ref-filter: introduce handler function for each atom
Introduce a handler function for each atom, which is called when the
atom is processed in show_ref_array_item().
In this context make append_atom() as the default handler function and
extract quote_formatting() out of append_atom(). Bump this to the top.
Mentored-by: Christian Couder <christian.couder@gmail.com>
Mentored-by: Matthieu Moy <matthieu.moy@grenoble-inp.fr>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>