Re: RFC: libgit2 is slow/inefficient; switch to git command?

[Wojtek Kosior]

Hi,

I just want to add my 2 cents :)

Another issue with libgit2 is that is gives a very misleading error
report when trying to http-clone a repo that only support the old
"dumb" git protocol (as opposed to the newer "smart" one). More details
here[1].

Missing support for that dumb protocol is probably not that big issue
in practice. The misleading error Guix presents to the users trying to
access some poor git repo is :/

Wojtek

[1] https://issues.guix.gnu.org/58555


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On Tue, 22 Nov 2022 11:49:26 -0500
"Philip McGrath" <philip@philipmcgrath.com> wrote:

> Hi,
> 
> On Tue, Nov 22, 2022, at 10:39 AM, zimoun wrote:
> > Hi,
> >
> > On Mon, 21 Nov 2022 at 21:21, Maxim Cournoyer <maxim.cournoyer@gmail.com> 
> > wrote:
> >  
> >> Given that:
> >>
> >> * the git CLI doesn't suffer from such poor performance;
> >> * This kind of performance problem has been known for years in libgit2
> >>   [0] with no fix in sight;
> >> * other projects such as Cargo support using the git CLI and that
> >>   projects are using it for that reason [1];  
> >
> > And I would add the lack of «Support for shallow repositories» [1].
> >
> > 1: <https://github.com/libgit2/libgit2/issues/3058>
> >  
> 
> >
> > PS: For the record, Software Heritage, which ingests *a lot* of Git
> > repositories, relies on Dulwhich [2] (pure Python implementation), IIUC.
> >
> > 2: <https://www.dulwich.io/>  
> 
> Along those lines, there’s an implementation of clone/checkout in pure Racket 
> (for the package manager) that could probably be ported to Guile relatively 
> easily. I’d expect libgit2 to be faster for the things that it supports, but 
> the Racket implementation does support shallow checkout, so it might pay off 
> if that skips a lot of work.
> 
> Code: 
> https://github.com/racket/racket/blob/master/racket/collects/net/git-checkout.rkt
> Docs: https://docs.racket-lang.org/net/git-checkout.html
> 
> (More broadly, I haven’t investigated performance issues, but my basic 
> inclination would be toward improving libgit2 over running the git 
> executable.)
> 
> -Philip
>

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