I think he wants the the full path of the project (cbp file) which is the parant (owner) of the file open in the active editor.
To be honest we should do something similar on the inside, since I also have a nice use case for this :
addition in our right click menu : activate project containing "this" file.
Why : my workspace contains a whole lot of projects, sometimes starting from project x I include file open and end up at file foo.h (F11 to foo.cpp) and suddenly I want to change it's code and build the project it belongs too ...., and searching for the project is hard, even with the find file (since that one is really case sensitive, and no wildcards)