Add {short_file_name} as log format option (backport #541)

[mergify]

Description

Add a new {short_file_name} format token to the rcutils logging system that outputs only the basename of the source file (e.g., my_node.cpp) instead of the full path (e.g., /opt/ros_ws/src/my_package/src/my_node.cpp).

The existing {file_name} token continues to output the full path as before. The new token uses strrchr to find the last path separator (/ on POSIX, \ on Windows) and returns everything after it.

Changed files

• src/logging.c — Added expand_short_file_name() handler and registered the {short_file_name} token in the tokens[] array
• include/rcutils/logging.h — Added short_file_name to the documented list of available format tokens
• test/test_logging_console_output_handler.cpp — Added unit tests verifying basename extraction from full paths and passthrough for bare filenames
• test/test_logging_output_format.py — Added integration test launching with {short_file_name}:{line_number} format and validating output
• test/test_logging_output_format_short_file_name.txt — Expected output fixture for the integration test

Is this user-facing behavior change?

Yes. Users can now use {short_file_name} in the RCUTILS_CONSOLE_OUTPUT_FORMAT environment variable to display only the source file basename in log output, reducing log line length and improving readability.

Did you use Generative AI?

Yes — GitHub Copilot (Claude Opus 4.6)

Additional Information

• The implementation handles both POSIX (/) and Windows (\) path separators via #ifdef _WIN32. Tested on Ubuntu Linux but I don't have a way to test on Windows.
• If the file name contains no path separator, the full string is returned unchanged
• No changes to rcutils_log_location_t struct — the basename is extracted at format-expansion time
• Docs update PR: Add short_file_name placeholder to logging configuration options ros2_documentation#6226

  ---

  This is an automatic backport of pull request Add {short_file_name} as log format option #541 done by Mergify.

[fujitatomoya]

Pulls: #543
Gist: https://gist.githubusercontent.com/fujitatomoya/0d49a8534d24e933005cb2e40e98c7d9/raw/bc17dc3c34c5d709ddbda8a9d9252ba652c90641/ros2.repos
BUILD args: --packages-above-and-dependencies rcutils
TEST args: --packages-above rcutils
ROS Distro: kilted
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/18289

• Linux
• Linux-aarch64
• Linux-rhel
• Windows

[tonynajjar]

@fujitatomoya @ahcorde looks like an unrelated CI failure:

02:17:25     error: downloading 'https://github.com/foxglove/mcap/archive/refs/tags/releases/cpp/v1.4.2.tar.gz' failed
02:17:25           status_code: 22
02:17:25           status_string: "HTTP response code said error"
02:17:25           log:
02:17:25           --- LOG BEGIN ---
02:17:25           Host github.com:443 was resolved.

Can you restart?