GitHubCheckFiles.ps1

#environment variables to set in build config
$env:gh_user = "<github_user>"
$env:gh_repo = "<github_repo>"
$env:gh_token = "<your_sha>" #secure variable

$headers = @{
  "Authorization" = "Bearer $env:gh_token"
  "Content-type" = "application/json"
}

$commit = Invoke-RestMethod -Uri "https://api.github.com/repos/$env:gh_user/$env:gh_repo/commits/$env:APPVEYOR_REPO_COMMIT" -Headers $headers  -Method GET
Write-host "Files changed:"
$commit.files | % {$_.filename}
if (($commit.files.filename -like "*.md") -and !($commit.files.filename -notlike "*.md")) {
Write-host "only *.md files found, exiting..."; Exit-AppveyorBuild
}