Remove unnecessary uses of head

src/ShellCheck/Checks/Commands.hs

@@ -279,10 +279,10 @@ checkGrepRe = CommandCheck (Basename "grep") check where
         grepGlobFlags = ["fixed-strings", "F", "include", "exclude", "exclude-dir", "o", "only-matching"]
 
     wordStartingWith c =
-        head . filter ([c] `isPrefixOf`) $ candidates
+        headOrDefault (c:"test") . filter ([c] `isPrefixOf`) $ candidates
       where
         candidates =
-            sampleWords ++ map (\(x:r) -> toUpper x : r) sampleWords ++ [c:"test"]
+            sampleWords ++ map (\(x:r) -> toUpper x : r) sampleWords
 
     getSuspiciousRegexWildcard str =
         if not $ str `matches` contra

src/ShellCheck/Checks/ShellSupport.hs

@@ -457,8 +457,8 @@ checkEchoSed = ForShell [Bash, Ksh] f
     -- This should have used backreferences, but TDFA doesn't support them
     sedRe = mkRegex "^s(.)([^\n]*)g?$"
     isSimpleSed s = fromMaybe False $ do
-        [first,rest] <- matchRegex sedRe s
-        let delimiters = filter (== head first) rest
+        [h:_,rest] <- matchRegex sedRe s
+        let delimiters = filter (== h) rest
         guard $ length delimiters == 2
         return True
     checkIn id s =