Run rustc-pull CI every day, don't notify when there is nothing to update

Author: Kobzol

Diff for: .github/workflows/rustc-pull.yml

@@ -3,15 +3,16 @@ name: rustc-pull
 on:
   workflow_dispatch:
   schedule:
-    # Run at 04:00 UTC every Monday
-    - cron: '0 4 * * 1'
+    # Run at 04:00 UTC every day
+    - cron: '0 4 * * *'
 
 jobs:
   pull:
     if: github.repository == 'rust-lang/rustc-dev-guide'
     runs-on: ubuntu-latest
     outputs:
       pr_url: ${{ steps.update-pr.outputs.pr_url }}
+      pull_result: ${{ steps.rustc-pull.outputs.pull_result }}
     permissions:
       contents: write
       pull-requests: write
@@ -34,7 +35,18 @@ jobs:
           git config --global user.name 'The rustc-dev-guide Cronjob Bot'
           git config --global user.email '[email protected]'
       - name: Perform rustc-pull
-        run: cargo run --manifest-path josh-sync/Cargo.toml -- rustc-pull
+        id: rustc-pull
+        # Turn off -e to disable early exit
+        shell: bash {0}
+        run: |
+          cargo run --manifest-path josh-sync/Cargo.toml -- rustc-pull
+          exitcode=$?
+
+          if [ $exitcode -eq 2 ]; then
+            echo "pull_result=skipped" >> $GITHUB_OUTPUT
+          fi
+
+          exit ${exitcode}
       - name: Push changes to a branch
         run: |
           # Update a sticky branch that is used only for rustc pulls
@@ -54,13 +66,14 @@ jobs:
             echo "pr_url=$PR_URL" >> $GITHUB_OUTPUT
           else
             PR_URL=`gh pr list --author github-actions[bot] --state open -q 'map(select(.title=="Rustc pull update")) | .[0].url' --json url,title`
+            echo "Updating pull request ${PR_URL}"
             echo "pr_url=$PR_URL" >> $GITHUB_OUTPUT
           fi
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
   send-zulip-message:
     needs: [pull]
-    if: ${{ !cancelled() }}
+    if: ${{ !cancelled() && needs.pull.outputs.pull_result != 'skipped' }}
     runs-on: ubuntu-latest
     steps:
       - name: Compute message