Building Git

We build Git for Windows using an MSYS2 based Git for Windows SDK. This SDK can be installed via the SDK installer

Installing a build environment

An initial git clone and make should have already occurred when running the SDK installer.
Open the Git for Windows SDK MinGW shell 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.
Change directory to the initial clone: cd /usr/src/git. If the directory is empty you may have the master branch checked out: git checkout main.
(Optional) build Git: make install
Run the test suite: make test. If you are a fan of statistics, you can use the following prove invocation to run the testsuite. But first we have to change to the test directory with the command cd t. After that you can issue /usr/bin/time prove -j 15 --state=failed,save ./t[0-9]*.sh. If 15 threads are too many for your system, you can provide the number of threads via the -j <num> (j for jobs) parameter.

Once the SDK built Git, it is very easy to build another revision of Git, such as per a different branch or Pull Request.

open the Git Bash of the SDK unless it is still open: execute the git-bash.exe binary in the top-level directory of the SDK,
switch the working directory: cd /usr/src/git,
fetch the Pull Request's revision or the branch:
if you want to test a Pull Request, call git fetch origin refs/pull/<id>/head, where <id> is the number of the Pull Request (e.g. if you want to test Pull Request #606, you would call git fetch origin refs/pull/606/head),
if you want to test a custom branch, call git fetch <url> <branch> instead, where <url> is the URL of the repository and <branch> is the name of the branch to test (e.g. if you wanted to test @dscho's cool-new-feature branch, you would call git fetch https://github.com/dscho/git cool-new-feature),
check out the revision that was just fetched: git checkout FETCH_HEAD,
continue as above either by make install or make test.

cd /usr/src/git
git pull
make -j15 install install-html

As before:

cd /usr/src/git/t
/usr/bin/time prove -j 5 --state=failed,save ./t[0-9]*.sh