RFR: Section on backporting [v7]

[Goetz Lindenmaier]

On Thu, 2 Dec 2021 19:34:09 GMT, Jesper Wilhelmsson <jwilhelm at openjdk.org> wrote:

>> Guidance on backporting.
>> Also moved "Backing out a change" to the testing section where I believe it fits better. This section is unchanged.
>
> Jesper Wilhelmsson has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fixes after review

Hi,

Yes, what happened is what Jesper describes.  A change that is good in head
and seems to be fine in an older release still can have problems not noticed
during standard testing.  I think so far we saw this twice in 11u.
Besides introducing a bug in the old release, it might also turn out
that the fix changes the behavior in an undesired way, e.g. breaking the standard.

Yes, replacing the backported-by-link by relates-to is what I would propose, too.
But should we change the type of issue from "Backport" to something  else, probably "Bug"?

And yes, it must be put into this documentation in a way that it is clear that this only applies to backouts of backported issues.

Anyways, thanks for picking this up!

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PR: https://git.openjdk.java.net/guide/pull/66