download-commands: rename REPO_DOWNLOAD to REPO

The "download" suffix is redundant and reflects how `repo` used to
be used in the download plugin -- as kind of a pseudo download
bolted onto the side.  Since we've reworked the plugin, we can
rename this constant to better reflect its usage.

We have to duplicate it here since the download-commands plugin is
using this.  Once that migrates, we can delete the old name.

Change-Id: I948c7f2f427dec64c2617f834a5f7b35e7179543
diff --git a/java/com/google/gerrit/entities/CoreDownloadSchemes.java b/java/com/google/gerrit/entities/CoreDownloadSchemes.java
index 37c10f1..9bcd365 100644
--- a/java/com/google/gerrit/entities/CoreDownloadSchemes.java
+++ b/java/com/google/gerrit/entities/CoreDownloadSchemes.java
@@ -21,6 +21,7 @@
   public static final String HTTP = "http";
   public static final String SSH = "ssh";
   public static final String REPO_DOWNLOAD = "repo";
+  public static final String REPO = "repo";
 
   private CoreDownloadSchemes() {}
 }
diff --git a/java/com/google/gerrit/extensions/client/GeneralPreferencesInfo.java b/java/com/google/gerrit/extensions/client/GeneralPreferencesInfo.java
index 681d0bd..4cb52b7 100644
--- a/java/com/google/gerrit/extensions/client/GeneralPreferencesInfo.java
+++ b/java/com/google/gerrit/extensions/client/GeneralPreferencesInfo.java
@@ -27,7 +27,6 @@
 
   /** Preferred method to download a change. */
   public enum DownloadCommand {
-    REPO_DOWNLOAD,
     PULL,
     CHECKOUT,
     CHERRY_PICK,