Recursive github repo downloader

gitdown.ps1

# Create a new API token by going to
# https://github.com/settings/tokens/new (provide a description and check "repo" scope")


param (
    # github repo path to download, e.g.
    # 'https://github.com/microsoft/CsWinRT/tree/master/src/Samples/NetProjectionSample'
    [Uri]$RepoPath = 'https://github.com/microsoft/CsWinRT/tree/master/src/Samples/NetProjectionSample',
    # Folder to download to.
    [Parameter(Mandatory)][string]$Path,
    # GitHub API token for "repo" scope.
    [string]$AccessToken
)

function Invoke-GitHubWebRequest {
    [CmdletBinding()]
    param(
        [Parameter(Mandatory)][Uri]$Uri,
        [string]$OutFile
    )

    Write-Verbose "Downloading $Uri"

    $prevProgressPreference = $global:ProgressPreference
    $originalSecurityProtocol = [Net.ServicePointManager]::SecurityProtocol

    $global:ProgressPreference = 'SilentlyContinue'
    try {

        # Enforce TLS v1.2 Security Protocol
        [Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12

        $headers = @{
            'User-Agent'           = 'GitDown for PowerShell'
            'X-GitHub-Api-Version' = '2022-11-28'
        }

        if ($AccessToken) {
            $headers += @{'Authorization' = "token $AccessToken" }
        }

        $invokeWebRequestParms = @{
            'Uri'                   = $Uri
            'Method'                = 'GET'
            'Headers'               = $headers
            'UseDefaultCredentials' = $true
            'UseBasicParsing'       = $true
            'TimeoutSec'            = 60
            'Verbose'               = $false
        }

        if ($OutFile) {
            $invokeWebRequestParms += @{ 'OutFile' = $OutFile }
        }

        Invoke-WebRequest @invokeWebRequestParms
    }
    finally {
        [Net.ServicePointManager]::SecurityProtocol = $originalSecurityProtocol
        $global:ProgressPreference = $prevProgressPreference
    }
}

function Invoke-RepoWalk {
    [CmdletBinding()]
    param (
        [Parameter(Mandatory)][Uri]$Uri,
        [string]$AccessToken
    )

    Write-Verbose "Walking $Uri"

    $response = Invoke-GitHubWebRequest -Uri $Uri

    $content = $response.Content | ConvertFrom-Json
    foreach ($obj in $content) {
        if ($obj.type -eq 'file') {
            [PSCustomObject]@{
                Name         = $obj.name # e.g. 'README.md'
                RelativePath = (Split-Path -Parent  $obj.path) # e.g. 'src\Samples\NetProjectionSample'
                Size         = $obj.size # File size
                Sha1         = $obj.Sha # Is this SHA1?!?
                Url          = $obj.download_url # full download url
            }
        }
        elseif ($obj.type -eq 'dir') {
            Invoke-RepoWalk -Uri $obj.url -AccessToken $AccessToken
        }
        else {
            throw "Unknown type $($obj.type)"
        }
    }
}

# e.g. 'https://github.com/microsoft/CsWinRT/tree/master/src/Samples/NetProjectionSample'
$info = @{
    Author     = $RepoPath.Segments[1] -replace '/', ''  # e.g. 'microsoft'
    Repository = $RepoPath.Segments[2] -replace '/', '' # e.g. 'CsWinRT'
    Branch     = $RepoPath.Segments[4] -replace '/', '' # e.g. 'master'
}

# e.g. 'src/Samples/NetProjectionSample'
$resourcePath = $RepoPath.Segments[-3..-1] -join ''

# e.g. https://api.github.com/repos/microsoft/CsWinRT/contents/src/Samples/NetProjectionSample?ref=master
$apiUri = 'https://api.github.com/repos/{0}/{1}/contents/{2}?ref={3}' -f $info['author'], $info['repository'], $resourcePath, $info['branch']

$downloadList = Invoke-RepoWalk -Uri $apiUri -AccessToken $AccessToken

foreach ($obj in $downloadList) {
    $targetFolder = Join-Path $Path $obj.RelativePath
    if (-not (Test-Path $targetFolder)) {
        mkdir $targetFolder | Out-Null
    }
    $targetFile = Join-Path $targetFolder $obj.Name

    $response = Invoke-GitHubWebRequest -Uri $obj.Url -OutFile $targetFile

    $item = Get-Item -LiteralPath $targetFile
    if ($item.Length -ne $obj.Size) {
        throw "Incorrect size for $targetFile : $($item.Length); expected: $($obj.Size)"
    }

    $hash = (Get-FileHash -LiteralPath $targetFile -Algorithm SHA1).Hash
    if ($hash -ne $obj.Sha1) {
        # throw "Incorrect hash for $targetFile : $hash; expected: $($obj.Sha1)"
    }
}