checkForGitHubPortNewVersion.ps1

# Place it in vcpkg\scripts folder
function Get-BasicAuthCreds {
    param([PSCredential]$Credential)
    $AuthString = "{0}:{1}" -f $Credential.Username,$Credential.GetNetworkCredential().Password
    $AuthBytes  = [System.Text.Encoding]::Ascii.GetBytes($AuthString)
    return [Convert]::ToBase64String($AuthBytes)
}
$username = Read-host "GitHub username"
$password = Read-host "GitHub password" -AsSecureString
$cred = New-Object PSCredential $username, $password
$BasicCreds = Get-BasicAuthCreds -Credential $cred
$ports = Get-ChildItem ..\ports | ? {$_.PSIsContainer}
Foreach ($port in $ports)
{
    $fileContent = Get-Content (join-path $port.FullName "portfile.cmake")  -Raw
    $match = $fileContent | Select-String 'vcpkg_from_github\([\s\S]*\bREPO\s+(\S+)[\s\S]+\bREF\s+(\S+)[\s\S]*?\)' |
            %{ $_.Matches }
    if (!$match)
    {
        continue
    }
    $githubPage = $match.Groups[1].Value
    $version = $match.Groups[2].Value
    $status = $null
    $versionMatch = $version | Select-String '\${(\w+)}' | %{ $_.Matches }
    if ($versionMatch.Success)
    {
        $varName = $versionMatch.Groups[1].Value
        $variableMatch = $fileContent | Select-String "set\($varName\s+(\S+)\)" |
            %{$_.Matches}
        if ($versionMatch.Success)
        {
            $varValue = $variableMatch.Groups[1].Value
            $version = "$($version.replace("`${$varName}", "$varValue"))"
        }
    }
    try
    {
        $wr = Invoke-WebRequest -Uri "https://api.github.com/repos/$githubPage/releases/latest" -Headers @{"Authorization"="Basic $BasicCreds"}
        $tag_name = $wr.Content | ConvertFrom-Json | %{ $_.tag_name }
        if ($version -eq $tag_name)
        {
            $status = "Latest"
        }
        else
        {
            $status = "New version $tag_name is available"
        }
    }
    catch [System.Net.WebException]
    {
        $statusCode = $_.Exception.Response.StatusCode
        if ($statusCode -eq "Forbidden")
        {
            $status = "API rate limit exceeded"
        }
        elseif ($statusCode -eq "NotFound")
        {
            # Try with latest tag
            try
            {
                $wr = Invoke-WebRequest -Uri "https://api.github.com/repos/$githubPage/tags" -Headers @{"Authorization"="Basic $BasicCreds"}
                $name = $wr.Content | ConvertFrom-Json | %{ $_.name } | Select-Object -first 1
                if ($name.Count -eq 0)
                {
                    $status = $null
                }
                elseif ($version -eq $name)
                {
                    $status = "Latest"
                }
                else
                {
                    $status = "New tag $name is available"
                }
            }
            catch [System.Net.WebException]
            {
                $statusCode = $_.Exception.Response.StatusCode
                if ($statusCode -eq "Forbidden")
                {
                    $status = "API rate limit exceeded"
                }
                elseif ($statusCode -eq "NotFound")
                {
                    $status = $null
                }
                else
                {
                    $status = "Unknown error: $statusCode"
                }
            }
        }
        else
        {
            $status = "Unknown error: $statusCode"
        }
    }
    catch
    {
        $_
    }
    if ($status)
    {
        $port.Name
        "  $githubPage $version"
        if ($status.StartsWith("New "))
        {
            write-host "  $status" -foregroundcolor "green"
        }
        else
        {
            "  $status"
        }
    }
}

This is great and there might be a room for improvement i.e. opus and opusfile newer and older versions are interchanged

It's because they forgot to create new GitHub releases for 0.8 and 0.9 version: https://github.com/xiph/opusfile/releases

I see. What are your thoughts on a PR? Would love to see this merged?