The logic for what constitutes a valid hash and how different hash schemes
are represented was starting to get sprawled over many different files and
packages.
Consistently with other cases where we've used named types to gather the
definition of a particular string into a single place and have the Go
compiler help us use it properly, this introduces both getproviders.Hash
representing a hash value and getproviders.HashScheme representing the
idea of a particular hash scheme.
Most of this changeset is updating existing uses of primitive strings to
uses of getproviders.Hash. The new type definitions are in
internal/getproviders/hash.go.
The "acceptable hashes" for a package is a set of hashes that the upstream
source considers to be good hashes for checking whether future installs
of the same provider version are considered to match this one.
Because the acceptable hashes are a package authentication concern and
they already need to be known (at least in part) to implement the
authenticators, here we add AcceptableHashes as an optional extra method
that an authenticator can implement.
Because these are hashes chosen by the upstream system, the caller must
make its own determination about their trustworthiness. The result of
authentication is likely to be an input to that, for example by
distrusting hashes produced by an authenticator that succeeds but doesn't
report having validated anything.
We previously had this just stubbed out because it was a stretch goal for
the v0.13.0 release and it ultimately didn't make it in.
Here we fill out the existing stub -- with a minor change to its interface
so it can access credentials -- with a client implementation that is
compatible with the directory structure produced by the
"terraform providers mirror" subcommand, were the result to be published
on a static file server.
Martin Atkins