Revert "use existing debug machinery for explain"

This reverts commit 409572c9e4.

Annex/Debug.hs

@@ -1,6 +1,6 @@
 {- git-annex debugging
  -
- - Copyright 2021-2023 Joey Hess <id@joeyh.name>
+ - Copyright 2021 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU AGPL version 3 or higher.
  -}
@@ -8,11 +8,8 @@
 module Annex.Debug (
 	DebugSelector(..),
 	DebugSource(..),
-	RawDebugMessage(..),
 	debug,
-	debug',
 	fastDebug,
-	fastDebug',
 	configureDebug,
 	debugSelectorFromGitConfig,
 	parseDebugSelector,
@@ -20,7 +17,7 @@ module Annex.Debug (
 
 import Common
 import qualified Annex
-import Utility.Debug hiding (fastDebug, fastDebug')
+import Utility.Debug hiding (fastDebug)
 import qualified Utility.Debug
 import Annex.Debug.Utility
 
@@ -28,11 +25,7 @@ import Annex.Debug.Utility
 -- is read from the Annex monad, which avoids any IORef access overhead
 -- when debugging is not enabled.
 fastDebug :: DebugSource -> String -> Annex.Annex ()
-fastDebug = fastDebug'
-
-fastDebug' :: DebugMessage msg => DebugSource -> msg -> Annex.Annex ()
-fastDebug' src msg = do
+fastDebug src msg = do
 	rd <- Annex.getRead id
 	when (Annex.debugenabled rd) $
-		liftIO $ Utility.Debug.fastDebug' (Annex.debugselector rd) src msg
-	
+		liftIO $ Utility.Debug.fastDebug (Annex.debugselector rd) src msg