Update Dart manifest for Scoop

dart-dev.json

{
    "version":  "1.13.0-dev.7.3",
    "license":  "BSD",
    "homepage":  "https://www.dartlang.org/",
    "extract_dir":  "dart-sdk",
    "env_add_path":  [
                         "bin"
                     ],
    "architecture":  {
                         "64bit":  {
                                       "url":  "https://storage.googleapis.com/dart-archive/channels/dev/release/1.13.0-dev.7.3/sdk/dartsdk-windows-x64-release.zip",
                                       "hash":  "510cc9037f3d1000990e30b0e83808d2293b24e679bfab0321cce0dba35aed41"
                                   },
                         "32bit":  {
                                       "url":  "https://storage.googleapis.com/dart-archive/channels/dev/release/1.13.0-dev.7.3/sdk/dartsdk-windows-ia32-release.zip",
                                       "hash":  "da0fc25f9d11bcf2d43fa0f4a0d6bda0d1c9d70fbae2a9ff27465a0d1d9198eb"
                                   }
                     },
    "checkver":  {
                     "url":  "http://storage.googleapis.com/dart-archive/channels/dev/release/latest/VERSION",
                     "re":  "\\s*\"version\"\\s*:\\s*(\\d+\\.\\d+\\.\\d+.*)"
                 }
}

dart.json

{
    "version":  "1.12.2",
    "license":  "BSD",
    "homepage":  "https://www.dartlang.org/",
    "extract_dir":  "dart-sdk",
    "env_add_path":  [
                         "bin"
                     ],
    "architecture":  {
                         "64bit":  {
                                       "url":  "https://storage.googleapis.com/dart-archive/channels/stable/release/1.12.2/sdk/dartsdk-windows-x64-release.zip",
                                       "hash":  "6fba96dbdaa8169e2c6a6ed5ea0f490c1ef41509aa51f88d7ebd6d5a60ef7091"
                                   },
                         "32bit":  {
                                       "url":  "https://storage.googleapis.com/dart-archive/channels/stable/release/1.12.2/sdk/dartsdk-windows-ia32-release.zip",
                                       "hash":  "fc1ab8d53caf1eaa63273ca10e64e467ca0721bca91e97281f35cd3c4f6d1b9d"
                                   }
                     },
    "checkver":  {
                     "url":  "http://storage.googleapis.com/dart-archive/channels/stable/release/latest/VERSION",
                     "re":  "\\s*\"version\"\\s*:\\s*(\\d+\\.\\d+\\.\\d+.*)"
                 }
}

updateDartManifestForScoop.ps1

# TODO(guillermooo): add dartium manifest

function getManifest {
    param($url)
    invoke-restmethod $url
}

function getLatestVersion {
    param($manifest)
    invoke-restmethod $manifest.checkver.url | select -expandproperty version
}

function getCheckSum {
    param($manifest, $arch)
    $type = "$($arch)bit"
    [void] ((invoke-restmethod "$($manifest.architecture.$type.url).sha256sum") -match "^(.+?)\s")
    $matches.1
}

function buildUrl {
	param($manifest, $arch, $latestVersion)
	$url = [System.Uri] $manifest.architecture."$($arch)bit".url
	$segments = $url.segments
	$segments[5] = "$latestVersion/"
	[System.UriBuilder]::new($url.scheme, $url.host, -1, $($segments -join '')).ToString()
}

function updateManifest {
    param($url)
    $manifest = getManifest $url
    $latestVersion = getLatestVersion $manifest
    if ($latestVersion -eq $manifest.version) {
        return
    }
    $manifest.version = $latestVersion
    $manifest.architecture."64bit".url = buildUrl $manifest 64 $latestVersion
    $manifest.architecture."32bit".url = buildUrl $manifest 32 $latestVersion
    $manifest.architecture."64bit".hash = getCheckSum $manifest 64
    $manifest.architecture."32bit".hash = getCheckSum $manifest 32
    $manifest
}

function writeManifest {
    param($manifest, $fileName)
    if ($manifest -eq $null) {
        write-output "Dart manifest is up to date: $fileName."
        return
    }
    $manifest | convertto-json | out-file $fileName -encoding ascii
    write-output "Updated manifest: $fileName."
}

$stableManifest = "https://raw.githubusercontent.com/lukesampson/scoop/master/bucket/dart.json"
$devManifest = "https://raw.githubusercontent.com/lukesampson/scoop-extras/master/dart-dev.json"

writeManifest (updateManifest $stableManifest) "dart.json"
writeManifest (updateManifest $devManifest) "dart-dev.json"