+ # This method does what the user expects when giving an argument to a Nit tool.
+ #
+ # * If `path` is an existing Nit source file (with the `.nit` extension),
+ # then the associated ModulePath is returned
+ # * If `path` is a directory (with a `/`),
+ # then the ModulePath of its default module is returned (if any)
+ # * If `path` is a simple identifier (eg. `digraph`),
+ # then the main module of the project `digraph` is searched in `paths` and returned.
+ #
+ # Silently return `null` if `path` does not exists or cannot be identified.