The git plugin truncates changelog by adding linebreaks in the commit message for improved presentation. See: JENKINS-29977

This is all well and good for the changelog page in Jenkins, but a side-effect is that when Jenkins updates referenced Jira issues with a comment, only the first line of the modified commit message is included in the Jira comment. This can often result in broken, partial sentences that aren't of much use to issue watchers who don't have necessary Jenkins access.

This didn't used to be a problem, and my guess it started when the linebreaks were added to the git plugin.