[llvm-dev] Enable Contributions Through Pull-request For LLVM

Thu Nov 7 12:58:38 PST 2019

Hi all,

from me also a big -1 due to the many reasons others have already mentioned (especially Roman).

I want to give an additional consideration: One thing I always liked at the Phabricator workflow is that it is based on diffs only. Pull requests are no git but a Github feature. That means that by adopting Github's pull request workflow you essentially adopt a proprietary feature that will only work on this specific proprietary platform. Phabricator is essentially just a convenient tool to review plain diffs (first class git citizens) and the fact that it works relatively independent of the underlying repository is something I really like.

My -1 holds even more since I personally find the Phabricator workflow to be very good in particular as it even got easier since arcanist works perfectly fine with git and the complete arc workflow can be used since the migration. In contrast to e.g. Bugzilla where we searched for an alternative since the current situation was bad, this is not the case for Phabricator.

Regarding the hurdle for new contributors: Is the Github workflow really easier or is it just the case that more people have Github accounts? As I've already said I think the current workflow is absolutely fine and really intuitive. We should however make our contribution guide more welcoming and complete (I know, there are people working on this which is awesome!).

    David

> On 7. Nov 2019, at 10:53, Aaron Ballman via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> 
> On Thu, Nov 7, 2019 at 3:09 AM Roman Lebedev via llvm-dev
> <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
>> 
>> Strong -1 personally.
> 
> Likewise, for many of the same reasons detailed below.
> 
> ~Aaron
> 
>> * What is the endgoal? To fully kill phab and move to github pullrequests?
>>  it might be best to discuss *that* first. (did i miss an RFC?)
>> * Separation of attention - does everyone who cares
>>  now has to also look at pull requests for reviews;
>>  or should they be exempt from general review attention?
>> * For me personally after using phabricator, github now seems
>>  extremely crude, laggy, limited. To name a few:
>>  * There is no way to see previous version of the patch.
>>    I don't think there is any way to disable force-push for PR's.
>>    While this is only 'slightly' limiting for the reviewer,
>>    this can be more limiting for the author - how do i go back
>>    to previous revision? I can't, i need to maintain a copy
>>    of every branch i pushed manually.
>>  * Impossible to chain reviews - a PR diff can only be made
>>    on top of git master branch. Any non-trivial change consists of
>>    separable PR's. Now either one will only be able to submit
>>    dependent PR after the prereqs are merged, or the diff will be
>>    impossible to read.
>>  * Does not load large diffs by default.
>>    That caught me by surprise several times
>>    when i was searching for something.
>>  * No diffs in mail - *super* inconvenient.
>>    One has to open each pr in browser (or fetch via git etc etc)
>>  * Github is an official US-based commercial organisation.
>>    It *has* to follow U.S. export law. In particular i'm thinking of
>>      https://techcrunch.com/2019/07/29/github-ban-sanctioned-countries/
>>      https://github.com/tkashkin/GameHub/issues/289
>>    Does phabricator already have such restrictions, blocks?
>>    If not, wouldn't you say adding such restrictions is not being
>>    more open for contributors?
>>    What happens when, in not so long in the future, the entirety of, say,
>>    china or russian federation is blocked as such?
>>  * Same question can be asked about internet "iron" curtains
>>    certain (*cough*) countries are raising. That also has already happened
>>    before (and *will* happen again), and i was personally affected:
>>      https://en.wikipedia.org/wiki/Censorship_of_GitHub#Russia
>>    I don't recall that happening to phabricator yet.
>>    I fail to see how that is more contributor-friendly.
>>  * Not sure anyone cares, but while using github as main git
>>    repository "mirror" is perfectly fine - git is distributed, only canonical
>>    write-repo would be affected anything bad happen. But that isn't the case
>>    for reviews, issues; as it has been discussed in the "let's migrate bugzilla
>>    to github issues", it is far more involved.
>>  * What about DMCA? Not sure how this is currently handled.
>>  * UI feels laggy. Not much to add here, pretty subjective.
>>  * I'm sure i'm missing a few.
>> 
>> The github does come with it's benefits, sure:
>> * It is *simpler* to preserve git commit author.
>>  Currently one has to ask the author for the "Author: e at ma.il" line,
>>  and do `git commit --amend --author="<>"`.
>> * @mention is wide-r-reaching - whole github, not just llvm phabricator
>> * No more "phabricator disk full" issues
>> * ???
>> 
>> TLDR: such migration lowers the bar for new, first time,
>> unestabilished contributors, but i personally feel it *significantly*
>> raises the bar for the existing contributors, reviewers.
>> We don't live in perfect world. Aspirational goals are aspirational.
>> They should be attempted to be reached, but they shouldn't shadow and
>> overweight, take over the main goal of the LLVM project.
>> 
>> Personally, i don't see that benefits out-/over- weight the drawbacks.
>> 
>> Roman.
>> 
>> On Thu, Nov 7, 2019 at 8:32 AM Mehdi AMINI via llvm-dev
>> <llvm-dev at lists.llvm.org> wrote:
>>> 
>>> Hi all,
>>> 
>>> Now that we're on GitHub, we can discuss about pull-requests.
>>> I'd like to propose to enable pull-request on GitHub, as a first step as an experimental channel alongside the existing methods for contributing to LLVM.
>>> This would allow to find workflow issues and address them, and also LLVM contributors in general to start getting familiar with pull-requests without committing to switching to pull-requests immediately. The community should evaluate after a few months what would the next steps be.
>>> 
>>> GitHub pull-requests is the natural way to contribute to project hosted on GitHub: this feature is so core to GitHub that there is no option to disable it!
>>> 
>>> The current proposal is to allow to integrate contributions to the LLVM project directly from pull-requests. In particular the exact setup would be the following:
>>> 
>>>  - Contributors should use their own fork and push a branch in their fork.
>>>  - Reviews can be performed on GitHub. The canonical tools are still the mailing-list and Phabricator: a reviewer can request the review to move to Phabricator.
>>>  - The only option available will be to “squash and merge”. This mode of review matches the closest our current workflow (both phabricator and mailing-list): conceptually independent contributions belongs to separate review threads, and thus separate pull-requests.
>>> This also allow the round of reviews to not force-push the original branch and accumulate commits: this keeps the contextual history of comments and allow to visualize the incremental diff across revision of the pull-request.
>>>  - Upon “merge” of a pull-request: history is linear and a single commit lands in master after review is completed.
>>> 
>>> As an alternative staging proposal: we could enable pull-requests only for a small subset of sub-projects in LLVM (i.e. not LLVM/clang to begin with for example) in the repo. In this case, we would propose to begin with the MLIR project (as soon as it gets integrated in the monorepo). This would be a good candidate to be the guinea pig for this process since it does not yet have a wide established community of contributors, and the current contributors are already exclusively using pull-requests.
>>> 
>>> Here is a more complete doc on the topic: https://docs.google.com/document/d/1DSHQrfydSjoqU9zEnj3rIcds6YN59Jxc37MdiggOyaI
>>> 
>>> Cheers,
>>> 
>>> --
>>> Mehdi
>>> 
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