New version aims to simplify main vault and support deeper merging
strategies.  We'll see...

Another proof that 640KB won't be enough for everybody.

This should enable reading upper parts of window even while the output
is still being produced (tail -f).

IOW, the auto-scroll is disabled after scrolling back manually using
S-PageUp or S-PageDown, and re-enabled on another keypress such as
typing when a prompt is expected at the bottom.

Not particularly bright idea.

With transition to tiled window managers, tabbed makes less sense.