This interface was deployed at archive.softwareheritage.org a few days
ago. Our main use case will be looking up directories by “nar-sha256”
hashes.
* guix/swh.scm (<external-id>): New JSON-mapped record type.
(lookup-external-id, lookup-directory-by-nar-hash): New procedures.
* tests/swh.scm (%external-id): New variable.
("lookup-directory-by-nar-hash"): New test.
Change-Id: Ib671c7798aeb6f8132ac78f2b06b9285da8e7bd5