gitattributes

name	gitattributes
description	Define and modify .gitattributes to standardize line endings, merge drivers, diff generation, and GitHub linguist overrides.
license	MIT

Skill gitattributes

Define attributes per path to enforce line-ending conversions, custom merge drivers, textual diff strategies, and language statistics overrides across repositories.

WHEN TO USE

• When line endings (CRLF vs LF) are causing cross-platform issues for developers.
• To prevent merge conflicts in auto-generated files (e.g., package-lock.json) by setting a custom merge driver.
• When GitHub's language statistics are incorrectly classifying repository code.
• To exclude vendored or binary files from standard diff outputs.

WHEN NOT TO USE

• For ignoring files from version control entirely (use .gitignore instead).
• When resolving a single, isolated merge conflict manually.
• To enforce coding style or formatting rules inside the files themselves (use linters or .editorconfig).

Common Pitfalls

• Using Trailing Slashes: Writing docs/ expecting it to match all files inside, instead of the correct docs/** or docs/*.
• Negative Patterns: Attempting to use !pattern syntax, which is strictly forbidden and unsupported in .gitattributes.
• Precedence Confusion: Forgetting that later lines in the file override earlier ones, or that deeper directories override root files.

Core Principles

• Global Consistency: Ensure line endings (text, eol) and text normalization are explicitly controlled.
• Merge Conflict Mitigation: Use built-in or custom merge drivers (e.g., merge=ours) for auto-generated files (like lockfiles) to prevent spurious conflicts.
• Diff Management: Exclude binary files from diff generation (-diff) or enable binary diffs in patches (diff) for small assets using custom macros.
• Linguist Overrides: Control language statistics and diff suppression on GitHub using linguist-generated=true or linguist-language=<lang>.
• Precedence: In-tree .gitattributes overrides are evaluated top-down; $GIT_DIR/info/attributes has the highest precedence for local uncommitted overrides.

Commands / Usage Patterns

• Text Normalization (Line Endings) * text=auto *.sh text eol=lf *.vcproj text eol=crlf

• Handling Binary Files *.png binary *.jpg -text -diff

• GitHub Linguist Control & Merge Strategy .github/workflows/*.lock.yml linguist-generated=true merge=ours

• Macro Attributes Define custom macros at top-level .gitattributes: [attr]custom_text text eol=lf whitespace=blank-at-eol *.ext custom_text

• Verify Applied Attributes git check-attr -a -- <file> git check-attr --cached <attr> -- <file>

• Renormalize Line Endings git add --renormalize .

Diagnostics and Troubleshooting

• Ignored Patterns: Ensure you are not using trailing slashes for directories (use path/** instead of path/).
• Overlapping Rules: Later lines in the same file override earlier lines. Closest .gitattributes directory takes precedence.
• Reversible Conversions: If core.safecrlf is true, Git rejects irreversible end-of-line conversions.

Example

# git normalization file
# @docs https://www.kernel.org/pub/software/scm/git/docs/gitattributes.html

# Shorthand for text files.
# - Treat them as text.
# - Ensure no CRLF line-endings, neither on checkout nor on check-in.
# - Detect whitespace errors.
#   - Exposed by default in `git diff --color` on the CLI.
#   - Validate with `git diff --check`.
#   - Deny applying with `git apply --whitespace=error-all`.
#   - Fix automatically with `git apply --whitespace=fix`.
[attr]code    text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2

# Custom shorthand for binary files with diff enabled.
# - Do not treat them as text.
# - Include binary diff in patches instead of "binary files differ."
[attr]binpatch  -text diff

# Define file attributes.
*.bat     eol=crlf
*.cmd     eol=crlf
*.ex?     binpatch
*.h       code diff=c
CHANGELOG merge=union

# Mark all agentic workflow .lock.yml files as generated.
.github/workflows/*.lock.yml linguist-generated=true merge=ours

# Ignore whitespace warnings for generated files.
backups/*.txt whitespace=-blank-at-eol,-space-before-tab,-indent-with-non-tab,-tab-in-indent,-blank-at-eof,-cr-at-eol

Another example which can be used in .github/aw/imports/.gitattributes:

# Mark all cached import files as generated
* linguist-generated=true

# Use 'ours' merge strategy to keep local cached versions
* merge=ours

What to Avoid

• Negative Patterns: Never use negative patterns (e.g., !pattern); they are explicitly forbidden in .gitattributes.
• Directory Syntax: Do not use the trailing-slash syntax (dir/) as it does not recursively match paths.

Limitations

• gitattributes do not follow symbolic links.
• Macro attributes can only be defined in top-level .gitattributes or $GIT_DIR/info/attributes.