Re: refactoring basebackup.c

Hi,

Thanks for the feedback, I have incorporated the suggestions and
updated a new patch v2.

> I spent some time thinking about test coverage for the server-side
> backup code today and came up with the attached (v12-0003). It does an
> end-to-end test that exercises server-side backup and server-side
> compression and then untars the backup and validity-checks it using
> pg_verifybackup. In addition to being good test coverage for these
> patches, it also plugs a gap in the test coverage of pg_verifybackup,
> which currently has no test case that untars a tar-format backup and
> then verifies the result. I couldn't figure out a way to do that back
> at the time I was working on pg_verifybackup, because I didn't think
> we had any existing precedent for using 'tar' from a TAP test. But it
> was pointed out to me that we do, so I used that as the model for this
> test. It should be easy to generalize this test case to test lz4 and
> zstd as well, I think. But I guess we'll still need something
> different to test what your patch is doing.

I tried to add the test coverage for server side gzip compression with
plain format backup using pg_verifybackup. I have modified the test
to use a flag specific to plain format. If this flag is set then it takes a
plain format backup (with server compression enabled) and verifies
this using pg_verifybackup. I have updated (v2-0002) for the test
coverage.

> It's going to need some documentation changes, too.
yes, I am working on it.

Note: Before applying the patches, please apply Robert's v12 version
of the patches 0001, 0002 and 0003.

Thanks,
Dipesh