Update MD003 to support setext_with_atx.

doc/Rules.md

@@ -53,7 +53,7 @@ The first header in the document should be a h1 header:
 
 Tags: headers
 
-Parameters: style ("consistent", "atx", "atx_closed", "setext"; default "consistent")
+Parameters: style ("consistent", "atx", "atx_closed", "setext", "setext_with_atx"; default "consistent")
 
 This rule is triggered when different header styles (atx, setext, and 'closed'
 atx) are used in the same document:
@@ -71,9 +71,20 @@ Be consistent with the style of header used in a document:
 
     ## ATX style H2
 
+The setext_with_atx doc style allows atx-style headers of level 3 or more in
+documents with setext style headers:
+
+    Setext style H1
+    ===============
+
+    Setext style H2
+    ---------------
+
+    ### ATX style H3
+
 Note: the configured header style can be a specific style to use (atx,
-atx_closed, setext), or simply require that the usage be consistent within the
-document.
+atx_closed, setext, setext_with_atx), or simply require that the usage be
+consistent within the document.
 
 ## MD004 - Unordered list style
 

lib/rules.js

@@ -173,10 +173,14 @@ module.exports = [
     "func": function MD003(params, errors) {
       var style = params.options.style || "consistent";
       filterTokens(params, "heading_open", function forToken(token) {
+        var styleForToken = headingStyleFor(token);
         if (style === "consistent") {
-          style = headingStyleFor(token);
+          style = styleForToken;
         }
-        if (headingStyleFor(token) !== style) {
+        if ((styleForToken !== style) &&
+            !((style === "setext_with_atx") &&
+              (/h[12]/.test(token.tag) && (styleForToken === "setext")) ||
+               (/h[^12]/.test(token.tag) && (styleForToken === "atx")))) {
           errors.push(token.lineNumber);
         }
       });

test/headers_good_setext_with_atx.json

@@ -0,0 +1,6 @@
+{
+  "default": true,
+  "MD003": {
+    "style": "setext_with_atx"
+  }
+}

test/headers_good_setext_with_atx.md

@@ -0,0 +1,7 @@
+Header 1
+========
+
+Header 2
+--------
+
+### Header 3