public/build/Export-PSTSBuildDefinition.ps1

function Export-PSTSBuildDefinition
{
    param(
      [Parameter(Mandatory = $true, ValueFromPipelineByPropertyName = $true)][string] $project,
      [Parameter(Mandatory = $true, ValueFromPipelineByPropertyName = $true)][int] $BuildId,
      [Parameter(Mandatory = $true, ValueFromPipelineByPropertyName = $true)][string] $outFile
    )

    process {

        $content = Get-PSTSBuildDefinition `
        -project $project `
        -buildId $BuildId

        $($content | ConvertTo-json) | Out-File -FilePath $outFile
    }
}