In tog's tree view, the page up/down handling is different from the
log and blame views as well as buggy.

There are two aspects to this:
(1) how many lines to move up or down
(2) which entry to select afterwards

Each of those views has a fixed header and a certain number of
visible lines below.

(1)
log and blame always move the full number of visible lines up and
down (assuming there are sufficient entries).

For page down, tree moves too many lines.  It uses the full window
height.  It needs to subtract the height of the fixed header.

For page up, tree moves one line too little.

(2)
If the nth visible entry is selected, log and blame will also select
the nth visible entry after scrolling up/down (assuming there are
sufficient entries).

For page down, tree behaves like log and blame.

For page up, tree always moves the selection to the first visible
entry.


There may be an additional logic bug in the tree view when going a
page up from the bottom; or maybe it's just the combination of the
two above, I'm not sure.

The ref view scroll logic was copied from the tree view, so it
shares these problems, along with the problem I already reported
that feels like an off-by-one somewhere.

-- 
Christian "naddy" Weisgerber                          naddy@mips.inka.de