Disable commitWithin when running Reindex

Disable the 'commitWithin' from within Reindex by overriding
the configuration with '-1'. Treat negative values as the
original behavior, auto-flushing but not auto-committing, which
is the least safe but the most efficient for reindexing the
entire site. 

Change-Id: Ifdba797bee871d2a3d8928810a6304bacb850c8c

gerrit-pgm/src/main/java/com/google/gerrit/pgm/Reindex.java

@@ -95,6 +95,7 @@ public class Reindex extends SiteProgram {
       throw die("index.type must be configured (or not SQL)");
     }
     limitThreads();
+    disableLuceneAutomaticCommit();
     if (version == null) {
       version = ChangeSchemas.getLatest().getVersion();
     }
@@ -162,6 +163,15 @@ public class Reindex extends SiteProgram {
     return dbInjector.createChildInjector(modules);
   }
 
+  private void disableLuceneAutomaticCommit() {
+    Config cfg =
+        dbInjector.getInstance(Key.get(Config.class, GerritServerConfig.class));
+    if (IndexModule.getIndexType(dbInjector) == IndexType.LUCENE) {
+      cfg.setLong("index", "changes_open", "commitWithin", -1);
+      cfg.setLong("index", "changes_closed", "commitWithin", -1);
+    }
+  }
+
   private class ReviewDbModule extends LifecycleModule {
     @Override
     protected void configure() {