bug#58555: [guile-git] Attempt to use git repositories that support older "dumb" HTTP protocol gives uninformative error message

[Maxime Devos]

On 15-10-2022 17:08, Wojtek Kosior via Bug reports for GNU Guix wrote:
> Hello,
>
> I was trying to set up a Guix channel and use it from guix.scm of my
> project. I got an error when using `guix shell`
>
> > Updating channel 'guix' from Git repository at 
> > 'https://git.savannah.gnu.org/git/guix.git'...
> > Updating channel 'hydrilla-guix' from Git repository at 
> > 'https://git.koszko.org/hydrilla-guix-packaging'...
> > SWH: revision "7ffa00d8923f518d4d3898d2b9f6673afe204660" originating from 
> > https://git.koszko.org/hydrilla-guix-packaging could not be found
> > guix shell: warning: revision 7ffa00d8923f518d4d3898d2b9f6673afe204660 of 
> > https://git.koszko.org/hydrilla-guix-packaging could not be fetched from 
> > Software Heritage
> > guix shell: error: failed to load 'guix.scm':
> > guix/git.scm:401:19: Git error: invalid content-type: 'text/plain; 
> > charset=UTF-8'
>
> I investigated this and found out it's guile-git that fails to HTTP
> clone repositories that use the older "dumb" git protocol instead of
> the newer "smart" one.
> [...]

This is a limitation of the libgit2 library that is used by guile-git:
<https://github.com/libgit2/libgit2/issues/4652#issuecomment-390903142>.
Currently there don't appear to be any plans upstream for supporting the 
'dumb' protocol.  If you would like support for the 'dumb' protocol, 
you'll need to contact libgit2, and probably write the patch yourself.

> [...]
> Nick's repo that I am using here only supports the dumb protocol. Hence
> the following error
>
> > Backtrace:
> > In ice-9/boot-9.scm:
> >    1752:10  7 (with-exception-handler _ _ #:unwind? _ # _)
> > In unknown file:
> >             6 (apply-smob/0 #<thunk 7fc3b96122e0>)
> > In ice-9/boot-9.scm:
> >      724:2  5 (call-with-prompt _ _ #<procedure default-prompt-handle…>)
> > In ice-9/eval.scm:
> >      619:8  4 (_ #(#(#<directory (guile-user) 7fc3b9617c80>)))
> > In ice-9/command-line.scm:
> >     185:19  3 (_ #<input: string 7fc3b9611850>)
> > In unknown file:
> >             2 (eval (clone "https://git.nicksphere.ch/calcurse"; "/…") #)
> > In git/clone.scm:
> >       46:8  1 (_ _ _ _)
> > In git/bindings.scm:
> >       77:2  0 (raise-git-error _)
> >
> > git/bindings.scm:77:2: In procedure raise-git-error:
> > Throw to key `git-error' with args `(#<<git-error> code: -1 message: "invalid 
> > content-type: 'text/plain; charset=UTF-8'" class: 34>)'.
>
> The expected behavior is that instead the user gets a meaningful
> message, e.g. "Repository at <URL> could not be used because it doesn't
> support the newer \"smart\" git HTTP protocol. Please ask the
> repository owner to add support for that protocol".
>
> I didn't see any mailing list for guile-git and I noticed most recent
> commits in guile-git are from Guix maintainer anyway so I decided to
> just submit to Guix bug mailing list. I hope I'm not doing something
> horribly wrong here :)

It uses GitLab's issue tracker.  I've added a link at 
<https://gitlab.com/guile-git/guile-git/-/issues/28>.

Greetings,
Maxime.

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