Don't render navbar.md metadata in html

After using a named link in navbar.md as metadata to activate extensions
they remained rendered in html as plain text

Change-Id: I5562853692f763f58be08e132be1ce550aafd9dd

java/com/google/gitiles/doc/Navbar.java

diff --git a/java/com/google/gitiles/doc/Navbar.java b/java/com/google/gitiles/doc/Navbar.java
index c05f9d9..c866aa9 100644
--- a/java/com/google/gitiles/doc/Navbar.java
+++ b/java/com/google/gitiles/doc/Navbar.java
@@ -89,8 +89,8 @@
   }
 
   private void parse(String markdown) {
-    extractMetadata(markdown);
-    node = GitilesMarkdown.parse(cfg, markdown);
+    String md = extractMetadata(markdown);
+    node = GitilesMarkdown.parse(cfg, md);
     extractSiteTitle();
   }
 
@@ -107,24 +107,33 @@
     }
   }
 
-  private void extractMetadata(String markdown) {
+  private String extractMetadata(String markdown) {
     Matcher m = META_LINK.matcher(markdown);
-    while (m.find()) {
-      String key = m.group(1).toLowerCase();
-      String url = m.group(2).trim();
-      switch (key) {
-        case "logo":
-          logoUrl = url;
-          break;
-        case "home":
-          homeUrl = url;
-          break;
-        case "extensions":
-          Set<String> names = splitExtensionNames(url);
-          cfg = cfg.copyWithExtensions(enabled(names), disabled(names));
-          break;
-      }
+    boolean foundMetadata = m.find();
+    if (foundMetadata) {
+      StringBuffer sb = new StringBuffer();
+      do {
+        String key = m.group(1).toLowerCase();
+        String url = m.group(2).trim();
+        switch (key) {
+          case "logo":
+            logoUrl = url;
+            break;
+          case "home":
+            homeUrl = url;
+            break;
+          case "extensions":
+            Set<String> names = splitExtensionNames(url);
+            cfg = cfg.copyWithExtensions(enabled(names), disabled(names));
+            break;
+        }
+        m.appendReplacement(sb, "");
+        foundMetadata = m.find();
+      } while (foundMetadata);
+      m.appendTail(sb);
+      return sb.toString();
     }
+    return markdown;
   }
 
   private static Set<String> splitExtensionNames(String url) {

javatests/com/google/gitiles/doc/DocServletTest.java

diff --git a/javatests/com/google/gitiles/doc/DocServletTest.java b/javatests/com/google/gitiles/doc/DocServletTest.java
index 5d47cd8..48300fc 100644
--- a/javatests/com/google/gitiles/doc/DocServletTest.java
+++ b/javatests/com/google/gitiles/doc/DocServletTest.java
@@ -40,7 +40,12 @@
 
   @Test
   public void includesNavbar() throws Exception {
-    String navbar = "# Site Title\n" + "\n" + "* [Home](index.md)\n" + "* [README](README.md)\n";
+    String navbar =
+        "# Site Title\n"
+            + "\n"
+            + "* [Home](index.md)\n"
+            + "* [README](README.md)\n"
+            + "[extensions]: blocknote\n";
     repo.branch("master")
         .commit()
         .add("README.md", "# page\n\nof information.")
@@ -53,6 +58,7 @@
     assertThat(html).contains("<span class=\"Header-anchorTitle\">Site Title</span>");
     assertThat(html).contains("<li><a href=\"/b/repo/+/master/index.md\">Home</a></li>");
     assertThat(html).contains("<li><a href=\"/b/repo/+/master/README.md\">README</a></li>");
+    assertThat(html).doesNotContain("extensions");
     assertThat(html)
         .contains("<h1><a class=\"h\" name=\"page\" href=\"#page\"><span></span></a>page</h1>");
   }