Manage System Parameters

• headTimeout：If a repos does not respond to a HEAD request in this timeout, this request is taken as failed. This parameter should have the format that scala.concurrent.duration.Duration.apply accepts, e.g. 3 seconds
• headRetryTimes：If no upstream repo answered 200 for a HEAD request, and not all of the response are 404, then resend requests to the failed upstream，this is max retry times before giving up.
• extraResources：If other dependency management tools such as maven/gradle have been used, there will be some artifacts that are already cached in local file system. To make use of these artifacts, includes the cache directory in extraResources. Separate multiple extra resource directories with : The default config has a single extraResources as $HOME/.m2/repository