Add copy method to VarSet

pkg/types/var.go

@@ -75,15 +75,20 @@ type VarSet struct {
 	set []Var
 }
 
-// Set returns a copy of the var set.
-func (vs *VarSet) Set() []Var {
+// AsSlice returns the vars as a slice.
+func (vs *VarSet) AsSlice() []Var {
 	s := make([]Var, len(vs.set))
 	copy(s, vs.set)
 	return s
 }
 
+// Copy returns a copy of the var set.
+func (vs *VarSet) Copy() VarSet {
+	return VarSet{set: vs.AsSlice()}
+}
+
 // MergeSet absorbs other vars with error on name collision.
-func (vs *VarSet) MergeSet(incoming *VarSet) error {
+func (vs *VarSet) MergeSet(incoming VarSet) error {
 	return vs.MergeSlice(incoming.set)
 }