I applaud the ingenuity on all levels in this patch. But it seems to me
that there is way too much backend knowledge encoded and/or duplicated
in a front-end program.
If this ends up shipping, it's going to be a massively popular tool. I
see it as a companion to pg_basebackup. So it should sort of work the
same way. One problem is that it doesn't use the replication protocol,
so the setup is going to be inconsistent with pg_basebackup. Maybe the
replication protocol could be extended to provide the required data.
Maybe something as simple as "give me this file" would work.
That might lose the local copy mode, but how important is that?
pg_basebackup doesn't have that mode. In any case, the documentation
doesn't explain this distinction. The option documentation is a bit
short in any case, but it's not clear that you can choose between local
and remote mode.
The test suite should probably be reimplemented in Perl. (I might be
able to help.) Again, ingenious, but it's very hard to follow the
sequence of what is being tested. And some Windows person is going to
complain. ;-)
Also, since you have been maintaining this tool for a while, what is the
effort for maintaining it from version to version?