Add gh action checking README helptext update

.github/workflows/readme-updated.yaml

@@ -0,0 +1,27 @@
+name: Check README.md helptext
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches: [main]
+
+jobs:
+  check_script_and_diff:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v2
+
+    - name: Install duct
+      run: |
+        pip install .
+    - name: Update README.md helptext
+      run: |
+        ./.update-readme-help.sh
+
+    - name: Ensure no diff
+      run: |
+        git diff --exit-code

.update-readme-help.sh

@@ -0,0 +1,5 @@
+#!/bin/bash
+duct --help > .help_content.txt
+sed -i '/<\!--- BEGIN HELP -->/,/<\!--- END HELP -->/{//!d;}' README.md
+sed -i '/<\!--- BEGIN HELP -->/r .help_content.txt' README.md
+rm .help_content.txt

README.md

@@ -23,7 +23,7 @@ positional arguments:
   command               The command to execute.
   inner_args            Arguments for the command.
 
-optional arguments:
+options:
   -h, --help            show this help message and exit
   --version             show program's version number and exit
   -p OUTPUT_PREFIX, --output-prefix OUTPUT_PREFIX