The filename "Jenkinsfile" is very inconvenient. In editor(s) like Intellij/Eclipse you have to override file type in order to get it working.
Consider renaming file "Jenkinsfile" to ".jenkins" (or ".jenkins.groovy") . It will ease interactions with projects and makes it fit into existing set of "file" rules.
Many others services like Jenkins use this concept: circle.yml, .travis.yaml etc.