RFR: 8322565 (zipfs) Files.setPosixPermissions should preserve 'external file attributes' bits [v4]

[Lance Andersen]

On Wed, 10 Jan 2024 18:29:40 GMT, Eirik Bjørsnøs <eirbjo at openjdk.org> wrote:

>> This PR suggests that `Files.setPosixPermissions`as implemented by `ZipFileSystem` should preserve the leading seven bits of the 'external file attributes' field. These bits contain the 'file type', 'setuid', 'setgid', and 'sticky' bits. These are unrelated to permissions and should not be modified by this operation.
>> 
>> The fix is to update `Entry.readCEN` to read all 16 bits instead of just the trailing 12 and to update `ZipFileSystem.setPermissions` to preserve the leading 7 bits when updating the trailing 9 permission-related bits of the `Entry.posixPerms` field.
>> 
>> The PR adds a new test `TestPosix.preserveRemainingBits()` which verifies that the leading 7 bits are not affected by `Files.setPosixPermissions`. This test also verifies that operations not related to POSIX, such as Files.setLastModifiedTime does not affect the 'external file attributes' value.
>> 
>> Note that this PR does not aim to preserve the leading seven bits for the case when `Files.setPosixPermissions` is called with a `null` permission set. (The implementation currently interprets this as a signal that the 'external file attributes'  should not be populated and the 'version made by' OS will be MSDOS instead of Unix)
>
> Eirik Bjørsnøs has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Convert TestPosix.java from testng to Junit 5

Thank you for the updates.  Looks good to go

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Marked as reviewed by lancea (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/17170#pullrequestreview-1814209477