docs: Rework CONTRIBUTING guidelines

Give better recommendations for contributors on how to propose start the
work, write commit messages, and handle review by explicitly stating
expectations, however make it clear that maintainers will help you if
you have issues.

Write down the guidelines for maintainers on how they should handle
contributions and interact with other maintainers to help maintaining
good code quality level by listing maintainers responsibilities and
providing suggestions on how to handle various situations.

Co-authored-by: John Nunley <dev@notgull.net>
Signed-off-by: John Nunley <dev@notgull.net>

CONTRIBUTING.md

@@ -1,52 +1,122 @@
-# Winit Contributing Guidelines
+# Contribution Guidelines
 
-## Scope
-[See `FEATURES.md`](./FEATURES.md). When requesting or implementing a new Winit feature, you should
-consider whether or not it's directly related to window creation or input handling. If it isn't, it
-may be worth creating a separate crate that extends Winit's API to add that functionality.
+This document contains guidelines for contributing code to winit. It has to be
+followed in order for your patch to be approved and applied.
 
+## Contributing
 
-## Reporting an issue
+Anyone can contribute to winit, however given that it's a cross platform
+windowing toolkit getting certain changes incorporated could be challenging.
 
-When reporting an issue, in order to help the maintainers understand what the problem is, please make
-your description of the issue as detailed as possible:
+To save your time it's wise to check already opened [pull requests][prs] and
+[issues][issues]. In general, bug fixes and missing implementations are always
+accepted, however larger new API proposals should go into the issue first. When
+in doubt contact us on [Matrix][matrix] or via opening an issue.
 
-- if it is a bug, please provide a clear explanation of what happens, what should happen, and how to
-  reproduce the issue, ideally by providing a minimal program exhibiting the problem
-- if it is a feature request, please provide a clear argumentation about why you believe this feature
-  should be supported by winit
+### Submitting your work and handling review
 
-## Making a pull request
+All patches have to be sent on Github as [pull requests][prs]. To simplify your
+life during review it's recommended to check the "give contributors write access
+to the branch" checkbox.
 
-When making a code contribution to winit, before opening your pull request, please make sure that:
+#### Handling review
 
-- your patch builds with Winit's minimal supported rust version - Rust 1.70.
-- you tested your modifications on all the platforms impacted, or if not possible, detail which platforms
-  were not tested, and what should be tested, so that a maintainer or another contributor can test them
-- you updated any relevant documentation in winit
-- you left comments in your code explaining any part that is not straightforward, so that the
-  maintainers and future contributors don't have to try to guess what your code is supposed to do
-- your PR adds an entry to the current changelog if the introduced change is relevant to winit users.
+During the review process certain events could require an action from your side,
+common patterns and reactions are described below.
 
-  You needn't worry about the added entry causing conflicts, the maintainer that merges the PR will
-  handle those for you when merging (see below).
-- if your PR affects the platform compatibility of one or more features or adds another feature, the
-  relevant sections in [`FEATURES.md`](https://github.com/rust-windowing/winit/blob/master/FEATURES.md#features)
-  should be updated.
+_Event:_ The CI fails to build, but it looks like it is not your fault. Not
+communicating so could result in maintainers not looking into your patch,
+since they may assume that you're still working on it.\
+_Desired behaviour:_ Write a message saying roughly the following "The CI
+failure is unrelated", so that the maintainers will fix it for you.
 
-Once your PR is open, you can ask for a review by a maintainer of your platform. Winit's merging policy
-is that a PR must be approved by at least two maintainers of winit before being merged, including
-at least a maintainer of the platform (a maintainer making a PR themselves counts as approving it).
+_Event:_ Maintainer requested changes to your PR.\
+_Desired behavior:_ Once you address the request, you should re-request a review
+with GitHub's UI. If you don't agree with what maintainer suggested, you
+should state your objections and re-request the review. That will indicate that
+the ball is on maintainer's side.
 
-Once your PR is deemed ready, the merging maintainer will take care of resolving conflicts in the
-`changelog` module (but you must resolve other conflicts yourself). Doing this requires that you check the
-"give contributors write access to the branch" checkbox when creating the PR.
+_Event:_ You've opened a PR, but maintainer shortly after commented that they
+want to work on that themselves.\
+_Desired behavior:_ Discuss with the maintainer regarding their plans if they
+were not outlined in the initial response, because such response means that they
+are not interested in reviewing your code. Such thing could happen when
+underestimating complexity of the task you're solving or when your patch
+mandate certain downstream designs. In general, the maintainer will likely
+close your PR in order to prevent work being done on it.
 
