pg_dumpall also has –exclude-database=pattern and –no-comments option doesn't that qualify it to benefits from this feature? And please add a test case for this option
This patch is related to pg_dump (in this moment), so pg_dumpall options are out of scope.
I am not sure if pg_dumpall needs this functionality - maybe, but I can use bash or some similar for implementation of this feature. There is no requirement to do it all necessary work under one transaction, one snapshot.
For pg_dump can be used different format, because it uses different granularity. Some like "{+/-} dbname"
"--no-comments" is a global parameter without arguments. I don't understand how this parameter can be related to this feature?