A scenario where this is useful is if you've started a project that compiles some binaries in a subfolder. You might have started this project with haste to start working on it's features. But during that time you've compiled it a few times and probably did the ol git add . && git commit -m "Initial commit". Now you want to go back and remove those binary files from git index. There are many different ways to do this but here's what I normally do.
First, create your .gitignore file however you choose. Here's an example using bash.
$ echo " # ignore compile python files *.pyc" > .gitignore
Now let's update the git index. The first thing we do is unstage and remove paths only from the index. Files, modified or not, will be left alone.
$ git rm -r --cached .
Then add everything back and commit the changes. Here's the entirety of the process.
$ git rm -r --cached . $ git add . $ git commit -am "Remove ignored files"
If you're using a GUI client for git like the one from Github or GitKraken, there may be a way to do this from the UI. Regardless of your preference, I encourage you to learn what these commands do and why. Taking the time to learn how git works has helped me speed up my development time and recover work that I previously thought was lost!
Authored by Anthony Fox on 2020-05-02