Auto merge of #7359 - joshrotenberg:clippy_guide, r=xFrednet

Clippy book

A work in progress Clippy Book using mdbook. See #6011.

This is currently just a moving around of things:

1. The current README.md split up a bit and put into sections.
1. A rough outline of Clippy lint categories (currently no content, potentially add a basic introduction for each and some example, see questions below.
1. The `docs` content repurposed into a top level `Development` section.
1. The current Roadmap.

Some big questions:

1. is `guide/` the right place? I'm modeling after mdbook itself.
1. What is the relationship between ALL the Clippy Lints and this guide? It seems like they can coexist. Does that mean the guide should just point to the current side with regard to actual lints, and maybe just include some examples to keep it interesting? Keeping both up to date seems like a maintenance nightmare unless its automated somehow. Or should the current ALL the Clippy lints somehow be incorporated into the book?
1. Related to the above, where should this guide be published since the `gh-pages` branch is already in use?
1. This PR doesn't currently change any existing content. Obviously that would make sense assuming the general structure and relocation is an acceptable approach.

---

Open Tasks for follow up PR:
- Set up CI/CD
- Split up Installation and Usage
- Add more content to Usage (and Installation) chapters
- Enhance CI chapter with more examples for different CIs

---

changelog: The first version of the *Clippy Book*
staring, *The Clippy Team*, *Bors* and *rustc*

Author: bors

.gitignore

@@ -39,3 +39,6 @@ helper.txt
 *.iml
 .vscode
 .idea
+
+# mdbook generated output
+/book/book

CONTRIBUTING.md

@@ -13,44 +13,44 @@ anything, feel free to ask questions on issues or visit the `#clippy` on [Zulip]
 All contributors are expected to follow the [Rust Code of Conduct].
 
 - [Contributing to Clippy](#contributing-to-clippy)
-  - [Getting started](#getting-started)
-    - [High level approach](#high-level-approach)
-    - [Finding something to fix/improve](#finding-something-to-fiximprove)
+  - [The Clippy book](#the-clippy-book)
+  - [High level approach](#high-level-approach)
+  - [Finding something to fix/improve](#finding-something-to-fiximprove)
   - [Writing code](#writing-code)
   - [Getting code-completion for rustc internals to work](#getting-code-completion-for-rustc-internals-to-work)
     - [IntelliJ Rust](#intellij-rust)
     - [Rust Analyzer](#rust-analyzer)
   - [How Clippy works](#how-clippy-works)
-  - [Syncing changes between Clippy and `rust-lang/rust`](#syncing-changes-between-clippy-and-rust-langrust)
-    - [Patching git-subtree to work with big repos](#patching-git-subtree-to-work-with-big-repos)
-    - [Performing the sync from `rust-lang/rust` to Clippy](#performing-the-sync-from-rust-langrust-to-clippy)
-    - [Performing the sync from Clippy to `rust-lang/rust`](#performing-the-sync-from-clippy-to-rust-langrust)
-    - [Defining remotes](#defining-remotes)
   - [Issue and PR triage](#issue-and-pr-triage)
   - [Bors and Homu](#bors-and-homu)
   - [Contributions](#contributions)
 
 [Zulip]: https://rust-lang.zulipchat.com/#narrow/stream/clippy
 [Rust Code of Conduct]: https://www.rust-lang.org/policies/code-of-conduct
 
-## Getting started
+## The Clippy book
 
-**Note: If this is your first time contributing to Clippy, you should
-first read the [Basics docs](doc/basics.md).**
+If you're new to Clippy and don't know where to start the [Clippy book] includes
+a developer guide and is a good place to start your journey.
 
