pgsql: Refactor error messages to reduce duplication - Mailing list pgsql-committers

Refactor error messages to reduce duplication

I also took the liberty of changing

        errmsg("COPY DEFAULT only available using COPY FROM")
to
        errmsg("COPY %s cannot be used with %s", "DEFAULT", "COPY TO")

because the original wording is unlike all other messages that indicate
option incompatibility.  This message was added by commit 9f8377f7a279
(16-era), in whose development thread there was no discussion on this
point.

Backpatch to 17.

Branch
------
REL_17_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/28b953f26343105ebf3a1a212092e2c3c0bb0914

Modified Files
--------------
src/backend/commands/copy.c         | 76 +++++++++++++++++++++++++++----------
src/backend/commands/copyfrom.c     | 10 +++--
src/backend/commands/copyto.c       |  5 ++-
src/test/regress/expected/copy2.out |  4 +-
4 files changed, 66 insertions(+), 29 deletions(-)