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

Two simple steps in SVN:
1. Add this directory in parent directory's svn:ignore property:

svn propedit svn:ignore .  

2. Remove directory:

svn rm mydir

3. Commit

Please note that when other developers do a svn update, that directory will not get deleted. SVN just unversions it instead.