The internal list representation of guards was leaking into the
output. The guards were always printed using repr(guard) and that
style was kept.
When "hg qguard -l" prints several guards for a patch, it does so by
joining the names with " " and that style was used for the error
messages too.
We can't assume that all pushable patches early in the series have already been
applied. If a hg qselect is done while you already have patches applied, some
patches with guards may now be pushable, even though they come earlier in the
series.
So instead of checking only applied patches, explicitly check where we are in
the series against the position of the patch we want to qpush to.
