Make the replication of deletion more prominent in logs

When replicating the deletion of a ref, the logs should not only
include the ref name but also the fact that the fetching causes
a deletion.

Include the "<<DELETED>>" prefix so that the operation is more
visible and searchable.

Change-Id: I6d5878fa2c8dad1e12c5738c0fcbf0358ff1475d

src/main/java/com/googlesource/gerrit/plugins/replication/pull/FetchOne.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/replication/pull/FetchOne.java b/src/main/java/com/googlesource/gerrit/plugins/replication/pull/FetchOne.java
index 69c00f9..86a44a1 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/replication/pull/FetchOne.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/replication/pull/FetchOne.java
@@ -346,7 +346,7 @@
         taskIdHex,
         replicationType,
         uri,
-        String.join(",", getRefs()));
+        getRefSpecs());
     Timer1.Context<String> context = metrics.start(config.getName());
     try {
       long startedAt = context.getStartTime();

src/main/java/com/googlesource/gerrit/plugins/replication/pull/FetchRefSpec.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/replication/pull/FetchRefSpec.java b/src/main/java/com/googlesource/gerrit/plugins/replication/pull/FetchRefSpec.java
index 613b0cf..f85f22a 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/replication/pull/FetchRefSpec.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/replication/pull/FetchRefSpec.java
@@ -43,4 +43,9 @@
   public String refName() {
     return MoreObjects.firstNonNull(getSource(), getDestination());
   }
+
+  @Override
+  public String toString() {
+    return getSource() == null ? "<<DELETED>>:" + getDestination() : super.toString();
+  }
 }