Deleting old remote branches which have been merged into master

git-cleanup.ps1

function CleanupRepo {
    param([string]$repo)

    <#work directory should be repo root#>
    cd $repo

    git fetch "origin"
    git reset --hard origin/master

    "getting branch list..."
    <#listing all remote branches which were merged into master#>
    $branchesToDelete =
        git branch -r --merged `
        | select  -First 0  <#delete this line when go to production#> `
        <#we don't want to delete origin/master#> `
        | ?{ $_ -notmatch 'origin/master'} `
        | %{ $_.Trim() } `
        `
        <#getting branch name and last commit date (if any) since 1 month#> `
        | Select-Object @{ n="Branch"; e={$_} }, `
                        @{ n="LastCommitDate"; e={git log -1 --since='1 month ago' --format="%aI" -s $_} } `
        `
        <#taking branches which DON'T have recent commits#> `
        | ?{ [string]::IsNullOrEmpty($_.LastCommitDate) } `
        | %{ $_.Branch.replace("origin/","") }

    workflow DeleteBranches {
        param([string[]] $branches,
              [string] $repo)
        foreach -parallel -throttlelimit 10 ($branch in $branches) {
            InlineScript {
                Set-Location $Using:repo
                "working on $Using:branch"

                <#delete reference from origin#>
                git push --delete origin $Using:branch
            }
        }
    }

    DeleteBranches -branches $branchesToDelete -repo $repo
}

CleanupRepo "C:\dev\superman_master"