There are some things that you don’t want to commit to source control. A common case is configuration files where your local setup differs than the canonical one. You can make git ignore entire files by adding them to .gitignore or ~/.gitignore. In the case of configuration files this isn’t really helpful.

Fortunately you can make git ignore changes you’ve made to a tracked file. I have the following options set in my ~/.gitconfig:

[alias]
  forget = update-index --assume-unchanged
  remember = update-index --no-assume-unchanged

That way I can tell git to forget the changes I just made to my database configuration by:

$ git forget config/database.yml

Then config/database.yml won’t show up as being altered when I do git status or make a commit.

This is handy but not flawless. For example, when you merge or rebase your HEAD your forgotten changes may disappear. Sometimes I keep a local copy of the changed file in a untracked location like tmp/config/database.yml. That way I can just copy it over after I merge or rebase.

Feel free to automate this if you like.