How to stop tracking and ignore changes to a file in Git?

Just calling git rm --cached on each of the files you want to remove from revision control should be fine. As long as your local ignore patterns are correct you won't see these files included in the output of git status.

Note that this solution removes the files from the repository, so all developers would need to maintain their own local (non-revision controlled) copies of the file

To prevent git from detecting changes in these files you should also use this command:

git update-index --assume-unchanged [path]

What you probably want to do: (from below @Ryan Taylor answer)

3. This is to tell git you want your own independent version of the file or folder. For instance, you don't want to overwrite (or delete) production/staging config files.

git update-index --skip-worktree <path-name>

The full answer is here in this URL: http://source.kohlerville.com/2009/02/untrack-files-in-git/

There are 3 options; you probably want #3

1. This will keep the local file for you, but will delete it for anyone else when they pull.

   git rm --cached <file-name> or git rm -r --cached <folder-name>

2. This is for optimization, like a folder with a large number of files, e.g. SDKs that probably won't ever change. It tells Git to stop checking that huge folder every time for changes, locally, since it won't have any. The assume-unchanged index will be reset and file(s) overwritten if there are upstream changes to the file/folder (when you pull).

   git update-index --assume-unchanged <path-name>
   

3. This is to tell Git that you want your own independent version of the file or folder. For instance, you don't want to overwrite (or delete) production/staging config files.

   git update-index --skip-worktree <path-name>
   

   It's important to know that git update-index will not propagate with Git, so each user will have to run it independently.