Add CI workflow for performing rustc-pull

.github/workflows/rustc-pull.yml

@@ -0,0 +1,55 @@
+name: rustc-pull
+
+on:
+  workflow_dispatch:
+  schedule:
+    # Run at 04:00 UTC every Monday
+    - cron: '0 4 * * 1'
+
+jobs:
+  pull:
+    if: github.repository == 'rust-lang/rustc-dev-guide'
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      pull-requests: write
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          # We need the full history for josh to work
+          fetch-depth: '0'
+      - name: Install stable Rust toolchain
+        run: rustup update stable
+      - uses: Swatinem/rust-cache@v2
+        with:
+          workspaces: "josh-sync"
+          # Cache the josh directory with checked out rustc
+          cache-directories: "/home/runner/.cache/rustc-dev-guide-josh"
+      - name: Install josh
+        run: RUSTFLAGS="--cap-lints warn" cargo +stable install josh-proxy --git https://github.com/josh-project/josh --tag r24.10.04
+      - name: Setup bot git name and email
+        run: |
+          git config --global user.name 'The rustc-dev-guide Cronjob Bot'
+          git config --global user.email 'github-actions@github.com'
+      - name: Perform rustc-pull
+        run: cargo run --manifest-path josh-sync/Cargo.toml -- rustc-pull
+      - name: Push changes to a branch
+        run: |
+          # Update a sticky branch that is used only for rustc pulls
+          BRANCH="rustc-pull"
+          git switch -c $BRANCH
+          git push -u origin $BRANCH --force
+      - name: Create pull request
+        run: |
+          # Check if an open pull request for an rustc pull update already exists
+          # If it does, the previous push has just updated it
+          # If not, we create it now
+          RESULT=`gh pr list --author github-actions[bot] --state open -q 'map(select(.title=="Rustc pull update")) | length' --json title`
+          if [[ "$RESULT" -eq 0 ]]; then
+            echo "Creating new pull request"
+            gh pr create -B master --title 'Rustc pull update' --body 'Latest update from rustc.'
+          else
+            echo "Updated existing pull request"
+          fi
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

triagebot.toml

@@ -6,3 +6,6 @@ allow-unauthenticated = [
     "waiting-on-author",
     "blocked",
 ]
+
+# Automatically close and reopen PRs made by bots to run CI on them
+[bot-pull-requests]