treat git tags as commits not branches

[haxwithaxe]

git checkout only works if they have the tag locally already. git clone doesn't grab tags so it craps itself when the installer tries to checkout the version tag in an existing repo.
see branch install-sh-issues install.sh

[virtadpt]

Doing the git clone followed by a git checkout $version seems like it would be workable.

Reference commit a05758a on the install-sh-issues tag.