remove Params constructor from Utility.SafeCommand

This removes a bit of complexity, and should make things faster
(avoids tokenizing Params string), and probably involve less garbage
collection.

In a few places, it was useful to use Params to avoid needing a list,
but that is easily avoided.

Problems noticed while doing this conversion:

	* Some uses of Params "oneword" which was entirely unnecessary
	  overhead.
	* A few places that built up a list of parameters with ++
	  and then used Params to split it!

Test suite passes.

Git/LsTree.hs

@@ -37,13 +37,26 @@ lsTree t repo = map parseLsTree
 	<$> pipeNullSplitZombie (lsTreeParams t) repo
 
 lsTreeParams :: Ref -> [CommandParam]
-lsTreeParams t = [ Params "ls-tree --full-tree -z -r --", File $ fromRef t ]
+lsTreeParams t =
+	[ Param "ls-tree"
+	, Param "--full-tree"
+	, Param "-z"
+	, Param "-r"
+	, Param "--"
+	, File $ fromRef t
+	]
 
 {- Lists specified files in a tree. -}
 lsTreeFiles :: Ref -> [FilePath] -> Repo -> IO [TreeItem]
 lsTreeFiles t fs repo = map parseLsTree <$> pipeNullSplitStrict ps repo
   where
-	ps = [Params "ls-tree --full-tree -z --", File $ fromRef t] ++ map File fs
+	ps =
+		[ Param "ls-tree"
+		, Param "--full-tree"
+		, Param "-z"
+		, Param "--"
+		, File $ fromRef t
+		] ++ map File fs
 
 {- Parses a line of ls-tree output.
  - (The --long format is not currently supported.) -}