visionmedia/git-extras — pull request #133 by nickl- (2012-08-13 20:21:17+00:00)
Title: Added ignore through assume unchanged.

As it turns out we have yet another scenario for wanting git to ignore something i.e when we made changes to a file that is already being tracked ex. database configuration for a local db, and we don't want git to report or accidentally add the changes to a commit we use:

$ git update-index --assume-unchanged

Added to git-ignore for completion...

When git is already tracking a file adding it to gitignore wont do anything but you can flag it assume-unchanged through update-index.
Added -c, --changes attribute to ignore space delimited list of files.
Added -a, --all-changes to flag all the currently tracked files that have been modified to be assumed unchanged.
Better verbosity and better output current configurations.
Added output list of currently configured assume-unchanged files.
Updated documentation and fixed a typo.

Njoy! =)