Allow disable=all to disable all warnings (fixes #2323)

src/ShellCheck/Checker.hs

@@ -306,6 +306,13 @@ prop_canDisableShebangWarning = null $ result
         csScript = "#shellcheck disable=SC2148\nfoo"
     }
 
+prop_canDisableAllWarnings = result == [2086]
+  where
+    result = checkWithSpec [] emptyCheckSpec {
+        csFilename = "file.sh",
+        csScript = "#!/bin/sh\necho $1\n#shellcheck disable=all\necho `echo $1`"
+    }
+
 prop_canDisableParseErrors = null $ result
   where
     result = checkWithSpec [] emptyCheckSpec {

src/ShellCheck/Parser.hs

@@ -984,6 +984,7 @@ prop_readAnnotation4 = isWarning readAnnotation "# shellcheck cats=dogs disable=
 prop_readAnnotation5 = isOk readAnnotation "# shellcheck disable=SC2002 # All cats are precious\n"
 prop_readAnnotation6 = isOk readAnnotation "# shellcheck disable=SC1234 # shellcheck foo=bar\n"
 prop_readAnnotation7 = isOk readAnnotation "# shellcheck disable=SC1000,SC2000-SC3000,SC1001\n"
+prop_readAnnotation8 = isOk readAnnotation "# shellcheck disable=all\n"
 readAnnotation = called "shellcheck directive" $ do
     try readAnnotationPrefix
     many1 linewhitespace
@@ -1004,8 +1005,12 @@ readAnnotationWithoutPrefix sandboxed = do
         key <- many1 (letter <|> char '-')
         char '=' <|> fail "Expected '=' after directive key"
         annotations <- case key of
-            "disable" -> readRange `sepBy` char ','
+            "disable" -> readElement `sepBy` char ','
               where
+                readElement = readRange <|> readAll
+                readAll = do
+                    string "all"
+                    return $ DisableComment 0 1000000
                 readRange = do
                     from <- readCode
                     to <- choice [ char '-' *> readCode, return $ from+1 ]