Determine the file differences between the currently included files and a previously captured list of files. This method will not look for a changed in content but sole in the list of files given.
The method will compare the given array of file Strings with the result of the last directory scan. It will execute a {@link #scan()} if noresult of a previous scan could be found.
The result of the diff can be queried by the methods {@link DirectoryScanResult#getFilesAdded()} and {@link DirectoryScanResult#getFilesRemoved()}
@param oldFiles the list of previously captured files names.