Stefan Fiedler:

package/base/bash/preconfig.in

@@ -22,8 +22,13 @@
 
 if pkgcheck bash X
 then
-        pkgfork bash bash2
-        pkgfork bash bash3 stages "-----5---9"
+	if [ "$ROCKCFG_PKG_BASH_DEFAULT" == "bash2" ]; then
+        	pkgfork bash bash2
+        	pkgfork bash bash3 stages "-----5---9"
+	elif [ "$ROCKCFG_PKG_BASH_DEFAULT" == "bash3" ]; then
+        	pkgfork bash bash2 stages "-----5---9"
+        	pkgfork bash bash3
+	fi
         pkgremove bash
 fi