mq: print "'foo' 'bar'", not "['foo', 'bar']" when showing guards
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.
ERROR: FIXME: This is a known failure of filelog.size for data starting with \1\n
OK.