1 files changed, 7 insertions, 3 deletions
diff --git a/build/install/rule b/build/install/rule
index af38587..54014e1 100644
--- a/build/install/rule
+++ b/build/install/rule
@@ -27,12 +27,16 @@ namespace build
     class file_rule: public rule
     {
     public:
-      virtual bool
-      filter (action, target&, prerequisite_member) const {return true;}
-
       virtual match_result
       match (action, target&, const std::string&) const;
 
+      // Return NULL if this prerequisite should be ignored and pointer to its
+      // target otherwise. The default implementation ignores prerequsites that
+      // are outside of this target's project.
+      //
+      virtual target*
+      filter (action, target&, prerequisite_member) const;
+
       virtual recipe
       apply (action, target&, const match_result&) const;