allow running precheck script

[mtbc]

Now that we routinely offer a sql/psql/new-version/old-version-precheck.sql perhaps omego could support doing a precheck.

[manics]

Is *-precheck.sql guaranteed to be read-only, now and in future?

[joshmoore]

Logically, I'd say yes, but we should document this. For me, this is a process of adding "API" to the sql/ directory.

[mtbc]

Agreed. I plan to always end it with ROLLBACK;. At very worst we may consider recording in dbpatch that it was run.