pgsql: pg_upgrade: Add --copy option

pg_upgrade: Add --copy option

This option selects the default transfer mode. Having an explicit
option is handy to make scripts and tests more explicit. It also
makes it easier to talk about a "copy" mode rather than "the default
mode" or something like that, since until now the default mode didn't
have an externally visible name.

Reviewed-by: Daniel Gustafsson <daniel(at)yesql(dot)se>
Reviewed-by: Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>
Discussion: https://www.postgresql.org/message-id/flat/50a97009-8ff9-ca4d-a0f6-6086a6775a5b%40enterprisedb.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/746915c6866953506379e996ce5198bc9e9e5b94

Modified Files
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doc/src/sgml/ref/pgupgrade.sgml | 10 ++++++++++
src/bin/pg_upgrade/option.c | 6 ++++++
2 files changed, 16 insertions(+)