fix some mixed space+tab indentation

This fixes all instances of " \t" in the code base. Most common case
seems to be after a "where" line; probably vim copied the two space layout
of that line.

Done as a background task while listening to episode 2 of the Type Theory
podcast.

Git/CatFile.hs

@@ -94,7 +94,7 @@ catTree :: CatFileHandle -> Ref -> IO [(FilePath, FileMode)]
 catTree h treeref = go <$> catObjectDetails h treeref
   where
 	go (Just (b, _, TreeObject)) = parsetree [] b
-  	go _ = []
+	go _ = []
 
 	parsetree c b = case L.break (== 0) b of
 		(modefile, rest)