Remove hashable dependency

[jaspervdj]

See #10140

• Patches conform to the coding conventions.
• Is this a PR that fixes CI? If so, it will need to be backported to older cabal release branches (ask maintainers for directions).

[jaspervdj]

Removing hashable from the test suite nerd-sniped me into writing a bit of whacky arbitrary machinery, but I think it's not necessarily worse than abusing hashable for this.

[ulysses4ever]

Pretty cool, thank you!

I'd hope for a smaller diff if we just had some of the compat code added to some sort of Prelude or Compat module (which we already have in vast numbers!). So, like

type Hash = HashValue
readFileHash = readFileHashValue 

But maybe this grows the codebase unnecessarily, so I'm split on this. It just feels like a hash library is something that may change once in a while, and a little abstraction from it woudln't hurt.

[jaspervdj]

I added some minimal comments to the code as well.

I'd hope for a smaller diff if we just had some of the compat code added to some sort of Prelude or Compat module

IMO, Distribution.Client.HashValue is this compat module. It just wasn't used in FileMonitor yet...

[ulysses4ever]

IMO, Distribution.Client.HashValue is this compat module. It just wasn't used in FileMonitor yet...

Oh, that's good, thank you!