/generating-patches

name: generating-patches
description: Generates git patch files from codebase modifications for local application. Use when user mentions patch, diff, export changes, bring changes back, apply locally, or after editing uploaded codebases.
metadata:
  version: 0.1.0

Generating Patches

Generate portable git patch files from codebase modifications, enabling users to apply Claude's edits to their local repositories.

When to Use

Activate after modifying files in an uploaded codebase when the user needs to transfer changes back to their local environment. Typical workflow: user uploads zip → Claude edits files → this skill exports changes as a patch.

Prerequisites

Verify git is available and the working directory is a git repository (or can be initialized as one):

git status 2>/dev/null || git init

If working with an uploaded codebase that lacks git history, initialize and create a baseline commit before making edits:

git init
git add -A
git commit -m "Baseline: original uploaded state"

Generating the Patch

After completing edits, generate a unified diff:

# For uncommitted changes (working tree modifications)
git diff > /mnt/user-data/outputs/changes.patch

# If changes are staged but not committed
git diff --cached > /mnt/user-data/outputs/changes.patch

# For both staged and unstaged
git diff HEAD > /mnt/user-data/outputs/changes.patch

For committed changes (preserves commit messages and metadata):

# All commits since baseline
git format-patch --stdout baseline..HEAD > /mnt/user-data/outputs/changes.patch

# Or specify number of commits
git format-patch --stdout -n 3 > /mnt/user-data/outputs/changes.patch

Handling Edge Cases

**Binary files**: Git diff excludes binaries by default. Warn the user if binary files were modified:

git diff --name-only --diff-filter=M | xargs file | grep -v "ASCII\|UTF-8\|empty"

**Large patches**: For extensive changes, consider splitting by directory or file type:

git diff -- "*.py" > /mnt/user-data/outputs/python-changes.patch
git diff -- src/ > /mnt/user-data/outputs/src-changes.patch

**No changes detected**: Verify files were actually modified. Common issues:

• Edits made to copies outside the git tree
• Files not tracked by git (need `git add` first)

Output Requirements

Always output to `/mnt/user-data/outputs/` with a descriptive filename. Provide the download link:

[Download changes.patch](computer:///mnt/user-data/outputs/changes.patch)

User Instructions

Include these instructions with every patch delivery:

---

**To apply this patch locally:**

cd /path/to/your/repo

# Preview changes (dry run)
git apply --check changes.patch

# Apply to working tree
git apply changes.patch

**If using format-patch output (includes commit metadata):**

git am changes.patch

**Troubleshooting:**

• `git apply --reject changes.patch` — applies what it can, writes `.rej` files for conflicts
• `git apply -R changes.patch` — reverses a previously applied patch
• `git apply --3way changes.patch` — enables three-way merge for conflicts

---

Optional: PR Description

When requested, generate a pull request description from the patch:

# Extract summary of changes
echo "## Summary"
git diff --stat
echo ""
echo "## Changes"
git diff --name-only | while read f; do echo "- \`$f\`"; done

Combine with a brief description of what was changed and why, suitable for GitHub PR body.