Some feedback for Java 28 diffs

[liach]

1. I hope reflective preview APIs are marked from the regular ones: reflective ones can be used by non-preview programs to support running in a preview enabled runtime. (IdentityException is not reflective, all other preview APIs added by value objects are reflective)
2. There are preview class files in the JDK 28 distributions: See https://github.com/openjdk/jdk/blob/master/doc/value-class-preview.md, they are in META-INF/preview. You can maybe create a separate diff page or notation to indicate the difference between the META-INF/preview classes and the normal classes.

According to #141 your tool uses ASM, so I anticipate these tweaks to be relatively easy to your tool.

[marchof]

@liach Thanks for the feedback!

• Reflective preview APIs: Actually for now we have only a flag for "preview" in general. There are no subtypes in the data model.
• Preview classes: For now I decided to filter out the preview classes. Another option would be to let the preview classes replace the regular ones. I have not plans to create different diffs, this would add too much complexity and is probably not usable for the regular user.

With Java Almanac we want to give a good overview for the typical Java user. I wonder how many details can be added without scaring the main user group and keep the maintainance effort managable. Also the official JavaDoc has a pretty nice view of the preview features.

[liach]

I think providing a flag for "reflective" for preview APIs still make sense - these APIs can be used without --enable-preview. This is a major difference from the user point of view.