The array of supported snapshot format is used and defined (with two
different names) in two routines, one of which (format_snapshot_links)
is often called multiple times per page.
Simplify code and speed up page generation by making the array global.
Signed-off-by: Giuseppe Bilotta <giuseppe.bilotta@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>