b0124c4fb0
The current logic for curl_download tries to restart any existing partial download, but this fails for some servers when the file is already fully downloaded, returning a status code 416. This updates the function to check for the file being already downloaded and if so bails early. The following command used to fail when run more than once but now works as expected: ``` brew cask info https://raw.githubusercontent.com/homebrew/homebrew-cask/master/Casks/docker.rb ```