Extend docker_compose tests, add Alpine to CI (#304)

* Add test where project is started with project_src only (#303).

* Work around bug in docker_compose.

* Add Alpine in CI.

.azure-pipelines/azure-pipelines.yml

@@ -129,6 +129,8 @@ stages:
               test: ubuntu1804
             - name: Ubuntu 20.04
               test: ubuntu2004
+            - name: Alpine 3
+              test: alpine3
           groups:
             - 4
             - 5
@@ -165,6 +167,8 @@ stages:
               test: fedora33
             - name: Ubuntu 18.04
               test: ubuntu1804
+            - name: Alpine 3
+              test: alpine3
           groups:
             - 4
             - 5