$ git clone -n https://src.fedoraproject.org/rpms/R-sysfonts.git /var/lib/mock/f45-build-6439-348/root/chroot_tmpdir/scmroot/R-sysfonts
Cloning into '/var/lib/mock/f45-build-6439-348/root/chroot_tmpdir/scmroot/R-sysfonts'...
$ git fetch origin f12fab352817a9cfa544757b94d66c1857ffe73a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-sysfonts
 * [new ref]         f12fab352817a9cfa544757b94d66c1857ffe73a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f12fab3 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild