Re: Software Heritage API

[ludovic.courtes@inria.fr (Ludovic Courtès)]

Hi Efraim,

Efraim Flashner <efraim@flashner.co.il> skribis:

> I've kept this tagged to take a look at it later. I checked the sha1sum
> of swig-3.0.10.tar.gz and it gave me a valid URL.
> https://archive.softwareheritage.org/api/1/content/c672b8535394cfb204c70de7c66e69fb20a95647/
> https://archive.softwareheritage.org/api/1/content/sha1:c672b8535394cfb204c70de7c66e69fb20a95647/
> https://archive.softwareheritage.org/api/1/content/sha256:2939aae39dec06095462f1b95ce1c958ac80d07b926e48871046d17c0094f44c/
> If you take a look at the page(s), '/raw' can only be appended to the
> sha1 (or blank) URLs to download the source, which currently returns
> 401.

Be aware that Software Heritage (SWH) stores only raw commits and not
tarballs (or not yet).  That means that you may be able to find the
“3.0.10” tag of SWIG, but not swig-3.0.10.tar.gz.  See:

  https://sympa.inria.fr/sympa/arc/swh-devel/2016-09/msg00000.html

> Currently our "magic mirrors" search hydra based on the hash; in order
> to check here also for the source we'd have to undo the base32 hash, and
> then either transform the sha256 hash to a sha1 hash, or use two API
> calls, the first to check for the source and the second to get and use
> the url to download it. A quick check online makes me think it's not
> possible to take a sha256 hash and get the sha1 hash of that file.

As it is now, SWH could only help us for Git checkouts, not for
tarballs.

There is no way to “convert” a SHA256 hash to SHA1 or similar, though,
but apparently SWH supports SHA256 anyway.

The second problem, though, is that the way we compute the hash of a
directory differs from the way they do:

  https://sympa.inria.fr/sympa/arc/swh-devel/2016-07/msg00018.html

Essentially, Guix computes the hash of the nar (“normalized archive”) of
the directory, whereas SWH computes a hash over the Git tree
representation.

AFAICS this cannot be overcome without manually specifying the
git-tree-hash in our ‘origin’ objects.

Ludo’.