I'm used to svn to use svn:propset to set bugtraq URLs, pus^H^H^Hcommit them to the server and all users who clo^H^H^Hcheckout from it have the settings.
In git I can store them in my local or repository specific configuration, but other users who clone from it don't benefit from it: they simply don't get my bugtraq configuration.
Do I need to educate every users to configure their checkouts (also unsatisfying when I move somewhere else have to do clone my repository again) or it possible to feed it when the repository is being cloned?
Scott Chacon on his excellent ProGit book's blog posted information about git notes.
Do be aware that you will need to tell everyone to pull all references, they will need to add this to their git config for that repository.
Git notes allow one to add a note to an existing commit without modifying the commit message it self. This can for instance be used to locally add information to a certain commit.
Notes however are only considered local and are not automatically pushed/pulled from a remote server, and if two people edit the same note conflicts happen much like with regular commits and they require fixing by checking out the notes head and manually fixing things up.
This makes using notes more difficult, and unfortunately it doesn't seem like this has been improved much in newer versions of git.