-### High level approach
+<!-- FIXME: Link to the deployed book, once it is deployed through CI -->
+[Clippy book]: book/src
+
+## High level approach
 
 1. Find something to fix/improve
 2. Change code (likely some file in `clippy_lints/src/`)
-3. Follow the instructions in the [Basics docs](doc/basics.md) to get set up
+3. Follow the instructions in the [Basics docs](book/src/development/basics.md)
+   to get set up
 4. Run `cargo test` in the root directory and wiggle code until it passes
 5. Open a PR (also can be done after 2. if you run into problems)
 
-### Finding something to fix/improve
+## Finding something to fix/improve
 
-All issues on Clippy are mentored, if you want help simply ask @Manishearth, @flip1995, @phansch
-or @llogiq directly by mentioning them in the issue or over on [Zulip]. This list may be out of date.
-All currently active mentors can be found [here](https://github.com/rust-lang/highfive/blob/master/highfive/configs/rust-lang/rust-clippy.json#L3)
+All issues on Clippy are mentored, if you want help simply ask someone from the
+Clippy team directly by mentioning them in the issue or over on [Zulip]. All
+currently active team members can be found
+[here](https://github.com/rust-lang/highfive/blob/master/highfive/configs/rust-lang/rust-clippy.json#L3)
 
 Some issues are easier than others. The [`good-first-issue`] label can be used to find the easy
 issues. You can use `@rustbot claim` to assign the issue to yourself.
@@ -91,20 +91,6 @@ an AST expression). `match_def_path()` in Clippy's `utils` module can also be us
 [let chains]: https://github.com/rust-lang/rust/pull/94927
 [nest-less]: https://github.com/rust-lang/rust-clippy/blob/5e4f0922911536f80d9591180fa604229ac13939/clippy_lints/src/bit_mask.rs#L133-L159
 
-## Writing code
-
-Have a look at the [docs for writing lints][adding_lints] for more details.
-
-If you want to add a new lint or change existing ones apart from bugfixing, it's
-also a good idea to give the [stability guarantees][rfc_stability] and
-[lint categories][rfc_lint_cats] sections of the [Clippy 1.0 RFC][clippy_rfc] a
-quick read.
-
-[adding_lints]: https://github.com/rust-lang/rust-clippy/blob/master/doc/adding_lints.md
-[clippy_rfc]: https://github.com/rust-lang/rfcs/blob/master/text/2476-clippy-uno.md
-[rfc_stability]: https://github.com/rust-lang/rfcs/blob/master/text/2476-clippy-uno.md#stability-guarantees
-[rfc_lint_cats]: https://github.com/rust-lang/rfcs/blob/master/text/2476-clippy-uno.md#lint-audit-and-categories
-
 ## Getting code-completion for rustc internals to work
 
 ### IntelliJ Rust
@@ -205,126 +191,6 @@ That's why the `else_if_without_else` example uses the `register_early_pass` fun
 [early_lint_pass]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint/trait.EarlyLintPass.html
 [late_lint_pass]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint/trait.LateLintPass.html
 
