Add ref for checkout for scheduled build (ros-controls#461)

Author: christophfroehlich

.github/workflows/humble-docker-build.yaml

@@ -18,5 +18,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
+      with:
+        ref: humble
     - name: Build the Docker image
-      run: docker build . --file Dockerfile/Dockerfile --tag ros2_control_demos_humble
+      run: docker build --file Dockerfile/Dockerfile --tag ros2_control_demos_humble --build-arg ROS_DISTRO=humble .

.github/workflows/iron-docker-build.yaml

@@ -18,5 +18,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
+      with:
+        ref: iron
     - name: Build the Docker image
-      run: docker build . --file Dockerfile/Dockerfile --tag ros2_control_demos_iron
+      run: docker build --file Dockerfile/Dockerfile --tag ros2_control_demos_iron --build-arg ROS_DISTRO=iron .

.github/workflows/rolling-docker-build.yaml

@@ -18,5 +18,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
+      with:
+        ref: master
     - name: Build the Docker image
-      run: docker build . --file Dockerfile/Dockerfile --tag ros2_control_demos_rolling
+      run: docker build --file Dockerfile/Dockerfile --tag ros2_control_demos_rolling --build-arg ROS_DISTRO=rolling .