$ git clone -n https://src.fedoraproject.org/rpms/R-gdata.git /var/lib/mock/f45-build-6135-346/root/chroot_tmpdir/scmroot/R-gdata
Cloning into '/var/lib/mock/f45-build-6135-346/root/chroot_tmpdir/scmroot/R-gdata'...
$ git fetch origin 375d81635836154dfc1e6f75c6ee155b50cedc3e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-gdata
 * [new ref]         375d81635836154dfc1e6f75c6ee155b50cedc3e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 375d816 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild