Обсуждение: pgsql: Rewrite comments in replication slot advance implementation

Rewrite comments in replication slot advance implementation

The code added by 9c7d06d60680 was a bit obscure; clarify that by
rewriting the comments.  Lack of clarity has already caused bugs, so
it's a worthy goal.

Co-authored-by: Arseny Sher <a.sher@postgrespro.ru>
Co-authored-by: Michaël Paquier <michael@paquier.xyz>
Co-authored-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Petr Jelínek <petr.jelinek@2ndquadrant.com>
Discussion: https://postgr.es/m/87y3fgoyrn.fsf@ars-thinkpad

Branch
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REL_11_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/96bd49437cca5d7a6e4024c602a9fdbdbf7c7433

Modified Files
--------------
src/backend/replication/logical/logical.c |  5 +-
src/backend/replication/slotfuncs.c       | 78 ++++++++++++++++++++-----------
2 files changed, 54 insertions(+), 29 deletions(-)