Minor version upgrades on PG13

[mattyw]

In d50c412 the base image for postgres 13 was changed from Debian:buster -> debian:bullseye. That means that if I had been using pg 13.4 and I wanted to upgrade to 13.5 then I would also be upgrading debian. OS upgrades can involve other headaches (e.g. #582)

My understanding from the thread in #582 is that I would have expected a 13-buster tag to be available. But this isn’t the case. Have I misunderstood the policy of minor version upgrades with respect to the OS base image or is this a bug?

[yosifkit]

The postgres:13-buster tag is still available, but is no longer rebuilt. The update to Bullseye did not have a known problem like the Stretch to Buster update had. We haven't seen another need for maintaining multiple Debian OS variants.