Check end of path for shell detection

[JoshStern]

Thank you for contributing to Pipenv!

The issue

Shell detection checks the entire path when looking for shell substrings. This can cause the wrong branch to get tripped if shells are installed in a path with another shell in the tree. In my case a li[nu]xbrew-installed zsh goes down the nu shell path.

The fix

This updates the check to only look at the end of cmd when detecting shells.

The checklist

• Associated issue: Linuxbrew shells are detected as nu shell #6197
• A news fragment in the news/ directory to describe this fix with the extension .bugfix.rst, .feature.rst, .behavior.rst, .doc.rst. .vendor.rst. or .trivial.rst (this will appear in the release changelog). Use semantic line breaks and name the file after the issue number or the PR #.

[oz123]

Actually, I prefer this over the split over .linuxbrew.
This solution will cause future maintainers to raise eyebrows and wrinkle their foreheads trying to figure it out without reading the original issue.

This approach is much more maintainable. However, I have a small suggestion:

Change:

cmd.endswith("<shell name>")

to:

cmd.endswith("/<shell name>"):

This will allow to for shortcutting the if ...elif at the head in favor of the most common shells (bash, zsh, sh):

if cmd.endswith("/sh","/bash","/zsh")":
   suffix = ""
  command = "."
elif cmd.endswith("/csh"):
  ...
  
else:
     raise ValueError("unknown shell ...") ....

This works for all three:

>>> cmd="/bin/sh"
>>> cmd.endswith(("/bash","/zsh", "/sh"))
True
>>> cmd="/bin/zsh"
>>> cmd.endswith(("/bash","/zsh", "/sh"))
True
>>> cmd="/bin/bash"
>>> cmd.endswith(("/bash","/zsh", "/sh"))
True
>>> 

[oz123]

@JoshStern thank you for your effort so far (immediately adding news file, is great! ).

I gave your PR some consideration and I think that your solution is better than what I initially suggested.
Adding a shortcut for the most common shells is only possible with your approach.

[JoshStern]

@oz123 updated! Thank you for the feedback and quick turnaround. Want me to also update the branch ordering?

[oz123]

Yes. Please. The zsh, bash and sh bash should be at the top. Unknown shells should not fall silently to imaginary default. They should raise exceptions.

[JoshStern]

Updated, I'm a little concerned about other sh or bash compatible shells out there that will get sent down the ValueError branch. ksh comes to mind.

I do think an explicit list is better though. I defer to you on the right balance.

[oz123]

Thanks! I merged your commits with one on top!

[JoshStern]

Thank you for the help with this! Glad I could contribute 😄