range-diff: suppress the diff headers

When showing the diff between corresponding patches of the two branch
versions, we have to make up a fake filename to run the diff machinery.

That filename does not carry any meaningful information, hence tbdiff
suppresses it. So we should, too.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/range-diff.c

@@ -33,6 +33,7 @@ int cmd_range_diff(int argc, const char **argv, const char *prefix)
 
 	diff_setup(&diffopt);
 	diffopt.output_format = DIFF_FORMAT_PATCH;
+	diffopt.flags.suppress_diff_headers = 1;
 	diffopt.output_prefix = output_prefix_cb;
 	strbuf_addstr(&four_spaces, "    ");
 	diffopt.output_prefix_data = &four_spaces;