$ git clone -n https://src.fedoraproject.org/rpms/gtkmm4.0.git /var/lib/mock/f40-build-2209859-52168/root/chroot_tmpdir/scmroot/gtkmm4.0
Cloning into '/var/lib/mock/f40-build-2209859-52168/root/chroot_tmpdir/scmroot/gtkmm4.0'...
$ git fetch origin 7b5532f23935b0c12202c3ac7aa1fbafe334fa62:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gtkmm4.0
 * [new ref]         7b5532f23935b0c12202c3ac7aa1fbafe334fa62 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 7b5532f Update to 4.13.2