-## Maintainers
+[prs]: https://github.com/rust-windowing/winit/pulls
+[issues]: https://github.com/rust-windowing/winit/issues
+[matrix]: https://matrix.to/#/#rust-windowing:matrix.org
 
-The current maintainers for each platform are listed in the [CODEOWNERS](.github/CODEOWNERS) file.
+## Maintainers
 
-## Release process
+Winit has plenty of maintainers with different backgrounds, different time
+available to work on Winit, and reasons to be winit maintainer in the first
+place. To ensure that Winit's code quality does not decrease over time and to
+make it easier to teach new maintainers the "winit way of doing things" the
+common policies and routines are defined in this section.
+
+The current maintainers for each platform are listed in [this file][CODEOWNERS].
+
+### Contributions handling
+
+The maintainers must ensure that the external contributions meet Winit's
+quality standards. If it's not, it **is the maintainer's responsibility** to
+bring it on par, which includes:
+
+  - Ensure that formatting is consistent and `CHANGELOG` messages are clear
+    for the end users.
+  - Improve the commit message, so it'll be easier for other maintainers to
+    understand the motivation without going through all the discussions on the
+    particular patch/PR.
+  - Ensure that the proposed patch doesn't break platform parity. If the
+    breakage is desired by contributor, an issue should be opened to discuss
+    with other maintainers before merging.
+  - Always fix CI issues before merging if they don't originate from the
+    submitted work.
+
+However, maintainers should give some leeway for external contributors, so they
+don't feel discouraged contributing, for example:
+
+  - Suggest a patch to resolve style issues, if it's the only issue with the
+    submitted work. Keep in mind that pushing the resolution yourself is not
+    desired, because the contributor might not agree with what you did.
+  - Be more explicit on how things should be done if you don't like the
+    approach.
+  - Suggest to finish the PR for them if they're absent for a while and you need
+    the proposed changes to move forward with something. In such cases the
+    maintainer must preserve attribution with `Co-authored-by`, `Suggested-by`,
+    or keep the original committer.
+  - Rebase their work for them when massive changes to the Winit codebase were
+    introduced.
+
+When reviewing code of other maintainers all of the above is on the maintainer
+who submitted the patch. Interested maintainers could help push the work over
+the finish line, but teaching other maintainers should be preferred.
+
+For a _regular_ contributor to winit, the maintainer should slowly start
+requiring contributor to match *maintainer* quality standards when writing
+patches and commit messages.
+
+### Contributing
+
+When submitting a patch, the maintainer should follow the general contributing
+guidelines, however greater attention to detail is expected in this case.
+
+To make life simpler for other maintainers it's suggested to create your branch
+under the project repository instead of your own fork. The naming scheme is
+`github_user_name/branch_name`. Doing so will make your work easier to rebase
+for other maintainers when you're absent.
+
+### Administrative Actions
+
+Some things (such as changing required CI steps, adding contributors, ...)
+require administrative permissions. If you don't have those, ask about the
+change in an issue. If you have the permissions, discuss it with at least one
+other admin before making the change.
+
+### Release process
 
 Given that winit is a widely used library, we should be able to make a patch
 releases at any time we want without blocking the development of new features.
@@ -58,7 +128,8 @@ The exact steps for an exemplary `0.2.0` release might look like this:
   1. Initially, the version on the latest master is `0.1.0`
   2. A new `v0.2.x` branch is created for the release
   3. Update released `cfg_attr` in `src/changelog/mod.rs` to `v0.2.md`
-  4. Move entries from `src/changelog/unreleased.md` into `src/changelog/v0.2.md`
+  4. Move entries from `src/changelog/unreleased.md` into
+     `src/changelog/v0.2.md`
   5. In the branch, the version is bumped to `v0.2.0`
   6. The new commit in the branch is tagged `v0.2.0`
   7. The version is pushed to crates.io
@@ -69,4 +140,6 @@ When doing a patch release, the process is similar:
   1. Initially, the version of the latest release is `0.2.0`
   2. Checkout the `v0.2.x` branch
   3. Cherry-pick the required non-breaking changes into the `v0.2.x`
-  4. Follow steps 4-9 of the regular release example
+  4. Follow steps 3-7 of the regular release example
+
+[CODEOWNERS]: .github/CODEOWNERS