RFR: Section on backporting [v2]

[Jesper Wilhelmsson]

On Tue, 23 Nov 2021 17:28:59 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> Jesper Wilhelmsson has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fixes after reviews
>
> src/index.md line 1492:
> 
>> 1490: In general there is no need to create backport issues in JBS manually. All work that is done in JBS in preparation for a backport (requesting approvals etc) is done in the main issue. The backport issue will be created automatically by the bots when you integrate the change to the source code repository.
>> 1491: 
>> 1492: There can be cases where it is motivated to create a backport issue before the fix is done. In these cases set the fix version of the backport to `N-pool`, where `N` is the release train the backport is targeting. E.g. `17-pool`
> 
> You might want to add a sentence saying that if a backport record is created ahead of time, all work done in JBS is still done in the main issue.

Thank you for reviewing! Added the sentence.

-------------

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