Make SubmoduleOp#superProjectSubscriptionsForSubmoduleBranch public

Change I5e55693bd8 made this method private because it appeared to be
unused from outside the class. However it turned out that the
delete-project plugin is using it. Make it back public and annotate it
as used by the delete-project plugin so that it is not turned private
later again.

Bug: Issue 9597
Change-Id: I3a885383a816207d523db948e750984c3d351e4c
Signed-off-by: Edwin Kempin <ekempin@google.com>
diff --git a/java/com/google/gerrit/server/submit/SubmoduleOp.java b/java/com/google/gerrit/server/submit/SubmoduleOp.java
index 51e3c5d..50be62a 100644
--- a/java/com/google/gerrit/server/submit/SubmoduleOp.java
+++ b/java/com/google/gerrit/server/submit/SubmoduleOp.java
@@ -28,6 +28,7 @@
 import com.google.gerrit.reviewdb.client.RefNames;
 import com.google.gerrit.reviewdb.client.SubmoduleSubscription;
 import com.google.gerrit.server.GerritPersonIdent;
+import com.google.gerrit.server.UsedAt;
 import com.google.gerrit.server.config.GerritServerConfig;
 import com.google.gerrit.server.config.VerboseSuperprojectUpdate;
 import com.google.gerrit.server.git.CodeReviewCommit;
@@ -365,7 +366,8 @@
     return ret;
   }
 
-  private Collection<SubmoduleSubscription> superProjectSubscriptionsForSubmoduleBranch(
+  @UsedAt(UsedAt.Project.PLUGIN_DELETE_PROJECT)
+  public Collection<SubmoduleSubscription> superProjectSubscriptionsForSubmoduleBranch(
       Branch.NameKey srcBranch) throws IOException {
     logger.atFine().log("Calculating possible superprojects for %s", srcBranch);
     Collection<SubmoduleSubscription> ret = new ArrayList<>();