-## Syncing changes between Clippy and [`rust-lang/rust`]
-
-Clippy currently gets built with a pinned nightly version.
-
-In the `rust-lang/rust` repository, where rustc resides, there's a copy of Clippy
-that compiler hackers modify from time to time to adapt to changes in the unstable
-API of the compiler.
-
-We need to sync these changes back to this repository periodically, and the changes
-made to this repository in the meantime also need to be synced to the `rust-lang/rust` repository.
-
-To avoid flooding the `rust-lang/rust` PR queue, this two-way sync process is done
-in a bi-weekly basis if there's no urgent changes. This is done starting on the day of
-the Rust stable release and then every other week. That way we guarantee that we keep
-this repo up to date with the latest compiler API, and every feature in Clippy is available
-for 2 weeks in nightly, before it can get to beta. For reference, the first sync
-following this cadence was performed the 2020-08-27.
-
-This process is described in detail in the following sections. For general information
-about `subtree`s in the Rust repository see [Rust's `CONTRIBUTING.md`][subtree].
-
-### Patching git-subtree to work with big repos
-
-Currently, there's a bug in `git-subtree` that prevents it from working properly
-with the [`rust-lang/rust`] repo. There's an open PR to fix that, but it's stale.
-Before continuing with the following steps, we need to manually apply that fix to
-our local copy of `git-subtree`.
-
-You can get the patched version of `git-subtree` from [here][gitgitgadget-pr].
-Put this file under `/usr/lib/git-core` (taking a backup of the previous file)
-and make sure it has the proper permissions:
-
-```bash
-sudo cp --backup /path/to/patched/git-subtree.sh /usr/lib/git-core/git-subtree
-sudo chmod --reference=/usr/lib/git-core/git-subtree~ /usr/lib/git-core/git-subtree
-sudo chown --reference=/usr/lib/git-core/git-subtree~ /usr/lib/git-core/git-subtree
-```
-
-_Note:_ The first time running `git subtree push` a cache has to be built. This
-involves going through the complete Clippy history once. For this you have to
-increase the stack limit though, which you can do with `ulimit -s 60000`.
-Make sure to run the `ulimit` command from the same session you call git subtree.
-
-_Note:_ If you are a Debian user, `dash` is the shell used by default for scripts instead of `sh`.
-This shell has a hardcoded recursion limit set to 1000. In order to make this process work,
-you need to force the script to run `bash` instead. You can do this by editing the first
-line of the `git-subtree` script and changing `sh` to `bash`.
-
-### Performing the sync from [`rust-lang/rust`] to Clippy
-
-Here is a TL;DR version of the sync process (all of the following commands have
-to be run inside the `rust` directory):
-
-1. Clone the [`rust-lang/rust`] repository or make sure it is up to date.
-2. Checkout the commit from the latest available nightly. You can get it using `rustup check`.
-3. Sync the changes to the rust-copy of Clippy to your Clippy fork:
-    ```bash
-    # Make sure to change `your-github-name` to your github name in the following command. Also be
-    # sure to either use a net-new branch, e.g. `sync-from-rust`, or delete the branch beforehand
-    # because changes cannot be fast forwarded
-    git subtree push -P src/tools/clippy [email protected]:your-github-name/rust-clippy sync-from-rust
-    ```
-
-    _Note:_ This will directly push to the remote repository. You can also push
-    to your local copy by replacing the remote address with `/path/to/rust-clippy`
-    directory.
-
-    _Note:_ Most of the time you have to create a merge commit in the
-    `rust-clippy` repo (this has to be done in the Clippy repo, not in the
-    rust-copy of Clippy):
-    ```bash
-    git fetch origin && git fetch upstream
-    git checkout sync-from-rust
-    git merge upstream/master
-    ```
-4. Open a PR to `rust-lang/rust-clippy` and wait for it to get merged (to
-   accelerate the process ping the `@rust-lang/clippy` team in your PR and/or
-   ~~annoy~~ ask them in the [Zulip] stream.)
-
-### Performing the sync from Clippy to [`rust-lang/rust`]
-
-All of the following commands have to be run inside the `rust` directory.
-
-1. Make sure Clippy itself is up-to-date by following the steps outlined in the previous
-section if necessary.
-
-2. Sync the `rust-lang/rust-clippy` master to the rust-copy of Clippy:
-    ```bash
-    git checkout -b sync-from-clippy
-    git subtree pull -P src/tools/clippy https://github.com/rust-lang/rust-clippy master
-    ```
-3. Open a PR to [`rust-lang/rust`]
-
-### Defining remotes
-
-You may want to define remotes, so you don't have to type out the remote
-addresses on every sync. You can do this with the following commands (these
-commands still have to be run inside the `rust` directory):
-
-```bash
-# Set clippy-upstream remote for pulls
-$ git remote add clippy-upstream https://github.com/rust-lang/rust-clippy
-# Make sure to not push to the upstream repo
-$ git remote set-url --push clippy-upstream DISABLED
-# Set clippy-origin remote to your fork for pushes
-$ git remote add clippy-origin [email protected]:your-github-name/rust-clippy
-# Set a local remote
-$ git remote add clippy-local /path/to/rust-clippy
-```
-
-You can then sync with the remote names from above, e.g.:
-
-```bash
-$ git subtree push -P src/tools/clippy clippy-local sync-from-rust
-```
-
-[gitgitgadget-pr]: https://github.com/gitgitgadget/git/pull/493
-[subtree]: https://rustc-dev-guide.rust-lang.org/contributing.html#external-dependencies-subtree
-[`rust-lang/rust`]: https://github.com/rust-lang/rust
-
 ## Issue and PR triage
 
 Clippy is following the [Rust triage procedure][triage] for issues and pull

book/README.md

@@ -0,0 +1,4 @@
+# Clippy Book
+
+This is the source for the Clippy Book. See the
+[book](src/infrastructure/book.md) for more information.

