gitc

A git toolkit in Rust. Two things ship in this crate:

• a library — pure-Rust readers for git's on-disk formats, plus an optional git filter-repo port; and
• a binary — a drop-in git that is git: git's own C source compiled in via the C ABI.

$ gitc --version
git version 2.55.GIT          # the binary is real git, byte-for-byte

Library

Pure Rust, no external service, no gate — just git formats parsed directly. Only depends on flate2 (zlib inflate) and, behind the scrub feature, regex.

module	what it does
gitobj	read git objects by id — loose first, then packed
gitpack	read objects from packfiles (.git/objects/pack/*.{idx,pack})
gitindex	parse .git/index and enumerate the staged blobs
gitwalk	enumerate the blobs reachable from a set of commits
gitargs	a minimal git argv parser
filterrepo	a git filter-repo port for history rewriting (feature scrub)

cargo test                 # runs the library's unit tests
cargo build --features scrub

Binary — git via FFI

git's process entry on Windows is its own wmain (compat/mingw.c), reached via wmainCRTStartup because the binary is linked with -municode. wmain performs all of git's mandatory Windows startup and then calls main(argc, argv) with clean UTF-8 argv. This crate provides that main (via #![no_main] + an exported extern "C" fn main), replacing git's common-main.c main(). Our main does exactly what git's does — init_git(argv) then cmd_main(argc, argv) — passing the original argv straight through. The result is 1:1 git.

src/main.rs   the exported extern "C" main → init_git → cmd_main
src/ffi.rs    the two FFI declarations (init_git, cmd_main)
build.rs      merges git.o + builtin/*.o + libgit.a into one archive and links it
vendor/git    git's C source, as a submodule (github.com/git/git)

common-main.o is deliberately NOT linked (Rust owns main); git's wmain lives in mingw.o inside the combined git archive.

Build (binary)

The binary links git's own mingw/gnu-ABI objects, so it must be built for a *-windows-gnu target with the msys2 UCRT64 toolchain (the same one that builds git). The library builds on any host; only the binary needs this.

1. Toolchain — install msys2 and the UCRT64 gcc:

   pacman -S mingw-w64-ucrt-x86_64-gcc
   rustup target add x86_64-pc-windows-gnu
   

   .cargo/config.toml points the gnu-target linker at C:/msys64/ucrt64/bin/gcc.exe — override via CARGO_TARGET_X86_64_PC_WINDOWS_GNU_LINKER if yours differs.

2. git source — check out the vendored submodule:

   git submodule update --init --recursive vendor/git
   

3. Build git's C objects once, in the msys2 UCRT64 shell — note curl is required (HTTPS transport) so NO_CURL is deliberately absent:

   cd vendor/git
   make -j4 MSYSTEM=MINGW64 NO_RUST=1 NO_OPENSSL=1 NO_EXPAT=1 \
        NO_GETTEXT=1 NO_TCLTK=1 NO_PERL=1 NO_PYTHON=1 git.exe git-remote-http.exe
   

   This produces git.o, builtin/*.o, libgit.a (the FFI inputs), and the separate git-remote-http.exe (installed at run time for https).

4. Build gitc:

   cargo build --release --target x86_64-pc-windows-gnu
   

   The runtime needs libpcre2-8-0.dll / zlib1.dll / libiconv-2.dll on PATH, and — for https remotes — git-remote-http(s).exe + its DLL closure + a CA bundle installed under the binary's libexec/git-core. See REQUIREMENTS.md for the complete build- and run-time spec (toolchain, artifacts, HTTPS helper, templates, and the GITC_* build env overrides).

Licensing

The Rust code in this repository is BSD-3-Clause. The built binary statically incorporates git's own C source (vendor/git, git/git), which is GPL-2.0 — so the distributed binary is governed by git's license. See vendor/git/COPYING. The library links no git C and is BSD-3-Clause on its own.