Avoid excessive escaping for rsync special remotes that are not accessed over ssh.

This is actually tricky, 45bbf210a1 added
the escaping because it's needed for rsync that does go over ssh.
So I had to detect whether the remote's rsync url will use ssh or not,
and vary the escaping.

Utility/RsyncFile.hs

@@ -8,6 +8,7 @@
 module Utility.RsyncFile where
 
 import Data.String.Utils
+import Data.List
 
 import Utility.SafeCommand
 
@@ -48,3 +49,18 @@ rsync = boolSystem "rsync"
 
 rsyncExec :: [CommandParam] -> IO ()
 rsyncExec params = executeFile "rsync" True (toCommand params) Nothing
+
+{- Checks if an rsync url involves the remote shell (ssh or rsh).
+ - Use of such urls with rsync or rsyncExec requires additional shell
+ - escaping. -}
+rsyncUrlIsShell :: String -> Bool
+rsyncUrlIsShell s
+	| "rsync://" `isPrefixOf` s = False
+	| otherwise = go s
+	where
+		-- host:dir is rsync protocol, while host:dir is ssh/rsh
+		go [] = False
+		go (c:cs)
+			| c == '/' = False -- got to directory with no colon
+			| c == ':' = not $ ":" `isPrefixOf` cs
+			| otherwise = go cs