Show case incremental compile with Questasim and the excellent emacs vhdl mode hierarchy sidebar.
#do
source sourceme.csh
#or if you are lucky enough to use bash
source sourceme.bash
make
emacs -q -l emacs_vhdl_project_config_gui.el rtl/top-e.vhd
touch rtl/block_bb-rtl-a.vhd
make
make conf