fix humble Dockerfiles - use humble, not rolling

.docker/ci-testing/Dockerfile

@@ -1,12 +1,20 @@
-# ghcr.io/ros-planning/moveit2:${ROS_DISTRO}-ci-testing
+# ghcr.io/ros-planning/moveit2:${OUR_ROS_DISTRO}-ci-testing
 # CI image using the ROS testing repository
 
-ARG ROS_DISTRO=rolling
 FROM osrf/ros2:testing
 LABEL maintainer Robert Haschke rhaschke@techfak.uni-bielefeld.de
 
 ENV TERM xterm
 
+# Overwrite the ROS_DISTRO set in osrf/ros2:testing to the distro tied to this Dockerfile (OUR_ROS_DISTRO).
+# In case ROS_DISTRO is now different from what was set in osrf/ros2:testing, run `rosdep update` again
+# to get any missing dependencies.
+# https://docs.docker.com/engine/reference/builder/#using-arg-variables explains why ARG and ENV can't have
+# the same name (ROS_DISTRO is an ENV in the osrf/ros2:testing image).
+ARG OUR_ROS_DISTRO=rolling
+ENV ROS_DISTRO=${OUR_ROS_DISTRO}
+RUN rosdep update --rosdistro $ROS_DISTRO
+
 # Install ROS 2 base packages and build tools
 # We are installing ros-<distro>-ros-base here to mimic the behavior of the ros:<distro>-ros-base images.
 # This step is split into a separate layer so that we can rely on cached dependencies instead of having

.github/workflows/docker.yaml

@@ -131,7 +131,7 @@ jobs:
         uses: docker/build-push-action@v4
         with:
           file: .docker/${{ github.job }}/Dockerfile
-          build-args: ROS_DISTRO=${{ matrix.ROS_DISTRO }}
+          build-args: OUR_ROS_DISTRO=${{ matrix.ROS_DISTRO }}
           push: ${{ env.PUSH }}
           no-cache: true
           tags: |