Improve primary shell activation heuristics

[MatthijsBurgh]

I asked our friends from ChatGPT for a robust check.

It suggested the following:

import os
import subprocess

def parent_process_name():
    ppid = os.getppid()
    try:
        return subprocess.check_output(
            ["ps", "-p", str(ppid), "-o", "comm="],
            text=True
        ).strip()
    except Exception:
        return None

parent = parent_process_name()
print(parent)  # likely "pwsh"

os.getppid should also be available on Windows. I am not so sure about ps. Depending on the availability of ps on Windows, this check can also be used on Windows, otherwise only on unix systems.

update: It is not available on Windows.

I think this is an improvement compared to the current heuristics.

[MatthijsBurgh]

When we allow psutil as a dependency, we can use the following check, which is platform independent.

import psutil

parent = psutil.Process().parent()
print(parent.name())  # pwsh / powershell.exe

[cottsay]

...It is not available on Windows.

I think the Windows heuristic is pretty good. Not airtight, but no worse than just using SHELL on *nix.

[MatthijsBurgh]

@cottsay any preference for the os/subprocess or the psutil solution?