Review request: jar tool to transform a plain jar file to a modular jar

[Alan Bateman]

Mandy Chung wrote:
>  Updated webrev:
>     http://cr.openjdk.java.net/~mchung/jigsaw/webrevs/modularize-jar.01/
I see Sherman has done a detailed review on the sun.tools.jar changes.

I'm looking at additions to java.util.jar.JarFile and I'm wondering if 
the class or method descriptions should having wording to explain that a 
JAR file can have a legacy manifest and also a module-info. I also 
wonder if we will need to update the JAR specification too. Minor 
comment is that the new methods should have @since 1.8.

A passing comment on SimpleLibrary lines 980-988 is that they could be 
replaced with Files.write(is, md.toPath().resolve("info"));

The sun.tools.jar.ModuleInfo class looks very useful and I'm sure we 
will have other places that need to generate module-info classes. Would 
it make sense to put it in org.openjdk.jigsaw? If so then it would be 
good to have it support requires optional too.

-Alan.