Looking ahead: proposed Hg forest consolidation for JDK 10

Erik Helin erik.helin at oracle.com
Wed Oct 12 14:48:03 UTC 2016

On 2016-10-11, Weijun Wang wrote:
> I am very glad to see history preserved. Is it possible to also merge the
> history for src files before modularization and after it with this magical
> script? I can call "hg log -f" on the command line but the web interface
> only shows partial history.

You mean that for example [0] only shows you the history up until the
modularization? Sorry, I don't know if this is possible in the Mercurial
web interface. The history is there in the repository, but as you've
already noticed, the web interface from `hg serve` does not use --follow
when showing the history for a file.

If you want to reach out to Mercurial upstream and see if it possible to
configure this, then you can find them at mercurial at mercurial-scm.org.


> Thanks
> Max
> On 10/11/2016 10:11, joe darcy wrote:
> >Hello,
> >
> >Looking ahead to JDK 10, a group of JDK engineers have been exploring
> >consolidating the large number of Hg repositories in an open JDK forest
> >to a single one with the goal of using the consolidated arrangement for
> >JDK 10.
> >
> >This message is being sent to jdk9-dev since a jdk10-dev alias to
> >discuss JDK 10 doesn't exist yet.
> >
> >A JEP describing the project has been submitted :
> >
> >    JDK-8167368: Consolidate JDK 10 OpenJDK repositories to a single
> >repository
> >    https://bugs.openjdk.java.net/browse/JDK-8167368
> >
> >The text of the JEP describes the motivation and current state of the
> >work in more detail, including proposed changes to the file layout.
> >Publication of the prototype consolidated repository is planned, but not
> >done yet. The email below has a list of additional anticipated questions
> >and answers.
> >
> >We feel this consolidated arrangement offers some significant structural
> >advantages for managing the JDK's source code and we are now asking for
> >feedback on this potential change. In particular, if you feel there is a
> >show-stopper problem with making this change, please let us know!
> >
> >I'd like to acknowledge the work of Stefan Sarne, Stuart Marks, and
> >Ingemar Aberg participating in discussions leading up to the prototype
> >and I'd like to especially recognize the contributions of Erik Helin for
> >savvy Hg manipulations and Erik Joelsson for skillful build wrangling in
> >this project.
> >
> >Please send initial comments by October 18, 2016.
> >
> >Cheers,
> >
> >-Joe
> >
> >Q: What about the set of forests for JDK 10? Are we going to have
> >master, dev, client, hotspot, etc. the same set as in 9?
> >A: That is a separate question from the repository consolidation, but
> >there will likely be simplifications here too. Discussions on that point
> >will come later.
> >
> >Q: I usually just build the code in repo X today. Will I have have to
> >build the *whole JDK* now?
> >A: Not necessarily. The same top-level build targets should work in the
> >consolidated forest.
> >
> >Q: Does disk usage change?
> >A: The total disk usage of the current forest compared to the
> >consolidated forest is nearly the same.
> >
> >Q: In more detail, how were the changesets imported?
> >A: The scripts used for the consolidation conversion are attached to the
> >JEP.
> >
> >Q: What happens to the Hg hashes?
> >A: The conversion scheme used in the prototype does *not* preserve Hg
> >hashes of changesets compared the current forests. However, the bug ids
> >are preserved and can be searched for. In addition, one or more
> >pre-consolidation forests should be archived in perpetuity so that URLs
> >in bug comments continue to work, etc.
> >
> >A mapping of the old hashes to the corresponding new hashes might be
> >generated and placed in the final new repo.
> >
> >Q: I'm allergic to tabs; what about jcheck?
> >A: If history is preserved, the checking done by jcheck needs to be
> >modified for the consolidated forest. One way to do this is to augment
> >the white lists used in jcheck with the conflicting changesets. This
> >approach may not be elegant, but it is effective and doesn't appear to
> >appreciably impact jcheck running times.
> >
> >Q: Will the future 9 update forest also have this consolidation
> >restructuring?
> >A: The script used to do the consolidation conversion is deterministic
> >and could be run to create the  9 update forest in the future at the
> >discretion of the 9 update team.
> >
> >Q: For backports for forwardports, will there be a script to translate
> >patch files across the consolidation boundary?
> >A: That work is planned, but not yet done; see JDK-8165623: Create patch
> >translator to update paths pre/post consolidation.
> >
> >Q: It's the 21st century and I develop using an IDE. That is still going
> >to work, right?
> >A: The prototype to date does include updating the various IDE support
> >files, but bug JDK-8167142 has been filed to track that work.
> >

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