Clarify sorting haddocks for Ord ProjectConfigPath

cabal-install-solver/src/Distribution/Solver/Types/ProjectConfigPath.hs

@@ -51,7 +51,13 @@ import Distribution.Simple.Utils (ordNub)
 newtype ProjectConfigPath = ProjectConfigPath (NonEmpty FilePath)
     deriving (Eq, Show, Generic)
 
--- | Sorts URIs after local paths and longer paths after shorter ones.
+-- | Sorts URIs after local file paths and longer file paths after shorter ones
+-- as measured by the number of path segments. If still equal, then sorting is
+-- lexical.
+--
+-- The project itself, a single element root path, compared to any of the
+-- configuration paths it imports, should always sort first. Comparing one
+-- project root path against another is done lexically.
 instance Ord ProjectConfigPath where
     compare pa@(ProjectConfigPath (NE.toList -> as)) pb@(ProjectConfigPath (NE.toList -> bs)) =
         case (as, bs) of