Script to cleanup merged branches locally

.gitconfig

[alias]
  cb = "!f() { git branch --merged | grep -v "master" | while read i; do git branch -d $i; done; }; f"

merge-local-branches.ps1

function Cleanup-GitBranches()
{
    $branches = git branch --merged | ?{$_ -notmatch "\* master"} | ?{$_ -notmatch "master"} | ?{$_ -notmatch "\* *"} | %{$_.Trim() }

    if (-not $branches) {
        echo "No merged branches detected"
        exit 0
    }

    echo $branches

    $title = "Delete Merged Branches"
    $message = "Do you want to delete the already-merged local branches displayed above??"

    $yes = New-Object System.Management.Automation.Host.ChoiceDescription "&Yes", `
        "Delete the remote branches listed."

    $no = New-Object System.Management.Automation.Host.ChoiceDescription "&No", `
        "Leave the branches alone."
    $options = [System.Management.Automation.Host.ChoiceDescription[]]($yes, $no)

    $result = $host.ui.PromptForChoice($title, $message, $options, 1) 

    if ($result -eq 1) {
        exit 0
    }

    $branches | %{ git branch -d "$_" }
}

Drop that into a known location (such as %Documents%\WindowsPowerShell) and add this to get it enabled for all Powershell sessions:

. 'C:\Users\<username>\Documents\WindowsPowerShell\Cleanup-GitBranches.ps1'

Added a git alias as well for if using bash