Download the Git for Windows SDK, install it and run sdk build installer.

If you need to include a Git version built with custom patches, call sdk cd git, then make sure that it is at the commit you want, then call sdk build git-and-installer.

Sometimes the wording needs to be changed, or the layout, or something, in a single page of the installer. To avoid having to build the entire installer (and compressing all of Git for Windows), run sdk cd installer and run ./release.sh -d <page>. For example, to modify the page where Git's default editor can be configured, run this:

sdk cd installer
./release.sh -d Editor

As the installer is made by putting together files from the Git SDK, it is advisable to update those files first. To update the packages, call pacman -Syu (caveats apply).

If you want to test Git changes or make an installer from your own Git fork, you need to call

cd /usr/src/git
make install

for documentation changes:

make install-html

and afterwards

prefix=/mingw64 make -C contrib/subtree install-html

without this second make you get an error message about a missing git-subtree.html file).

To make an installer, install the SDK and run it

Git for Windows SDK MinGW shell can be run by double-clicking either the Shortcut on the desktop Git SDK 32-bit.lnk or by double-clicking mingw32_shell.bat in the install folder. That is Git SDK 64-bit.lnk and mingw64_shell.bat for the 64bit SDK installer.

then issue the following commands:

cd /usr/src/build-extra
git pull main
./installer/release.sh <version>-test

where <version> is the Git version (please note that the <version> cannot contain dots after the numerical version: 2.7.2-hello-world is okay while 2.7.2.hello.world is not okay).

Short version: you will need to run make strip in /usr/src/git before make install, and you will also need to run to call pacman -S mingw-w64-x86_64-git-extra afterwards (replace x86_64 with i686 for 32-bit builds and with clang-aarch64 for Windows/ARM64 builds).

The make strip command removes the debug information from the .exe files. That is not quite the same as the official release process does: it calls cv2pdb which splits out the debug information from the .exe files into separate .pdb files, but that processing is not defined in /usr/src/git/Makefile, but instead in /usr/src/MINGW-packages/mingw-w64-git/PKGBUILD.

The pacman -S mingw-w64-x86_64-git-extra part is defined elsewhere yet: in /usr/src/build-extra/please.sh. Its purpose is to replace many hardlinked copies in /mingw64/libexec/git-core/git-*.exe with what Git for Windows calls the "Git wrapper": a small executable that does nothing else but call git.exe with the appropriate subcommand name.

You see, many "built-in" commands are implemented right there in git.exe, with no need to actually execute anything else. For example, when you call git show, the show part is executed inside git.exe itself.

This is in contrast to, say, git send-email, which actually executes /mingw64/libexec/git-core/git-send-email (a Perl script). For historical reasons, Git wants to provide also git-show.exe in /mingw64/libexec/git-core/, even if that is not at all necessary because the show command is a built-in command. Therefore, Git has this quirk where it first looks at the name of the executable via which it was called (e.g. if it was called via /mingw64/libexec/git-core/git-show.exe, it extracts the show part and knows that it should internally execute git show instead. And then, Git simply installs hardlinked copies of git.exe in /mingw64/libexec/git-core/ for all built-in commands.

Since they are hard-links, they only use a minuscule amount of disk space. However, too many Git for Windows users looked at the disk usage of those hard-linked copies using the Windows Explorer, which historically completely ignored the fact that hard-linked copies did not use additional disk space (apart from the directory entry). As a consequence, we had many reports that Git for Windows occupied way too much space. That was not true, of course, but those reports took so much time to address that it was easier to install the Git wrapper (which is copied, but it is tiny compared to git.exe).