# gitignore, LFS, and Submodules

Your repo should hold your work and nothing else. But somehow it keeps filling up with junk: a `node_modules/` folder the size of a small planet, build output, an `.env` file with a live API key in it, a 2GB demo video that makes every clone crawl. And then there's the submodule - that nested repo someone added that now shows up as a confusing single line in your diff and dumps you into "detached HEAD" the moment you `cd` into it.

This guide is about the three tools that draw the line between *your work* and *everything else*: the ignore file (what Git pretends not to see), Git LFS (how to version huge binaries without bloating history), and submodules (a repo inside a repo, with all the pain that implies). By the end you'll know why a file you ignored *still* shows up, how to get a leaked secret out, and when a submodule is the right call versus a trap.

## How to read this

Read the phases in order - each builds on the last. Phase 1 gives you the mental model for all three (what Git is actually tracking, and why "ignore" is narrower than you think). Phase 2 is the everyday core: writing ignore patterns that work, untracking files, and reaching for LFS when a binary is too big. Phase 3 is where it bites: leaked secrets, submodule detached-HEAD pain, and knowing when to walk away from a submodule entirely.

If you're new to how Git tracks files at all, skim [/guides/git-from-zero](/guides/git-from-zero) first - this guide assumes you've committed before.

## The phases

1. [What Git tracks (and what "ignore" really means)](01-what-git-tracks.md)
2. [Ignoring, untracking, and LFS for big files](02-ignoring-untracking-lfs.md)
3. [Leaked secrets and the submodule trap](03-secrets-and-submodules.md)