$ git clone -n https://src.fedoraproject.org/rpms/R-xfun.git /var/lib/mock/f40-build-2216064-52475/root/chroot_tmpdir/scmroot/R-xfun
Cloning into '/var/lib/mock/f40-build-2216064-52475/root/chroot_tmpdir/scmroot/R-xfun'...
$ git fetch origin 77a616bce4aeb633e7ce140b2b812a5873812050:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-xfun
 * [new ref]         77a616bce4aeb633e7ce140b2b812a5873812050 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 77a616b 0.41