RFR: 827: Copyright year differences can be regarded as a clean backport [v3]

[Zhao Song]

On Tue, 12 Sep 2023 20:47:54 GMT, Zhao Song <zsong at openjdk.org> wrote:

>> As many users requested, when determining whether a backport is clean, our bot should ignore copyright year difference.
>
> Zhao Song has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - fix whitespace issue
>  - add unit test

Thanks for the review!

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PR Comment: https://git.openjdk.org/skara/pull/1556#issuecomment-1728438813