ref-filter: introduce refname_atom_parser_internal()

Since there are multiple atoms which print refs ('%(refname)',
'%(symref)', '%(push)', '%(upstream)'), it makes sense to have a common
ground for parsing them. This would allow us to share implementations of
the atom modifiers between these atoms.

Introduce refname_atom_parser_internal() to act as a common parsing
function for ref printing atoms. This would eventually be used to
introduce refname_atom_parser() and symref_atom_parser() and also be
internally used in remote_ref_atom_parser().

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

Author: KarthikNayak

ref-filter.c

@@ -32,6 +32,11 @@ struct if_then_else {
 		condition_satisfied : 1;
 };
 
+struct refname_atom {
+	enum { R_NORMAL, R_SHORT, R_STRIP } option;
+	unsigned int strip;
+};
+
 /*
  * An atom is a valid field atom listed below, possibly prefixed with
  * a "*" to denote deref_tag().
@@ -64,6 +69,7 @@ static struct used_atom {
 			enum { O_FULL, O_LENGTH, O_SHORT } option;
 			unsigned int length;
 		} objectname;
+		struct refname_atom refname;
 	} u;
 } *used_atom;
 static int used_atom_cnt, need_tagged, need_symref;
@@ -77,6 +83,21 @@ static void color_atom_parser(struct used_atom *atom, const char *color_value)
 		die(_("unrecognized color: %%(color:%s)"), color_value);
 }
 
+static void refname_atom_parser_internal(struct refname_atom *atom,
+					 const char *arg, const char *name)
+{
+	if (!arg)
+		atom->option = R_NORMAL;
+	else if (!strcmp(arg, "short"))
+		atom->option = R_SHORT;
+	else if (skip_prefix(arg, "strip=", &arg)) {
+		atom->option = R_STRIP;
+		if (strtoul_ui(arg, 10, &atom->strip) || atom->strip <= 0)
+			die(_("positive value expected refname:strip=%s"), arg);
+	} else
+		die(_("unrecognized %%(%s) argument: %s"), name, arg);
+}
+
 static void remote_ref_atom_parser(struct used_atom *atom, const char *arg)
 {
 	struct string_list params = STRING_LIST_INIT_DUP;