tests: filter out external projects

GitLab: #3
Change-Id: I94bea5fd9cec166d92ad8323d2888355ae106cc7
diff --git a/Dockerfile b/Dockerfile
index 9478cfd..939da81 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -36,6 +36,6 @@
 
 # Generate HTML report
 RUN cd build_dev/CMakeFiles/dhtnet.dir \
-    && lcov --capture --directory . --output-file coverage.info \
-    && mkdir /result \
-    && genhtml coverage.info --output-directory /result
\ No newline at end of file
+    && lcov --capture --no-external --directory /dhtnet --output-file coverage.info \
+    && mkdir /coverage \
+    && genhtml coverage.info --output-directory /coverage
\ No newline at end of file