tags: extract fnode retrieval into its own function
My main goal here is to be able to reuse this logic easily. As a side effect
this important logic is now insulated and the code is clearer.
%include map-cmdline.default
changeset = '{cset}{branches}{bookmarks}{tags}{lphase}{parents}{user}{ldate}{summary}\n'
changeset_verbose = '{cset}{branches}{bookmarks}{tags}{lphase}{parents}{user}{ldate}{lfiles}{lfile_copies_switch}{description}\n'