Update contribution guides

[DenisGorbachev]

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Summary

This PR follows the discussion in "Merge contribution guides?".
This PR's submission was approved by @semorrison.

Currently, there are two guides: CONTRIBUTING.md and doc/contributions.md.

It would be better to merge the guides into a single CONTRIBUTING.md, and link to that file from PULL_REQUEST_TEMPLATE.md.

Notes

I tried to preserve the original wording, but I've shortened some paragraphs & removed ambiguous sentences. Please correct if wrong.

For review, it may be easier to read the final files instead of the diffs.

Questions

• What should we write in "Feature requests"? (I added my proposal directly to the file)
• Should we keep "Asking questions" section?
  • In the "Asking questions" section: should we keep the following sentence: "A lot of people report feeling that they are "wasting expert time", but nobody on the team feels this way"? (I propose to keep since it encourages people to reach out)
• In "Making commits" section, there is a sentence: "Check that your changes do not introduce performance regressions". How exactly should the contributors check for performance regressions?

[semorrison]

Too many arbitrary changes that would need discussion.

Perhaps you could try again with the absolute minimal changes required to merge the files? Otherwise we will get to it: even the report about the duplication is very helpful.

[DenisGorbachev]

@semorrison I'd love to make minimal changes, but the sentences are interrelated - can't change one without changing the other.

I've fixed some points that you've mentioned and replied to others.

Sorry if I did something wrong - please let me know if it needs more improvements.

[semorrison]

The basic problem is that doc/contributions.md is the new version that should take priority, and was recently written by Leo. By merging it into the other document is has essentially been lost.

I think the only viable path to combining these documents is:

• doc/contributions.md stays exactly as is, except moved to CONTRIBUTING.md
• anything currently in CONTRIBUTING.md which is genuinely additional to anything mentioned in docs/contributions.md could perhaps just be added at the end.

But really anything that is much beyond deleting CONTRIBUTING.md and replacing it with docs/contributions.md unmodifed is going to require too much editorial input to be viable via PR.

[leanprover-community-mathlib4-bot]

• ✅ Mathlib branch lean-pr-testing-2624 has successfully built against this PR. (2023-10-05 09:31:57) View Log
• ✅ Mathlib branch lean-pr-testing-2624 has successfully built against this PR. (2023-10-09 06:45:20) View Log

[DenisGorbachev]

Updated https://github.com/DenisGorbachev/lean4/blob/contribution-guidelines/CONTRIBUTING.md:

• Fully reused doc/contributions.md
• Added "Helpful links" section
• Replaced:
  • Old: In the past, we accepted most pull requests. This practice produced hard to maintain code, performance problems, and bugs. In order to improve the quality and maintainability of our codebase, we've established the following guidelines for external contributions.
  • New: Thank you for your interest in contributing to Lean! There are many ways to contribute and we appreciate all of them.

Reason for replacement: since CONTRIBUTING.md should help people who want to contribute, it's better to start with a welcome message.

---

Is it correct?

If yes - should I open a new PR or would you like to reopen the current one?

[semorrison]

Please revert the change from the "replaced:" bullet point. That's a significant editorial change!

[DenisGorbachev]

Done

[DenisGorbachev]

awaiting-review

(commenting to change the label)

[DenisGorbachev]

@semorrison Is there anything else that should be done on this PR?

[semorrison]

In principle I'm happy now, but the problem is that there is a slide deck for the community meeting that uses the old URL, so I'm very hesitant to merge now. :-)

[semorrison]

Sorry, on further reflection the right solution is to leave docs/contributions.md in place (it becomes part of the online manual, there are links to it, etc. etc.), and instead to just delete the contents of CONTRIBUTING.md and replace it with "Please see docs/contribuctions.md."

[DenisGorbachev]

Understood :)

Actually, https://lean-lang.org/lean4/doc/contributions.html returns 404. This is because doc/contributions.md is never mentioned in doc/SUMMARY.md, so it is never rendered by mdBook. Also, in the whole lean4 repo, there are two references to doc/contributions.md: in README.md and in PULL_REQUEST_TEMPLATE.md (both references are fixed in the PR).

Meanwhile, CONTRIBUTING.md is linked to by GitHub on every new PR page (that's just how GitHub works).

Let me know if you'd still like to move the text back to doc/contributions.md or keep it in CONTRIBUTING.md.

[DenisGorbachev]

Also, is it OK to provide additional info (like I've done in the previous comment), or would it be better to just implement your suggestions immediately?

[semorrison]

Thanks for your patience on this one, @DenisGorbachev! Just checking what we want to do here.

[DenisGorbachev]

@semorrison Is there any way I can help regarding this PR?

[DenisGorbachev]

@semorrison Would you like me to do anything else on this PR?