Add tab completion for Git branches in Powershell

I wrote this little PS "gem", if posh-git is too much.
Just put it in your PowerShell profile to be able to type co  (with a space) and hit Tab to trigger completion and cycle through the list of branches:

function co
{
    param(
        [Parameter(Mandatory)]
        [ValidateNotNullOrEmpty()]
        [ArgumentCompleter({
            param($pCmd, $pParam, $pWord, $pAst, $pFakes)

            $branchList = (git branch --format='%(refname:short)')

            if ([string]::IsNullOrWhiteSpace($pWord)) {
                return $branchList;
            }

            $branchList | Select-String "$pWord"
        })]
        [string] $branch
    )

    git checkout $branch;
}

UPDATE: refactored to return a list of branches when tab-completion invoked after space and no partial string can be matched. Will return "master" if this is only one branch

As a bonus, did you know you can call TortoiseGit from shell?

function dif
{
    TortoiseGitProc.exe /command:repostatus
}