Create a ghc-simple-patch-propose list? Re: Notes from Ben's "contribute to ghc" discussion

Moritz Angermann moritz at
Wed Sep 28 01:49:20 UTC 2016


I think it would be great if this was proposed formally. If we could
integrate this with the improved ghc development proposal[1], this
would be great! Or turn it into a separate proposal and remove the
similar parts from the one mentioned.

However, on the topic, I’d like to share a few thoughts:

Do we know how many of these GitHub Pull Requests we will actually
receive? If we migrate *everything* over to phabricator, isn’t that
just going to increase complexity for most of the minor pull request?

If someone fixes a spelling mistake or adds a short comment to
explain something in more detail, I see no reason why we need to employ
any heavy machinery and duplication across different tools. These, so
I would hope, would be trivially merged by a small team of ghc devs
watching the GitHub PR, especially if we don’t even know how much PRs
we will receive through GitHub.

On the other hand, if a PR is non-trivial (yes this is a bit of an
ambiguous term), I’m in favor of asking the person who issued the PR
to open an account with Phabricator[2], and run `$ arc diff origin/master`
on his branch, or let us know that he considers this too much effort
(and is willing to have someone else take over, should there be interest).

The reasoning behind this is the following: first of all it’s the persons
work, and unless someone else is willing to take it through the review
process, this is going to end up being a dead diff in phabricator which
adds additional overhead there. If there is not enough interest to follow
a simple few steps document on how to push a non-trivial patch to
phabricator, can we expect there to be sufficient interest in actually
following up on the review process?

I see this more as an onboarding problem than a continuous development
issue. Those who are in the phabricator workflow, will likely just
continue using it, no? I certainly would! However I might be browsing
ghc source on GH just because I don’t have that code locally available
right now and stumble on a spelling mistake, quickly use the editor
provided by GH and submit one of these trivial PRs.

Those who haven’t used phabricator yet, but are accustomed to the GH
PR Flow, would start there and then be gently guided towards using
phabricator and arc. We can do much better at explaining and showing
the phabricator and arc workflow.

In essence I’d like us see accepting GH Pull Requests and then do 
more data-driven on-demand incremental improvements, instead of trying
to go all out with excessive tooling.


