Debian

$ sudo $apt_pref update
$ sudo $apt_pref install git-extras

Mac

$ brew install git-extras

Clone / Tarball:

$ git clone https://github.com/tj/git-extras.git
$ cd git-extras
# checkout the latest tag
$ git checkout $(git describe --tags $(git rev-list --tags --max-count=1))
$ [sudo] make install

One-liner:

curl -sSL http://git.io/git-extras-setup | sudo bash /dev/stdin

Windows (use it at your own risk)

First, please install Git for Windows 2.x from 'https://github.com/git-for-windows/git/releases' and the basic msys2. Second, clone the git-extras repo into any folder you like.

git clone https://github.com/tj/git-extras.git
# checkout the latest tag (optional)
git checkout $(git describe --tags $(git rev-list --tags --max-count=1))

After that, execute the install.cmd in the command prompt, with the path your Git for Windows 2.x is installed. For example, I install it in the folder called C:\SCM\PortableGit and the PREFIX should be C:\SCM\PortableGit\mingw64 (for 64-bit release) or C:\SCM\PortableGit\mingw32 (for 32-bit release). So I will execute the install.cmd like this:

install.cmd "C:\SCM\PortableGit\mingw64"

Last, please copy colrm.exe and column.exe from folder-your-msys2-installed/usr/bin to folder-your-git-installed/usr/bin. Enjoy git-extras!