Update docs/source/architecture.md

docs/source/architecture.md

@@ -124,7 +124,8 @@ commands:
 
   > For example, the [`Local` ContentProvider](https://github.com/jupyter/repo2docker/blob/80b979f8580ddef184d2ba7d354e7a833cfa38a4/repo2docker/contentproviders/base.py#L64)
   > checks whether the argument is a valid local path. If so, then `detect(`
-  > returns true.
+  > returns a dictionary: `{'path': source}` which defines the path to the repository.
+  > This path is used by `fetch()` to check that it matches the output directory.
 * If `detect()` returns something other than `None`, run `fetch()` with the
   returned value as its argument. This should
   result in the contents of the repository being placed locally to a folder.