.gitignore and "The following untracked working tree files would be overwritten by checkout"

So I added a folder to my .gitignore file.

Once I do a git status it tells me

# On branch latest
nothing to commit (working directory clean)

However, when I try to change branches I get the following:

My-MacBook-Pro:webapp marcamillion$ git checkout develop
error: The following untracked working tree files would be overwritten by checkout:
    public/system/images/9/thumb/red-stripe.jpg
    public/system/images/9/original/red-stripe.jpg
    public/system/images/8/thumb/red-stripe-red.jpg
    public/system/images/8/original/red-stripe-red.jpg
    public/system/images/8/original/00-louis_c.k.-chewed_up-cover-2008.jpg
    public/system/images/7/thumb/red-stripe-dark.jpg
    public/system/images/7/original/red-stripe-dark.jpg
    public/system/images/7/original/DSC07833.JPG
    public/system/images/6/thumb/red-stripe-bw.jpg
    public/system/images/6/original/website-logo.png
    public/system/images/6/original/red-stripe-bw.jpg
    public/system/images/5/thumb/Guy_Waving_Jamaican_Flag.jpg
    public/system/images/5/original/logocompv-colored-squares-100px.png
    public/system/images/5/original/Guy_Waving_Jamaican_Flag.jpg
    public/system/images/4/thumb/DSC_0001.JPG
    public/system/images/4/original/logo.png
    public/system/images/4/original/DSC_0001.JPG
    public/system/images/4/original/2-up.jpg
    public/system/images/3/thumb/logo2.gif
    public/system/images/3/original/logo2.gif
    public/system/images/3/original/Guy_Waving_Jamaican_Flag.jpg
    public/system/images/3/original/11002000962.jpg
    public/system/images/2/thumb/Profile Pic.jpg
    public/system/images/2/original/Profile Pic.jpg
    public/system/images/2/original/02 Login Screen.jpg
    public/system/images/1/original/Argentina-2010-World-Cup.jpg
Please move or remove them before you can switch branches.
Aborting

This is what my .gitignore file looks like:

.bundle
.DS_Store
db/*.sqlite3
log/*.log
tmp/**/*
public/system/images/*
public/system/avatars/*

How do I get this working so I can switch branches without deleting those files?

If I make a change, will it affect those files? In other words, if I came back to this branch afterwards would everything be perfect as up to my latest commit?

I don't want to lose those files, I just don't want them tracked.

Solution

It seems like you want the files ignored but they have already been commited. .gitignore has no effect on files that are already in the repo so they need to be removed with git rm --cached. The --cached will prevent it from having any effect on your working copy and it will just mark as removed the next time you commit. After the files are removed from the repo then the .gitignore will prevent them from being added again.

But you have another problem with your .gitignore, you are excessively using wildcards and its causing it to match less than you expect it to. Instead lets change the .gitignore and try this.

.bundle
.DS_Store
db/*.sqlite3
log/*.log
tmp/
public/system/images/
public/system/avatars/