grouping in menu

[amonks]

idea from @jellevandenhooff:

Some grouping or dependency information in the TUI sidebar. Could the top-level task(s) somehow stand out? I suppose a natural hierarchy is tricky to make when a dependency is used by many different tasks.

[amonks]

yes yes yes!

as part of the Big Forthcoming Change, I'd like to add a task-browser UI if you invoke run with no arguments (#57).

But instead of making a separate task-browsing mode, I expect to always* show all tasks in the left menu, with sections for (1) requested/root tasks, (2) active/dependency tasks, and (3) inactive tasks, so that you can select an inactive task and start it along with its dependencies.

I've gotten as far as making the runner support add/remove-root operations (I expect this new API to ship in 1.0), but I haven't gotten into the ui work yet (this may end up following after 1.0).

*maybe not always visible but always available, subject to Responsive Design