[dockerfile mode] Clean up state machine

Issue #2964

mode/dockerfile/dockerfile.js

@@ -24,14 +24,12 @@
       // Block comment: This is a line starting with a comment
       {
         regex: /#.*$/,
-        token: "comment",
-        next: "start"
+        token: "comment"
       },
       // Highlight an instruction without any arguments (for convenience)
       {
         regex: instructionOnlyLine,
-        token: "variable-2",
-        next: "start"
+        token: "variable-2"
       },
       // Highlight an instruction followed by arguments
       {
@@ -39,10 +37,9 @@
         token: ["variable-2", null],
         next: "arguments"
       },
-      // Fail-safe return to start
       {
-        token: null,
-        next: "start"
+        regex: /./,
+        token: null
       }
     ],
     arguments: [
@@ -54,8 +51,7 @@
       },
       {
         regex: /[^#]+\\$/,
-        token: null,
-        next: "arguments"
+        token: null
       },
       {
         // Match everything except for the inline comment