Publish bevy_lint docs to Github Pages (#160)

Closes #155, extracted from #152.

While refactoring I moved `extract-rust-version` to a separate, callable
workflow that can be used by both `ci.yml` and `docs.yml`.

.github/workflows/ci.yml

@@ -6,32 +6,12 @@ on:
   pull_request:
   workflow_dispatch:
 
+env:
+  CARGO_TERM_COLOR: always
+
 jobs:
-  # Find the nightly Rust version and required components from `rust-toolchain.toml` using
-  # <https://taplo.tamasfe.dev>, so that we install can install them in later jobs.
   extract-rust-version:
-    name: Extract Rust version
-    runs-on: ubuntu-latest
-    outputs:
-      channel: ${{ steps.toolchain.outputs.toolchain }}
-      components: ${{ steps.toolchain.outputs.components }}
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@v4
-
-      - name: Install Taplo
-        run: |
-          curl -fsSL https://github.com/tamasfe/taplo/releases/latest/download/taplo-linux-x86_64.gz \
-            | gzip -d - | install -m 755 /dev/stdin /usr/local/bin/taplo
-
-      - name: Extract toolchain
-        id: toolchain
-        run: |
-          TOOLCHAIN=$(taplo get -f='rust-toolchain.toml' 'toolchain.channel')
-          COMPONENTS=$(taplo get -f='rust-toolchain.toml' --separator=', ' 'toolchain.components')
-
-          echo toolchain=$TOOLCHAIN >> $GITHUB_OUTPUT
-          echo components=$COMPONENTS >> $GITHUB_OUTPUT
+    uses: ./.github/workflows/extract-rust-version.yml
 
   test:
     name: Run tests

.github/workflows/docs.yml

@@ -0,0 +1,73 @@
+name: Docs
+
+on:
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+env:
+  CARGO_TERM_COLOR: always
+
+# Only allow one deployment to run at a time, however do not cancel runs in progress.
+concurrency:
+  group: pages
+  cancel-in-progress: false
+
+jobs:
+  extract-rust-version:
+    uses: ./.github/workflows/extract-rust-version.yml
+
+  build-lint-docs:
+    name: Build `bevy_lint` docs
+    runs-on: ubuntu-latest
+    needs: extract-rust-version
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Install Rust
+        uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: ${{ needs.extract-rust-version.outputs.channel }}
+          components: ${{ needs.extract-rust-version.outputs.components }}
+
+      - name: Cache build artifacts
+        uses: Leafwing-Studios/cargo-cache@v2
+        with:
+          sweep-cache: true
+
+      - name: Build with `rustdoc`
+        # We don't need to document dependencies since this is not intended to be consumed as a
+        # library. Furthermore, we pass `--lib` to prevent it from documenting binaries
+        # automatically.
+        run: cargo doc --package bevy_lint --no-deps --lib
+
+      - name: Finalize documentation
+        run: |
+          # Redirect root `index.html` to `bevy_lint/index.html`.
+          echo '<meta http-equiv="refresh" content="0; url=bevy_lint/index.html">' > target/doc/index.html
+
+          # Sometimes Github Pages fails to bundle and publish `rustdoc` websites due to the weird
+          # permissions of this file. Remove it, just in case.
+          rm --force target/doc/.lock
+
+      - name: Upload pages artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: target/doc
+
+  deploy:
+    name: Deploy docs
+    runs-on: ubuntu-latest
+    needs: build-lint-docs
+    environment:
+      name: github-pages
+      url: ${{ steps.deploy.outputs.page_url }}
+    # These are the permissions required to deploy websites to Github Pages.
+    permissions:
+      pages: write
+      id-token: write
+    steps:
+      - name: Deploy to Github Pages
+        id: deploy
+        uses: actions/deploy-pages@v4

.github/workflows/extract-rust-version.yml

@@ -0,0 +1,40 @@
+# Find the nightly Rust version and required components in `rust-toolchain.toml` using
+# <https://taplo.tamasfe.dev>. The output of this workflow can then be used in
+# `@dtolnay/rust-toolchain` to install Rust.
+
+name: Extract Rust Version
+
+on:
+  workflow_call:
+    outputs:
+      channel:
+        description: The Rustup channel extracted from `rust-toolchain.toml`.
+        value: ${{ jobs.extract-rust-version.outputs.channel }}
+      components:
+        description: A comma-separated list of Rustup components extracted from `rust-toolchain.toml`.
+        value: ${{ jobs.extract-rust-version.outputs.components }}
+
+jobs:
+  extract-rust-version:
+    name: Extract Rust version
+    runs-on: ubuntu-latest
+    outputs:
+      channel: ${{ steps.toolchain.outputs.channel }}
+      components: ${{ steps.toolchain.outputs.components }}
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Install Taplo
+        run: |
+          curl -fsSL https://github.com/tamasfe/taplo/releases/latest/download/taplo-linux-x86_64.gz \
+            | gzip -d - | install -m 755 /dev/stdin /usr/local/bin/taplo
+
+      - name: Extract toolchain
+        id: toolchain
+        run: |
+          CHANNEL=$(taplo get -f='rust-toolchain.toml' 'toolchain.channel')
+          COMPONENTS=$(taplo get -f='rust-toolchain.toml' --separator=', ' 'toolchain.components')
+
+          echo channel=$CHANNEL >> $GITHUB_OUTPUT
+          echo components=$COMPONENTS >> $GITHUB_OUTPUT