Re: [PATCH v3 3/8] upload/receive-pack: allow hiding ref hierarchies

From: Junio C Hamano <gitster@pobox.com>
Date: Feb 5, 2013, 15:45 UTC
Message-ID: <7vwqumvk76.fsf@alter.siamese.dyndns.org>
In-Reply-To: <20130205085047.GA24973@sigill.intra.peff.net>

Jeff King <peff@peff.net> writes:

Show 19 quoted lines

> On Wed, Jan 30, 2013 at 10:45:37AM -0800, Junio C Hamano wrote:
>
>> Teach upload-pack and receive-pack to omit some refs from their
>> initial advertisements by paying attention to the transfer.hiderefs
>> multi-valued configuration variable.  Any ref that is under the
>> hierarchies listed on the value of this variable is excluded from
>> responses to requests made by "ls-remote", "fetch", "clone", "push",
>> etc.
>> 
>> A typical use case may be
>> 
>> 	[transfer]
>> 		hiderefs = refs/pull
>> 
>> to hide the refs that are internally used by the hosting site and
>> should not be exposed over the network.
>
> In the earlier review, I mentioned making this per-service, but I see
> that is not the case here. Do you have an argument against doing so?

Perhaps then I misunderstood your intention. By reminding me of the receive-pack side, I thought you were hinting to unify these two into one, which I did. There is no argument against it.

> And I
> have not seen complaints about the current system.

Immediately after I added github to the set of places I push into, which I think is long before you joined GitHub, I noticed that _my_ repository gets contaminated by second rate commits called pull requests, and I may even have complained, but most likely I didn't, as I could easily tell that, even though I know it is _not_ the only way, nor even the best way [*1*], to implement the GitHub's pull request workflow, I perfectly well understood that it would be the most expedient way for GitHub folks to implement this feature.

I think you should take lack of complaints with a huge grain of salt. It does not suggest much.

> Gerrit's refs/changes may be a different story, if they have a large
> enough number of them to make upload-pack's ref advertisement
> overwhelming.

This is probably a stale count, but platform/frameworks/base part of AOSP has 3200+ refs; the corresponding repository internal to Google has 60k+ refs (this is because there are many in-between states recorded in the internal repository, even though the end result published to the open source repository may be the same) and results in ~4MB advertisement. Which is fairly significant when all you are interested in doing is an "Am I up to date?" poll.

[Footnote]

*1* From the ownership point of view, objects that are only reachable from these refs/pull/* refs do *not* belong to the requestee, until the requestee chooses to accept the changes.

A malicious requestor can fork your repository, add an objectionable blob to it, and throw a pull request at you. GitHub shows that the blob now belongs to your repository, so the requestor turns around and file a DMCA takedown complaint against your repository. A clueful judge would then agree with the complaint after running a "clone --mirror" and seeing the blob in your repository. Oops?

A funny thing is that you cannot "push :refs/pull/1/head" to remove it anymore (I think in the early days, I took them out by doing this a few times, but I may be misremembering), so you cannot make yourself into compliance, even though you are not the offending party. Your repository is held responsible for whatever the rogue requestor added. That is not very nice, is it?

In an ideal world, I would have chosen to create a dedicated fork managed by the hosting company (i.e. GitHub) for your repository whose only purpose is to house these refs/pull/ refs (the hosting site is ultimately who has to respond to DMCA notices anyway, and an arrangement like this makes it clear who is reponsible for what).

The e-mail sent to you to let you know about outstanding pull requests and the web UI could just point at that forked repository, not your own (you also could choose to leave the outging pull requests in the requestor's repository, but that is only OK if you do not worry about (1) a requestor sending a pull request, then updating the branch the pull request talks about later, to trick you with bait-and-switch, or (2) a requestor sending a pull request, thinks he is done with the topic and removes the repository).