doc/stdenv/meta.chapter.md: explain difference between broken and badPlatforms

[ghost]

Description of changes

There has been a longstanding ambiguity between broken and badPlatforms, which seem to serve overlapping purposes.

This commit adds to the documentation two examples of constraints which cannot be expressed by platforms and badPlatforms.

This commit also mentions NIXPKGS_ALLOW_BROKEN=1 for overriding broken.

Things done

• Fits CONTRIBUTING.md.

[thiagokokada]

Please amend all your subsequent commits in the first.

[ghost]

Please amend all your subsequent commits in the first.

Done.

[fricklerhandwerk]

Thanks, yet again great stuff. Also makes me a bit sad that conventions seem to be all over the place – but that's one point of improved documentation: making such warts more visible and thus easier to address. Related: #140325

[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/tweag-nix-dev-update-47/27387/1

[zowoq]

The commits in this PR don't follow the commit format in https://github.com/NixOS/nixpkgs/blob/master/CONTRIBUTING.md

[zowoq]

Same in https://github.com/NixOS/nixpkgs/pull/208848/commits.

[ghost]

Same in https://github.com/NixOS/nixpkgs/pull/208848/commits.

nmh: init at 1.7.1

[ghost]

The commits in this PR don't follow the commit format in https://github.com/NixOS/nixpkgs/blob/master/CONTRIBUTING.md

(pkg-name | nixos/<module>):

Neither of these applies to documentation updates (except for a few cases where the commit updates the documentation about a specific package or module).

Based on reviewing the commit history, most people seem to be using

path/to/modified-file.ext: description

so I followed that convention.

Do you have a different recommendation?

[zowoq]

bece493

[zowoq]

This PR should have been merge as one commit, not four. These are not acceptable commit messages.

Update doc/stdenv/meta.chapter.md
Update doc/stdenv/meta.chapter.md
remove trailing whitespace

[ghost]

@zowoq, a more helpful comment would have been "please remember to squash before merging".

[zowoq]

a more helpful comment would have been "please remember to squash before merging".

It is easier for everyone if the PR is rebased and kept in a mergable state as people forget to squash.

Also sometimes squash should be avoided anyway:

https://github.com/NixOS/nixpkgs/blob/master/CONTRIBUTING.md#writing-good-commit-messages
Pull requests should not be squash merged in order to keep complete commit messages and GPG signatures intact and must not be when the change doesn't make sense as a single commit. This means that, when addressing review comments in order to keep the pull request in an always mergeable status, you will sometimes need to rewrite your branch's history and then force-push it with git push --force-with-lease.