Require that the SHA256 backend can be used when building, since it's the default.

Backend/SHA.hs

@@ -45,7 +45,7 @@ genBackendE size =
 
 shaCommand :: SHASize -> Maybe String
 shaCommand 1 = SysConfig.sha1
-shaCommand 256 = SysConfig.sha256
+shaCommand 256 = Just SysConfig.sha256
 shaCommand 224 = SysConfig.sha224
 shaCommand 384 = SysConfig.sha384
 shaCommand 512 = SysConfig.sha512

Build/Configure.hs

@@ -26,15 +26,16 @@ tests =
 	, TestCase "bup" $ testCmd "bup" "bup --version >/dev/null"
 	, TestCase "gpg" $ testCmd "gpg" "gpg --version >/dev/null"
 	, TestCase "ssh connection caching" getSshConnectionCaching
-	] ++ shaTestCases [1, 256, 512, 224, 384]
+	] ++ shaTestCases False [1, 512, 224, 384] ++ shaTestCases True [256]
 
-shaTestCases :: [Int] -> [TestCase]
-shaTestCases l = map make l
+shaTestCases :: Bool -> [Int] -> [TestCase]
+shaTestCases required l = map make l
 	where make n =
 		let
 			cmds = map (\x -> "sha" ++ show n ++ x) ["", "sum"]
 			key = "sha" ++ show n
-		in TestCase key $ maybeSelectCmd key cmds "</dev/null"
+			selector = if required then selectCmd else maybeSelectCmd
+		in TestCase key $ selector key cmds "</dev/null"
 
 tmpDir :: String
 tmpDir = "tmp"

debian/changelog

@@ -6,6 +6,8 @@ git-annex (3.20120523) UNRELEASED; urgency=low
     and adds them.
   * Fix display of warning message when encountering a file that uses an
     unsupported backend.
+  * Require that the SHA256 backend can be used when building, since it's the
+    default.
 
  -- Joey Hess <joeyh@debian.org>  Sun, 27 May 2012 20:55:29 -0400