Re: [Question] Is extensions.partialClone defunct?

From: Jonathan Nieder <jrnieder@gmail.com>
Date: Mar 12, 2020, 23:09 UTC
Message-ID: <20200312230931.GF120942@google.com>
In-Reply-To: <CAP8UFD0+fyz=S_VN=EzPOOxNSNkge0uB84kEqQD_mudsFtR8Lg@mail.gmail.com>

Hi,

Christian Couder wrote:

>> Jonathan Tan wrote:

Show 5 quoted lines

>>> Hmm...besides giving the name of the promisor remote, the
>>> extensions.partialClone setting is there to prevent old versions of Git
>>> (that do not know this extension) from manipulating the repo.
>
> That could be true of "remote.<name>.promisor = true".

To be clear, Jonathan is referring to a specific feature of the extensions.* settings. See Documentation/technical/repository-version.txt for details:

  2. If a version-1 repository specifies any `extensions.*` keys that
     the running git has not implemented, the operation MUST NOT
     proceed. Similarly, if the value of any known key is not understood
     by the implementation, the operation MUST NOT proceed.

No other config key has that property.

[...]

> On Thu, Mar 12, 2020 at 6:51 PM Jonathan Nieder <jrnieder@gmail.com> wrote:

>> Christian, what would your prefered way be to fix this?  Should
>> extensions.partialclone specify a particular "default" promisor
>> remote, or should we use a new repository extension for multiple
>> promisors?

[...]

> So I'd rather obsolete "extensions.partialClone = <remote>" and to
> find other ways.

I *think* that means "new repository extension".

That suggests something like

	[extensions]
		multiplePromisors = true

[...]

>                                                              or maybe
> we could have another extension alltogether like
> "[extensions]\npromisorremotes=<bool>" and over time obsolete
> "extensions.partialClone" altogether. I prefer the later.

I think we're going to have to continue to support extensions.partialClone=<remote> for a long time anyway (breaking the ability to work with existing repositories is expensive), so I'm reasonably comfortable with multiplePromisors being a separate extension. Some faraway day, we can introduce "repositoryFormatVersion = 2" that mandates support for these extensions by default, allowing us to clean up and simplify.

I can start writing a proposed patch to send this evening or tomorrow. This behavior has been around for a few releases so it would want to cook until the 2.27 cycle.

Thanks, Jonathan