Changing repo requirements (was: Re: [PATCH 1 of 5 requirements-tidy] localrepo: add requirements helper functions)

[Augie Fackler]

On Fri, Oct 16, 2015 at 1:17 PM, Matt Mackall <mpm at selenic.com> wrote:
> On Wed, 2015-10-14 at 15:58 -0400, Augie Fackler wrote:
>> On Tue, Oct 13, 2015 at 01:48:13PM -0500, Matt Mackall wrote:
>> > On Thu, 2015-10-01 at 15:47 -0700, Gregory Szorc wrote:
>> > > This series was mostly cosmetic cleanup and not critical to my end goal of
>> > > modernizing stream clones. Are there any parts worth salvaging or should I
>> > > throw it all away?
>> >
>> > I think everything but the post-init write access seemed reasonable.
>>
>> So, this is actually now screwing me for treemanifests. In particular,
>> the repo is already initialized when we start applying the changegroup
>> to it, but as part of receiving the changegroup we find out we're
>> getting treemanifests. Thoughts?
>
> My point is not that you shouldn't be able to change requirement, but
> that -it should not be this easy-. Greg's patches are way too friendly
> to this and people who just read his API will assume it's totally ok to
> slap on new requirements whenever it's convenient without considering
> the attendant headaches.

*nod*. I think for both our needs it'd be fine to make it possible to
change requirements only on repositories that are empty (or were
before the current transaction). Would that be reasonable at least for
now?

>
> We can provide a way to do it (I've already mentioned a user), but it
> needs to be marked as a serious undertaking. Something like requiring a
> breakbackwardcompatibility=True flag.
>
> Also, the locking story for the requires files is.. unclear.
>
> --
> Mathematics is the supreme nostalgia of our time.
>
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