Install extension to a pgrx-managed Postgres instance

[SergeiPatiakin]

It would be nice to have a pgrx command to install an extension into pgrx-managed instance $PG_MAJOR, without starting that instance or starting psql.

• cargo pgrx install installs to wherever pg_config points, not necessarily a pgrx-managed instance. A shell command like cargo pgrx install "$PGRX_HOME"/$PG_MAJOR*/pgrx-install/bin/pg_config does what I want, but it would be nice if it was a built-in command.
• cargo run $PG_MAJOR does what I want, but it also starts the instance and psql.

The syntax for this improvement could be:

• a new optional PG_VERSION positional argument in cargo pgrx install (i.e. it would become cargo pgrx install [OPTIONS] [PG_VERSION])
• a new option in cargo pgrx run, but I can't think of an appropriate name. cargo pgrx run $PG_MAJOR --install-only?

Does this makes sense? Maybe it's already built in but I couldn't find it?

[eeeebbbbrrrr]

a new option in cargo pgrx run, but I can't think of an appropriate name. cargo pgrx run $PG_MAJOR --install-only

This one seems reasonable. Would you like to PR it?

[SergeiPatiakin]

Yes, I can give it a go

[YohDeadfall]

@eeeebbbbrrrr, it's completed by #1988.