Public/New-PSGitLabBranch.ps1

function New-PSGitLabBranch {
    <#
    .SYNOPSIS
        A short one-line action-based description, e.g. 'Tests if a function is valid'
    .DESCRIPTION
        A longer description of the function, its purpose, common use cases, etc.
    .NOTES
        Information or caveats about the function e.g. 'This function is not supported in Linux'
    .LINK
        Specify a URI to a help page, this will show when Get-Help -Online is used.
    .EXAMPLE
        New-PSGitLabBranch -OrganizationName 'gitlab.com' -PrivateToken 'XXXXXX' -ProjectFullPath 'group/projectfullpath' -BranchName 'branchname' -SourceBranchName 'main'
        Explanation of the function or its result. You can include multiple examples with additional .EXAMPLE lines
    #>

    
    
    [CmdletBinding()]
    param (
        [string]
        $OrganizationName,

        [string]
        $PrivateToken,

        [string]
        $ProjectFullPath,

        [string]
        $BranchName,

        [string]
        $SourceBranchName
    )
    
    $query = @{
        query = @"
            mutation {
                createBranch(input: {projectPath: "$($ProjectFullPath)", name: "$($BranchName)", ref: "$($SourceBranchName)"}) {
                branch {
                    name
                }
                errors
                }
            }
                     
"@

    } | ConvertTo-Json 

    $response = Invoke-RestMethod -Uri "https://$($OrganizationName)/api/graphql" -Headers @{Authorization = "Bearer $($PrivateToken)" } -Method Post -Body $query -ContentType 'application/json' 
    
    if ($response.errors) {
        Write-Error -Message $($response.errors.message) -InformationAction Continue
    }
    else {
        $response.data.createBranch.branch
    }
}