git clone https://github.com/mathiasertl/Download/GitHub.git Download/GitHub
Older versions are marked as tags, you can view available tags with git tag -l and move back to the current HEAD with git checkout <tag-name>. Versions for older versions of MediaWiki, if available, are managed as branches, use git branch and git checkout <branch> to move to a specific branch. To move back to the newest version, use git checkout master.
Note that GitHub allows you to download older different commits as tarball if you do not want to install git.