ensure file is added even if a file already exists for which it is a substring (e.g. Class1.cs and Subfolder/Class1.cs, or Class1.cs and AnotherClass1.cs)

git-svn-id: https://svn.apache.org/repos/asf/incubator/npanday/trunk@1572104 13f79535-47bb-0310-9956-ffa450edef68