Implement a psql command.

[fluca1978]

Could be an implementation to avoid problems reported in issue #31.
The problem is that often there is a system-wide installed PostgreSQL
and/or client interfaces (psql). When using psql the user
gets the system wide that could be incompatible with the installed PostgreSQL
version from pgenv.
Using the psql command it is possible to run the version installed along-side
the PostgreSQL version used by pgenv.

[fluca1978]

Could it be worth making the "machinery" to allow for running any $PGDATA/bin executables?
I imagine something like:

$ pgenv use 12.0
$ pgenv cmd psql -U luca template1 # $PGDATA/bin/psql -U luca template1
$ pgenv cmd pg_config --libs            # $PGDATA/bin/pg_config --libs

so that even scripts outside the pgenv environment can get a kind of wrapper to execute "rightmost" commands against the database?

[theory]

Aren’t psql and pg_config already in the path after pgenv use 12.0?

[theory]

Could fix the original issue by pretending the pgenv path to the $PATH environment variable, rather than appending it, no?

[fluca1978]

Could fix the original issue by pretending the pgenv path to the $PATH environment variable, rather than appending it, no?

We don't modify PATH from within pgenv.
My personal usage is to have a fixed entry in my PATH that points to $PGENV_ROOT/pgsql/bin, so whenever I'm using a pgenv instance I've got preprended to any system wide path.
However, my doubt in prepending the path within the script is for external tools (e.g., testing) that could not have such variable inherited (and this is also true for your shell).
Kind of a chicken-egg problem for me to decide.

[fluca1978]

Another possible solution could be to warn the user, after a use or start if the current executable are not in the PATH. Or implement a kind of shell command that opens a new shell with all variables (PATH, PGDATA etc) set up correctly.

[theory]

Oh yeah, I have the path closer to the front of my $PATH variable. It think that's the way to do it. I like the idea of a warning on use or start.

[fluca1978]

See commit 5cb7d4c that warns the user if the path does not include the PGENV one or if it has another PostgreSQL binary path before.

I'm closing this PR.