RFR: 8268613: jar --validate should check inital entries of a JAR file [v5]

[Christian Stein]

On Thu, 13 Nov 2025 08:39:37 GMT, Christian Stein <cstein at openjdk.org> wrote:

>> Please review this change to include a validation check for expecting an optional JAR manifest entry being the first or second entry in JAR file. As the second entry, it must be only preceeded by an entry for the `META-INF/` directory.
>
> Christian Stein has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Use dedicated error messages

Thanks for the reviews! Tier1-3 tests look good, thus:

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PR Comment: https://git.openjdk.org/jdk/pull/28154#issuecomment-3540403447