RFR: 8378876: jpackage: facilitate testing with mocks

[Alexey Semenyuk]

On Wed, 25 Feb 2026 02:14:33 GMT, Alexey Semenyuk <asemenyuk at openjdk.org> wrote:

> - Decouple jpackage implementation and test helpers from the current OS: replace OperatingSystem.current() calls with parameters and/or fields of type jdk.internal.util.OperatingSystem where feasible.
>  - Support running jpackage without making it run actual packaging. jpackage will exit after it parses the command line, validates the options, and builds a model.

@sashamatveev PTAL

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PR Comment: https://git.openjdk.org/jdk/pull/29908#issuecomment-3975424941