An ability to run sh/sql each start (like docker-entrypoint-initdb.d)

[viatsyshyn]

For example /docker-entrypoint.d/ folder with scripts that execute each start (maintenance, db schema migrations, health checks, etc). DB server should be started like in case with docker-entrypoint-initdb.d

[tianon]

See #496, which when finalized will allow you to implement this without much code (I swear there was another issue about this very thing, but I can't find it right now 😅).

[viatsyshyn]

@tianon, yes this definitely addresses my case. Hope that makes to master soon. Also I'd vote for quick way to drop in a script (like docker-entrypoint-always.d).