Make Lucene case insensitive when searching for hashtags

The Hashtags will still be stored as case sensitive. A
future HashtagValidator/HashtagTransformer @Extensionpoint
could allow users to finetune how the hashtags are
stored and accepted.

Change-Id: Ibb6d6343a228fcafb6f482597655281792f85a62

gerrit-server/src/main/java/com/google/gerrit/server/index/ChangeField.java

@@ -14,8 +14,11 @@
 
 package com.google.gerrit.server.index;
 
+import com.google.common.base.Function;
 import com.google.common.base.MoreObjects;
 import com.google.common.base.Splitter;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Iterables;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Sets;
 import com.google.gerrit.reviewdb.client.Account;
@@ -232,7 +235,15 @@ public class ChangeField {
         @Override
         public Iterable<String> get(ChangeData input, FillArgs args)
             throws OrmException {
-          return input.notes().load().getHashtags();
+          return ImmutableSet.copyOf(Iterables.transform(input.notes().load()
+              .getHashtags(), new Function<String, String>() {
+
+            @Override
+            public String apply(String input) {
+              return input.toLowerCase();
+            }
+
+          }));
         }
       };
 

gerrit-server/src/main/java/com/google/gerrit/server/query/change/HashtagPredicate.java

@@ -20,12 +20,17 @@ import com.google.gwtorm.server.OrmException;
 
 class HashtagPredicate extends IndexPredicate<ChangeData> {
   HashtagPredicate(String hashtag) {
-    super(ChangeField.HASHTAG, hashtag);
+    super(ChangeField.HASHTAG, hashtag.toLowerCase());
   }
 
   @Override
   public boolean match(final ChangeData object) throws OrmException {
-    return object.notes().load().getHashtags().contains(getValue());
+    for (String hashtag : object.notes().load().getHashtags()) {
+      if (hashtag.equalsIgnoreCase(getValue())) {
+        return true;
+      }
+    }
+    return false;
   }
 
   @Override