Preload all cache when fetching all refs

When calling the RefDatabase.getRefs() the entire refs
are loaded and present in memory: use the opportunity
to cache the all set of refs into the in-memory key-value
store for allowing a fast preloading of the refs cache.

Change-Id: I24423089305490befe3156e80b3dbd1c7010304d

src/main/java/com/googlesource/gerrit/plugins/cachedrefdb/CachedRefDatabase.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/cachedrefdb/CachedRefDatabase.java b/src/main/java/com/googlesource/gerrit/plugins/cachedrefdb/CachedRefDatabase.java
index 04541bd..e40e41b 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/cachedrefdb/CachedRefDatabase.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/cachedrefdb/CachedRefDatabase.java
@@ -140,7 +140,12 @@
 
   @Override
   public List<Ref> getRefs() throws IOException {
-    return delegate.getRefs();
+    List<Ref> allRefs = delegate.getRefs();
+    for (Ref ref : allRefs) {
+      refsCache.computeIfAbsent(
+          repo.getProjectName(), ref.getName(), () -> Optional.ofNullable(ref));
+    }
+    return allRefs;
   }
 
   @Override