I put a file that was previously being tracked by Git onto the .gitignore list. However, the file still shows up in git status after it is edited. How do I force Git to completely forget the file?

.gitignore will prevent untracked files from being added (without an add -f) to the set of files tracked by Git. However, Git will continue to track any files that are already being tracked.

To stop tracking a file, we must remove it from the index:

git rm --cached <file>

To remove a folder and all files in the folder recursively:

git rm -r --cached <folder>

The removal of the file from the head revision will happen on the next commit.

WARNING: While this will not remove the physical file from your local machine, it will remove the files from other developers' machines on their next git pull.