MD023 should not report violations for proper blockquotes in lists (fixes #146).

lib/md023.js

@@ -4,7 +4,7 @@
 
 const shared = require("./shared");
 
-const spaceBeforeHeadingRe = /^\s+\S/;
+const spaceBeforeHeadingRe = /^((?:\s+)|(?:[>\s]+\s\s))[^>\s]/;
 
 module.exports = {
   "names": [ "MD023", "heading-start-left", "header-start-left" ],

test/blockquote-headings.md

@@ -0,0 +1,36 @@
+# Heading
+
+## Sub-heading
+
+> # Quoted heading {MD025}
+
+Text
+
+> > # Double-quoted heading {MD025}
+
+Text
+
+> ## Quoted sub-heading
+
+Text
+
+>  ## Quoted indented sub-heading {MD023} {MD027}
+
+Text
+
+- Item
+  item
+  > # Quoted heading in list {MD025}
+- Item
+  item
+  > > # Double-quoted heading in list {MD025}
+- Item
+  item
+  > ## Quoted sub-heading in list
+- Item
+- Item
+  item
+  >  ## Quoted indented sub-heading in list {MD023}
+- Item
+
+Text