docs: break up CONTRIBUTING.md into several parts (#7762)

Author: mattiapitossi

CONTRIBUTING.md

@@ -131,7 +131,7 @@ question. You can also ask your question on [the discussions page][discussions].
 you! We have a [contributing guide][guide] to help you get involved in the Tokio
 project.
 
-[guide]: https://github.com/tokio-rs/tokio/blob/master/CONTRIBUTING.md
+[guide]: https://github.com/tokio-rs/tokio/blob/master/docs/contributing/README.md
 
 ## Related Projects
 

README.md

@@ -0,0 +1,45 @@
+# Contributing
+
+This guide will help you get started. **Do not let this guide intimidate you**.
+It should be considered a map to help you navigate the process.
+
+## Quick start
+
+If you are unsure where to begin, use the following guides:
+
+- Want to report or triage a bug? Start with [Contributing in Issues](contributing-in-issues.md).
+- Looking for something to work on? Filter issues by [`E-help-wanted`](https://github.com/tokio-rs/tokio/labels/E-help-wanted).
+- Planning to submit a PR? Read [Pull Requests](pull-requests.md) for the full workflow and required checks.
+- Want to understand what the labels on issues mean? See [Keeping track of issues and PRs](keeping-track-of-issues-and-prs.md).
+- Interested in code review? See [Reviewing Pull Requests](reviewing-pull-requests.md).
+
+## Table of Contents
+
+- [Contributing in Issues](contributing-in-issues.md)
+    - [Asking for General Help](contributing-in-issues.md#asking-for-general-help)
+    - [Submitting a Bug Report](contributing-in-issues.md#submitting-a-bug-report)
+    - [Triaging a Bug Report](contributing-in-issues.md#triaging-a-bug-report)
+    - [Resolving a Bug Report](contributing-in-issues.md#resolving-a-bug-report)
+- [Pull Requests](pull-requests.md)
+    - [Cargo Commands](pull-requests.md#cargo-commands)
+    - [Performing spellcheck on tokio codebase](pull-requests.md#performing-spellcheck-on-tokio-codebase)
+    - [Tests](pull-requests.md#tests)
+        - [Integration tests](pull-requests.md#integration-tests)
+        - [Fuzz tests](pull-requests.md#fuzz-tests)
+        - [Documentation tests](pull-requests.md#documentation-tests)
+    - [Benchmarks](pull-requests.md#benchmarks)
+    - [Commits](pull-requests.md#commits)
+        - [Commit message guidelines](pull-requests.md#commit-message-guidelines)
+    - [Opening the Pull Request](pull-requests.md#opening-the-pull-request)
+    - [Discuss and update](pull-requests.md#discuss-and-update)
+    - [Commit Squashing](pull-requests.md#commit-squashing)
+- [Reviewing Pull Requests](reviewing-pull-requests.md)
+    - [Review a bit at a time](reviewing-pull-requests.md#review-a-bit-at-a-time)
+    - [Be aware of the person behind the code](reviewing-pull-requests.md#be-aware-of-the-person-behind-the-code)
+    - [Abandoned or Stalled Pull Requests](reviewing-pull-requests.md#abandoned-or-stalled-pull-requests)
+- [Keeping track of issues and PRs](keeping-track-of-issues-and-prs.md)
+    - [Area](keeping-track-of-issues-and-prs.md#area)
+    - [Category](keeping-track-of-issues-and-prs.md#category)
+    - [Calls for participation](keeping-track-of-issues-and-prs.md#calls-for-participation)
+    - [Module](keeping-track-of-issues-and-prs.md#module)
+    - [Topic](keeping-track-of-issues-and-prs.md#topic)

docs/contributing/README.md

@@ -0,0 +1,79 @@
+## Contributing in Issues
+
+For any issue, there are fundamentally three ways an individual can contribute:
+
+1. By opening the issue for discussion: For instance, if you believe that you
+   have discovered a bug in Tokio, creating a new issue in [the tokio-rs/tokio
+   issue tracker][issue] is the way to report it.
+
+2. By helping to triage the issue: This can be done by providing
+   supporting details (a test case that demonstrates a bug), providing
+   suggestions on how to address the issue, or ensuring that the issue is tagged
+   correctly.
+
+3. By helping to resolve the issue: Typically this is done either in the form of
+   demonstrating that the issue reported is not a problem after all, or more
+   often, by opening a Pull Request that changes some bit of something in
+   Tokio in a concrete and reviewable manner.
+
+[issue]: https://github.com/tokio-rs/tokio/issues
+
+**Anybody can participate in any stage of contribution**. We urge you to
+participate in the discussion around bugs and participate in reviewing PRs.
+
+### Asking for General Help
+
+If you have reviewed existing documentation and still have questions or are
+having problems, you can [open a discussion] asking for help.
+
+In exchange for receiving help, we ask that you contribute back a documentation
+PR that helps others avoid the problems that you encountered.
+
+[open a discussion]: https://github.com/tokio-rs/tokio/discussions/new/choose
+
+### Submitting a Bug Report
+
+When opening a new issue in the Tokio issue tracker, you will be presented
+with a basic template that should be filled in. If you believe that you have
+uncovered a bug, please fill out this form, following the template to the best
+of your ability. Do not worry if you cannot answer every detail, just fill in
+what you can.
+
+The two most important pieces of information we need in order to properly
+evaluate the report is a description of the behavior you are seeing and a simple
+test case we can use to recreate the problem on our own. If we cannot recreate
+the issue, it becomes impossible for us to fix.
+
+In order to rule out the possibility of bugs introduced by userland code, test
+cases should be limited, as much as possible, to using only Tokio APIs.
+
+See [How to create a Minimal, Complete, and Verifiable example][mcve].
+
+[mcve]: https://stackoverflow.com/help/mcve
+
+### Triaging a Bug Report
+
+Once an issue has been opened, it is not uncommon for there to be discussion
+around it. Some contributors may have differing opinions about the issue,
+including whether the behavior being seen is a bug or a feature. This discussion
+is part of the process and should be kept focused, helpful, and professional.
+
+Short, clipped responses—that provide neither additional context nor supporting
+detail—are not helpful or professional. To many, such responses are simply
+annoying and unfriendly.
+
+Contributors are encouraged to help one another make forward progress as much as
+possible, empowering one another to solve issues collaboratively. If you choose
+to comment on an issue that you feel either is not a problem that needs to be
+fixed, or if you encounter information in an issue that you feel is incorrect,
+explain why you feel that way with additional supporting context, and be willing
+to be convinced that you may be wrong. By doing so, we can often reach the
+correct outcome much faster.
+
+### Resolving a Bug Report
+
+In the majority of cases, issues are resolved by opening a Pull Request. The
+process for opening and reviewing a Pull Request is similar to that of opening
+and triaging issues, but carries with it a necessary review and approval
+workflow that ensures that the proposed changes meet the minimal quality and
+functional guidelines of the Tokio project.

