add a manual workflow trigger where a one-off diff can be requested

.github/workflows/manual.yml

@@ -0,0 +1,31 @@
+name: manual
+
+on:
+  workflow_dispatch:
+    inputs:
+      diffbase:
+        description: the version or commit to diff against
+        required: false
+        type: string
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}
+
+jobs:
+  # Use the latest container to render the samples with the given diff
+  render-samples:
+    needs: build-container
+    uses: ./.github/workflows/render.yml
+    with:
+      container-version: latest
+      input: guide.tcg
+      workflow: pr
+  render-samples:
+    needs: build-container
+    uses: ./.github/workflows/render.yml
+    with:
+      container-version: latest
+      input: guide.tcg
+      workflow: pr
+      manual_diffbase: ${{ inputs.diffbase }}

.github/workflows/render.yml

@@ -20,9 +20,13 @@ on:
         required: true
         type: string
       workflow:
-        description: the workflow to run ('pr', 'push', 'release')
+        description: the workflow to run ('pr', 'push', 'release', 'manual')
         required: true
         type: string
+      manual_diffbase:
+        description: diffbase for manual workflow
+        required: false
+        type: string
 
 jobs:
   render:
@@ -77,9 +81,18 @@ jobs:
           diffbase: "${{ github.event.pull_request.base.sha }}"
           pr-number: "${{ github.event.number }}"
           pr-repo: "${{ github.repository }}"
+      # Render the document with diffs in the 'manual' mode.
+      - name: Render
+        if: inputs.workflow == 'manual'
+        uses: ./.github/actions/render
+        with:
+          input-md: ${{ inputs.input }}
+          output-basename: ${{ steps.gen_output_name.outputs.OUTPUT_FILENAME }}
+          pdf: true
+          diffbase: "${{ inputs.manual_diffbase }}"
       # Render the document without diffs in other modes.
       - name: Render
-        if: inputs.workflow != 'pr'
+        if: inputs.workflow != 'pr' && inputs.workflow != 'manual'
         uses: ./.github/actions/render
         with:
           input-md: ${{ inputs.input }}