How to “unversion” a file in either svn and/or git

Question

It happens to me all the time. I accidentally version a file, I do not want to be versioned (i.e. developer/machine specific config-files).

If I commit this file, I

Answer 1

You can exclude files from subversion with the global-ignore setting
http://svnbook.red-bean.com/en/1.1/ch07.html#svn-ch-7-sect-1.3.2
check out the documentation for details