allow building w/o rsync installed

rsync is needed to run, but may not be on the build machine; that's ok

Build/Configure.hs

@@ -24,14 +24,14 @@ tests :: [TestCase]
 tests =
 	[ TestCase "version" (Config "packageversion" . StringConfig <$> getVersion)
 	, TestCase "UPGRADE_LOCATION" getUpgradeLocation
-	, TestCase "git" $ requireCmd "git" "git --version >/dev/null"
+	, TestCase "git" $ testCmd "git" "git --version >/dev/null"
 	, TestCase "git version" getGitVersion
 	, testCp "cp_a" "-a"
 	, testCp "cp_p" "-p"
 	, testCp "cp_preserve_timestamps" "--preserve=timestamps"
 	, testCp "cp_reflink_auto" "--reflink=auto"
-	, TestCase "xargs -0" $ requireCmd "xargs_0" "xargs -0 </dev/null"
-	, TestCase "rsync" $ requireCmd "rsync" "rsync --version >/dev/null"
+	, TestCase "xargs -0" $ testCmd "xargs_0" "xargs -0 </dev/null"
+	, TestCase "rsync" $ testCmd "rsync" "rsync --version >/dev/null"
 	, TestCase "curl" $ testCmd "curl" "curl --version >/dev/null"
 	, TestCase "wget" $ testCmd "wget" "wget --version >/dev/null"
 	, TestCase "wget unclutter options" checkWgetUnclutter

Build/TestConfig.hs

@@ -61,18 +61,6 @@ runTests (TestCase tname t : ts) = do
 	rest <- runTests ts
 	return $ c:rest
 
-{- Tests that a command is available, aborting if not. -}
-requireCmd :: ConfigKey -> String -> Test
-requireCmd k cmdline = do
-	ret <- testCmd k cmdline
-	handle ret
-  where
-	handle r@(Config _ (BoolConfig True)) = return r
-	handle r = do
-		testEnd r
-		error $ "** the " ++ c ++ " command is required"
-	c = head $ words cmdline
-
 {- Checks if a command is available by running a command line. -}
 testCmd :: ConfigKey -> String -> Test
 testCmd k cmdline = do