Get optional ros2_tracing branch from git commit trailer for CI

Signed-off-by: Christophe Bedard <bedard.christophe@gmail.com>

.gitlab-ci.yml

@@ -19,9 +19,10 @@ variables:
 build:
   image: $BASE_IMAGE_ID:$DISTRO
   before_script:
-    - git clone https://gitlab.com/micro-ROS/ros_tracing/ros2_tracing.git --branch $ROS2TRACING_BRANCH
     - . /root/ws/install/local_setup.sh
   script:
+    - python3 get_branch.py --check
+    - git clone https://gitlab.com/micro-ROS/ros_tracing/ros2_tracing.git --branch $(python3 get_branch.py)
     - colcon build --symlink-install --event-handlers console_cohesion+ --packages-up-to $PACKAGES_LIST
     - colcon test --event-handlers console_cohesion+ --packages-select $PACKAGES_LIST
     - colcon test-result --all

get_branch.py

@@ -0,0 +1,122 @@
+# Copyright 2020 Christophe Bedard
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Get ros2_tracing branch name from the last commit or a default value."""
+
+import argparse
+import os
+import sys
+from typing import List
+from typing import Optional
+
+
+ENV_DEFAULT_BRANCH = 'ROS2TRACING_BRANCH'
+ENV_COMMIT_DESCRIPTION = 'CI_COMMIT_DESCRIPTION'
+ROS2_TRACING_BRANCH_TRAILER_TOKEN = 'Ros2-tracing-branch'
+
+
+def add_args(parser: argparse.ArgumentParser) -> None:
+    parser.add_argument(
+        '-c', '--check',
+        action='store_true',
+        default=False,
+        help='only process and print resulting branch in a verbose way',
+    )
+
+
+def parse_args() -> argparse.Namespace:
+    parser = argparse.ArgumentParser(
+        description='Extract name of the (optional) ros2_tracing branch to be used for CI',
+    )
+    add_args(parser)
+    return parser.parse_args()
+
+
+def get_trailer_value(
+    trailer_name: str,
+    commit_description: str,
+    check: bool = False,
+) -> Optional[str]:
+    # Get trailer line
+    trailer_lines = [
+        line for line in commit_description.split('\n') if trailer_name in line
+    ]
+    if len(trailer_lines) == 0:
+        if check:
+            print(f'could not find any trailer lines for: \'{trailer_name}\'')
+        return None
+    elif len(trailer_lines) > 1:
+        if check:
+            print(
+                f'found more than one trailer lines for: \'{trailer_name}\' '
+                '(will use the first one)'
+            )
+
+    # Extract value
+    line = trailer_lines[0]
+    if not (trailer_name + ':') in line:
+        if check:
+            print(f'could not find: \'{trailer_name}:\'')
+        return None
+    key_value = line.split(':')
+    if len(key_value) != 2:
+        if check:
+            print(f'misformed trailer line: \'{key_value}\'')
+        return None
+    value = key_value[1].strip()
+    if len(value) == 0:
+        if check:
+            print(f'misformed trailer value: \'{value}\'')
+        return None
+
+    return value
+
+
+def main() -> int:
+    args = parse_args()
+    check = args.check
+
+    # Get default value
+    default_branch = os.environ.get(ENV_DEFAULT_BRANCH, None)
+    if default_branch is None:
+        if check:
+            print(f'could not get environment variable: \'{ENV_DEFAULT_BRANCH}\'')
+        return 1
+
+    # Get commit description
+    commit_description = os.environ.get(ENV_COMMIT_DESCRIPTION, None)
+    if commit_description is None:
+        if check:
+            print(f'could not get environment variable: \'{ENV_COMMIT_DESCRIPTION}\'')
+        return None
+
+    # Get value
+    branch = get_trailer_value(
+        ROS2_TRACING_BRANCH_TRAILER_TOKEN,
+        commit_description,
+        check,
+    )
+
+    # Print value
+    prefix = 'branch: ' if check else ''
+    if branch is None:
+        print(prefix + default_branch)
+    else:
+        print(prefix + branch)
+
+    return 0
+
+
+if __name__ == '__main__':
+    sys.exit(main())