book/book.toml

@@ -0,0 +1,28 @@
+[book]
+authors = ["The Rust Clippy Developers"]
+language = "en"
+multilingual = false
+src = "src"
+title = "Clippy Documentation"
+
+[rust]
+edition = "2018"
+
+[output.html]
+edit-url-template = "https://github.com/rust-lang/rust-clippy/edit/master/book/{path}"
+git-repository-url = "https://github.com/rust-lang/rust-clippy/tree/master/book"
+mathjax-support = true
+site-url = "/rust-clippy/"
+
+[output.html.playground]
+editable = true
+line-numbers = true
+
+[output.html.search]
+boost-hierarchy = 2
+boost-paragraph = 1
+boost-title = 2
+expand = true
+heading-split-level = 2
+limit-results = 20
+use-boolean-and = true

book/src/README.md

@@ -0,0 +1,34 @@
+# Clippy
+
+[![Clippy Test](https://github.com/rust-lang/rust-clippy/workflows/Clippy%20Test/badge.svg?branch=auto&event=push)](https://github.com/rust-lang/rust-clippy/actions?query=workflow%3A%22Clippy+Test%22+event%3Apush+branch%3Aauto)
+[![License: MIT OR Apache-2.0](https://img.shields.io/crates/l/clippy.svg)](#license)
+
+A collection of lints to catch common mistakes and improve your
+[Rust](https://github.com/rust-lang/rust) code.
+
+[There are over 500 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
+
+Lints are divided into categories, each with a default [lint
+level](https://doc.rust-lang.org/rustc/lints/levels.html). You can choose how
+much Clippy is supposed to ~~annoy~~ help you by changing the lint level by
+category.
+
+| Category              | Description                                                                         | Default level |
+| --------------------- | ----------------------------------------------------------------------------------- | ------------- |
+| `clippy::all`         | all lints that are on by default (correctness, suspicious, style, complexity, perf) | **warn/deny** |
+| `clippy::correctness` | code that is outright wrong or useless                                              | **deny**      |
+| `clippy::suspicious`  | code that is most likely wrong or useless                                           | **warn**      |
+| `clippy::complexity`  | code that does something simple but in a complex way                                | **warn**      |
+| `clippy::perf`        | code that can be written to run faster                                              | **warn**      |
+| `clippy::style`       | code that should be written in a more idiomatic way                                 | **warn**      |
+| `clippy::pedantic`    | lints which are rather strict or might have false positives                         | allow         |
+| `clippy::nursery`     | new lints that are still under development                                          | allow         |
+| `clippy::cargo`       | lints for the cargo manifest                                                        | allow         |                                   | allow         |
+
+More to come, please [file an
+issue](https://github.com/rust-lang/rust-clippy/issues) if you have ideas!
+
+The [lint list](https://rust-lang.github.io/rust-clippy/master/index.html) also
+contains "restriction lints", which are for things which are usually not
+considered "bad", but may be useful to turn on in specific cases. These should
+be used very selectively, if at all.

book/src/SUMMARY.md

@@ -0,0 +1,23 @@
+# Summary
+
+[Introduction](README.md)
+
+- [Installation](installation.md)
+- [Usage](usage.md)
+- [Configuration](configuration.md)
+- [Clippy's Lints](lints.md)
+- [Continuous Integration](continuous_integration/README.md)
+    - [GitHub Actions](continuous_integration/github_actions.md)
+    - [Travis CI](continuous_integration/travis.md)
+- [Development](development/README.md)
+    - [Basics](development/basics.md)
+    - [Adding Lints](development/adding_lints.md)
+    - [Common Tools](development/common_tools_writing_lints.md)
+    - [Infrastructure](development/infrastructure/README.md)
+        - [Syncing changes between Clippy and rust-lang/rust](development/infrastructure/sync.md)
+        - [Backporting Changes](development/infrastructure/backport.md)
+        - [Updating the Changelog](development/infrastructure/changelog_update.md)
+        - [Release a New Version](development/infrastructure/release.md)
+        - [The Clippy Book](development/infrastructure/book.md)
+    - [Proposals](development/proposals/README.md)
+        - [Roadmap 2021](development/proposals/roadmap-2021.md)