Add rel=nofollow parameter to links in comments

Spamming a Gerrit site is a real issue:

https://groups.google.com/d/msg/repo-discuss/Q9x23wnOQXg/aAtXSGqNAwAJ

Google recommends adding rel="nofollow"[1] to links on comments:

"This can discourage spammers from targeting your site, and will help
keep your site from inadvertently passing PageRank to bad neighborhoods
on the web".

[1] https://support.google.com/webmasters/answer/96569?hl=en

Change-Id: I17c2c6f009d31db1c91b39d37227edebf923373a

gerrit-gwtexpui/src/main/java/com/google/gwtexpui/safehtml/client/SafeHtml.java

@@ -138,7 +138,7 @@ public abstract class SafeHtml
           "(?:[(]" + part + "*" + "[)])*" +
           part + "*" +
         ")",
-        "<a href=\"$1\" target=\"_blank\">$1</a>");
+        "<a href=\"$1\" target=\"_blank\" rel=\"nofollow\">$1</a>");
   }
 
   /**

gerrit-gwtexpui/src/test/java/com/google/gwtexpui/safehtml/client/SafeHtml_LinkifyTest.java

@@ -25,7 +25,8 @@ public class SafeHtml_LinkifyTest {
     final SafeHtml n = o.linkify();
     assertThat(o).isNotSameAs(n);
     assertThat(n.asString()).isEqualTo(
-        "A <a href=\"http://go.here/\" target=\"_blank\">http://go.here/</a> B");
+        "A <a href=\"http://go.here/\" target=\"_blank\" rel=\"nofollow\""
+        + ">http://go.here/</a> B");
   }
 
   @Test
@@ -34,7 +35,8 @@ public class SafeHtml_LinkifyTest {
     final SafeHtml n = o.linkify();
     assertThat(o).isNotSameAs(n);
     assertThat(n.asString()).isEqualTo(
-        "A <a href=\"https://go.here/\" target=\"_blank\">https://go.here/</a> B");
+        "A <a href=\"https://go.here/\" target=\"_blank\" rel=\"nofollow\""
+        + ">https://go.here/</a> B");
   }
 
   @Test
@@ -43,7 +45,8 @@ public class SafeHtml_LinkifyTest {
     final SafeHtml n = o.linkify();
     assertThat(o).isNotSameAs(n);
     assertThat(n.asString()).isEqualTo(
-        "A (<a href=\"http://go.here/\" target=\"_blank\">http://go.here/</a>) B");
+        "A (<a href=\"http://go.here/\" target=\"_blank\" rel=\"nofollow\""
+        + ">http://go.here/</a>) B");
   }
 
   @Test
@@ -52,7 +55,8 @@ public class SafeHtml_LinkifyTest {
     final SafeHtml n = o.linkify();
     assertThat(o).isNotSameAs(n);
     assertThat(n.asString()).isEqualTo(
-        "A <a href=\"http://go.here/#m()\" target=\"_blank\">http://go.here/#m()</a> B");
+        "A <a href=\"http://go.here/#m()\" target=\"_blank\" rel=\"nofollow\""
+        + ">http://go.here/#m()</a> B");
   }
 
   @Test
@@ -61,7 +65,8 @@ public class SafeHtml_LinkifyTest {
     final SafeHtml n = o.linkify();
     assertThat(o).isNotSameAs(n);
     assertThat(n.asString()).isEqualTo(
-        "A &lt;<a href=\"http://go.here/\" target=\"_blank\">http://go.here/</a>&gt; B");
+        "A &lt;<a href=\"http://go.here/\" target=\"_blank\" rel=\"nofollow\""
+        + ">http://go.here/</a>&gt; B");
   }
 
   @Test
@@ -70,7 +75,8 @@ public class SafeHtml_LinkifyTest {
     final SafeHtml n = o.linkify();
     assertThat(o).isNotSameAs(n);
     assertThat(n.asString()).isEqualTo(
-        "A <a href=\"http://go.here/foo\" target=\"_blank\">http://go.here/foo</a> B");
+        "A <a href=\"http://go.here/foo\" target=\"_blank\" rel=\"nofollow\""
+        + ">http://go.here/foo</a> B");
   }
 
   @Test
@@ -79,7 +85,8 @@ public class SafeHtml_LinkifyTest {
     final SafeHtml n = o.linkify();
     assertThat(o).isNotSameAs(n);
     assertThat(n.asString()).isEqualTo(
-        "A <a href=\"http://go.here/\" target=\"_blank\">http://go.here/</a>. B");
+        "A <a href=\"http://go.here/\" target=\"_blank\" rel=\"nofollow\""
+        + ">http://go.here/</a>. B");
   }
 
   @Test
@@ -88,7 +95,8 @@ public class SafeHtml_LinkifyTest {
     final SafeHtml n = o.linkify();
     assertThat(o).isNotSameAs(n);
     assertThat(n.asString()).isEqualTo(
-        "A <a href=\"http://go.here/\" target=\"_blank\">http://go.here/</a>, B");
+        "A <a href=\"http://go.here/\" target=\"_blank\" rel=\"nofollow\""
+        + ">http://go.here/</a>, B");
   }
 
   @Test
@@ -97,7 +105,8 @@ public class SafeHtml_LinkifyTest {
     final SafeHtml n = o.linkify();
     assertThat(o).isNotSameAs(n);
     assertThat(n.asString()).isEqualTo(
-        "A <a href=\"http://go.here/.\" target=\"_blank\">http://go.here/.</a>. B");
+        "A <a href=\"http://go.here/.\" target=\"_blank\" rel=\"nofollow\""
+        + ">http://go.here/.</a>. B");
   }
 
   private static SafeHtml html(String text) {

gerrit-gwtexpui/src/test/java/com/google/gwtexpui/safehtml/client/SafeHtml_WikifyTest.java

@@ -65,7 +65,8 @@ public class SafeHtml_WikifyTest {
     final SafeHtml n = o.wikify();
     assertThat(o).isNotSameAs(n);
     assertThat(n.asString()).isEqualTo(
-        "<p>A <a href=\"http://go.here/\" target=\"_blank\">http://go.here/</a> B</p>");
+        "<p>A <a href=\"http://go.here/\" target=\"_blank\" rel=\"nofollow\""
+        + ">http://go.here/</a> B</p>");
   }
 
   @Test
@@ -74,7 +75,8 @@ public class SafeHtml_WikifyTest {
     final SafeHtml n = o.wikify();
     assertThat(o).isNotSameAs(n);
     assertThat(n.asString()).isEqualTo(
-        "<p>A <a href=\"https://go.here/\" target=\"_blank\">https://go.here/</a> B</p>");
+        "<p>A <a href=\"https://go.here/\" target=\"_blank\" rel=\"nofollow\""
+        + ">https://go.here/</a> B</p>");
   }
 
   @Test
@@ -83,7 +85,8 @@ public class SafeHtml_WikifyTest {
     final SafeHtml n = o.wikify();
     assertThat(o).isNotSameAs(n);
     assertThat(n.asString()).isEqualTo(
-        "<p>A (<a href=\"http://go.here/\" target=\"_blank\">http://go.here/</a>) B</p>");
+        "<p>A (<a href=\"http://go.here/\" target=\"_blank\" rel=\"nofollow\""
+        + ">http://go.here/</a>) B</p>");
   }
 
   @Test
@@ -92,7 +95,8 @@ public class SafeHtml_WikifyTest {
     final SafeHtml n = o.wikify();
     assertThat(o).isNotSameAs(n);
     assertThat(n.asString()).isEqualTo(
-        "<p>A <a href=\"http://go.here/#m()\" target=\"_blank\">http://go.here/#m()</a> B</p>");
+        "<p>A <a href=\"http://go.here/#m()\" target=\"_blank\" rel=\"nofollow\""
+        + ">http://go.here/#m()</a> B</p>");
   }
 
   @Test
@@ -101,7 +105,8 @@ public class SafeHtml_WikifyTest {
     final SafeHtml n = o.wikify();
     assertThat(o).isNotSameAs(n);
     assertThat(n.asString()).isEqualTo(
-        "<p>A &lt;<a href=\"http://go.here/\" target=\"_blank\">http://go.here/</a>&gt; B</p>");
+        "<p>A &lt;<a href=\"http://go.here/\" target=\"_blank\" rel=\"nofollow\""
+        + ">http://go.here/</a>&gt; B</p>");
   }
 
   private static SafeHtml html(String text) {