The .rakeTasks file is created by the IntelliJ IDEA Ruby plugin (and maybe using JetBrains Ruby-specific RubyMine , I'm not sure). As stated in the comment in the file:
It provides a list of Rake tasks that appear when you select Tools / Run Rake Task ... :

If you do not need to customize this list for any reason, you probably never have to edit the file. Personally, I exclude it from version control in my .gitignore , as well as the .ipr , .iml and .iws . (I could check this if I worked in a uniform IDEA store, but I don't know.)
source share