Re: Git/Mercurial interoperability (and what about bzr?) (was: Re: [VOTE] git versus mercurial)

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Oct 28, 2008, 14:59 UTC
Message-ID: <alpine.DEB.1.00.0810281551040.22125@pacific.mpi-cbg.de.mpi-cbg.de>
In-Reply-To: <Pine.LNX.4.64.0810281536360.27029@ds9.cixit.se>

Hi,

On Tue, 28 Oct 2008, Peter Krefting wrote:

Show 5 quoted lines

> How difficult are the storage formats? Would it be possible, in a
> reasonable amount of work, to add support for the Mercurial protocol
> and format in "git clone", so that I could clone a Mercurial repository
> and work on it with Git, and then possibly use "git push" to possibly
> push the result back to Mercurial?

There was talk about imitating Mercurial's wire protocol in order to have an efficient HTTP server. Shawn is working on that front;

We discussed it briefly, and there might be some cute ways to copy it: since we are not append-only, we have to download the pack index first (which is not downloaded ATM, as we generate it from the downloaded pack while verifying it). With that index, we can determine which parts we need in order to regenerate the pack; it would still be pretty stupid when there are a lot of branches and we are really only interested in one of them.

But I doubt that it will be possible to use the wire protocol to pull/push between different DVCSes. I _strongly_ doubt that the SHA-1s in the Mercurial repositories could _ever_ be reused in Git mirrors of them, as our data format (on which the hash depends) is different.

Show 6 quoted lines

> It would be nice to have easy interoperability between the systems, at 
> least as far as can be covered by the lowest common denominator of what 
> they support. I would love to be able to use Git to clone a Bzr 
> repository that I need to be able to access, since bzr is just different 
> enough from Git to be annoying. Same goes for Mercurial. And I am sure 
> that users of the other tools feel the same.

Wasn't bzr touting it as one of their major features that they could have foreign-scm remotes? If I remembered that correctly, that might be the route you want to take.

Ciao, Dscho