There are several programs for using git on Windows. Github for Windows and TortoiseGit are both good alternatives.
Github for Windows
- Downlad Github for Windows
- Setting up Github for Windows
TortoiseGit
File comparison tools
To merge two files with the help of a file comparison tool you can see a comprehensive list of programs on this Wikipedia site. Meld is a recommended choice.
License
When you are asked for a license when creating a new repository, choose the GPLv3 license.