hash-object: reduce file-scope statics
Most of the knobs that affect helper functions called from
cmd_hash_object() were passed to them as parameters already, and the
only effect of having them as file-scope statics was to make the
reader wonder if the parameters are hiding the file-scope global
values by accident. Adjust their initialisation and make them
function-local variables.
The only exception was no_filters hash_stdin_paths() peeked from the
file-scope global, which was converted to a parameter to the helper
function.
Signed-off-by: Junio C Hamano <gitster@pobox.com>