UpdateBuildVersion.ps1

$token = $env:API_TOKEN #should be defined as scure variable

$headers = @{
  "Authorization" = "Bearer $token"
  "Content-type" = "application/json"
}

$apiURL = "https://ci.appveyor.com/api/projects/$env:APPVEYOR_ACCOUNT_NAME/$env:APPVEYOR_PROJECT_SLUG"
$history = Invoke-RestMethod -Uri "$apiURL/history?recordsNumber=2" -Headers $headers  -Method Get

$pomVersion = ([xml](Get-Content .\pom.xml)).project.version

if ($history.builds.Count -eq 2)
{
    $previousVersion = $history.builds[1].version
    $previousMajor = $previousVersion.Substring(0, $previousVersion.LastIndexOf("."))
    
    Write-Host "Previous major version: $previousMajor"
    Write-Host "Current version from pom.xml: $pomVersion"

    if ($previousMajor -ne $pomVersion)
    {
        Write-Warning "Major version has been changed, resetting build number"
        
        #reset current build number to 1 and next one to 2
        $env:APPVEYOR_BUILD_NUMBER = "1"

        $body = @{
        nextBuildNumber="2"
        }
        $body = $body | ConvertTo-Json
        Invoke-RestMethod -Uri "$apiURL/settings/build-number" -Headers $headers -Body $body  -Method Put        
    }
}

Update-AppveyorBuild -Version "$pomVersion.$env:APPVEYOR_BUILD_NUMBER"