Change default branch on all your Github repos

ChangeDefaultBranch.ps1

$token = <your github personal token>
$headers = @{"Authorization"="token $token"}
$body = (ConvertTo-Json @{ default_branch='main' })

Write-Host "Fetching repo list"
[Console]::Out.Flush()
$repos = Invoke-RestMethod -Headers $headers -Method GET -Uri "https://api.github.com/user/repos?type=owner&per_page=80"
foreach($repo in $repos) {
    if($repo.default_branch -eq "master")
    {
        $branch = $null
        $branch = Invoke-RestMethod -Headers $headers -Method GET -Uri "$($repo.url)/branches/main"
        if ($branch -ne $null) {
            Write-Host "Updating default branch to main for $($repo.name)"
            [Console]::Out.Flush()

            $result = Invoke-RestMethod -Headers $headers -Method PATCH -Uri $repo.url -Body $body
            Write-Host "New default branch is $($result.default_branch)"
            [Console]::Out.Flush()
        }
    }
}