Encouraging best practices through server communication

[Augie Fackler]

On Tue, Dec 10, 2013 at 07:41:50PM +0900, Gregory Szorc wrote:

[snip wall of text]

> While the extension isn't finished and has yet to be deployed outside of
> testing, I thought I'd share it with this list for a few reasons. First, I
> think people may find it interesting. Second, I have technical
> concerns/questions about the implementation. There are a number of aspects
> of the implementation that feel too hacky to me. There is also functionality
> not possible with Mercurial today (mainly due to the wire protocol design).
> I'd like to have a discussion about supporting these use cases in a future
> Mercurial release. Notably:
>
> * Client doesn't self-advertise capabilities like servers do. It would be
> cool if servers could proactively sniff for missing capabilities and be like
> "upgrade your Mercurial install!"
>
> * Passing messages for user display from server to client is not well
> supported. Only some commands have their output sent to the client. I would
> like a dedicated "band" in the protocol for transporting messages back to
> clients for *any* command. I think allowing servers to "advertise" message
> of the day or such on pull could be very useful.

Yeah. Right now I think this only works for push, which is a slight
bummer. Not sure how fixable this is though.

>
> * Possibly a superset of the above - it's not possible to exchange arbitrary
> metadata as part of client-server communication. My extension would be much,
> much easier if every command request and response could have arbitrary
> (key-value?) metadata attached to it.

pushkey lets you do this for an extension

>
> Is there any interesting in pursuing these features? Do people think my
> extension has wheels?

I think this is actually a great idea - it'd offer a way for large
projects and companies to enforce (at some level) use of some
extensions. I've been thinking about this a little on my own, but the
idea of an extension and pushkey (or similar) hadn't occurred to me as
a way to detect this.

Might be worth putting together a wiki page to sketch out a more
detailed plan and talking on -devel about it. I'd definitely be interested.

>
> [1] https://bugzilla.mozilla.org/show_bug.cgi?id=941856
>
> Gregory Szorc
> gregory.szorc at gmail.com
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