Try github script

.github/actions/post-checkout/action.yml

@@ -7,22 +7,23 @@ runs:
 
     - name: Check for documentation only changes
       id: docs-only
-      run: |
-        git log --max-count=10;
-        docs_only="true";
-        while read filepath; do
-          if [ $filepath == *.md ]; then
-            echo "${filepath} is a documentation file";
-          else
-            echo "${filepath} is a non documentation file";
-            docs_only="false";
-          fi;
-        done < <(git diff --name-only "${GITHUB_BASE_BRANCH}" "${GITHUB_PR_BRANCH}");
-        echo "docs_only=${docs_only}" >> $GITHUB_OUTPUT;
-      shell: bash
-      env:
-          GITHUB_BASE_BRANCH: ${{ github.event.pull_request.base.ref }}
-          GITHUB_PR_BRANCH: ${{ github.event.pull_request.head.ref }}
+      uses: actions/github-script@d7906e4ad0b1822421a7e6a35d5ca353c962f410 # v6.4.1
+      with:
+        script: |
+          const opts = github.rest.pulls.listFiles.endpoint.merge({
+            owner: context.repo.owner,
+            repo: context.repo.repo,
+            pull_number: context.payload.pull_request.number,
+          })
+          const files = await github.paginate(opts)
+          for (const file of files) {
+            console.log(file)
+            if (!file.endsWith('.md')) {
+              return "false"
+            }
+          }
+          return "true"
+        result-encoding: string
 
     - name: Get Composer cache directory
       id: composer-cache