Unit tests for now --plugin-secret option

Also added new --show-files option to  - useful for debugging.

tests/test_publish_now.py

@@ -1,6 +1,7 @@
 from click.testing import CliRunner
 from datasette import cli
 from unittest import mock
+import json
 import subprocess
 
 
@@ -105,3 +106,58 @@ def test_publish_now_multiple_aliases(mock_run, mock_which):
                 ),
             ]
         )
+
+
+@mock.patch("shutil.which")
+@mock.patch("datasette.publish.now.run")
+def test_publish_now_plugin_secrets(mock_run, mock_which):
+    mock_which.return_value = True
+    mock_run.return_value = mock.Mock(0)
+    mock_run.return_value.stdout = b"https://demo.example.com/"
+
+    runner = CliRunner()
+    with runner.isolated_filesystem():
+        open("test.db", "w").write("data")
+        result = runner.invoke(
+            cli.cli,
+            [
+                "publish",
+                "now",
+                "test.db",
+                "--token",
+                "XXX",
+                "--plugin-secret",
+                "datasette-auth-github",
+                "client_id",
+                "x-client-id",
+                "--show-files",
+            ],
+        )
+        dockerfile = (
+            result.output.split("==== Dockerfile ====\n")[1]
+            .split("\n====================\n")[0]
+            .strip()
+        )
+        expected = """FROM python:3.6
+COPY . /app
+WORKDIR /app
+
+ENV DATASETTE_AUTH_GITHUB_CLIENT_ID 'x-client-id'
+RUN pip install -U datasette
+RUN datasette inspect test.db --inspect-file inspect-data.json
+ENV PORT 8001
+EXPOSE 8001
+CMD datasette serve --host 0.0.0.0 -i test.db --cors --inspect-file inspect-data.json --metadata metadata.json --config force_https_urls:on --port $PORT""".strip()
+        assert expected == dockerfile
+        metadata = (
+            result.output.split("=== metadata.json ===\n")[1]
+            .split("\n==== Dockerfile ====\n")[0]
+            .strip()
+        )
+        assert {
+            "plugins": {
+                "datasette-auth-github": {
+                    "client_id": {"$env": "DATASETTE_AUTH_GITHUB_CLIENT_ID"}
+                }
+            }
+        } == json.loads(metadata)