GitHub Actions cleanup

- only attempted scheduled job on `push` (where secrets are around)
- use more Homebrew actions
- fix `pull_request: []` warning
- use `@main` actions

.github/workflows/scheduled.yml

@@ -1,6 +1,6 @@
 name: Scheduled regeneration
 on:
-  pull_request:
+  push:
     paths:
       - .github/workflows/scheduled.yml
   schedule:
@@ -12,10 +12,17 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Set up Git repository
-      uses: actions/checkout@master
+      uses: actions/checkout@main
+      with:
+        fetch-depth: 0
+        ref: ${{ github.event.pull_request.head.sha }}
+
+    - name: Set up Homebrew
+      id: set-up-homebrew
+      uses: Homebrew/actions/setup-homebrew@master
 
     - name: Set up Ruby
-      uses: actions/setup-ruby@v1
+      uses: actions/setup-ruby@main
       with:
         ruby-version: '2.6'
 
@@ -24,18 +31,22 @@ jobs:
         gem install bundler -v "~>1"
         bundle install --jobs 4 --retry 3
 
+    - name: Configure Git user
+      uses: Homebrew/actions/git-user-config@master
+      with:
+        username: BrewTestBot
+
     - name: Generate site
       run: |
-        git clone --depth=1 https://github.com/Homebrew/brew
-        bundle exec rake yard build
+        git checkout -b master
 
-        # commit and push generated files
-        git add docs
+        ln -s $(brew --repo) brew
+        bundle exec rake yard build
 
         if ! git diff --no-patch --exit-code HEAD -- docs; then
-          git config --global user.name "BrewTestBot"
-          git config --global user.email "[email protected]"
+          git add docs
           git commit -m "docs: updates from Homebrew/brew" docs
-          git pull --rebase origin master
-          git push
         fi
+
+    - name: Push commits
+      uses: Homebrew/actions/git-try-push@master

.github/workflows/tests.yml

@@ -2,16 +2,16 @@ name: GitHub Actions CI
 on:
   push:
     branches: master
-  pull_request: []
+  pull_request:
 jobs:
   tests:
     runs-on: ubuntu-latest
     steps:
     - name: Set up Git repository
-      uses: actions/checkout@master
+      uses: actions/checkout@main
 
     - name: Set up Ruby
-      uses: actions/setup-ruby@v1
+      uses: actions/setup-ruby@main
       with:
         ruby-version: '2.6'