Add a rustc-dev-guide chapter

Author: BoxyUwU

src/SUMMARY.md

@@ -61,6 +61,7 @@
     - [Triage and Prioritization](./compiler/prioritization.md)
     - [Working Areas](./compiler/working-areas.md)
     - [Operations](./compiler/operations.md)
+- [Rustc Dev Guide](./wg-rustc-dev-guide/README.md)
 - [crates.io](./crates-io/README.md)
     - [Crate removal](./crates-io/crate-removal.md)
     - [Database maintenance](./crates-io/db-maintenance.md)

src/wg-rustc-dev-guide/README.md

@@ -0,0 +1,57 @@
+# Rustc Dev Guide
+
+The rustc-dev-guide working group is responsible for maintaining the rustc-dev-guide (located at 
+[rust-lang/rustc-dev-guide](https://github.com/rust-lang/rustc-dev-guide)). This includes things such
+as: 
+- Performing subtree syncs between the main rust repo and the rustc-dev-guide repo
+- Triaging the state of the guide to look for out of date information or missing information
+- Miscellaneous editorial work of the pages in the guide or fixing links that have bitrot
+- Reviewing simple PRs to the guide that don't need domain-specific expertise
+- Connect domain-specific doc changes with domain expert reviewers
+
+## Review Policy
+
+The dev guide has a much lower bar for changes to merged compared to the compiler itself. Incomplete
+and/or WIP documentation is preferred over no documentation. Stubbed out TODOs for sub-parts of chapters
+are useful to indicate known gaps in documentation that may otherwise leave the reader confused.
+
+Contributors confident in the area being documented should also feel free to merge their own
+documentation without review. For this reason the dev guide does not have a reviewer automatically
+assigned to each PR, instead PR authors can manually request a PR reviewer if they believe it necessary.
+
+A reviewer can be assigned by writing a comment containing: `r? rustc-dev-guide` or `r? @username`. 
+
+A good rule of thumb for whether you should feel comfortable merging your own rustc-dev-guide PR is whether
+you would feel comfortable approving an involved PR touching the relevant area of the compiler. See the
+compiler [review policy](../compiler/reviews.md).
+
+## Subtree Syncs
+
+The dev guide is a [josh](https://josh-project.github.io/josh/intro.html) subtree of the main rust-lang/rust
+repo. This makes it easier for compiler contributors to update documentation in the dev guide in tandem with
+changes to the compiler itself.
+
+This necessitates a manual process of syncing any changes made to the dev guide between its own repo, and the
+copy maintained in the rust-lang/rust repo.
+
+1. Wait at least a week since the last subtree sync took place.
+2. There will either be an automatically opened rustc-pull PR, or performing a rustc-pull encountered merge 
+conflicts. If there is a rustc-pull PR open, merge it[^1], otherwise a manual rustc-pull should be performed.
+See [rustc-dev-guide#2451] for an example rustc-pull.
+3. Post in the [zulip channel for coordinating subtree syncs][subtree_coordination] that you're doing a sync
+4. Do a manual rustc-push and open the PR. The PR should be assigned to a rustc-dev-guide lead
+(currently @BoxyUwU or @jieyouxu). We tend to assign rustc-push PRs to people instead of self
+approving like some other teams. This is because there were some accidents when the subtree was originally
+setup so it felt scary to not have someone check things over.
+5. Post the rustc-push PR in the [zulip channel for coordinating subtree syncs][subtree_coordination] so everyone is aware that a subtree
+sync has been performed. See [rust-lang/rust#141962] for an example rustc-push.
+
+
+Documentation about *how* to perform a rustc-pull or rustc-push can be found in the dev guide's README.
+
+[^1]: If the automatically opened rustc-pull doesn't contain any actual changes to the dev
+guide, then the subtree sync can be delayed until there are actual changes to sync.
+
+[rust-lang/rust#141962]: https://github.com/rust-lang/rust/pull/141962
+[rustc-dev-guide#2451]: https://github.com/rust-lang/rustc-dev-guide/pull/2451
+[subtree_coordination]: https://rust-lang.zulipchat.com/#narrow/channel/196385-t-compiler.2Frustc-dev-guide/topic/Subtree.20sync.20automation/with/522133712

triagebot.toml

@@ -32,3 +32,4 @@ fallback = [
 "/src/platforms" = ["infra"]
 "/src/release" = ["release"]
 "/src/triagebot" = ["triagebot"]
+"/src/wg-rustc-dev-guide" = ["wg-rustc-dev-guide"]