Reconfigure branch specifications with pull_request target (#609)

Related to #581

Author: zkoppert

.github/workflows/book.yml

@@ -19,8 +19,6 @@ jobs:
 
     steps:
     - uses: actions/checkout@v3
-      with:
-        ref: ${{ github.head_ref }}
 
     - uses: ruby/setup-ruby@v1
       with:
@@ -38,3 +36,4 @@ jobs:
       uses: stefanzweifel/git-auto-commit-action@v4
       with:
         commit_message: Writing updated toc.md for the ${{ matrix.language }} book
+        branch: ${{ github.head_ref }}