Update generate-query-help-docs.yml

.github/workflows/generate-query-help-docs.yml

@@ -3,9 +3,13 @@ name: Generate CodeQL query help documentation using Sphinx
 on:
   workflow_dispatch:
       inputs:
-      description:
-        description: A description of the purpose of this job. For human consumption.
-        required: false
+        description:
+          description: A description of the purpose of this job. For human consumption.
+          required: false
+        ref: 
+          description: The branch in github/codeql to checkout when generating query help.
+          required: false
+          default: 'lgtm.com'
   push:
     branches:
      - 'lgtm.com'
@@ -21,7 +25,8 @@ jobs:
     - name: Clone github/codeql
       uses: actions/checkout@v2
       with:
-        path: codeql 
+        path: codeql
+        ref: '{{ github.event.inputs.ref }}' 
     - name: Clone github/codeql-go
       uses: actions/checkout@v2
       with: