[llvm-dev] GitHub anyone?

Tanya Lattner via llvm-dev llvm-dev at lists.llvm.org
Thu Jun 2 09:21:20 PDT 2016

I personally find this email thread very hard to follow and read (this isn’t anyones fault.. its just a lot of replies). I am sure others do as well. I think it would be good to have a form/survey of some sort that can get feedback from users such as: who they are, how they use LLVM/contributions/etc,  if they are pro-github move, how it impacts them, etc. People could then submit their feedback in an organized way and we could get a better idea of how the community feels on the topic. 

I am happy to try to set something like this up.


> On Jun 2, 2016, at 8:48 AM, Renato Golin via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> A little summary...
> After a lot of discussion, I think we converged to a few issues that
> we need to solved before we finally decide to move.
> Firstly, the responses were overwhelmingly positive (I counted 20 of
> the ~25 people strongly supporting and another 2~3 weakly supporting).
> This is a good indication that the move could be very beneficial to
> the community as a whole, including downstream infrastructure, not
> just the reduction in upstream infrastructure admin costs.
> But that doesn't mean we have cleared up all the issues...
>    The benefits I gathered from the thread:
> * Infrastructure admin (not just server costs) is too expensive.
> We're not sysadmins and maintaining all the tools is a full time job.
> Volunteering works for odd problems, not for production services.
> Furthermore, most of the infrastructure we need is covered by
> GitHub/Lab/BB for free, on a scale that we would not have, even with a
> full time sysadmin. Gratis.
> * Having one official repository instead of two is beneficial to most
> developers. A lot of people (most people replying on this thread), use
> Git in addition to SVN. Git also seems to be used more on validation
> infrastructure than SVN (no example was put forward on this thread, at
> least), due to the simplicity of controlling the repository and the
> tools available. Reports of how teams decided to script Git to have
> linear behaviour instead of falling back to SVN are enlightening.
> * Git developer tooling is a growing trend, while SVN tooling is
> dying. This is not just about GUIs, but repository management (GitHub,
> GitLab, BitBucket, etc versus SourceForge), bisects, branches,
> remotes, hooks, workdir, submodules and all the new development seem
> to be done on Git nowadays, not SVN. Windows may be an odd one related
> to GUIs, but Visual Studio has Git integration and I hear it's similar
> to the other MSVC VCSs. GitHub's desktop interface seems pretty cool,
> too.
> * Web repositories make it *a lot* easier to create add-hoc pull
> requests by non-developers, which could boost the number of
> contributions and future contributors, as well as external projects
> using LLVM components.
> * GitHub's SVN RW interface has been reported to work well for
> simpler projects, but we need a more thorough examination before
> declare it good enough for our purposes.
> * All reports on the thread pointed that downstream infrastructure is
> already using Git, so that's one less problem to worry about if we do
> move.
>    The issues that were raised:
> * Co-dependent patches already break buildbots, but the sequential ID
> helps us identify and ignore. They will continue to break, even if we
> use git sub-modules, so that doesn't change much, but it will be
> harder to spot the issue. Server side hooks may help, as well as
> sub-modules.
> * Windows tooling may be an issue. There's a separate thread handling
> that part, so I won't cover it here. But I have to say it wasn't by a
> long shot a resonant problem. It may also have some problem with
> symlinks and in-tree checkouts (when interacting with llvm-projects
> and sub-modules).
> * Sub-modules may help with a lot of the current relationship we have
> inside the SVN repo, but it also has some problems. Namely they:
>   - require a modern version of git (1.7/1.9), but that's 2013 onward.
>   - may need additional server side scripting, but we can keep that
> in another repo to control it.
>   - won't replace SVN's monotonic IDs, but do we *really* need them?
> Sub-modules have a bad fame, I gather, but people in the thread
> reported success on using it to build validation and release
> infrastructure as well as doing bisects, checking out code, etc. We
> probably need some documentation on how to do these things, as well as
> some scripts to help people work out the dependencies (or use them).
> * GitHub/Lab/BB are not perfect. They have some interface issues, but
> nothing more serious than we already have on our current
> infrastructure. We'll probably have to keep Bugzilla (as GitHub's own
> is really poor), but we can replace all our repos (SVN, Git),
> visualisation tools (ViewVC, Klaus) and Phabricator.
> Of all those issues, Windows tooling is a minor problem that shouldn't
> impact decision that much and sub-modules need a lot of ironing out to
> be considered good enough. My *personal* take away is that sub-modules
> (or an alternative server side solution) is the only strong technical
> issue we need to solve before we decide.
>  How does a move look like?
> If we decide to move, the proposed schedule is something like this:
> STEP #1 : Pre Move
> 0. Update docs to mention the move, so people are aware the it's going on.
> 1. Register an official GitHub project with the LLVM foundation.
> 2. Setup another (read-only) mirror of llvm.org/git at this GitHub project
> 3. Make sure we have a la llvm-project-submodules setup in the
> official account. (Optional or necessary for the buildbots?)
> 4. Make sure bisecting with llvm-project-submodules is a good experience
> 5. Make sure no one has any blocker
> STEP #2 : Git Move
> 6. Update the buildbots to pick up updates and commits from the
> official git repository
> 7. Update Phabricator to pick up commits from the official git repository
> 8. Tell people living downstream to pick up commits from the official
> git repository
> 9. Give things time to settle. We could play some games like disabling
> the svn repository for a few hours on purpose so that people can test
> that their infrastructure has really become independent of the svn
> repository.
> ... Until this point nothing has changed for developers, it will just
> boil down to a lot of work for buildbot and other infrastructure
> owners ...
> STEP #3: Write Access Move
> 10. Collect peoples GitHub account information, give them push access.
> Ideally while still locking the GitHub repository somehow...
> 11. Switch SVN repository to read-only and allow pushes to the GitHub
> repository.
> 12. Mirror Git to SVN.
> STEP #4 : Post Move
> 13. Archive the SVN repository, if GitHub's SVN is good enough.
> 14. Review and update *all* LLVM documentation.
> 15. Review website links pointing to viewvc/klaus/phab etc. to point
> to GitHub instead.
> This is an adapted version of Matthias' and Mehdi's proposal, and it's
> not a final version in any way, but these are the basic things we need
> to worry about.
>    Steps from here...
> Aaron has started the Windows tooling thread, and if you have any
> comments, please follow from there. I suggest sub-modules supporters
> to start another thread to iron that out separately.
> Once those issues are resolved, we shall start another thread to
> finally take a decision to move or not.
> Thanks everyone!
> cheers,
> --renato
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