core: add Generic, Show for Signature and NarSignature

Author: sorki

hnix-store-core/CHANGELOG.md

@@ -8,6 +8,8 @@
    * `BuildResult`s `timesBuild` field changes type from `Integer` to `Int` [#231](https://github.com/haskell-nix/hnix-store/pull/231)
 
 * Additions:
+   * Added `Generic` and `Show` instances for
+     `Signature` and `NarSignature` [#231](https://github.com/haskell-nix/hnix-store/pull/231)
    * Added `Eq` and `Ord` instances for `SomeNamedDigest` [#231](https://github.com/haskell-nix/hnix-store/pull/231)
    * `BuildStatus` grows `NoSubstituters` and `ResolvesToAlreadyValid` constructors [#231](https://github.com/haskell-nix/hnix-store/pull/231)
    * `InvalidPathError` replacing previous stringy error [#231](https://github.com/haskell-nix/hnix-store/pull/231)

hnix-store-core/src/System/Nix/Internal/Signature.hs

@@ -23,7 +23,7 @@ import qualified Crypto.Saltine.Internal.ByteSizes as NaClSizes
 
 -- | A NaCl signature.
 newtype Signature = Signature ByteString
-  deriving (Eq, Ord)
+  deriving (Eq, Generic, Ord, Show)
 
 instance IsEncoding Signature where
   decode s
@@ -42,4 +42,4 @@ data NarSignature = NarSignature
   , -- | The archive's signature.
     sig       :: Signature
   }
-  deriving (Eq, Ord)
+  deriving (Eq, Generic, Ord, Show)