ci: submit coverage information to coveralls.io

We cannot easily use the official GitHub Action from
https://github.com/marketplace/actions/coveralls-github-action because
it expects its input to be in LCOV format, which is not what coverage.py
emits. See coverallsapp/github-action#4 for
more discussion about this.

If coverallsapp/github-action#25 were merged to
support the Cobertura XML format, then `coverage xml` could be used to
generate that format. Since it's not, it's simplest to just install the
Python client for coveralls from PyPI.

.coveragerc

@@ -0,0 +1,2 @@
+[run]
+source = src,tests

.github/workflows/run-tests.yml

@@ -14,7 +14,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v1
-      - name: docker build
+      - name: Build container
         run: docker build -t flatpak-external-data-checker .
-      - name: run tests
-        run: docker run -v $PWD:/opt -w /opt flatpak-external-data-checker python3 -m unittest discover --verbose --buffer
+      - name: Run tests in container
+        run: docker run -v $PWD:/opt -w /opt flatpak-external-data-checker python3-coverage run -m unittest discover --verbose --buffer
+      - name: Submit code coverage to Coveralls.io
+        run: docker run --env COVERALLS_REPO_TOKEN=${{ secrets.COVERALLS_REPO_TOKEN }}  -v $PWD:/opt -w /opt flatpak-external-data-checker coveralls

.gitignore

@@ -1 +1,3 @@
 __pycache__
+/.coverage
+/coverage.xml

Dockerfile

@@ -13,13 +13,18 @@ RUN apt-get update \
       gir1.2-glib-2.0 \
       gir1.2-json-1.0 \
       python3-apt \
+      python3-coverage \
       python3-gi \
       python3-github \
+      python3-pip \
       python3-ruamel.yaml \
+      python3-setuptools \
       python3-tenacity \
   && apt-get clean \
   && rmdir /var/cache/apt/archives/partial
 
+RUN pip3 install coveralls
+
 ARG USER_ID=1000
 ARG GROUP_ID=1000
 RUN groupadd -g $GROUP_ID user && \