After reviewing this, it appears to me that this is really just a very
verbose version of
archive_command = 'sleep $initialsleep; while test $(psql -AtX -c "select pg_xlogfile_name(something) < $$%f$$ collate
\"C\";") = t; sleep $sleep; done'
I think it might be better to just document this as an example. I don't
quite see the overhead of maintaining another tool justified.