docs/contributing/contributing-in-issues.md

@@ -0,0 +1,89 @@
+## Keeping track of issues and PRs
+
+The Tokio GitHub repository has a lot of issues and PRs to keep track of. This
+section explains the meaning of various labels, as well as our [GitHub
+project][project]. The section is primarily targeted at maintainers.  Most
+contributors aren't able to set these labels.
+
+### Area
+
+The area label describes the crates relevant to this issue or PR.
+
+- **A-ci** This issue concerns our GitHub Actions setup.
+- **A-tokio** This issue concerns the main Tokio crate.
+- **A-readme** This issue is related to documentation such as README.md.
+- **A-benches** This issue concerns the benchmarks.
+- **A-examples** This issue concerns the examples.
+- **A-tokio-test** The issue concerns the `tokio-test` crate.
+- **A-tokio-util** This issue concerns the `tokio-util` crate.
+- **A-tokio-macros** This issue concerns the `tokio-macros` crate. Should only
+  be used for the procedural macros, and not `join!` or `select!`.
+- **A-tokio-stream** This issue concerns the `tokio-stream` crate.
+
+### Category
+
+- **C-bug** This is a bug-report. Bug-fix PRs use `C-enhancement` instead.
+- **C-enhancement** This is a PR that adds a new features.
+- **C-maintenance** This is an issue or PR about stuff such as documentation,
+  GitHub Actions or code quality.
+- **C-feature-request** This is a feature request. Implementations of feature
+  requests use `C-enhancement` instead.
+- **C-feature-accepted** If you submit a PR for this feature request, we won't
+  close it with the reason "we don't want this". Issues with this label should
+  also have the `C-feature-request` label.
+- **C-musing** Stuff like tracking issues or roadmaps. "musings about a better
+  world"
+- **C-proposal** A proposal of some kind, and a request for comments.
+- **C-question** A user question. Large overlap with GitHub discussions.
+- **C-request** A non-feature request, e.g. "please add deprecation notices to
+  `-alpha.*` versions of crates"
+
+### Calls for participation
+
+- **E-help-wanted** Stuff where we want help. Often seen together with `C-bug`
+  or `C-feature-accepted`.
+- **E-easy** This is easy, ranging from quick documentation fixes to stuff you
+  can do after reading the tutorial on our website.
+- **E-medium** This is not `E-easy` or `E-hard`.
+- **E-hard** This either involves very tricky code, is something we don't know
+  how to solve, or is challenging for some other reason.
+- **E-needs-mvce** This bug is missing a minimal complete and verifiable
+  example.
+
+The "E-" prefix is the same as used in the Rust compiler repository. Some
+issues are missing a difficulty rating, but feel free to ask on our Discord
+server if you want to know how challenging an issue likely is.
+
+### Module
+
+The module label provides a more fine grained categorization than **Area**.
+
+- **M-blocking** Things relevant to `spawn_blocking`, `block_in_place`.
+- **M-codec** The `tokio_util::codec` module.
+- **M-compat** The `tokio_util::compat` module.
+- **M-coop** Things relevant to coop.
+- **M-fs** The `tokio::fs` module.
+- **M-io** The `tokio::io` module.
+- **M-macros** Issues about any kind of macro.
+- **M-metrics** Things relevant to `tokio::runtime::metrics`.
+- **M-net** The `tokio::net` module.
+- **M-process** The `tokio::process` module.
+- **M-runtime** The `tokio::runtime` module.
+- **M-signal** The `tokio::signal` module.
+- **M-sync** The `tokio::sync` module.
+- **M-task** The `tokio::task` module.
+- **M-time** The `tokio::time` module.
+- **M-tracing** Tracing support in Tokio.
+- **M-taskdump** Things relevant to taskdump.
+
+### Topic
+
+Some extra information.
+
+- **T-docs** This is about documentation.
+- **T-performance** This is about performance.
+- **T-v0.1.x** This is about old Tokio.
+
+Any label not listed here is not in active use.
+
+[project]: https://github.com/orgs/tokio-rs/projects/1