$ git clone -n https://src.fedoraproject.org/rpms/R-data.table.git /var/lib/mock/f43-build-side-110352-58906856-6569159/root/chroot_tmpdir/scmroot/R-data.table
Cloning into '/var/lib/mock/f43-build-side-110352-58906856-6569159/root/chroot_tmpdir/scmroot/R-data.table'...
$ git fetch origin 6ebde1173a8b147e5b6d2e59a9c43f271e728725:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-data.table
 * [new ref]         6ebde1173a8b147e5b6d2e59a9c43f271e728725 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6ebde11 R-maint-sig mass rebuild