Package management

Modern software development relies heavily on a way to manage dependencies, i.e. to keep track of required software libraries and their versions. Examples are apt-get for Linux, homebrew for MacOSX, Maven for Java and pip for Python.

Git for Windows is based on MSys2 which bundles Arch Linux' Pacman tool for dependency management.

How to use pacman

There is a man page for pacman and the tool also sports a --help option. These resources are recommended to address questions not covered by the following, brief descriptions.

Install/upgrade packages

To install a package, run

pacman -S <package-name>

To ensure that the newest package version is installed, it is recommended to pass the -y option, too, which asks Pacman to download the newest package list:

pacman -Sy <package-name>

Remove packages

pacman -R <package-name>

List packages

To list the installed packages, call

pacman -Q

To list the contents of a package, call

pacman -Ql <package-name>

Technical details

Rebuild packages

To build MinGW packages, you need to start the appropriate MinGW shell (32-bit or 64-bit – this sets MSYSTEM=MINGW32 or MSYSTEM=MINGW64 respectively), clone the MINGW-packages repository (recommended location: /usr/src/MINGW-packages), cd to the appropriate subdirectory and call

makepkg-mingw -s

(The -s flag tells makepkg that it should install dependencies automatically as needed)

Note: To compile 32-bit packages, you might need to set MINGW_INSTALLS=mingw32 first.

To build MSys packages, you need to start the MSys shell (which sets MSYSTEM=MSYS before running the Bash), clone the MSYS2-packages repository (recommended location: /usr/src/MSYS2-packages), cd to the appropriate subdirectory and call

makepkg -s

To rebuild the msys2-runtime (i.e. msys-2.0.dll), you will need to have a second MSys2 installation and quit all applications from the first MSys2 installation. In the second installation, as above, start the MSys shell and clone MSYS2-packages to /usr/src/.

Inside the msys2-runtime subdirectory, you need to use makepkg -s for the initial build.

For subsequent builds, after modifying the source files in src/msys2-runtime/winsup/cygwin/ you can switch to src/build-<arch>-pc-msys/<arch>-pc-msys/winsup/cygwin and type make. This will generate an msys0.dll file in the latter directory that you can then copy to the first MSys2 installation to test.

The process to rebuild the Bash is very similar to the msys2-runtime one; You will just need to work in the src/bash-<version>/ subdirectory of /usr/src/MSYS2-packages/bash/ (both the sources and the generated bash.exe live there).

Perl package management

Perl packages are managed outside of the pacman realm, but instead with CPAN:

perl -MCPAN -e 'install <package-name>'

CPAN also offers an interactive shell:

perl -MCPAN -e shell

Repository structure

Pacman repositories are served via HTTP, as static files in a single directory. The most important file in that directory is the package index, called <name>.db.tar.xz by convention. This package index can be updated via repo-add <package-index> <package-file>... (this updated only the package index, it does not copy the package files into the same directory). Pacman expects to find the package files referenced in the package index in the same directory as the index.

The Git for Windows-specific packages are served from Bintray, see below. We ship MSys2 packages for two architectures, i686 and x86_64 and also MinGW packages for i686 and x86_64.

Bintray

Bintray hosts repositories of binary files, much like GitHub hosts repositories of source files. Git for Windows' binary files are hosted on Bintray.

Git for Windows' most important repository hosted on Bintray contains the Pacman repositories described above. The section to add to pacman.conf to access this repository is:

[git-for-windows]
Server = https://dl.bintray.com/$repo/pacman/mingw/$arch^
Server = https://dl.bintray.com/$repo/pacman/msys2/$arch^
SigLevel = Optional

How to upload new versions (Git for Windows maintainers only)

To upload new files, a maintainer needs to have permission to write to the pacman repository on Bintray. We have a helpful tool in the build-extra repository to assist in the process, called pacman-mirror.sh. After building a new package version (preferably for 32-bit and 64-bit), the tool should be used thusly:

/path/to/build-extra/pacman-mirror.sh fetch
/path/to/build-extra/pacman-mirror.sh add \
    /path/to/<package>-<version>-i686.pkg.tar.xz \
    /path/to/<package>-<version>-x86_64.pkg.tar.xz
/path/to/build-extra/pacman-mirror.sh push

The fetch step will initialize or synchronize the local mirror of the Pacman repository, the add step will copy the packages into the appropriate location, and the push step will update the package index, and upload the packages that are not yet on Bintray as well as the package index.

Note: The pacman-mirror.sh tool takes no precaution against simultaneous use. You will want to coordinate with your fellow maintainers to avoid running it at the same time as somebody else.