|path||The physical path to the file on the filesystem.|
|projectPath||The project path to the file.|
|sourceTree||The source tree the path is relative to. By default it's PBXSourceTree.Source. The PBXSourceTree.Group tree is not supported.|
string The GUID of the added file. It can later be used to add the file for building to targets, etc.
Adds a new file reference to the list of known files.
The group structure is automatically created to correspond to the project path. To add the file to the list of files to build, pass the returned value to AddFileToBuild.