cleanupArmHistory.ps1

$resourceGroupName = "some-deployment-group"

Login-AzureRmAccount
Save-AzureRmProfile "$PSScriptRoot\.azureprofile"

function Delete-History {
    $batch = 80

    Get-AzureRmResourceGroupDeployment -ResourceGroupName $resourceGroupName | ForEach-Object { 
        $batch = $batch -1
        Start-Job -ScriptBlock {
         param($deployment)
         Select-AzureRmProfile -Path "$PSScriptRoot\.azureprofile"
         $deployment | Remove-AzureRmResourceGroupDeployment
        } -ArgumentList $_
    
        if ($batch -lt 0){
            continue
        } 
    }
}

$runningJobCount = (Get-job | ?{ $_.State -ne "Completed"} | Measure).Count
$remainingHistory = (Get-AzureRmResourceGroupDeployment -ResourceGroupName $resourceGroupName).Count

while ($remainingHistory -gt 0){
    if ($runningJobCount -lt 5){
        Delete-History
    } else {
        sleep -Seconds 15
    }

    $runningJobCount = (Get-job | ?{ $_.State -ne "Completed"} | Measure).Count
    $remainingHistory = (Get-AzureRmResourceGroupDeployment -ResourceGroupName $resourceGroupName).Count

    Write-host "Running jobs $runningJobCount Remaining Histories $remainingHistory"
}

##[error]Creating the deployment 'xxxxx' would exceed the quota of '800'. The current deployment count is '800', please delete some deployments before creating a new one. Please see https://aka.ms/arm-deploy for usage details.