for-each-ref: fix setup of option-parsing for --sort

The option value for --sort is already a pointer to a pointer to struct
ref_sort, so just use it.
Signed-off-by: NLars Hjemli <hjemli@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin-for-each-ref.c

@@ -847,7 +847,7 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 		OPT_GROUP(""),
 		OPT_INTEGER( 0 , "count", &maxcount, "show only <n> matched refs"),
 		OPT_STRING(  0 , "format", &format, "format", "format to use for the output"),
-		OPT_CALLBACK(0 , "sort", &sort_tail, "key",
+		OPT_CALLBACK(0 , "sort", sort_tail, "key",
 		            "field name to sort on", &opt_parse_sort),
 		OPT_END(),
 	};

t/t6300-for-each-ref.sh

@@ -148,4 +148,26 @@ test_expect_success 'Check format "rfc2822" date fields output' '
 	git diff expected actual
 '
 
+cat >expected <<\EOF
+refs/heads/master
+refs/tags/testtag
+EOF
+
+test_expect_success 'Verify ascending sort' '
+	git-for-each-ref --format="%(refname)" --sort=refname >actual &&
+	git diff expected actual
+'
+
+
+cat >expected <<\EOF
+refs/tags/testtag
+refs/heads/master
+EOF
+
+test_expect_success 'Verify descending sort' '
+	git-for-each-ref --format="%(refname)" --sort=-refname >actual &&
+	git diff expected actual
+'
+
+
 test_done