Try getting commit message from file.

.github/workflows/automatic-pr-to-dash-copy.yml

@@ -4,6 +4,10 @@ on:
     branches:
       - main
       - master
+  pull_request:
+    branches:
+      - main
+      - master
 
 permissions:
   contents: write
@@ -20,6 +24,13 @@ jobs:
       with:
         ref: loopy-dash-only
         path: loopy-dash
+    - name: Copy commit message
+      run: |
+        cd loopy
+        git log \
+            --format='(GitHub Action) %s%n%nCommit: %H%nAuthor: %an <%ae>%nDate: %ai%n%n%B' \
+            -n 1 --no-color --encoding=utf8 HEAD > ../commit-msg.txt
+        cd ..
     - name: Copy file to directory
       run: cp loopy/loopy-dash.el loopy-dash/loopy-dash.el
     - name: Commit new changes and push.
@@ -28,7 +39,7 @@ jobs:
         git config --local user.name "github-actions[bot]"
         git config --local user.email "41898282+github-actions[bot]@users.noreply.github.com"
         git add --force loopy-dash.el
-        git commit --allow-empty -m "Automatic commit of changes from master branch."
+        git commit --allow-empty -F ../commit-msg.txt
         git push
       env:
         USERNAME: github-actions[bot]