Add initial support for --color

ShellCheck/Formatter/TTY.hs

@@ -46,11 +46,11 @@ colorForLevel level =
         otherwise -> 0 -- none
 
 outputError file error = do
-    color <- getColorFunc
-    hPutStrLn stderr $ color "error" $ file ++ ": " ++ error
+    color <- getColorFunc $ ColorAuto -- FIXME: should respect --color
+    hPutStrLn stderr $ color "error ZZZ" $ file ++ ": " ++ error
 
 outputResult result contents = do
-    color <- getColorFunc
+    color <- getColorFunc $ crColorOption result
     let comments = crComments result
     let fileLines = lines contents
     let lineCount = fromIntegral $ length fileLines
@@ -75,10 +75,15 @@ cuteIndent comment =
 
 code code = "SC" ++ show code
 
-getColorFunc = do
+getColorFunc colorOption = do
     term <- hIsTerminalDevice stdout
     let windows = "mingw" `isPrefixOf` os
-    return $ if term && not windows then colorComment else const id
+    let isUsableTty = term && not windows
+    let useColor = case colorOption of
+                       ColorAlways -> True
+                       ColorNever -> False
+                       ColorAuto -> isUsableTty
+    return $ if useColor then colorComment else const id
   where
     colorComment level comment =
         ansi (colorForLevel level) ++ comment ++ clear