Add `Tap#command_file?` method.
Add `Tap#command_file?` method.

nandub/brew,Homebrew/brew,nandub/brew,nandub/brew,Linuxbrew/brew,DomT4/brew,reitermarkus/brew,reitermarkus/brew,sjackman/homebrew,JCount/brew,DomT4/brew,maxim-belkin/brew,sjackman/homebrew,mahori/brew,konqui/brew,EricFromCanada/brew,Homebrew/brew,EricFromCanada/brew,JCount/brew,JCount/brew,reitermarkus/brew,maxim-belkin/brew,DomT4/brew,vitorgalvao/brew,maxim-belkin/brew,EricFromCanada/brew,DomT4/brew,claui/brew,claui/brew,MikeMcQuaid/brew,MikeMcQuaid/brew,vitorgalvao/brew,mahori/brew,MikeMcQuaid/brew,sjackman/homebrew,Homebrew/brew,konqui/brew,claui/brew,Homebrew/brew,konqui/brew,claui/brew,Linuxbrew/brew,EricFromCanada/brew,Linuxbrew/brew,sjackman/homebrew,mahori/brew,MikeMcQuaid/brew,nandub/brew,vitorgalvao/brew,Linuxbrew/brew,mahori/brew,JCount/brew,reitermarkus/brew,konqui/brew,vitorgalvao/brew