Repository? -- How to keep JDK 10 up to date with changes in JDK 9 until JDK 9 GA?

[Erik Helin]

On 12/03/2016 02:26 AM, Joseph D. Darcy wrote:
> Therefore, I think a different approach should be used this time around.
> Rather than protracted cherry-picking, I think changes in JDK 9 promoted
> builds should be merged into JDK 10, at least until JDK 9 ZBB.
>
> Comments?

I don't really follow how this makes backporting easier. If the code 
mostly stays the same in JDK 10, then backporting is relatively easy 
(since the patch for JDK 10 will mostly just apply to JDK 9). If this is 
the case, then re-merging the changes from JDK 9 into JDK 10 will also 
be relatively easy (again, the assumption is that the code in JDK 10 
hasn't changed much).

Then comes the other, hard case: I have made large, sweeping changes to 
the code in JDK 10 (there already such changes being worked on). In that 
case, backporting will be difficult: a patch for JDK 10 will *not* apply 
in JDK 9, the classes, files and/or methods might not even exist in JDK 
9. I don't see how merging the changes made to JDK 9 into JDK 10 will 
help here? That merge will be very hard to get right, if not impossible 
(again, under the assumption that a lot of code has been changed).

In more abstract terms: if the source code for JDK 10 and JDK 9 
significantly diverges, will trying to merge the changes from JDK 9 into 
JDK 10 help? Will it even be possible?

Please note that I'm not talking about changes to the version control 
system, such as unifying the forest. I'm trying to describe large 
refactorings of the source code that are independent of the kind of 
version control system used.

Thanks,
Erik

> Thanks,
>
> -Joe
>
> [1] http://openjdk.java.net/projects/jdk9/
>
> [2]
> http://mail.openjdk.java.net/pipermail/jdk9-dev/2013-December/000146.html
>
> [3] http://mail.openjdk.java.net/pipermail/announce/2014-March/000166.html
>
> [4]
> http://mail.openjdk.java.net/pipermail/jdk8-dev/2013-December/003766.html,
> http://mail.openjdk.java.net/pipermail/jdk9-dev/2013-December/000158.html