gitignore and gitattributes¶

Overview¶

Without .gitignore, engineers commit .terraform/ directories, node_modules/, and .env files containing secrets — triggering security incidents and bloated repositories. Without .gitattributes, Windows and Linux developers fight line-ending wars in YAML and shell scripts. These two files are infrastructure-as-code hygiene essentials.

This is Tutorial 12 in Module 4: Collaboration of the REBASH Academy Git series.

Prerequisites¶

• Basic Git Workflow — Add, Commit, Push
• Pull Requests and Code Review

Learning Objectives¶

By the end of this tutorial, you will be able to:

• Write .gitignore patterns for common DevOps stacks
• Understand gitignore precedence and negation rules
• Remove accidentally tracked files from Git history scope
• Configure .gitattributes for line endings and diff behavior
• Mark binary files and generated files appropriately
• Use global gitignore for personal editor files
• Apply linguist and export-ignore attributes for GitHub

Ignore Flow Diagram¶

flowchart TB
    FILES[Working Directory Files]
    GI[.gitignore patterns]
    GA[.gitattributes rules]
    STAGE["git add / staging"]
    REPO[Repository]

    FILES --> GI
    GI -->|excluded| SKIP[Not tracked]
    GI -->|allowed| STAGE
    GA --> STAGE
    STAGE --> REPO```

## Theory

### .gitignore Purpose

Gitignore tells Git which files to **ignore** — never stage or commit unless forced with `git add -f`.

Patterns apply to:

- Untracked files (primary use)
- Already tracked files are NOT ignored until removed from index

### Pattern Syntax

| Pattern | Matches |
|---------|---------|
| `*.log` | Any `.log` file in any directory |
| `/build/` | `build/` at repo root only |
| `**/tmp/` | `tmp/` anywhere |
| `!important.log` | Negation — do track this file |
| `config/**` | Everything under config/ |

Later rules override earlier; negation un-ignores specific paths.

### DevOps gitignore Essentials

**Terraform:**

```gitignore
.terraform/
*.tfstate
*.tfstate.*
.terraform.lock.hcl
# Note: some teams commit .terraform.lock.hcl — document policy
crash.log
override.tf
*.tfvars
!example.tfvars

Python:

__pycache__/
*.py[cod]
.venv/
.env

Kubernetes / general:

*.pem
*.key
secrets/
.env.local

Use templates from gitignore.io or GitHub's gitignore repository.

Global gitignore¶

Personal editor files shouldn't be in project gitignore:

git config --global core.excludesfile ~/.gitignore_global

# ~/.gitignore_global
.DS_Store
.idea/
*.swp
.vscode/

Removing Tracked Files That Should Be Ignored¶

git rm --cached secrets.env
git commit -m "chore: stop tracking secrets.env"
echo "secrets.env" >> .gitignore

--cached removes from index only — keeps local file.

.gitattributes Purpose¶

Controls how Git handles files:

• Line ending normalization (text, eol=lf)
• Diff driver (how diffs display)
• Merge strategy for specific files
• Linguist language detection (GitHub)
• Export-ignore for archive

Line Endings¶

* text=auto
*.sh text eol=lf
*.bat text eol=crlf
*.png binary

* text=auto lets Git normalize line endings on checkout/commit — critical for cross-platform teams editing YAML and shell scripts.

Custom Diff Drivers¶

*.tf diff=terraform

Requires config:

git config diff.terraform.xfuncmd "terraform fmt -check"

Merge Strategies for Lock Files¶

package-lock.json merge=ours

Controversial — many teams regenerate lock files post-merge instead.

export-ignore¶

Exclude CI artifacts from git archive:

.github/ export-ignore
tests/ export-ignore

Hands-on Lab¶

Step 1 – Create repo and demonstrate ignore¶

Command:

mkdir -p /tmp/gitignore-lab && cd /tmp/gitignore-lab
git init -b main
cat > .gitignore << 'EOF'
*.log
.terraform/
.env
!example.env
EOF
echo "secret=1" > .env
echo "secret=example" > example.env
echo "debug" > app.log
mkdir .terraform && echo "state" > .terraform/plugin
git status

Explanation: .env and .log ignored; example.env tracked via negation.

Step 2 – Commit allowed files¶

Command:

git add .
git status
git commit -m "chore: add gitignore and example env"
git check-ignore -v app.log .env example.env

Step 3 – Add gitattributes¶

Command:

cat > .gitattributes << 'EOF'
* text=auto eol=lf
*.sh text eol=lf
*.png binary
*.md diff=markdown
EOF
echo '#!/bin/sh' > deploy.sh
echo 'echo deploy' >> deploy.sh
git add .gitattributes deploy.sh && git commit -m "chore: add gitattributes"

Step 4 – Remove accidentally tracked file¶

Command:

echo "oops" > .env
git add -f .env && git commit -m "mistake: tracked secret"
git rm --cached .env
git commit -m "chore: untrack .env"
git status
test ! -f .env && echo "file missing" || echo ".env still on disk"

Step 5 – Verify attributes¶

Command:

git check-attr -a deploy.sh
git check-attr binary -- *.png 2>/dev/null || echo "no png files"

Step 6 – Clean up¶

Command:

cd /tmp && rm -rf gitignore-lab

Commands & Code¶

Terraform starter .gitignore¶

# Local .terraform directories
.terraform/

# .tfstate files contain sensitive data
*.tfstate
*.tfstate.*

# Variable files with secrets
*.tfvars
*.tfvars.json
!terraform.tfvars.example

# CLI config
.terraformrc
terraform.rc

# Crash logs
crash.log
crash.*.log

Common Mistakes¶

Best Practices¶

Troubleshooting¶

Summary¶

• .gitignore excludes files from tracking — essential for secrets, build output, and local state
• Negation patterns (!) re-include specific files under broad rules
• git rm --cached stops tracking without deleting local files
• .gitattributes controls line endings, binary handling, and diff/merge behavior
• DevOps repos need stack-specific patterns for Terraform, Python, Node, and secrets

Interview Questions¶

1. What is the purpose of .gitignore?
2. How do you stop tracking a file without deleting it locally?
3. What does the negation pattern !important.log do?
4. Why doesn't gitignore affect already-tracked files?
5. What is .gitattributes used for?
6. What should a Terraform .gitignore include?
7. What does * text=auto eol=lf accomplish?
8. What is a global gitignore, and when use it?
9. Why mark files as binary in gitattributes?
10. How would you prevent secrets.env from ever being committed again?

Related Tutorials¶

• Pull Requests and Code Review (previous)
• Undoing Changes — Reset, Revert, and Stash (next — Module 5)
• Basic Git Workflow — Add, Commit, Push
• Git Installation and Configuration
• Git – Category Overview

References¶

• gitignore documentation
• gitattributes documentation
• GitHub gitignore templates
• HashiCorp – Terraform gitignore recommendations
• REBASH Academy – Git Overview