Thanks to Raphaël Hertzog for spotting the issue
when investigating build errors in dpkg's Jenkins job.
JFTR:
| jenkins@grml-jenkins:~/jobs/dpkg-source/workspace/source$ git pull
| Updating fb18783..91495b8
| error: Your local changes to 'debian/changelog' would be overwritten by merge. Aborting.
| Please, commit your changes or stash them before you can merge.
| jenkins@grml-jenkins:~/jobs/dpkg-source/workspace/source$