Understanding .gitattributes for Better Language Detection

4 min read
#git #github #development-tools #documentation

Have you ever noticed that GitHub sometimes incorrectly identifies your project’s primary programming language? Or perhaps your repository is showing up as mostly HTML when it’s actually a JavaScript project? The solution lies in a powerful but often overlooked Git feature: .gitattributes.

What is .gitattributes?

The .gitattributes file is Git’s way of defining attributes for specific file paths in your repository. While Git uses it for various purposes like line ending normalization and merge strategies, GitHub extends its functionality to control language detection and repository statistics.

The Problem: Misleading Language Statistics

GitHub uses a tool called Linguist to detect languages in your repository and generate those colorful language bars you see on every repo. However, Linguist can sometimes get confused:

  • Documentation files like README.md might be counted as “Markdown”
  • Generated files like compiled CSS or bundled JavaScript can skew statistics
  • Vendor dependencies in node_modules or similar directories can dominate
  • Configuration files might be misclassified as the primary language

The Solution: Strategic .gitattributes Configuration

In a recent commit to this blog, I added a simple but effective .gitattributes file:

*.mdx linguist-documentation

This single line tells GitHub’s Linguist that all .mdx files should be treated as documentation rather than code. Let’s break down what this accomplishes:

The linguist-documentation Attribute

When you mark files with linguist-documentation, GitHub:

  • Excludes them from language statistics - They won’t affect your repository’s primary language detection
  • Hides them in diffs by default - Large documentation changes won’t clutter pull request views
  • Still indexes them for search - Your documentation remains discoverable

For a blog like this one, where .mdx files contain the actual blog posts, this prevents GitHub from thinking the repository is primarily “MDX” when it’s actually an Astro/TypeScript project.

Common .gitattributes Patterns

Here are some practical patterns you can use in your projects:

Marking Documentation

*.md linguist-documentation
*.mdx linguist-documentation
*.rst linguist-documentation
docs/ linguist-documentation

Excluding Generated Files

dist/ linguist-generated
build/ linguist-generated
*.min.js linguist-generated
*.bundle.js linguist-generated

Excluding Vendor Code

vendor/ linguist-vendored
node_modules/ linguist-vendored
third_party/ linguist-vendored

Detecting Specific Languages

*.blade.php linguist-language=PHP
Dockerfile.* linguist-language=Dockerfile

Real-World Example: This Blog

Before adding the .gitattributes file, GitHub might have shown this repository as:

  • 60% MDX (blog posts)
  • 30% TypeScript (actual code)
  • 10% Other files

After the change, it correctly identifies it as primarily a TypeScript/Astro project, which better represents the actual codebase structure.

Best Practices

  1. Place .gitattributes in your repository root - This ensures it applies to the entire project
  2. Use wildcards strategically - *.ext patterns are more maintainable than listing individual files
  3. Test your changes - Push to GitHub and check the language statistics after a few minutes
  4. Document your decisions - Add comments in complex .gitattributes files to explain unusual configurations
  5. Consider case sensitivity - Use patterns like *.[Dd]ockerfile for files that might have different casings

Advanced Usage

You can combine multiple attributes for more precise control:

# Mark as documentation AND specify language for syntax highlighting
*.api.md linguist-documentation linguist-language=YAML

# Generated files that should be excluded completely
dist/** linguist-generated=true

# Vendor files in a specific language
vendor/jquery.js linguist-vendored linguist-language=JavaScript

Implementation Steps

To implement .gitattributes in your project:

  1. Analyze your current language statistics on GitHub
  2. Identify problematic files that are skewing the results
  3. Create a .gitattributes file in your repository root
  4. Add appropriate patterns using the attributes above
  5. Commit and push the changes
  6. Wait a few minutes for GitHub to reprocess your repository
  7. Verify the results in your repository’s language statistics

Conclusion

The .gitattributes file is a small but powerful tool for maintaining accurate repository metadata. By properly classifying your files, you help both GitHub and other developers understand your project’s true nature at a glance.

Whether you’re building a documentation-heavy project, working with generated files, or managing a polyglot codebase, .gitattributes gives you the control you need to present your repository accurately.

Next time you notice your repository’s language statistics don’t match reality, remember this simple solution. A few lines in .gitattributes can make your project’s purpose crystal clear to anyone who discovers it.