RFR: JDK-8260966 (fs) Consolidate Linux and macOS implementations of UserDefinedFileAttributeView

[Sebastian Stenzel]

> Am 03.02.2021 um 15:03 schrieb Alan Bateman <Alan.Bateman at oracle.com>:
> 
> Also moving/combining files and significantly changing them at the same time means the diffs are harder to read.

Just to save you some time: the PR has three separate commits, the first of them purely focused on moving stuff between files, actual code changes are in the two later commits.

I forgot to mention that.