Naive Git setup, Is it possible to untrack files which are listed on my .gitignore?

Question

I have made a naive mistake while setting up my project. We are 3 developers working on one remote repository. While setting up git we never thought that Xcode would produce non-development files and push them to our remote repo. Now once I learnt after crash and burn I made a .gitignore file.

.gitignore looks like this, please do let me know if I should edit this too. (File credit goes too : This question's answer given by Abizem)

# Mac OS X
*.DS_Store

# Xcode
*.pbxuser
*.mode1v3
*.mode2v3
*.perspectivev3
*.xcuserstate
project.xcworkspace/
xcuserdata/

But now question is there any possibilities that I can untrack all of those listed files from our source control?

or

Can I list all tracked files with their path and later I know a painful way to remove one by one with,

git rm --cached 'file path'

Answer 1

Something I've done a few times in these situations, is move all of the files in the repository somewhere else on the filesystem (except .gitignore), then run:

git add --all
git commit -m "Remove all files"

Then add your files back in and run the following:

git add --all
git commit -m "Re-add files"

This second add & commit will adhere to your gitignore file.