ci: add uncovered lines report to test

.github/ci/bashcov.dockerfile

@@ -0,0 +1,23 @@
+FROM ruby:latest
+
+# https://github.com/infertux/bashcov/issues/43#issuecomment-1423015292
+
+RUN gem install bashcov simplecov-lcov
+RUN useradd -m bashcov
+
+RUN apt-get update && \
+    apt-get install -y libpng-dev pkg-config build-essential bison git curl
+
+COPY . /rgbenv
+WORKDIR /rgbenv
+RUN chown -R bashcov:bashcov /rgbenv
+
+USER bashcov
+
+RUN make bats
+RUN echo "require 'simplecov-lcov'" > .simplecov && \
+    echo "SimpleCov.formatter = SimpleCov::Formatter::LcovFormatter" >> .simplecov
+
+CMD ["bash", ".github/ci/bashcov.sh"]
+
+

.github/ci/bashcov.sh

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+
+bashcov -- /rgbenv/bats/bin/bats tests
+
+cat coverage/lcov/rgbenv.lcov | grep ",0"

.github/workflows/testing.yml

@@ -23,7 +23,9 @@ jobs:
         with:
           path: rgbenv
 
-      - name: Run tests
-        run: make test
+      - name: Run tests and print lines without coverage
+        run: |
+            docker build -t rgbenv-test -f .github/ci/bashcov.dockerfile .
+            docker run -t --rm rgbenv-test
         working-directory: rgbenv/