service/ci.md

@@ -109,6 +109,10 @@ One final note: the Gitlab CI examples show that a debug image is used as a base
 image in Gitlab CI. That is important as the non-debug flavor does not come with
 a shell which is a requirement for Gitlab CI.
 
+This work came out of [issue #90](https://gitlab.torproject.org/tpo/tpa/gitlab/-/issues/90) which may have more background
+information or alternative implementations. In particular, it
+documents attempts at building containers with `buildah` and Docker.
+
 ## FAQ
 
  * do runners have **network access**? **yes**, but that might