$ git clone -n https://src.fedoraproject.org/rpms/mutter.git /var/lib/mock/f40-build-2256127-54272/root/chroot_tmpdir/scmroot/mutter
Cloning into '/var/lib/mock/f40-build-2256127-54272/root/chroot_tmpdir/scmroot/mutter'...
$ git fetch origin 585024ef9700aef7bc35ceaec46e450ea0c2426b:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mutter
 * [new ref]         585024ef9700aef7bc35ceaec46e450ea0c2426b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 585024e Fix i686 build