repo-attributes

Configures the file-level attribute layer of a repository: .gitattributes, .editorconfig, .gitignore, and Git LFS filter patterns.

This is repository-only configuration. It does not touch pre-commit hooks, CI pipelines, org-level custom properties, or community health files.

Where this skill fits

Protocol

1. Detect language markers and existing config

Scan the repo root for language markers, reusing the same detection approach as /prek:

Multiple markers mean a polyglot project. Cover every detected language in the generated files.

Check for existing .gitattributes, .editorconfig, .gitignore, and .gitmodules. Read each file present and treat its content as a floor, not a target for replacement.

Check for Git LFS usage:

git lfs ls-files

When git lfs is not installed, skip LFS detection and say so; do not guess at LFS-tracked paths.

2. Propose .gitattributes

Use assets/gitattributes.example as the starting shape. Include, based on step 1 detection:

• * text=auto — let Git normalize line endings for text files it detects.
• Explicit eol=lf for scripts and other files that must never gain CRLF, for example *.sh text eol=lf.
• Binary markers for asset types that must skip line-ending and diff conversion, for example *.png binary.
• linguist-generated, linguist-vendored, and linguist-documentation for paths that should not count toward the GitHub language bar or code review diffs.
• merge=union for append-only files such as CHANGELOG.md, so parallel entries merge instead of conflicting.
• export-ignore for paths that should not ship in git archive output, for example CI-only directories.
• diff= drivers for file types with a more useful semantic diff (for example *.md diff=markdown, when the driver is already configured).
• LFS patterns (filter=lfs diff=lfs merge=lfs -text) for any path already tracked by git lfs ls-files, or ones the user names.

Diff the proposal against any existing .gitattributes and ask before overwriting a line that already exists with different content.

3. Propose .editorconfig

Use assets/editorconfig.example. Include root = true, a [*] section with charset, end_of_line, insert_final_newline, trim_trailing_whitespace, indent_style, and indent_size, then one override section per detected language for its idiomatic indent style (for example tabs for Go and Makefiles, four-space indents for Python).

4. Propose .gitignore

Fetch the templates GitHub ships for the detected languages:

gh api /gitignore/templates
gh api /gitignore/templates/{name} --jq .source

Merge the fetched template content with any existing .gitignore. Append missing template lines; never remove an existing user entry, even one that looks redundant.

5. Renormalize line endings (only when authorized)

When .gitattributes changes alter how tracked files should be stored, git add --renormalize . rewrites tracked file content to match the new rules. This is a destructive rewrite of tracked content, so:

• Require a clean working tree first: git status --porcelain must print nothing.
• Require explicit user authorization before running the command. Never renormalize as a side effect of proposing .gitattributes.
• If the tree is dirty, stop and ask the user to commit or stash before renormalizing.

6. Verify

git check-attr -a <file>
git ls-files --eol
gh api repos/{owner}/{repo}/languages

Use git check-attr -a <file> to confirm the attributes applied match the proposal. Use git ls-files --eol to confirm working-tree and index line endings agree with .gitattributes. Use the GitHub languages API call to confirm linguist overrides changed the reported language mix, after the change reaches GitHub.

What this skill is NOT for

• Pre-commit or prek hook selection — that's /prek.
• GitHub custom properties or other organization-level metadata — out of scope for this skill.
• Community health files (README, LICENSE, CODE_OF_CONDUCT, CONTRIBUTING, SECURITY) — that's /oss-hygiene.
• CI pipeline configuration — not a repo-attributes concern.

Gotchas

• * text=auto alone does not force LF for scripts on a contributor's Windows checkout; pair it with an explicit eol=lf rule for files that must not gain CRLF.
• linguist-generated and linguist-vendored change the GitHub language bar and default PR diff collapsing, not local git diff output.
• git add --renormalize . only rewrites the index and working tree; it does not rewrite history. Existing clones still show the old line endings until they pull and re-run it themselves.
• LFS filter patterns without git lfs install run locally have no effect; confirm LFS is installed before proposing filter patterns as the fix for a large-file problem.
• .gitignore only affects untracked files. A path already tracked keeps being tracked until it is explicitly removed with git rm --cached.

References

• references/attributes.md — cited sources for .gitattributes, linguist overrides, .editorconfig, line-ending configuration, .gitignore, and Git LFS.