$ git clone -n https://src.fedoraproject.org/rpms/gnome-builder.git /var/lib/mock/f40-build-1945555-25181/root/chroot_tmpdir/scmroot/gnome-builder
Cloning into '/var/lib/mock/f40-build-1945555-25181/root/chroot_tmpdir/scmroot/gnome-builder'...
$ git fetch origin 18cb29a78a553e83b593dcc0dcbf2d977aa9c4fb:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gnome-builder
 * [new ref]         18cb29a78a553e83b593dcc0dcbf2d977aa9c4fb -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 18cb29a Update to 46.3