for-each-ref: consistently pass WM_IGNORECASE flag

The match_name_as_path() function learned to set
WM_IGNORECASE in the "flags" field when the user passed
--ignore-case. But it forgot to actually pass the flags to
wildmatch()!

As a result, the --ignore-case feature has been broken since
it was added in 3bb16a8bf2 (tag, branch, for-each-ref: add
--ignore-case for sorting and filtering, 2016-12-04). We
didn't notice because we added tests only for git-branch and
git-tag. Whereas git-for-each-ref has slightly different
matching rules, and thus uses a different function (the
related function match_pattern() does it correctly).

Incidentally, this also caused clang's scan-build to
complain about the code; the assignment to "flags" was dead
code.

Note that we can't flip the test in t6300 to expect_success
yet. There's another bug, which will be dealt with in the
next patch.

Commit-message-by: Jeff King <peff@peff.net>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

ref-filter.c

@@ -1714,7 +1714,7 @@ static int match_name_as_path(const struct ref_filter *filter, const char *refna
 		     refname[plen] == '/' ||
 		     p[plen-1] == '/'))
 			return 1;
-		if (!wildmatch(p, refname, WM_PATHNAME))
+		if (!wildmatch(p, refname, flags))
 			return 1;
 	}
 	return 0;