public VirtualFile getFile(VirtualFile mountPoint, VirtualFile target) {
        final String path = target.getPathNameRelativeTo(mountPoint);
        return rootNode.getFile(new Path(path), mountPoint);
    }
public VirtualFile getFile ( VirtualFile mountPoint , VirtualFile target ) { final String path = target . getPathNameRelativeTo ( mountPoint ) ; return rootNode . getFile ( new Path ( path ) , mountPoint ) ; }
Get the VirtualFile from the assembly.  This will traverse VirtualFiles in assembly
to find children if needed.

@param mountPoint
@param target
@return
@throws IOException