ref-filter: add empty values to technical fields

Atoms like "align" or "end" do not have string representation.
Earlier we had to go and parse whole object with a hope that we
could fill their string representations. It's easier to fill them
with an empty string before we start to work with whole object.

Signed-off-by: Olga Telezhnaia <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: telezhnaya

ref-filter.c

@@ -1497,6 +1497,7 @@ static int populate_value(struct ref_array_item *ref, struct strbuf *err)
 			refname = get_symref(atom, ref);
 		else if (starts_with(name, "upstream")) {
 			const char *branch_name;
+			v->s = "";
 			/* only local branches may have an upstream */
 			if (!skip_prefix(ref->refname, "refs/heads/",
 					 &branch_name))
@@ -1509,6 +1510,7 @@ static int populate_value(struct ref_array_item *ref, struct strbuf *err)
 			continue;
 		} else if (atom->u.remote_ref.push) {
 			const char *branch_name;
+			v->s = "";
 			if (!skip_prefix(ref->refname, "refs/heads/",
 					 &branch_name))
 				continue;
@@ -1549,22 +1551,26 @@ static int populate_value(struct ref_array_item *ref, struct strbuf *err)
 			continue;
 		} else if (starts_with(name, "align")) {
 			v->handler = align_atom_handler;
+			v->s = "";
 			continue;
 		} else if (!strcmp(name, "end")) {
 			v->handler = end_atom_handler;
+			v->s = "";
 			continue;
 		} else if (starts_with(name, "if")) {
 			const char *s;
-
+			v->s = "";
 			if (skip_prefix(name, "if:", &s))
 				v->s = xstrdup(s);
 			v->handler = if_atom_handler;
 			continue;
 		} else if (!strcmp(name, "then")) {
 			v->handler = then_atom_handler;
+			v->s = "";
 			continue;
 		} else if (!strcmp(name, "else")) {
 			v->handler = else_atom_handler;
+			v->s = "";
 			continue;
 		} else
 			continue;