DiffMind - AI Code Review Memory

한국어 문서

DiffMind learns from your team's bug history and warns when similar patterns appear in new code changes.

Why DiffMind?

ESLint:     "Variable used before declaration"                     (generic rule)
DiffMind:   "This pattern is 93% similar to a bug fixed in PR #142"   (team-specific)

Other tools check generic rules. DiffMind remembers your team's actual past mistakes.

How It Works

git diff → embed code changes (sentence-transformers)
     ↓
compare against past bugfix history (TurboQuant compressed)
     ↓
"This pattern was a bug 3 months ago in PR #142" warning
     ↓
auto-run via VS Code / git hook / GitHub Action

---

Installation

CLI

git clone https://github.com/wjddusrb03/diffmind.git
cd diffmind
pip install -e .

VS Code Extension

cd vscode-extension
npm install && npm run compile
npx @vscode/vsce package --no-dependencies
code --install-extension diffmind-0.1.1.vsix

Restart VS Code after installation. You'll see 🛡 DiffMind in the status bar.

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VS Code Usage (Step-by-Step)

Step 1: Open a Git Project

Open any folder that has a .git directory in VS Code.

Step 2: Learn History (One-Time)

Ctrl+Shift+P → "DiffMind: Learn" → Enter

• Leave the date input empty to learn all history
• Or enter a date like 2024-01-01 to limit scope

Step 3: Review Changes

After modifying any file:

Ctrl+Shift+D

Where to see results:

Location	Content
Status Bar (bottom)	✓ Clean or ⚠ N warnings
Problems Panel (Ctrl+Shift+M)	File-by-file warnings list
Popup	"Show Details" or "Show Problems" buttons

Step 4: Search Bug History

Ctrl+Shift+F6

Enter a query like "null check", "authentication error", or "memory leak".

Step 5: View Statistics

Ctrl+Shift+P → "DiffMind: Stats"

Shows total commits, bugfix ratio, top buggy files, and memory usage.

Step 6: Auto-Review on Save (Optional)

Ctrl+Shift+P → "DiffMind: Toggle Auto-Review on Save"

When enabled, every file save triggers an automatic review.

Right-Click Menu

Right-click in the editor to see:

• Review Current Changes
• AI Review
• Search Bug History

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Keyboard Shortcuts

Shortcut	Action	Description
Ctrl+Shift+D	Review	Compare changes against past bugs
Ctrl+Shift+A	AI Review	LLM analysis + fix suggestions
Ctrl+Shift+F6	Search	Semantic search of bug history
Ctrl+Shift+M	Problems	View warnings list (VS Code built-in)

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VS Code Settings

Ctrl+, → search "diffmind":

Setting	Default	Description
diffmind.pythonPath	python	Python interpreter path
diffmind.autoReviewOnSave	false	Auto-review when saving files
diffmind.threshold	0.75	Similarity threshold (lower = more warnings)
diffmind.aiProvider	claude	LLM provider (claude/openai/ollama)
diffmind.aiLanguage	en	AI output language (en/ko)
diffmind.maxWarningsPerHunk	3	Max warnings per code hunk
diffmind.showStatusBar	true	Show status bar item

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CLI Usage

Quick Start

# 1. Learn from repository history (one-time)
diffmind learn .

# 2. Review current changes
diffmind review

# 3. Review only staged changes
diffmind review --staged

# 4. JSON output (for CI)
diffmind review --json

# 5. Search past changes
diffmind search "null check missing"

# 6. View statistics
diffmind stats

# 7. Install pre-commit hook
diffmind install --pre-commit

# 8. Generate GitHub Action
diffmind install --github-action

Commands

Command	Description
diffmind learn [PATH]	Learn bug patterns from git history
diffmind review	Review current changes against past bugs
diffmind search "QUERY"	Semantic search over diff history
diffmind stats	Show index statistics
diffmind install	Install git hooks / GitHub Action

