Make the passenv environment setting case sensitive

[gnikonorov]

Description

Make the passenv environment setting case sensitive. Before this change it was including all environment variables that matched in a case insensitive fashion ( FOO included FOO, fOo, and foo for example )

Closes #1534

Contribution checklist:

(also see CONTRIBUTING.rst for details)

• wrote descriptive pull request text
• added/updated test(s)
• updated/extended the documentation - Not applicable in this case
• added relevant issue keyword
  in message body
• added news fragment in changelog folder
  • fragment name: <issue number>.<type>.rst for example (588.bugfix.rst)
  • <type> is must be one of bugfix, feature, deprecation,breaking, doc, misc
  • if PR has no issue: consider creating one first or change it to the PR number after creating the PR
  • "sign" fragment with "by :user:<your username>"
  • please use full sentences with correct case and punctuation, for example: "Fix issue with non-ascii contents in doctest text files - by :user:superuser."
  • also see examples
• added yourself to CONTRIBUTORS (preserving alphabetical order)

[asottile]

at least on posix this is correct, A and a are two separate environment variables:

$ a=1 A=2 env | grep -i '^a='
A=2
a=1

[asottile]

on windows however, a and A are the same variable:

C:\Users\Anthony>set A=1

C:\Users\Anthony>set a=2

C:\Users\Anthony>echo %A% %a%
2 2

[gnikonorov]

on windows however, a and A are the same variable:

C:\Users\Anthony>set A=1

C:\Users\Anthony>set a=2

C:\Users\Anthony>echo %A% %a%
2 2

Thank you @asottile. I forgot about Windows. I'll add an exclusion for it.

[asottile]

I'm 50/50 on whether we should change this, or whether we should just document it as case insensitive

[gnikonorov]

Since this is my first time opening a PR in this repo, I'll defer to more experienced committers. Thoughts @gaborbernat ( since we spoke on the linked issue ) ?

FWIW I think it would be easy and clean enough to just uppercase name and spec if platform.system() == "Windows":

[gaborbernat]

FWIW I think it would be easy and clean enough to just uppercase name and spec if platform.system() == "Windows":

Yeah, on Windows we need to be the case insensitive.

[asottile]

On second thought, changing this behaviour is likely to break a lot of people even tox itself

I'm leaning more towards not changing the behaviour and just documenting the case insensitivity

[gnikonorov]

On second thought, changing this behaviour is likely to break a lot of people even tox itself

I'm leaning more towards not changing the behaviour and just documenting the case insensitivity

At the very least, it sounds like a major version bump

[gaborbernat]

Ok. Let's not address here in the code. But document the behavior.