RFR: 2304: /backport jdk23 should provide a more helpful message [v3]

[Erik Joelsson]

On Wed, 3 Jul 2024 17:28:07 GMT, Zhao Song <zsong at openjdk.org> wrote:

>> This patch is trying to improve the bot's replies of backport command.
>> 
>> 1. If the user issued `/backport jdkX`, the bot would check if there is a `jdkX` branch in current repo, if so, the bot would tell the user that to target a backport to `jdkX` branch in current repo, he should issue `/backport :jdkX`.
>> 
>> 2. When user specified branch name in the command but the branch doesn't exist, the bot will list 10 branch names in the target repo, the branch names are just sorted in reverse alphabetical order, so we can't guarantee they are the most relevant ones.
>
> Zhao Song has updated the pull request incrementally with one additional commit since the last revision:
> 
>   review comment

Marked as reviewed by erikj (Lead).

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PR Review: https://git.openjdk.org/skara/pull/1667#pullrequestreview-2157019938