bug#43442: Code stored with Subversion (SVN) cannot be retrieved from SWH

[Ludovic Courtès]

Ludovic Courtès <ludovic.courtes@inria.fr> skribis:

> The attached patch does that:
>
> scheme@(guile-user)> (lookup-subversion-revision 
> "https://scm.gforge.inria.fr/anonscm/svn/mpfi"; 680)
> $12 = #<<revision> id: "72102de7605a2459ebcb016338ebbf1a997e8c8d" date: 
> #<date nanosecond: 938388 second: 35 minute: 32 hour: 11 day: 6 month: 9 
> year: 2018 zone-offset: 0> directory: 
> "5c89c025a4cd9d16befdfec12dfc23f7318d0d5b" directory-url: 
> "https://archive.softwareheritage.org/api/1/directory/5c89c025a4cd9d16befdfec12dfc23f7318d0d5b/";
>  parents-ids: ("16da41f1848d77a93aec565320b72b460c429b61") extra-headers: 
> (("svn_repo_uuid" . "e2f78e0c-bb60-4709-9413-9660a31d4696") ("svn_revision" . 
> "680"))>
> scheme@(guile-user)> (lookup-subversion-revision 
> "https://scm.gforge.inria.fr/anonscm/svn/mpfi"; 666)
> $13 = #<<revision> id: "148eb1e7206b111af4075c73c656e54c9efed6cb" date: 
> #<date nanosecond: 654167 second: 2 minute: 52 hour: 12 day: 2 month: 8 year: 
> 2018 zone-offset: 0> directory: "ed7b0bd7019fb85cd86d948a97c23b9d43aa8728" 
> directory-url: 
> "https://archive.softwareheritage.org/api/1/directory/ed7b0bd7019fb85cd86d948a97c23b9d43aa8728/";
>  parents-ids: ("0ba2aa7e0d3fc0a1eb3ba72b32094515415ae47a") extra-headers: 
> (("svn_repo_uuid" . "e2f78e0c-bb60-4709-9413-9660a31d4696") ("svn_revision" . 
> "666"))>
>
> The implementation is pretty bad though, because it walks the revision
> history until it finds the right revision number—so you’re likely to
> reach the bandwidth rate limit before you’ve found the revision you’re
> looking for.
>
> More importantly, most svn origins cannot be found, or at least not
> by passing the URL as-is:
>
>   https://sympa.inria.fr/sympa/arc/swh-devel/2023-03/msg00009.html
>
> This whole hack looks like a dead end.
>
> It would be ideal if SWH would compute nar hashes, as you proposed:
>
>   https://gitlab.softwareheritage.org/swh/meta/-/issues/4538

Happy to report that this is solved with nar-sha256 ExtIDs at SWH, which
commit 0e73f933b291c7e154c7e019b6de1e2f3a97e4c1 uses to implement the
SWH fallback for Subversion checkouts.  Wo0t!

Ludo’.