A fast, zero-config CLI that parses git unified diffs and extracts every variable, function, test, and import introduced in the changeset, grouped by file. Also flags security-sensitive patterns (hardcoded secrets, dangerous calls, injection risks).

Built in Rust with parallel file processing via rayon — each file section is extracted concurrently for maximum throughput on large diffs.

1. Install Rust — via rustup (recommended):

   curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

   This installs rustc, cargo, and rustup. Follow the on-screen instructions and restart your shell.

   Alternatively, see the official install page for other methods (Homebrew, distro packages, etc.).

2. Verify installation:

   cargo --version   # e.g. cargo 1.82.0
   rustc --version   # e.g. rustc 1.82.0

3. Make (optional) — for using the Makefile targets. Pre-installed on macOS and most Linux distributions. On Windows, use cargo commands directly.

# Option 1: Install to ~/.cargo/bin (available system-wide)
make install
# or: cargo install --path .

# Option 2: Build release binary locally
make release
# Binary at: target/release/differ_helper

git pull && make reinstall

make reinstall removes the old binary from ~/.cargo/bin and installs the new version from source.

make uninstall

# Auto-detect: diffs current branch against its origin
differ_helper

# Diff against a specific branch, tag, or commit
differ_helper main
differ_helper origin/develop
differ_helper v1.2.0
differ_helper abc123f

# Range syntax
differ_helper main..HEAD
differ_helper main...feature

# Read a diff file directly
differ_helper /path/to/diff.txt

When run without arguments, differ_helper automatically finds the best diff:

1. Finds the merge-base between HEAD and its upstream (tracked branch, origin/main, origin/master, origin/develop, or origin/next).
2. Diffs everything the current branch has that's different from that base.
3. Falls back to unstaged changes (git diff), then staged changes (git diff --cached).

This means you can just cd into your repo and run differ_helper — it figures out the right diff automatically.

When you pass an argument, differ_helper detects what it is:

1. If it contains .. → treated as a git range (git diff main..HEAD).
2. If it resolves to a git ref (branch, tag, commit hash) → diffs against the merge-base with HEAD.
3. If it's a file on disk → reads it as a unified diff file.

VARIABLES:
- count -> src/lib.rs
- MAX_RETRIES -> app/models.py

FUNCTIONS:
- process -> src/lib.rs
- UserService -> app/models.py

TESTS:
- it_works -> src/lib.rs
- test_user_creation -> app/models.py

IMPORTS:
- std::collections::HashMap -> src/lib.rs
- os -> app/models.py

WARNINGS:
- hardcoded password -> config/secrets.py
- dangerous eval() -> utils/parser.js

Entries are deduplicated by (name, file) and sorted by file path, then name. Warnings are deduplicated by (pattern, file).

The WARNINGS section flags 22 built-in patterns including:

• Secrets: password, secret, api_key, access_token, private_key, credential
• Dangerous calls: eval(), exec(), subprocess, os.system, Runtime.exec
• XSS risks: innerHTML, dangerouslySetInnerHTML, document.write
• Raw SQL: SELECT, INSERT INTO, DELETE FROM (case-insensitive)
• Code markers: TODO, FIXME, HACK
• Rust-specific: unsafe, unwrap()

Comments are automatically skipped.

To build binaries for other platforms, install cross:

cargo install cross

make cross-linux       # x86_64 Linux
make cross-linux-arm   # aarch64 Linux
make cross-windows     # x86_64 Windows
make cross-all         # All platforms + macOS

src/
├── main.rs          # CLI + smart arg detection + parallel diff orchestration (rayon)
├── lang.rs          # Language detection by extension
├── extract.rs       # Extractor trait + result types
├── ident.rs         # Shared identifier parsing helpers
├── output.rs        # Dedup + sorted output
├── security.rs      # Built-in security pattern detection
├── langs/
│   ├── mod.rs       # Extractor factory
│   ├── rust.rs      # Rust extractor
│   ├── python.rs    # Python extractor
│   ├── go.rs        # Go extractor
│   ├── c.rs         # C extractor
│   ├── cpp.rs       # C++ extractor (inherits C)
│   ├── jsts.rs      # JS/TS extractor
│   ├── css.rs       # CSS extractor
│   ├── sql.rs       # SQL extractor
│   ├── masm.rs      # MASM extractor
│   └── ADDING_LANGUAGES.md  # Guide for adding new languages
└── tests/
    ├── main_test.rs
    ├── ident_test.rs
    ├── lang_test.rs
    ├── output_test.rs
    ├── security_test.rs
    └── langs/
        ├── rust_test.rs
        ├── python_test.rs
        ├── go_test.rs
        ├── c_test.rs
        ├── cpp_test.rs
        ├── jsts_test.rs
        ├── css_test.rs
        ├── sql_test.rs
        └── masm_test.rs

Adding a new language: see src/langs/ADDING_LANGUAGES.md for a step-by-step guide.

make test               # 119 unit + integration tests
cargo tarpaulin         # line coverage report

GitHub Actions runs on every push/PR to main:

• cargo fmt --check
• cargo clippy -D warnings
• cargo test

MIT