Enable it with
git config --global --add commit.template ~/.commit-template
or just for KDE without the --global from a repo directory.
It's very complete, so once you get the hang of it you might want to remove the first 16 lines so you'll have a nice reminder of the BUG:, FIXED-IN:, etc commit-hooks (I'm looking at you rengles ;) ).
Amarok contributors should also remember to include a Changelog entry to any commits introducing features, changes or bugfixes. Probably a good practice for all.
If you use vim as the commit editor (core.editor=vim) you could use this git commit template as well.