topic: provide more information when behind count cannot be computed The behind count has been confusing for various user and the associated error message is even worth. We try to clarify it to see if that helps.

syntax: re
/figures/[^/]+\.png$
^html/
\.pyc$
~$
\.swp$
\.orig$
\.rej$
\.err$
^tests/easy_run.sh$
^build/
^dist/
^MANIFEST$
^docs/tutorials/.*\.rst$
\.ico$
tests/\.testtimes