let's use Maybe String for commands that may not be avilable

Backend/SHA.hs

@@ -27,7 +27,7 @@ import qualified SysConfig
 import Key
 
 type SHASize = Int
-
+ 
 backends :: [Backend Annex]
 -- order is slightly significant; want sha1 first ,and more general
 -- sizes earlier
@@ -35,8 +35,8 @@ backends = catMaybes $ map genBackend [1, 256, 512, 224, 384]
 
 genBackend :: SHASize -> Maybe (Backend Annex)
 genBackend size
-	| shaCommand size /= "" = Just b
+	| shaCommand size == Nothing = Nothing
-	| otherwise = Nothing
+	| otherwise = Just b
 	where
 		b = Backend.File.backend 
 			{ name = shaName size
@@ -44,13 +44,13 @@ genBackend size
 			, fsckKey = Backend.File.checkKey $ checkKeyChecksum size
 			}
 
-shaCommand :: SHASize -> String
+shaCommand :: SHASize -> Maybe String
 shaCommand 1 = SysConfig.sha1
 shaCommand 256 = SysConfig.sha256
 shaCommand 224 = SysConfig.sha224
 shaCommand 384 = SysConfig.sha384
 shaCommand 512 = SysConfig.sha512
-shaCommand _ = ""
+shaCommand _ = Nothing
 
 shaName :: SHASize -> String
 shaName size = "SHA" ++ show size
@@ -65,7 +65,7 @@ shaN size file = do
 			then error $ command ++ " parse error"
 			else return $ head bits
 	where
-		command = shaCommand size
+		command = fromJust $ shaCommand size
 
 {- A key is a checksum of its contents. -}
 keyValue :: SHASize -> FilePath -> Annex (Maybe Key)

TestConfig.hs

@@ -7,7 +7,10 @@ import System.Cmd
 import System.Exit
 
 type ConfigKey = String
-data ConfigValue = BoolConfig Bool | StringConfig String
+data ConfigValue =
+	BoolConfig Bool |
+	StringConfig String |
+	MaybeStringConfig (Maybe String)
 data Config = Config ConfigKey ConfigValue
 
 type Test = IO Config
@@ -17,15 +20,17 @@ data TestCase = TestCase TestName Test
 instance Show ConfigValue where
 	show (BoolConfig b) = show b
 	show (StringConfig s) = show s
+	show (MaybeStringConfig s) = show s
 
 instance Show Config where
-        show (Config key value) = unlines
+	show (Config key value) = unlines
 		[ key ++ " :: " ++ valuetype value
 		, key ++ " = " ++ show value
 		]
 		where
 			valuetype (BoolConfig _) = "Bool"
 			valuetype (StringConfig _) = "String"
+			valuetype (MaybeStringConfig _) = "Maybe String"
 
 writeSysConfig :: [Config] -> IO ()
 writeSysConfig config = writeFile "SysConfig.hs" body
@@ -83,12 +88,13 @@ whichCmd :: ConfigKey -> [String] -> Test
 whichCmd k cmds = search cmds
 	where
 		search [] = do
-			testEnd $ Config k (StringConfig "")
+			let r = Config k (MaybeStringConfig Nothing)
-			return $ Config k (StringConfig "")
+			testEnd r
+			return r
 		search (c:cs) = do
 			ret <- system $ quiet c
 			if (ret == ExitSuccess)
-				then return $ Config k (StringConfig $ head $ words c)
+				then return $ Config k (MaybeStringConfig $ Just $ head $ words c)
 				else search cs
 
 quiet :: String -> String
@@ -103,3 +109,5 @@ testEnd :: Config -> IO ()
 testEnd (Config _ (BoolConfig True)) = putStrLn $ " yes"
 testEnd (Config _ (BoolConfig False)) = putStrLn $ " no"
 testEnd (Config _ (StringConfig s)) = putStrLn $ " " ++ s
+testEnd (Config _ (MaybeStringConfig (Just s))) = putStrLn $ " " ++ s
+testEnd (Config _ (MaybeStringConfig Nothing)) = putStrLn $ " not available"

debian/changelog

@@ -14,6 +14,7 @@ git-annex (0.20110402) UNRELEASED; urgency=low
   * Add doc-base file. Closes: #621408
   * Periodically flush git command queue, to avoid boating memory usage
     too much.
+  * Support "sha1" and "sha512" commands on FreeBSD. Thanks, Fraser Tweedale
 
  -- Joey Hess <joeyh@debian.org>  Sat, 02 Apr 2011 13:45:54 -0400