$ git clone -n https://src.fedoraproject.org/rpms/R-xopen.git /var/lib/mock/f42-build-side-1-3502110-45977/root/chroot_tmpdir/scmroot/R-xopen
Cloning into '/var/lib/mock/f42-build-side-1-3502110-45977/root/chroot_tmpdir/scmroot/R-xopen'...
$ git fetch origin 62290a34cd3efe40582fa856ad7c2889be122faa:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-xopen
 * [new ref]         62290a34cd3efe40582fa856ad7c2889be122faa -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 62290a3 R-maint-sig mass rebuild