On Tue, Oct 13, 2020 at 4:12 PM Konstantin Tokarev <annu...@yandex.ru> wrote:
>
>
>
> 14.10.2020, 02:01, "Ryosuke Niwa" <rn...@webkit.org>:
> > On Tue, Oct 13, 2020 at 3:53 PM Konstantin Tokarev <annu...@yandex.ru>
> > wrote:
> >> 14.10.2020, 01:45, "Ryosuke Niwa" <rn...@webkit.org>:
> >> > On Tue, Oct 13, 2020 at 3:40 PM Konstantin Tokarev <annu...@yandex.ru>
> >> wrote:
> >> >> 14.10.2020, 01:30, "Ryosuke Niwa" <rn...@webkit.org>:
> >> >> > On Tue, Oct 13, 2020 at 2:37 PM Konstantin Tokarev
> >> <annu...@yandex.ru> wrote:
> >> >> >> 13.10.2020, 22:33, "Maciej Stachowiak" <m...@apple.com>:
> >> >> >> >> On Oct 2, 2020, at 10:59 AM, Michael Catanzaro
> >> <mcatanz...@gnome.org> wrote:
> >> >> >> >>
> >> >> >> >> On Fri, Oct 2, 2020 at 6:36 pm, Philippe Normand
> >> <ph...@igalia.com> wrote:
> >> >> >> >>> Would you also consider preventing merge commits in order to
> >> keep a
> >> >> >> >>> clean mainline branch?
> >> >> >> >>
> >> >> >> >> Big +1 to blocking merge commits. Merge commits in a huge
> >> project like WebKit would make commit archaeology very frustrating. (I
> >> assume this is implied by the monotonic commit identifiers proposal, but
> >> it doesn't exactly say that.)
> >> >> >> >
> >> >> >> > I’m assuming your objection is to regular merges, but how do you
> >> feel about squash merges? Or do you think all PRs should be landed by
> >> rebasing?
> >> >> >>
> >> >> >> I'm not Michael but will add my 2 dollars anyway :)
> >> >> >>
> >> >> >> In these two approaches commits inside PR have different meaning,
> >> and workflow is different.
> >> >> >>
> >> >> >> Below I use a term "atomic change" to describe minimal code change
> >> which is a self-contained work unit with following properties:
> >> >> >> * It implements well-defined task which can be summarized as a
> >> short English sentence (typical soft limit is 60 characters)
> >> >> >> * It doesn't introduce defects (e.g. bugs, compilation breakages,
> >> style errors, typos) which were discovered during review process
> >> >> >> * It doesn't include any code changes unrelated to main topic. This
> >> separation is sometimes subjective, but it's usually recommended to split
> >> refactoring and implementation of feature based on that, bug fix and new
> >> feature, big style change and fix or feature.
> >> >> >>
> >> >> >> AFAIU our current review process has similar requirements to
> >> patches submitted to Bugzilla, though sometimes patches include unrelated
> >> changes. This can be justified by weakness of webkit-patch/Bugzilla
> >> tooling which has no support for patch series, and by fact that SVN
> >> doesn't support keeping local patch series at all.
> >> >> >>
> >> >> >> 1. Workflow 1 - "Squash merge" policy
> >> >> >>
> >> >> >> * Whole PR is considered to be a single atomic change of WebKit
> >> source tree. If work is supposed to be landed as a series of changes which
> >> depend on each other (e.g. refactoring and feature based on it, or
> >> individual separate features touching same parts of code), each change
> >> needs a separate PR, and, as a consequence, only one of them can be
> >> efficiently reviewed at the moment of time
> >> >> >> * Commits in PR represent review iterations or intermediate
> >> implementation progress
> >> >> >> * Reviewers' comments are addressed by pushing new commits without
> >> rewriting history, which works around GitHub's lack of "commit revisions".
> >> Also this workflow has lower entry barrier for people who haven't mastered
> >> git yet, as it requires only "git commit" and "git push" without rebases.
> >> >> >>
> >> >> >> 2. Workflow 2 - "Rebase" ("cherry-pick")) or "Merge" policy
> >> >> >>
> >> >> >> * PR is considered to be a series of atomic changes. If work
> >> consists of several atomic changes, each commit represent an atomic change
> >> >> >> * Review iterations are done by fixing commits in place and
> >> reuploading entire series using force push (of course if review discovers
> >> that substantial part of work is missing it can be added as a new atomic
> >> commit to the series)
> >> >> >> * It's possible to review each commit in the series separately
> >> >> >> * Workflow requires developers to have more discipline and
> >> experience with using git rebase for history rewriting. Entry barrier can
> >> be lowered by providing step by step instructions like e.g. [1].
> >> >> >
> >> >> > I really dislike this workflow due to its inherent complexity. Having
> >> >> > to use Git is enough of a burden already. I don't want to deal with
> >> an
> >> >> > extra layer of complexity to deal with.
> >> >>
> >> >> There is simplified version of workflow 2 when you have only one
> >> commit in PR. In this case you can easily edit this single commit with gic
> >> commit --amend or GUI tools to address review comments. At the same time
> >> those who are more comfortable with git can use longer patch series.
> >> >
> >> > Except that reviewers would still have to review each commit
> >> > separately, and the time comes to revert someone's patch, we still
> >> > need to remember how to revert a sequence of commits that belong to a
> >> > single PR.
> >>
> >> Workflow 2 assumes that you forget about PR after it was merged and
> >> operate
> >> on its commits as equal parts of history.
> >>
> >> In this sequence of commits each one can be reverted on their own merits,
> >> like separate (but consequential) Bugzilla patches in current workflow.
> >> Sometimes it's not possible to revert one patch without reverting a few
> >> others
> >> or solving conflicts, but you rarely think about reverting a whole range
> >> of
> >> patches unless it becomes really necessary.
> >
> > Currently, when we revert a patch, we reopen the bug. If we're
> > reverting individual commits and they don't all correspond to a single
> > PR, then we would need a new system for tracking the partial(?)
> > introduction of the original issue that PR fixed. This is extremely
> > confusing because a single PR may have many to many relationships with
> > Bugzilla bugs / GitHub issues. In which case, there isn't a clear
> > communication of what got reverted and what needs to happen other than
> > the history in Git.
>
> Each commit could have a reference to issue it solves, which could be set up
> to be reopened automatically after revert. I guess webkitbot could do that.
So now we're talking about each PR containing multiple commits each of
which fixes some distinct issue?
I don't think we should have a single PR which fixes multiple distinct
issues like that.
> > Again, I dislike all these complexities that come with workflow 2.
> > Contributing to WebKit is already too damn complicated. Please don't
> > make it even more complicated.
>
> FWIW, having to create individual PR for every patch in a series (and wait
> before
> previous PR is merged to avoid confusion, because of git branch containing
> previous commit reviewed elsewhere) is also a complication which decrease
> developers' productivity.
I've contributed to WebKit for 11 years and this has never been an
issue because I've never found a need to upload a patch up review
before the previous patch had been landed.
This is only an issue if you're working on a large feature and trying
to upload a series of patches for a review. I do get that something
like that might be useful when reviewing a large WIP feature but then
you can just point to a branch in your fork for the entire patch /
diff. There isn't really a need to have a PR for it.
- R. Niwa
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