How much file list kept during incremental recursion?

[Matt McCutchen]

Wayne,

Sven's note made me curious about how much incremental recursion
actually reduces memory usage, so I'm asking: How much of the file
list do the rsync processes hold in memory at any one time in
incremental recursion mode?  Just the active file-list chunk(s) and
their ancestors?  Or does rsync store directories or even all files
permanently until the end of the run?  I could probably slog through
the source and figure out the answer, but you must know it off the top
of your head.

Matt