Interest in integrating hg-git into Mercurial

[Augie Fackler]

> On Aug 1, 2019, at 13:01, Gregory Szorc <gregory.szorc at gmail.com> wrote:
> 
> Is there any interest in integrating hg-git (or hg-git functionality) into the Mercurial distribution as an officially supported extension?
> 
> Given the popularity of Git and the difficulty of installing semi-complex Python software like hg-git, I was thinking it would be beneficial to end-users for Mercurial to support interacting with Git repositories out-of-the-box with as little set-up pain as possible. hg-git feels like the path of least resistance towards attaining that goal. (I would eventually like to see support for Mercurial opening Git repositories natively. While I think this is technically viable, it is probably a year or two away, as it needs significant work to shore up Mercurial's storage interfaces and internal code contracts to support such a significant invariant as interfacing with Git repositories.)
> 
> Vendoring hg-git would like also entail vendoring its dependencies: urllib3, certifi, and dulwich. Vendoring urllib3 and certifi is probably not the worst thing in the world, as it would give us an excuse to refactor Mercurial's HTTP internals to move off the ugly hacks we employ to use Python's standard library.
> 
> I'm not promising I will follow through and do this work. At this time I'm mostly interested in taking a quick pulse to see if there is any interest in doing it. If there is general support, I may follow through :)

I'm semi-enthusiastic, but I'd rather we took a storage-abstraction approach than the hg-git "convert the repo" approach. With our newfound storage abstractions, I think it's reasonable to index a git repository and present its data in an hg-friendly format. A few places in hg would likely need patching to handle more than two parents in a merge, but other than that I think things basically work.

Note that I'm also willing to try and push this forward, and have some experimental hacks lying around that should make a proof of concept fairly easy. The reaction at the last sprint took away some of my enthusiasm, but if people are receptive to the idea I'll carve out some time in August...

(I think your "a year or two" estimate is pessimistic on this front: I think it could be done very quickly by indexing the git repo at load time, and the indexing can be made reasonably quick, especially given that I had this _working_ in the 3.x era, albeit slowly.)

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