Backup-VSTSInstance.ps1

param

(
    [Parameter(Mandatory = $true)]
    [string]$pat,

    [Parameter(Mandatory = $true)]
    [string]$instance,

    [Parameter(Mandatory = $true)]
    [string]$backuppath
)

function Get-WebClient
{
 param
    (
        [string]$pat,
        [string]$contentType = "application/json"
    )

    $wc = New-Object System.Net.WebClient
    $wc.Headers["Content-Type"] = $contentType
    
    $pair = ":${pat}"
    $bytes = [System.Text.Encoding]::ASCII.GetBytes($pair)
    $base64 = [System.Convert]::ToBase64String($bytes)
    $wc.Headers.Add("Authorization","Basic $base64");
    $wc
}

function Get-AuthenticatedGitUri
{
    param
    (
        $uri,
        $token
    )

    $colonSlashSlash = "://";
    $protocol = $uri.substring(0, $uri.indexOf($colonSlashSlash))
    $address = $uri.substring($uri.indexOf($colonSlashSlash) + $colonSlashSlash.length)
    return $protocol + $colonSlashSlash + $token + "@" + $address
}

function Get-TeamProjectList
{
 param
    (
        $tfsUri ,
        $pat
    )
    
    write-host "Getting team project details for $tfsUri " -ForegroundColor Green

    $wc = Get-WebClient -pat $pat
        
    $uri = "$($tfsUri)/_apis/projects?api-version=1.0"

    $jsondata = $wc.DownloadString($uri) | ConvertFrom-Json 
    $jsondata.value | select-object -property @{Name="Name"; Expression = {$_.name}}
}

function Get-GitRepo
{
    param
    (
        $name,
        $uri,
        $backuppath,
        $pat
    )

    write-host "Cloning Git Repo $name into $backuppath"
    Set-Location -Path $backuppath
    $fixeduri = Get-AuthenticatedGitUri -uri $uri -token $pat
    # Git send info to stderr it should not, redirecting it 
    & git clone $fixeduri 2>&1 | % { $_.ToString() }
}

function Get-TfvcContent
{
 param
    (
        $instance ,
        $pat,
        $projectname,
        $backuppath

    )

    Write-Host "  Downloading TFVC ZIP for project $projectname"
    
    $url = "https://$instance.visualstudio.com/$projectname/_apis/tfvc/Items?path=%24%2F$projectname&versionDescriptor%5BversionType%5D=5&%24format=zip&api-version=4.1-preview.1"
    $file = "$backuppath\TFVC-$projectname.zip"
    
    $wc = Get-WebClient -pat $pat
    try
    {
        $wc.DownloadFile($url,$file)
        Write-Host "    Finished TFVC content download"
    } catch 
    {
        Write-Host "    No TFVC content for project"
    }
}

function Get-GitBranchesForRepo
{
 param
    (
        $instance ,
        $pat,
        $projectname,
        $repo

    )

    Write-Host "  Getting branches repo $repo in project $projectname"
    
    $url = "https://$instance.visualstudio.com/$projectname/_apis/git/repositories/$repo/stats/branches?api-version=4.1"
    
    try
    {
        $wc = Get-WebClient -pat $pat
        $jsondata = $wc.DownloadString($url) | ConvertFrom-Json 
        $jsondata.value | select-object -property @{Name="Name"; Expression = {$_.name}}
    } catch
    {
          Write-Host "    No Repos for project"
    }
}

function Get-GitContent
{
 param
    (
        $instance ,
        $pat,
        $projectname,
        $repo,
        $backuppath,
        $branch

    )

    Write-Host "  Downloading GIT ZIP for branch $branch in repo $repo in project $projectname"
    
    # A branch name may have a / in it which is not a valid file name
    $fixedbranch = $branch -replace "/", "-" 
    $url = "https://$instance.visualstudio.com/$projectname/_apis/git/repositories/$repo/Items?path=%2F&versionDescriptor%5BversionOptions%5D=0&versionDescriptor%5BversionType%5D=0&versionDescriptor%5Bversion%5D=$branch&%24format=zip&api-version=4.1-preview.1"
    $file = "$backuppath\GIT-$projectname-$repo-$fixedbranch.zip"
    
    $wc = Get-WebClient -pat $pat
    $wc.DownloadFile($url,$file)
    Write-Host "    Finished GIT content download"
}


function Git-GetRepos
{
 param
    (
        $instance,
        $pat,
        $projectname
    )
    

    $url = "https://$instance.visualstudio.com/$projectname/_apis/git/repositories?api-version=4.1"
    $wc = Get-WebClient -pat $pat

    $jsondata = $wc.DownloadString($url) | ConvertFrom-Json 
    $jsondata.value | select-object -property @{Name="Name"; Expression = {$_.name}},@{Name="RemoteUrl"; Expression = {$_.remoteUrl}}

}


function Add-Folder
{
param
    (
        $path
    )

    if ((Test-Path($path)) -eq $false)
    {
        Write-Host "  Creating folder $path"
        New-Item -ItemType directory -Path $path -force | Out-Null
    } else 
    {
        Write-Host "  Cleaning folder $path"
        Remove-Item "$path" -Force -Recurse
    }

}


$projects = Get-TeamProjectList -pat $pat -tfsUri "https://$instance.visualstudio.com"

$instancepath = Join-Path -Path $backuppath -ChildPath $instance
Add-Folder -path $instancepath

foreach ($project in $projects)
{
    $name = $project.Name
    Write-Host "Procesing project $name" -ForegroundColor Green

    $projectpath = Join-Path -Path $instancepath -ChildPath $name
    Add-Folder -path $projectpath
   
    $repos = Git-GetRepos -instance $instance -pat $pat -projectname $name 

    if ($repos.count -eq 0)
    {
        Write-Host "    No GIT content for project"
    } else
    {
        foreach ($repo in $repos)
        {
            Get-GitRepo -name $repo.Name -uri $repo.remoteurl -backuppath $projectpath -pat $pat
                   
            # If you wish to get the repo's as simple ZIPs
            # $branches = Get-GitBranchesForRepo -instance $instance -pat $pat -projectname $name -repo $repo.Name
            # foreach ($branch in $branches)
            # {
            #    Get-GitContent -instance $instance -pat $pat -projectname $name -path $projectpath -repo $repo.Name -branch $branch.Name
            # }
        }
    }
    
    Get-TfvcContent -instance $instance -pat $pat -projectname $name -path $projectpath 
}

Write-Host "`n"

Line 232, it should be -backuppath instead of -path
Otherwise Get-TfvcContent and Get-GitRepo will get an issue to save the backup.

With the new rebranding to Azure DevOPS... all URL should be changed with this syntax:
Replace All
"https://$instance.visualstudio.com"
By
"https://dev.azure.com/$instance"