ref-filter: make "%(symref)" atom work with the ':short' modifier

The "%(symref)" atom doesn't work when used with the ':short' modifier
because we strictly match only 'symref' for setting the 'need_symref'
indicator. Fix this by comparing with the valid_atom rather than the
used_atom.

Add tests for %(symref) and %(symref:short) while we're here.

Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Karthik Nayak <Karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: KarthikNayak

ref-filter.c

@@ -352,7 +352,7 @@ int parse_ref_filter_atom(const char *atom, const char *ep)
 		valid_atom[i].parser(&used_atom[at], arg);
 	if (*atom == '*')
 		need_tagged = 1;
-	if (!strcmp(used_atom[at].name, "symref"))
+	if (!strcmp(valid_atom[i].name, "symref"))
 		need_symref = 1;
 	return at;
 }

t/t6300-for-each-ref.sh

@@ -38,6 +38,7 @@ test_atom() {
 	case "$1" in
 		head) ref=refs/heads/master ;;
 		 tag) ref=refs/tags/testtag ;;
+		 sym) ref=refs/heads/sym ;;
 		   *) ref=$1 ;;
 	esac
 	printf '%s\n' "$3" >expected
@@ -566,6 +567,7 @@ test_expect_success 'Verify sort with multiple keys' '
 	test_cmp expected actual
 '
 
+
 test_expect_success 'do not dereference NULL upon %(HEAD) on unborn branch' '
 	test_when_finished "git checkout master" &&
 	git for-each-ref --format="%(HEAD) %(refname:short)" refs/heads/ >actual &&
@@ -600,4 +602,26 @@ test_expect_success 'basic atom: head contents:trailers' '
 	test_cmp expect actual.clean
 '
 
+test_expect_success 'Add symbolic ref for the following tests' '
+	git symbolic-ref refs/heads/sym refs/heads/master
+'
+
+cat >expected <<EOF
+refs/heads/master
+EOF
+
+test_expect_success 'Verify usage of %(symref) atom' '
+	git for-each-ref --format="%(symref)" refs/heads/sym >actual &&
+	test_cmp expected actual
+'
+
+cat >expected <<EOF
+heads/master
+EOF
+
+test_expect_success 'Verify usage of %(symref:short) atom' '
+	git for-each-ref --format="%(symref:short)" refs/heads/sym >actual &&
+	test_cmp expected actual
+'
+
 test_done