workflows: add `apidoc` workflow for rubydoc.brew.sh

.github/main.workflow

-workflow "Push" {
-  on = "push"
-  resolves = ["Generate rubydoc.brew.sh"]
-}
-
-action "Generate rubydoc.brew.sh" {
-  uses = "docker://ruby:latest"
-  runs = ".github/main.workflow.sh"
-  secrets = ["RUBYDOC_DEPLOY_KEY"]
-}

.github/main.workflow.sh

-#!/bin/bash
-
-set -e
-
-# silence bundler complaining about being root
-mkdir ~/.bundle
-echo 'BUNDLE_SILENCE_ROOT_WARNING: "1"' > ~/.bundle/config
-
-# configure git
-git config --global user.name "BrewTestBot"
-git config --global user.email "homebrew-test-bot@lists.sfconservancy.org"
-
-# setup SSH
-mkdir ~/.ssh
-chmod 700 ~/.ssh
-echo "$RUBYDOC_DEPLOY_KEY" > ~/.ssh/id_ed25519
-chmod 600 ~/.ssh/id_ed25519
-git config --global core.sshCommand "ssh -i ~/.ssh/id_ed25519 -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no"
-
-# clone rubydoc.brew.sh with SSH so we can push back
-git clone git@github.com:Homebrew/rubydoc.brew.sh
-cd rubydoc.brew.sh
-
-# clone latest Homebrew/brew
-git clone --depth=1 https://github.com/Homebrew/brew
-
-# run rake to build documentation
-gem install bundler
-bundle install
-bundle exec rake
-
-# commit and push generated files
-git add docs
-git diff --exit-code HEAD -- docs && exit 0
-git commit -m 'docs: update from Homebrew/brew push' docs
-git push

.github/workflows/apidoc.yml

+name: Generate rubydoc.brew.sh
+on:
+  push:
+    branches: master
+jobs:
+  apidoc:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: docker://ruby:latest
+      - uses: Homebrew/actions/git-ssh@master
+        with:
+          git_user: BrewTestBot
+          git_email: homebrew-test-bot@lists.sfconservancy.org
+          key: ${{ secrets.RUBYDOC_DEPLOY_KEY }}
+      - run: |
+          # silence bundler complaining about being root
+          mkdir ~/.bundle
+          echo 'BUNDLE_SILENCE_ROOT_WARNING: "1"' > ~/.bundle/config
+          
+          # clone rubydoc.brew.sh with SSH so we can push back
+          git clone git@github.com:Homebrew/rubydoc.brew.sh
+          cd rubydoc.brew.sh
+
+          # clone latest Homebrew/brew
+          git clone --depth=1 https://github.com/Homebrew/brew
+
+          # run rake to build documentation
+          gem install bundler
+          bundle install
+          bundle exec rake
+
+          # commit and push generated files
+          git add docs
+          
+          if ! git diff --exit-code HEAD -- docs; then
+            git commit -m 'docs: update from Homebrew/brew push' docs
+            git push
+          fi