Hey @tkimnguyen simples.
--plone option that I was referring to in ag (the "silver surfer"), just picks out the following file types to search:
.pt .cpt .metadata .cpy .py .xml .zcml
therefore it works with all versions of plone. It faster than grep -r (rgrep) anyway, but limiting it's search to these ploneish source files will speed it up even further. Though I must admit that on benchmarking them now, I do remember grep being a lot slower than this, not sure why....
$ time ag plonetoolbar-workfow-transition parts/omelette/ --follow --plone
689: 'li_class': 'plonetoolbar-workfow-transition'}
$ time grep -R plonetoolbar-workfow-transition parts/omelette/
Binary file parts/omelette/plone/app/contentmenu/menu.pyc matches
parts/omelette/plone/app/contentmenu/menu.py: 'li_class': 'plonetoolbar-workfow-transition'}
Keep up the good work!