[FIX] 20-postgres-wait: avoid assuming you have permission to list da…

…tabase

entrypoint.d/20-postgres-wait

@@ -6,6 +6,16 @@ fi
 
 log INFO Waiting until postgres is listening at $PGHOST...
 while true; do
- psql --list > /dev/null 2>&1 && break
+ # If your postgres connection has minimal permissions, you should
+ # have at least an empty PGDATABASE and rights on this
+ # databases. The following will then succeed:
+ [ -n "$PGDATABASE" ] && echo "SELECT 1;" | psql "$PGDATABASE" > /dev/null 2>&1 && break
+
+ # if previous check failed (if PGDATABASE is set, but not yet
+ # created), you are in a more common scenario where odoo is
+ # expected to manage databases, and it should have the permissions
+ # to create it and will attempt to do it. In that case, you'll
+ # probably also have the permissions to list the databases.
+ psql -l > /dev/null 2>&1 && break
  sleep 1
 done