cron-daily-update-nightly.yml

name: Update Nightly rustc
on:
  schedule:
    - cron: "0 0 * * *" # runs daily at 00:00
  workflow_dispatch: # allows manual triggering
jobs:
  format:
    name: Update nightly rustc
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: dtolnay/rust-toolchain@nightly
      - name: Update rust.yml to use latest nightly
        run: |
          set -x
          # Not every night has a nightly, so extract the date from whatever
          # version of the compiler dtolnay/rust-toolchain gives us.
          NIGHTLY_DATE=$(rustc +nightly --verbose --version | sed -ne 's/^commit-date: //p')
          # Update the nightly version in the reference file.
          echo "nightly-${NIGHTLY_DATE}" > .github/nightly-version
          echo "nightly_date=${NIGHTLY_DATE}" >> $GITHUB_ENV
          # Some days there is no new nightly. In this case don't make an empty PR.
          if ! git diff --exit-code > /dev/null; then
              echo "Updated nightly. Opening PR."
              echo "changes_made=true" >> $GITHUB_ENV
          else
              echo "Attempted to update nightly but the latest-nightly date did not change. Not opening any PR."
              echo "changes_made=false" >> $GITHUB_ENV
          fi
      - name: Create Pull Request
        if: env.changes_made == 'true'
        uses: peter-evans/create-pull-request@v6
        with:
          author: Update Nightly Rustc Bot <bot@example.com>
          title: Automated daily update to rustc (to nightly-${{ env.nightly_date }})
          body: |
           Automated update to Github CI workflow `rust.yml` by [create-pull-request](https://github.com/peter-evans/create-pull-request) GitHub action
          commit-message: Automated update to Github CI to rustc nightly-${{ env.nightly_date }}