• install symbol-gen for Atom

  • restart Atom, enter your project and hit “cmd-alt-g”

  • add .tags to .gitignore

  • enter settings and add .tags to the Ignored Names

  • edit keybings of Atom:

    # add this to Atom's keymap.cson file:
    'atom-text-editor':
      'ctrl-alt-r': 'symbols-view:go-to-declaration'
    

Voila, click on a function, hit cmd-alt-r and jump the definition in a new tab