Comment the LocalDiskRepositoryManager in ApplyObject

The LocalDiskRepositoryManager is required specifically
for the ApplyObject for skipping any wrapper checks
like the multi-site one. Add a specific comment to highlight
the exception to the general injection rule of using
interfaces instead of implementations.

Change-Id: Id1bfb67de427b1dd2261d15dccf867f9065e5f68

src/main/java/com/googlesource/gerrit/plugins/replication/pull/fetch/ApplyObject.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/replication/pull/fetch/ApplyObject.java b/src/main/java/com/googlesource/gerrit/plugins/replication/pull/fetch/ApplyObject.java
index da63168..03362bf 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/replication/pull/fetch/ApplyObject.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/replication/pull/fetch/ApplyObject.java
@@ -15,7 +15,6 @@
 package com.googlesource.gerrit.plugins.replication.pull.fetch;
 
 import com.google.gerrit.entities.Project;
-import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.git.LocalDiskRepositoryManager;
 import com.google.inject.Inject;
 import com.googlesource.gerrit.plugins.replication.pull.api.data.RevisionData;
@@ -31,8 +30,12 @@
 
 public class ApplyObject {
 
-  private final GitRepositoryManager gitManager;
+  private final LocalDiskRepositoryManager gitManager;
 
+  // NOTE: We do need specifically the LocalDiskRepositoryManager to make sure
+  // to be able to write onto the directly physical repository without any wrapper.
+  // Using for instance the multi-site wrapper injected by Guice would result
+  // in a split-brain because of the misalignment of local vs. global refs values.
   @Inject
   public ApplyObject(LocalDiskRepositoryManager gitManager) {
     this.gitManager = gitManager;