push: unmark a local variable as static

push: unmark a local variable as static

There isn't any obvious reason for the 'struct string_list push_options'
and 'struct string_list_item *item' to be marked as static, so unmark
them as being static.  Also, clear the push_options string_list to
prevent memory leaking.

Signed-off-by: Brandon Williams <bmwill@google.com>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>