Options

diffmind learn

Option	Description	Example
--since DATE	Learn only after this date	--since 2024-01-01
--until DATE	Learn only before this date	--until 2024-12-31
--branch NAME	Specific branch only	--branch main
--bugfix-only	Only bugfix commits
--model NAME	Embedding model	--model all-MiniLM-L6-v2
--bits N	Compression bits (2, 3, 4)	--bits 3 (default)
--update	Incremental learn (new commits only)

diffmind review

Option	Description	Example
--staged	Only staged changes
--threshold N	Similarity threshold (0-1)	--threshold 0.80
-k N	Max similar items per warning	-k 5
--fail-on LEVEL	Exit 1 if risk >= level	--fail-on high
--json	JSON output

diffmind search

Option	Description	Example
-k N	Number of results	-k 10
--file PATH	Filter by file path	--file src/auth/
--author NAME	Filter by author	--author "john"
--lang LANG	Filter by language	--lang python
--bugfix-only	Only bugfix commits

---

Real-World Scenarios

Individual Developer

git add .
diffmind review --staged     # check before committing
git commit -m "feat: ..."

Team (Pre-Commit Hook)

# Team lead sets up once
diffmind learn . --since 2024-01-01
diffmind install --pre-commit

# Every team member's commit is auto-reviewed
git commit -m "update handler"
# → DiffMind: reviewing staged changes...
# → [!!!] HIGH RISK: 93% similar to bug in PR #142

CI/CD (GitHub Action)

name: DiffMind Review
on:
  pull_request:
    types: [opened, synchronize]

jobs:
  review:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
      - uses: actions/setup-python@v5
        with:
          python-version: "3.11"
      - name: Install & Review
        run: |
          pip install diffmind
          diffmind learn . --since 6months
          diffmind review --staged --fail-on high

---

Bug Detection

DiffMind identifies bugfix commits by:

Criteria	Examples
Conventional Commits	fix:, bugfix:, hotfix: prefix
Issue references	fix #123, closes #456, resolves #789
Keywords	fix, bug, resolve, patch
PR labels	bug, hotfix
Revert commits	Reverted commits = bug fixes

Risk Classification

Risk	Condition	VS Code Display	Meaning
HIGH	≥90% similar + bugfix commit	Red error	Very likely same bug
MEDIUM	≥80% similar + bugfix commit	Yellow warning	Needs attention
LOW	≥75% similar	Blue info	Reference only

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vs Other Tools

Tool	What It Does	What DiffMind Does
ESLint/Pylint	Generic rule violations	Team-specific bug patterns
GitHub Copilot	Code generation	Bug pattern memory
CodeRabbit	Generic AI review	Project-specific learned review
SonarQube	Static analysis	Semantic similarity analysis
git log --grep	Keyword search	Meaning-based search

---

Architecture

src/diffmind/
├── cli.py              # Click CLI (learn, review, search, stats, install)
├── models.py           # DiffHunk, ReviewWarning data models
├── parser.py           # Git log/diff parser, bugfix detection
├── indexer.py          # Embedding + TurboQuant compression
├── reviewer.py         # Similarity-based review engine
├── searcher.py         # Semantic search
├── storage.py          # Index persistence (.diffmind/index.pkl)
├── display.py          # Terminal + JSON formatting
└── hooks.py            # Git hooks + GitHub Action generation

vscode-extension/
├── src/extension.ts    # VS Code extension (TypeScript)
└── package.json        # Extension manifest

tests/                  # 318 tests

Tech Stack

• langchain-turboquant - 3-bit vector quantization
• sentence-transformers - all-MiniLM-L6-v2 embeddings (384 dim)
• Click - CLI framework
• NumPy - Vector operations
• TypeScript - VS Code Extension API

Tests

pytest tests/ -v

FAQ

Q: "No diff hunks found" error A: The project has too few git commits. You need at least 3-5 commits.

Q: Learning takes too long A: Use --since 2024-01-01 to limit the date range.

Q: VS Code warnings not showing A: Run Ctrl+Shift+P → Developer: Reload Window and try again.

Q: How to use AI Review? A: Set ANTHROPIC_API_KEY or OPENAI_API_KEY env variable, then press Ctrl+Shift+A.

License

MIT