New datasette skeleton command for generating metadata.json

Closes #164

datasette/cli.py

@@ -104,6 +104,64 @@ def publish(publisher, files, name, metadata, extra_options, force, branch, **ex
             call(["heroku", "builds:create", "-a", app_name])
 
 
+@cli.command()
+@click.argument('files', type=click.Path(exists=True), nargs=-1, required=True)
+@click.option(
+    '-m', '--metadata', default='metadata.json',
+    help='Name of metadata file to generate'
+)
+@click.option(
+    'sqlite_extensions', '--load-extension', envvar='SQLITE_EXTENSIONS', multiple=True,
+    type=click.Path(exists=True, resolve_path=True), help='Path to a SQLite extension to load'
+)
+def skeleton(files, metadata, sqlite_extensions):
+    "Generate a skeleton metadata.json file for specified SQLite databases"
+    if os.path.exists(metadata):
+        click.secho(
+            'File {} already exists, will not over-write'.format(metadata),
+            bg='red',
+            fg='white',
+            bold=True,
+            err=True,
+        )
+        sys.exit(1)
+    app = Datasette(files, sqlite_extensions=sqlite_extensions)
+    databases = {}
+    for database_name, info in app.inspect().items():
+        databases[database_name] = {
+            'title': None,
+            'description': None,
+            'description_html': None,
+            'license': None,
+            'license_url': None,
+            'source': None,
+            'source_url': None,
+            'queries': {},
+            'tables': {
+                table_name: {
+                    'title': None,
+                    'description': None,
+                    'description_html': None,
+                    'license': None,
+                    'license_url': None,
+                    'source': None,
+                    'source_url': None,
+                } for table_name in (info.get('tables') or {})
+            }
+        }
+    open(metadata, 'w').write(json.dumps({
+        'title': None,
+        'description': None,
+        'description_html': None,
+        'license': None,
+        'license_url': None,
+        'source': None,
+        'source_url': None,
+        'databases': databases
+    }, indent=4))
+    click.echo('Wrote skeleton to {}'.format(metadata))
+
+
 @cli.command()
 @click.argument('files', type=click.Path(exists=True), nargs=-1, required=True)
 @click.option(