$ git clone -n https://github.com/xcp-ng-rpms/libtasn1 /var/lib/mock/v8.3-u-pcoval1-11008-29442/root/chroot_tmpdir/scmroot/libtasn1
Cloning into '/var/lib/mock/v8.3-u-pcoval1-11008-29442/root/chroot_tmpdir/scmroot/libtasn1'...
$ git fetch origin 3ebe535be825f7ad0c2825264e4e16f198b9232c:KOJI_FETCH_HEAD
From https://github.com/xcp-ng-rpms/libtasn1
 * [new ref]         3ebe535be825f7ad0c2825264e4e16f198b9232c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3ebe535 bump release for test build