Allow reuse of DelegateRepository functionality

By allowing plugins to reuse DelegateRepository functionality
multi-site and high-availability plugins can avoid code
duplication and significantly reduce the code complexity.

Also, make the annotation @UsedAt repeatable for associating
the DelegateRepository functionality with the usage from multiple
plugins.

Bug: Issue 13429
Release-Notes: skip
Change-Id: I2b5f5b215395fc1ef2a8008a71f5c09278d1278b
(cherry picked from commit ed54a267dafeed829722b340ccaee2bbbc7f94b3)

2 files changed, 18 insertions, 3 deletions

diff --git a/java/com/google/gerrit/common/UsedAt.java b/java/com/google/gerrit/common/UsedAt.java
index 9f8b2551bd..085a6010e7 100644
--- a/java/com/google/gerrit/common/UsedAt.java
+++ b/java/com/google/gerrit/common/UsedAt.java
@@ -19,6 +19,8 @@ import static java.lang.annotation.ElementType.METHOD;
 import static java.lang.annotation.ElementType.TYPE;
 import static java.lang.annotation.RetentionPolicy.RUNTIME;
 
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Repeatable;
 import java.lang.annotation.Retention;
 import java.lang.annotation.Target;
 
@@ -28,6 +30,7 @@ import java.lang.annotation.Target;
  */
 @Target({METHOD, TYPE, FIELD})
 @Retention(RUNTIME)
+@Repeatable(UsedAt.Uses.class)
 public @interface UsedAt {
   /** Enumeration of projects that call a method/type/field. */
   enum Project {
@@ -36,9 +39,18 @@ public @interface UsedAt {
     PLUGIN_CHECKS,
     PLUGIN_DELETE_PROJECT,
     PLUGIN_SERVICEUSER,
+    PLUGIN_HIGH_AVAILABILITY,
+    PLUGIN_MULTI_SITE,
     PLUGINS_ALL, // Use this project if a method/type is generally made available to all plugins.
   }
 
   /** Reference to the project that uses the method annotated with this annotation. */
   Project value();
+
+  /** Allows to mark method/type/field with multiple UsedAt annotations. */
+  @Retention(RUNTIME)
+  @Target(ElementType.TYPE)
+  @interface Uses {
+    UsedAt[] value();
+  }
 }
diff --git a/java/com/google/gerrit/server/git/DelegateRepository.java b/java/com/google/gerrit/server/git/DelegateRepository.java
index b61488b657..9c860c49d5 100644
--- a/java/com/google/gerrit/server/git/DelegateRepository.java
+++ b/java/com/google/gerrit/server/git/DelegateRepository.java
@@ -14,6 +14,7 @@
 
 package com.google.gerrit.server.git;
 
+import com.google.gerrit.common.UsedAt;
 import java.io.IOException;
 import org.eclipse.jgit.attributes.AttributesNodeProvider;
 import org.eclipse.jgit.lib.BaseRepositoryBuilder;
@@ -24,11 +25,13 @@ import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.lib.StoredConfig;
 
 /** Wrapper around {@link Repository} that delegates all calls to the wrapped {@link Repository}. */
-class DelegateRepository extends Repository {
+@UsedAt(UsedAt.Project.PLUGIN_HIGH_AVAILABILITY)
+@UsedAt(UsedAt.Project.PLUGIN_MULTI_SITE)
+public class DelegateRepository extends Repository {
 
-  private final Repository delegate;
+  protected final Repository delegate;
 
-  DelegateRepository(Repository delegate) {
+  protected DelegateRepository(Repository delegate) {
     super(toBuilder(delegate));
     this.delegate = delegate;
   }