In order to do anything more capable with refspecs, the first step is
to keep the entire input. Additionally, validate patterns by checking
for the ref matching the rules for a pattern as given by
check_ref_format(). This requires a slight change to
check_ref_format() to make it enforce the requirement that the '*'
immediately follow a '/'.
Signed-off-by: Daniel Barkalow <barkalow@iabervon.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>