Git for w64devkit

[Curculigo]

Download Git and integrate it with w64devkit.

w64devkit claims to still support Windows 7, but Git has dropped support for Windows 7.

Please add a version of Git that is compatible with Windows 7.

[skeeto]

If w64devkit ever includes Git (#77) it will be patched appropriately. However, my plans for including Git are currently on hold.