Gitignore Builder

Gitignore Builder

Build and merge .gitignore files using templates from github/gitignore with smart project detection.

When to Use

Invoke this skill when:

• User explicitly requests /gitignore or asks to create/update a .gitignore
• Detecting git init or a newly cloned repo without .gitignore
• User mentions ignoring files, not wanting to track certain files
• Observing git status output with files that should typically be ignored (e.g., node_modules/, .env, __pycache__/, *.log)

Workflow

Step 1: Determine Target Location

1. Find the nearest .git directory to determine repo root
2. If no .git found, ask user if they want to create a global gitignore at ~

Location Rules:

Step 2: Detect Project Type

For project-level gitignore (basic detection):

For global gitignore (environment-aware detection):

Step 3: Present Recommendations

Show detected templates and ask for confirmation:

Detected project root: /path/to/repo
Found indicators: package.json, .vscode/

Recommended templates:
- Node.gitignore
- VisualStudioCode.gitignore (for global)

Proceed with these templates? [Y/n/edit]

Allow user to:

• Confirm (Y)
• Cancel (n)
• Edit the list (add/remove templates)

Step 4: Fetch and Merge

Use the bundled scripts/merge-gitignore.sh script from this skill directory:

scripts/merge-gitignore.sh Node Python macOS

Merge Order (later entries have higher priority in gitignore):

1. Templates section - github/gitignore templates with START/END markers (easiest to replace/update)
2. Local files section - Project-specific ignores
3. Overrides section - Custom overrides with highest priority (last wins in gitignore)

Step 5: Handle EOL Conflicts

If the script detects mixed line endings:

⚠️ EOL inconsistency detected:
  - Node.gitignore: LF
  - VisualStudio.gitignore: CRLF
  - Existing .gitignore: LF

Choose unified format:
1. LF (Unix/macOS) - recommended
2. CRLF (Windows)
3. Keep as-is (no conversion)

Wait for user confirmation before proceeding.

Step 6: Show Diff Preview

If target .gitignore already exists, show a diff:

📄 Will write to: /path/to/repo/.gitignore

--- Existing content
+++ Merged content

@@ -1,5 +1,60 @@
+# ╔═══════════════════════════════════════════════════════════════════════╗
+# ║ START - github/gitignore templates                                    ║
+# ╚═══════════════════════════════════════════════════════════════════════╝
+
+# --------------------------------------------
+# Source: Node.gitignore
+# --------------------------------------------
+node_modules/
+...
+
+# ╔═══════════════════════════════════════════════════════════════════════╗
+# ║ END - github/gitignore templates                                      ║
+# ╚═══════════════════════════════════════════════════════════════════════╝
+
+# ============================================
+# Local files (project-specific ignores)
+# ============================================
+
+# ============================================
+# Overrides (highest priority - last wins)
+# ============================================
+
 # User custom rules
 my-custom-file.txt

Confirm write? [Y/n]

Step 7: Write File

After user confirms, write the file and report success:

✅ Created /path/to/repo/.gitignore (150 lines, 3 templates merged)

Important Notes

Always Recommend *.local Pattern

At the end of every gitignore generation, suggest:

💡 Tip: Consider adding these patterns for local configuration files:
   *.local
   *.local.*

These patterns prevent accidentally committing local overrides.

Gitignore Syntax Reminders

When discussing or modifying gitignore:

• Negation: The exclamation mark prefix negates a pattern, re-including previously excluded files. Order is important: the negation must come after the exclusion. Example: !important.log re-includes important.log.
• Order matters: Later patterns override earlier ones.
• Comments: Lines starting with # are comments.
• Directory: Trailing / matches only directories (e.g., build/).
• Wildcards: * matches anything except /, ** matches everything including /.

Source Attribution & Structure

Templates section must be wrapped with START/END markers:

# ╔═══════════════════════════════════════════════════════════════════════╗
# ║                    github/gitignore templates                         ║
# ║           https://github.com/github/gitignore                         ║
# ╠═══════════════════════════════════════════════════════════════════════╣
# ║ START - Do not edit this section manually                             ║
# ╚═══════════════════════════════════════════════════════════════════════╝

# --------------------------------------------
# Source: Node.gitignore
# --------------------------------------------
node_modules/
...

# ╔═══════════════════════════════════════════════════════════════════════╗
# ║ END - github/gitignore templates                                      ║
# ╚═══════════════════════════════════════════════════════════════════════╝

This makes it easy to:

• Identify template content for updates (replace between START/END)
• Understand where each rule comes from
• Avoid accidental edits to generated content

Preserve User Content

If merging with an existing .gitignore, preserve user-added content in the appropriate section:

# ╔═══════════════════════════════════════════════════════════════════════╗
# ║ START - github/gitignore templates                                    ║
# ╚═══════════════════════════════════════════════════════════════════════╝

# --------------------------------------------
# Source: Node.gitignore
# --------------------------------------------
node_modules/
...

# ╔═══════════════════════════════════════════════════════════════════════╗
# ║ END - github/gitignore templates                                      ║
# ╚═══════════════════════════════════════════════════════════════════════╝

# ============================================
# Local files (project-specific ignores)
# ============================================

secret-folder/
local-config.json

# ============================================
# Overrides (highest priority - last wins)
# ============================================

# User custom rules (preserved from original)
my-custom-rule.txt
!important.log

Reference Files

• examples.md - Detailed workflow examples for various scenarios

Script Reference

The merge-gitignore.sh script handles:

1. Fetching templates from github/gitignore via raw.githubusercontent.com
2. Detecting and reporting EOL inconsistencies
3. Concatenating templates with source attribution
4. Outputting to stdout for preview/confirmation workflow

Usage:

# Fetch and merge templates
scripts/merge-gitignore.sh <template1> [template2] ...

# Templates can be:
# - Top-level: Node, Python, Rust, Go, etc.
# - Global: Global/macOS, Global/VisualStudioCode, etc.

Exit Codes: