darcs: ensure whole darcs query manifest output is consumed

darcs: ensure whole darcs query manifest output is consumed

By a stroke of luck, after a long & full day, I happened to
remember that in the morning, I had seen someone on irc mention
that darcs query manifest doesn't like it if its full output
is not consumed.

So contrary to the usual case where bug reports sent via irc are like
messages written in sand before the new tide, this one was seen and
fixed.

(But use http://ikiwiki.info/bugs/ next time!)