Merge pull request #262 from mhaid/patch-1

Improving documentation for --url parameter

datalad_container/containers_add.py

@@ -138,7 +138,8 @@ class ContainersAdd(Interface):
             the rest of the URL will be interpreted as the argument to
             'docker pull', the image will be saved to a location
             specified by `name`, and the call format will be auto-configured
-            to run docker, unless overwritten.""",
+            to run docker, unless overwritten. The auto-configured call to docker 
+            run mounts the CWD to '/tmp' and sets the working directory to '/tmp'.""",
             metavar="URL",
             constraints=EnsureStr() | EnsureNone(),
         ),