Make excludedRefsPattern() to return an empty list by default

The extension of the replication endpoints configuration done
with I42366148cfb1f introduced a breaking change that made other
plugins (e.g. pull-replication) to fail.

Restore a backward compatible implementation of the new
excludedRefPattern configuration and amend the documentation to
specify that is empty by default.

Change-Id: Iee92281ed41ca70819de783b3563832363c245fb

src/main/java/com/googlesource/gerrit/plugins/replication/RemoteConfiguration.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/replication/RemoteConfiguration.java b/src/main/java/com/googlesource/gerrit/plugins/replication/RemoteConfiguration.java
index 307017b..67d23b0 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/replication/RemoteConfiguration.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/replication/RemoteConfiguration.java
@@ -149,5 +149,7 @@
    *
    * @return list of successfully compiled patterns
    */
-  ImmutableList<Pattern> excludedRefsPattern();
+  default ImmutableList<Pattern> excludedRefsPattern() {
+    return ImmutableList.of();
+  }
 }

src/main/resources/Documentation/config.md

diff --git a/src/main/resources/Documentation/config.md b/src/main/resources/Documentation/config.md
index 197c0d0..0243ea1 100644
--- a/src/main/resources/Documentation/config.md
+++ b/src/main/resources/Documentation/config.md
@@ -602,6 +602,8 @@
   example refs created by plugins. Multiple excludedRefsPattern keys can be
   supplied, to specify multiple patterns to match against.
 
+  Do not exclude any refs pattern by default.
+
 Directory `replication`
 --------------------
 The optional directory `$site_path/etc/replication` contains Git-style