include passthrough params in --describe-other-params

Remote/External.hs

@@ -792,7 +792,10 @@ lenientRemoteConfigParser = addRemoteConfigParser specialRemoteConfigParsers $
 			, trueFalseParser readonlyField False
 				(FieldDesc "enable readonly mode")
 			]
-		, remoteConfigRestPassthrough = const True
+		, remoteConfigRestPassthrough = Just
+			( const True
+			, [("*", FieldDesc "all other parameters are passed to external special remote program")]
+			)
 		}
 
 {- When the remote supports LISTCONFIGS, only accept the ones it listed.
@@ -804,14 +807,14 @@ strictRemoteConfigParser external = listConfigs external >>= \case
 		let s = S.fromList (map fst l)
 		let listed f = S.member (fromProposedAccepted f) s
 		return $ lenientRemoteConfigParser
-			{ remoteConfigRestPassthrough = listed }
+			{ remoteConfigRestPassthrough = Just (listed, l) }
 
-listConfigs :: External -> Annex (Maybe [(Setting, Description)])
+listConfigs :: External -> Annex (Maybe [(Setting, FieldDesc)])
 listConfigs external = handleRequest external LISTCONFIGS Nothing (collect [])
   where
 	collect l req = case req of
 		CONFIG s d -> Just $ return $
-			GetNextMessage $ collect ((s, d) : l)
+			GetNextMessage $ collect ((s, FieldDesc d) : l)
 		CONFIGEND -> result (Just (reverse l))
 		UNSUPPORTED_REQUEST -> result Nothing
 		_ -> Nothing

Remote/Helper/Encryptable.hs

@@ -78,7 +78,7 @@ encryptionConfigs = S.fromList (map parserForField encryptionConfigParsers)
 parseEncryptionConfig :: RemoteConfig -> Either String ParsedRemoteConfig
 parseEncryptionConfig c = parseRemoteConfig
 	(M.restrictKeys c encryptionConfigs)
-	(RemoteConfigParser encryptionConfigParsers (const False))
+	(RemoteConfigParser encryptionConfigParsers Nothing)
 
 encryptionFieldParser :: RemoteConfigFieldParser
 encryptionFieldParser = RemoteConfigFieldParser

Remote/S3.hs

@@ -102,8 +102,13 @@ remote = specialRemoteType $ RemoteType
 			, optionalStringParser mungekeysField HiddenField
 			, optionalStringParser AWS.s3credsField HiddenField
 			]
-		, remoteConfigRestPassthrough = \f ->
-			isMetaHeader f || isArchiveMetaHeader f
+		, remoteConfigRestPassthrough = Just
+			( \f -> isMetaHeader f || isArchiveMetaHeader f
+			,
+				[ ("x-amz-meta-*", FieldDesc "http headers to add when storing on S3")
+				, ("x-archive-meta-*", FieldDesc "http headers to add when storing on Internet Archive")
+			  	]
+			)
 		}
 	, setup = s3Setup
 	, exportSupported = exportIsSupported