[Python-Dev] PEP 481 - Migrate Some Supporting Repositories to Git and Github

[Brett Cannon]

On Sat Nov 29 2014 at 7:16:34 PM Alex Gaynor <alex.gaynor at gmail.com> wrote:

> Donald Stufft <donald <at> stufft.io> writes:
>
> >
> > [words words words]
> >
>
> I strongly support this PEP. I'd like to share two pieces of information.
> Both
> of these are personal anecdotes:
>
> For the past several years, I've been a contributor on two major projects
> using
> mercurial, CPython and PyPy. PyPy has a strong culture of in-repo
> branching,
> basically all contributors regularly make branches in the main repo for
> their
> work, and we're very free in giving people commit rights, so almost
> everyone
> working on PyPy in any way has this level of access. This workflow works
> ok. I
> don't love it as much as git, but it's fine, it's not an impediment to my
> work.
>
> By contrast, CPython does not have this type of workflow, there are almost
> no
> in-tree branches besides the 2.7, 3.4, etc. ones. Despite being a regular
> hg
> user for years, I have no idea how to create a local-only branch, or a
> branch
> which is pushed to a remote (to use the git term). I also don't generally
> commit my own work to CPython, even though I have push privledges,
> because I
> prefer to *always* get code review on my work. As a result, I use a git
> mirror
> of CPython to do all my work, and generate patches from that.
>
> The conclusion I draw from this is that hg's workflow is probably fine if
> you're a committer on the project, or don't ever need to maintain multiple
> patches concurrently (and thus can just leave everything uncommitted in the
> repo). However, the hg workflow seems extremely defficient at non-committer
> contributors.
>

One way to come close to that using hg is to have your own clone that you
never push to hg.python.org/cpython (e.g. cloning the Bitbucket clone of
cpython or hosting on hg.python.org a personal clone). You can then specify
the repo and branch on the issue tracker to generate your patch:
https://docs.python.org/devguide/triaging.html#mercurial-repository . After
that it's just like any other patch workflow for core devs. It's not quite
as nice as maybe using named branches where you can just do a final hg
merge/commit to get your changes committed, but if you're not going to
commit your branches then you might as well get the automatic patch
generation perk in the issue tracker rather than using git (unless there is
some other git feature you use that you can't get in hg).


>
> The seconds experience I have is that of Django's migration to git and
> github.
> For a long time we were on SVN, and we were very resistant to moving to
> DVCS in
> general, and github in particular. Multiple times I said that I didn't see
> how
> exporting a patch and uploading it to trac was more difficult than sending
> a
> pull request. That was very wrong on my part.
>
> My primary observation is not about new contributors though, it's actually
> about the behavior of core developers. Before we were on github, it was
> fairly
> rare for core developers to ask for reviews for anything besides *gigantic*
> patches, we'd mostly just commit stuff to trunk. Since the switch to
> github,
> I've seen that core developers are *far* more likely to ask for reviews of
> their work before merging.
>

Why specifically? Did you have a web UI for reviewing patches previously?
Do you have CI set up for patches now and didn't before? What features did
you specifically gain from the switch to GitHub that you didn't have
before? IOW was it the "magic" of GitHub or some technical solution that
you got as part of the GitHub package and thus could theoretically be
replicated on python.org?

-Brett
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