[cfe-dev] GitHub anyone?

[Aaron Ballman via cfe-dev]

On Tue, May 31, 2016 at 3:31 PM, Renato Golin via cfe-dev
<cfe-dev at lists.llvm.org> wrote:
> Folks,
>
> There has been some discussion on IRC about SVN hosting and the perils
> of doing it ourselves. The consensus on the current discussion was
> that moving to a Git-only solution would have some disvantages, but
> many advantages. Furthermore, not hosting our own repos would save us
> a lot of headaches, admin costs and timed out connections.

Not everyone thinks git is a step forward. Please do not force people
to use a "git-only" solution.

> TL;DR: GitHub + git submodules [1] could replace all the functionality
> we have currently with SVN.
>
> (also GitLab, BitBucketc, etc).
>
> Here are some of the arguments made on IRC...
>
> 1. Due to SVN, we can't re-write history. If we use some GitHub
> properties [2], we could have the same effect.
>
> 2. Due to SVN, we have a mandatory time sequence, so commits go first
> in LLVM, then Clang (for example), and buildbots don't get lost. If we
> use submodules [1], we can have a similar relationship, but in a more
> explicit way, and the problem could be solved elegantly.

I actually consider the monotonically increasing revisions to be a
feature, but not sufficient to warrant a decision one way or the
other.

> 3. Some people still can only use SVN. For that, GitHub has an SVN
> interface [3] to the repositories.

Are we sure that github's svn integration works with common tools on
Windows, like TortoiseSVN?

> 4. We currently host our own SVN/Git, ViewVC and Klaus, Phabricator,
> etc. Not only this incurs in additional admin cost, but it also gets
> outdated, locally modified, and it needs to be backed up, etc. GitHub
> gives all that for us for free.
>
> 5. We can still use Bugzilla (and lock GitHub's own bug system), but
> we can also use GitHub's system to manage releases (it's actually
> quite good for that).
>
> 6. GitHub has automated testing of merge requests, meaning we can have
> pre-commit tests enabled on a set of fast bots, triggered by GitHub's
> own validation hooks. Even though that wouldn't cover everything,
> having a few pre-commit bots would considerably reduce the need to
> revert patches [citation needed].
>
> 7. With git submodules, we'd probably want to follow the same style we
> have today (llvm-projects/<prj>) instead of modelling how they look in
> tree (llvm/tools/clang still as a symlink).
>
> 8. Once we're solo Git, we can shop around *much* more easily. By
> using SVN, we're basically forced to host, or choose Source Forge.
> Using just Git, we can choose GitLab, BitBucket and many others, if
> GitHub is not appealing enough. Essentially, it doesn't matter where
> you are, the tools are good, there and largely replaceable [citation
> needed].
>
> What do people think? Any issue not covered that we should? How would
> that disrupt downstream users? Would it be a temporary disruption, but
> with long lasting benefits? Or will it just break everything for you?

I'm not opposed to moving to GitHub, provided its svn interface proves
to meet our needs. I am opposed to switching to a git-only solution,
but I'm unclear whether that's currently on the table or not.

~Aaron