Add a way to retrieve a comment from a file.

Retrieve review comment from files stored in gerrit etc_dir.
diff --git a/src/main/java/com/criteo/gerrit/plugins/automerge/AutomergeConfig.java b/src/main/java/com/criteo/gerrit/plugins/automerge/AutomergeConfig.java
index c850bef..9b84fdc 100644
--- a/src/main/java/com/criteo/gerrit/plugins/automerge/AutomergeConfig.java
+++ b/src/main/java/com/criteo/gerrit/plugins/automerge/AutomergeConfig.java
@@ -1,13 +1,24 @@
 package com.criteo.gerrit.plugins.automerge;
 
 import com.google.gerrit.server.config.GerritServerConfig;
+import com.google.gerrit.server.config.SitePaths;
+import com.google.inject.Inject;
 
+import org.apache.commons.io.FileUtils;
 import org.eclipse.jgit.lib.Config;
 
+import java.io.File;
+import java.io.IOException;
+
+
 public class AutomergeConfig {
 
+  public final static String ATOMIC_REVIEW_DETECTED_FILE = "atomic_review_detected.txt";
+  public final static String ATOMIC_REVIEWS_SAME_REPO_FILE = "atomic_review_same_repo.txt";
   public final static String AUTOMERGE_SECTION = "automerge";
   public final static String BOT_EMAIL_KEY = "botEmail";
+  public final static String CANT_MERGE_COMMENT_FILE = "cantmerge.txt";
+
   private final static String defaultBotEmail = "qabot@criteo.com";
   private final static String defaultTopicPrefix = "crossrepo/";
   public final static String TOPIC_PREFIX_KEY = "topicPrefix";
@@ -23,6 +34,9 @@
 
   private final Config config;
 
+  @Inject
+  private SitePaths sitePaths;
+
 
   public AutomergeConfig(@GerritServerConfig final Config config) {
     this.config = config;
@@ -36,6 +50,22 @@
     return botEmail;
   }
 
+  /**
+   * Return a comment from a file located in the gerrit etc_dir
+   *
+   * @param filename
+   * @return a string containing a comment.
+   * @throws IOException
+   */
+  public final String getCommentFromFile(final String filename) {
+    final File commentFile = new File(sitePaths.etc_dir, filename);
+    try {
+      return FileUtils.readFileToString(commentFile);
+    } catch (final IOException exc) {
+      return String.format("Cannot find %s file in gerrit etc dir. Please check your gerrit configuration", filename);
+    }
+  }
+
   public final String getTopicPrefix() {
     final String topicPrefix = config.getString(AUTOMERGE_SECTION, null, TOPIC_PREFIX_KEY);
     if (topicPrefix == null) {
@@ -43,4 +73,5 @@
     }
     return topicPrefix;
   }
+
 }