$ git clone -n https://src.fedoraproject.org/rpms/R-keyring.git /var/lib/mock/f43-build-side-110352-58907654-6569187/root/chroot_tmpdir/scmroot/R-keyring
Cloning into '/var/lib/mock/f43-build-side-110352-58907654-6569187/root/chroot_tmpdir/scmroot/R-keyring'...
$ git fetch origin 14688b8b2f1789f0911abd59981a970a22430ae6:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-keyring
 * [new ref]         14688b8b2f1789f0911abd59981a970a22430ae6 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 14688b8 R-maint-sig mass rebuild