A tolerant unified-diff applier in Python — designed for messy AI/chat-generated patches that git apply often rejects.

It applies unified diffs without requiring git or the patch utility, and it can handle common copy/paste problems like Markdown code fences, extra assistant text, and hunks that no longer match exact line numbers.

Built for real-world patch copy/paste chaos.

git apply is excellent when your patch is clean and generated inside a normal Git workflow.

But AI/chat-generated patch output is often messy:

• wrapped in ```diff fences
• mixed with prose / explanation text
• slightly shifted context
• whitespace differences
• copied into .diff files with extra noise

This tool is a forgiving fallback:

• it extracts probable diff content from chat output
• parses unified diffs (including git-style diff headers)
• applies hunks using context-based matching, not just strict line numbers
• falls back to whitespace-tolerant matching
• creates .bak backups before writing
• supports dry-run mode

• ✅ Parses unified diffs (git diff style supported)
• ✅ Strips Markdown fences and extra assistant text around diffs
• ✅ Applies hunks using context-based matching
• ✅ Whitespace-tolerant fallback matching
• ✅ Creates backup files (*.bak) before modifying files
• ✅ Dry-run mode to preview changes
• ✅ Pure Python (no git, no patch binary required)
• ✅ Prevents writing outside the target repo root

Use this when:

• git apply fails on a patch copied from ChatGPT/Claude/etc.
• you only have Python installed (no patch utility)
• you want a safer patch preview with --dry-run
• you need a quick way to apply small/medium diffs in scripts or tooling

No package install required — it’s a single script.

python3 diff.py --help