Very BAD:
Changelog: This fixes bug #4711
BAD:
Changelog: Change the handling of flags X Y Z because this fixes bug #4711
OK:
Changelog: Change a corner case in the handling of flags X Y Z (with tests). This resolve the issue from bug #4711.
The bug number is *only* additional information. It isn't the justification for a patch and definitely not the sole changelog.
ACK. This was my rationale until two hours ago ;)