| fileGuid | The GUID of the file reference. | 
| path | The physical path to the new file on the filesystem. | 
| sourceTree | The source tree the path is relative to. By default it's PBXSourceTree.Source. The PBXSourceTree.Group tree is not supported. | 
Replaces the file with given GUID with the specified file.
The path to the specified file is replaced while preserving the GUID of the old file.