Slight cleanups

src/libstore/content-address.cc

@@ -10,7 +10,7 @@ std::string FixedOutputHash::printMethodAlgo() const
 }
 
 
-std::string makeFileIngestionPrefix(const FileIngestionMethod m)
+std::string makeFileIngestionPrefix(FileIngestionMethod m)
 {
     switch (m) {
     case FileIngestionMethod::Flat:

src/libstore/content-address.hh

@@ -11,17 +11,16 @@ namespace nix {
  * Content addressing method
  */
 
+/* We only have one way to hash text with references, so this is a single-value
+   type, mainly useful with std::variant.
+*/
+struct TextHashMethod : std::monostate { };
+
 enum struct FileIngestionMethod : uint8_t {
     Flat = false,
     Recursive = true
 };
 
-/*
-  We only have one way to hash text with references, so this is single-value
-  type is only useful in std::variant.
-*/
-struct TextHashMethod { };
-
 struct FixedOutputHashMethod {
   FileIngestionMethod fileIngestionMethod;
   HashType hashType;
@@ -29,9 +28,13 @@ struct FixedOutputHashMethod {
 
 /* Compute the prefix to the hash algorithm which indicates how the files were
    ingested. */
-std::string makeFileIngestionPrefix(const FileIngestionMethod m);
+std::string makeFileIngestionPrefix(FileIngestionMethod m);
 
 
+/* Just the type of a content address. Combine with the hash itself, and we
+   have a `ContentAddress` as defined below. Combine that, in turn, with info
+   on references, and we have `ContentAddressWithReferences`, as defined
+   further below. */
 typedef std::variant<
     TextHashMethod,
     FixedOutputHashMethod
@@ -86,6 +89,7 @@ std::optional<ContentAddress> parseContentAddressOpt(std::string_view rawCaOpt);
 
 Hash getContentAddressHash(const ContentAddress & ca);
 
+
 /*
  * References set
  */