Setting __file__ in eval_file

[jeandet]

Hi,
I wonder if it wouldn't make sense to set file global variable by default inside pybind11::eval_file executed scripts might want to use it.
A kind of recurring pattern in python is:

import os
script_path = os.path.realpath(__file__)

[EricCousineau-TRI]

Seconded. Nominally, if you try and use trace in a file executed via py::eval_file without having set __file__, you won't see any commands for that file. An example usage (albeit a hacky motivation - for debugging in CLion):
Python code
C++ code