ref-filter: move "cmp_fn" assignment into "else if" arm

Further amend code changed in 7c5045fc18 (ref-filter: apply fallback
refname sort only after all user sorts, 2020-05-03) to move an
assignment only used in the "else if" arm to happen there. Before that
commit the cmp_fn would be used outside of it.

We could also just skip the "cmp_fn" assignment and use
strcasecmp/strcmp directly in a ternary statement here, but this is
probably more readable.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

ref-filter.c

@@ -2355,7 +2355,6 @@ static int cmp_ref_sorting(struct ref_sorting *s, struct ref_array_item *a, stru
 	struct atom_value *va, *vb;
 	int cmp;
 	cmp_type cmp_type = used_atom[s->atom].type;
-	int (*cmp_fn)(const char *, const char *);
 	struct strbuf err = STRBUF_INIT;
 
 	if (get_ref_atom_value(a, s->atom, &va, &err))
@@ -2363,10 +2362,11 @@ static int cmp_ref_sorting(struct ref_sorting *s, struct ref_array_item *a, stru
 	if (get_ref_atom_value(b, s->atom, &vb, &err))
 		die("%s", err.buf);
 	strbuf_release(&err);
-	cmp_fn = s->ignore_case ? strcasecmp : strcmp;
 	if (s->version) {
 		cmp = versioncmp(va->s, vb->s);
 	} else if (cmp_type == FIELD_STR) {
+		int (*cmp_fn)(const char *, const char *);
+		cmp_fn = s->ignore_case ? strcasecmp : strcmp;
 		cmp = cmp_fn(va->s, vb->s);
 	} else {
 		if (va->value < vb->value)