var/lib/mock/v8.3-incoming-10915-29394/root/chroot_tmpdir/scmroot/libidn2
Cloning into '/var/lib/mock/v8.3-incoming-10915-29394/root/chroot_tmpdir/scmroot/libidn2'...
$ git fetch origin a4a164647631ad22ebc0ea272548f46bc4860ae1:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/libidn2
 * [new ref]         a4a164647631ad22ebc0ea272548f46bc4860ae1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at a4a1646 Import libidn2-2.3.4-4.xs8.src.rpm