JDK 20 enters Rampdown Phase One this Thursday

[Mark Reinhold]

JDK 20 enters Rampdown Phase One this coming Thursday, 8 December.
Changes intended for JDK 20 should be in the main-line repository
(https://github.com/openjdk/jdk) by 16:00 UTC on that day [1].

At that time we’ll fork the main line to the JDK 20 stabilization
repository, jdk20, and promote next week’s build and all remaining
JDK 20 builds from there.

We’ll semi-automatically merge changes pushed to jdk20 into the
main-line repository, as we have in previous feature-release
transitions.  This means that:

  - If you make a change in JDK 20 then you needn’t do any extra
    work to get it into the main line, though if a merge conflict
    arises then you might be asked to help resolve it.

  - If you need to make a change in both JDK 20 and the main line
    then just push it to JDK 20, and wait for the automatic merge
    to complete.

Changes pushed to the main line after 16:00 UTC this Thursday will
be bound for JDK 21 only, unless they’re subsequently back-ported
to JDK 20.

The Rampdown Phase One process is defined in JEP 3 [2].

To answer a potential FAQ, yet again: Now that we’ve moved over to
Git, why don’t we just use a branch in the main-line repository for
JDK 20 stabilization work?  A few of us have given that some thought,
but a change of that scope requires a fair amount of preparation and
coordination.  We hope to revisit that option for JDK 21.

- Mark


[1] https://time.is/1600_8_December_2022_in_UTC/Stockholm/London/Boston/San_Francisco?JDK_20_Rampdown_Phase_One
[2] https://openjdk.org/jeps/3