[Distutils] Better version pinning in buildout (buildout-versions)

[Marius Gedminas]

On Tue, Jan 08, 2013 at 08:02:56AM -0500, Jim Fulton wrote:
> On Tue, Jan 8, 2013 at 7:45 AM, Marius Gedminas <marius at pov.lt> wrote:
> ...
> > If backwards-compatibility weren't an consideration, I'd be tempted to
> > have buildout 2.0 hardcode the versions section name to [versions] and
> > have the append-new-versions code append a "\n\n[versions]\n" line if
> > necessary.
> >
> > That way you could say
> >
> >   [buildout]
> >   append-picked-versions = buildout.cfg
> >
> > and have it Just Work with no extra bootstrapping.
> 
> It would work until someone added a new section at the end.

That's why I said "have the append-new-versions code append a [versions]
line if necessary"

> or
> 
> If append-new-versions added a versions section
> if the last section wasn't a versions section, at which point
> you could end up with multiple versions sections spread
> over the file.

Yes.  Better than appending version pins to an unrelated section, where
they would be silently ignored as unknown option values.

> Having buildout modify a hand-edited file just seems like
> a Bad Idea to me.

I think of it as a tool that helps me update a hand-edited file.

I haven't decided whether it's a good idea or a Bad Idea to have a
buildout.cfg do that updating automatically.  Pros:

  - whenever you add a new dependency, you'll get a pin for it, so you
    never commit a version of a project with floating dependencies

Cons:

  - if you decide that you want a certain dependency to float
    (pinning distribute caused weird failures on my buildbot, so I kept
    it floating), your buildbot keeps updating versions.cfg all the time
    and you need explicit svn revert steps to avoid merge conflicts on
    the next svn up.

Marius Gedminas
-- 
31337 is a prime number, go figure...
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