[2]: See the contributing to ghc section in [1].
> On Sep 28, 2016, at 5:32 AM, Michael Sloan <mgsloan at> wrote:
> You're welcome Richard!  I look forward to helping make it happen.  In
> the other thread, Alexander Vershilov mentioned that we might instead
> consider the following more straightforward workflow:
> 0) Have a bot that watches github for PRs.
> 1) Submit whatever you want to github as a PR.
> 2) It will be automatically closed and migrated to Phabricator.  I
> would like it to automatically create a Phabricator account if you do
> not already have one.  The message from the bot will tell you about
> this action, and explain how to log in, perhaps even linking to
> resources about Phabricator.
> Is this worth it?  I think it is for the one-off cases.  However, you
> will have to be prepared that this means that people won't have
> arcanist setup, and therefore are less likely to actually iterate on
> their PR.  Perhaps we should extend this to the following:
> 3) Subsequent pushes to the branch for the PR will update the
> Phabricator differential as if you had pushed via Arcanist.  I think
> with this in place, we would have a fully streamlined system that
> allows people to use their familiar GitHub workflows, without needing
> to learn Arcanist.  Interactions would then still occur on , of
> course.
> This way, GHC HQ doesn't even need to learn to use this new "ghc-hub"
> tool!  Could name the bot that, though!
> Thoughts?  I think it would be great for this to be proposed formally
> soon so that we can make it happen.  I am eager to be able to use my
> normal git workflows, as my little experience with Arcanist induced
> some head-scratching.  Not the fault of the tool, just a result of
> lack of familiarity.
> -Michael
> On Tue, Sep 27, 2016 at 8:46 AM, Richard Eisenberg <rae at> wrote:
>> To sum up, this proposes the following:
>> 1. Allow PRs on GitHub.
>> 2. Michael Sloan to write a new utility, ghc-hub, which automates tasks interfacing between GitHub and Phab. This utility would be used only by GHC HQ and not by contributors.
>> 3. Small GitHub PRs can be merged directly, by ghc-hub.
>> 4. Larger GitHub PRs can be migrated to Phab by ghc-hub. The contributor would be issued a polite email explaining how to set up a Phab account to continue to follow their contribution.
>> Have I captured this accurately? If so, a resounding +1 from me. I’ve wanted exactly this for a while.
>> Is this worth sending through ghc-proposals?
>> Thanks for volunteering item (2), Michael!
>> Richard
>> -=-=-=-=-=-=-=-=-=-=-
>> Richard A. Eisenberg
>> Asst. Prof. of Computer Science
>> Bryn Mawr College
>> Bryn Mawr, PA, USA
>>> On Sep 26, 2016, at 11:09 PM, Manuel M T Chakravarty <chak at> wrote:
>>> Sounds like a great idea to me and might alleviate SimonM’s concerns about fragmentation of dev attention.
>>> Manuel
>>>> Michael Sloan <mgsloan at>:
>>>> Argh, sent too soon.  The first paragraph, revised:
>>>> This sounds like an ideal solution, Ben!  As has been discussed many
>>>> times before, GitHub has many users familiar with its interface.  By
>>>> allowing GitHub PRs, the initial contribution barrier will be lowered. If
>>>> there is an easy and straightforward process for shifting big patches
>>>> to Phabricator, then people who are regularly contributing via GitHub
>>>> PRs can be incrementally on-boarded to the Phabricator / Arcanist
>>>> workflow.
>>>> On Mon, Sep 26, 2016 at 12:07 PM, Michael Sloan <mgsloan at> wrote:
>>>>> This sounds like an ideal solution, Ben!  As has been discussed many
>>>>> times before, GitHub has many users familiar with its interface.  By
>>>>> allowing GitHub PRs, the initial contribution
>>>>> I think it would be acceptable for larger GitHub PRs to have some
>>>>> automated boilerplate response.  Ideally this would look like:
>>>>> """
>>>>> Thanks for making this patch!  I've turned this into a Phab
>>>>> Differential xxx and closed this PR.  Please create a differential
>>>>> account associated with your email address ..."
>>>>> """
>>>>> The email address can be automatically pulled from commit metadata.
>>>>> If one is absent, then this automated process isn't possible.  If it
>>>>> is present and
>>>>> So, I'm imagining a utility that interfaces between both GitHub and
>>>>> Phab,allowing the following commands:
>>>>> * "ghc-hub migrate" - migrates the
>>>>> patch to differential.  It may attempt to migrate body and title of
>>>>> the initial post, but lets not bother with migrating any review data.
>>>>> * "ghc-hub merge" - merges the
>>>>> patch.  This is used for merging small patches.  It would not do an
>>>>> automated push.  Maybe have "--push" also perform the push?  So like
>>>>> if you are on master, then "ghc-hub merge
>>>>> --push" would merge the patches and
>>>>> push to master.
>>>>> How does this sound?  I like the idea a lot, and would enjoy helping
>>>>> with implementation, time permitting.  I could possibly start hacking
>>>>> on it if others give the go ahead of "Yes, lets do that".
>>>>> -Michael
>>>>> On Mon, Sep 26, 2016 at 11:45 AM, Ben Gamari <ben at> wrote:
>>>>>> Carter Schonwald <carter.schonwald at> writes:
>>>>>>> In writing the following huge wall of text, I had and idea that I think
>>>>>>> many folks would find palatable:
>>>>>>> What if simple small patches (such as hypothetical drive by doc patches )
>>>>>>> had a mailing list where folks could email the simple / small patches as
>>>>>>> email attachments plus a body text that summarizes the patch, what it does,
>>>>>>> and why it's simple!
>>>>>> I completely agree that for small (e.g. documentation) patches our
>>>>>> current system is quite heavy. For this reason I suggested at ICFP that
>>>>>> we simply begin accepting small patches via GitHub pull requests.
>>>>>> Frankly, this is less work for me than merging patches from a mailing
>>>>>> list and I believe many users feel that GitHub is more accessible than a
>>>>>> mailing list.
>>>>>> The problem of course is what subset of patches do we want to allow to
>>>>>> be taken via GitHub. My suggested answer to that is any patch which, if
>>>>>> I were to write it myself, I would feel comfortable pushing directly to
>>>>>> the tree.
>>>>>> Then there is the question of what do we do with pull requests opened
>>>>>> which do not satisfy this criterion. In this case I would likely open a
>>>>>> Phabricator Differential with the pull request and close the pull
>>>>>> request with a link to the Diff. In the ideal case this will inspire the
>>>>>> contributor to join the review process on Phabricator; in the worst case
>>>>>> review turns up issues in the patch and the user gives up. Either way, at
>>>>>> least the contributor feels his patch has been seen and given the
>>>>>> attention it deserves.
>>>>>> Cheers,
>>>>>> - Ben
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