Expose Sets helper to tests outside org.eclipse.jgit.api

A later patch will make use of this class in a org.eclipse.jgit.lib
test.

Change-Id: I2b268e6a5dbf12174201f45259f9f007686708d2
Signed-off-by: Jonathan Nieder <jrn@google.com>

org.eclipse.jgit.test/pom.xml

   </dependencies>
 
   <build>
+    <sourceDirectory>src/</sourceDirectory>
     <testSourceDirectory>tst/</testSourceDirectory>
 
     <testResources>

org.eclipse.jgit.test/tst/org/eclipse/jgit/api/Sets.java → org.eclipse.jgit.test/src/org/eclipse/jgit/lib/Sets.java

  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-package org.eclipse.jgit.api;
+package org.eclipse.jgit.lib;
 
 import java.util.HashSet;
 import java.util.Set;
 
-class Sets {
-	static <T> Set<T> of(T... elements) {
+public class Sets {
+	public static <T> Set<T> of(T... elements) {
 		Set<T> ret = new HashSet<T>();
 		for (T element : elements)
 			ret.add(element);

org.eclipse.jgit.test/tst/org/eclipse/jgit/api/MergeCommandTest.java

 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.lib.RepositoryState;
+import org.eclipse.jgit.lib.Sets;
 import org.eclipse.jgit.merge.MergeStrategy;
 import org.eclipse.jgit.merge.ResolveMerger.MergeFailureReason;
 import org.eclipse.jgit.revwalk.RevCommit;

org.eclipse.jgit.test/tst/org/eclipse/jgit/api/StatusCommandTest.java

 import org.eclipse.jgit.api.errors.NoFilepatternException;
 import org.eclipse.jgit.errors.NoWorkTreeException;
 import org.eclipse.jgit.junit.RepositoryTestCase;
+import org.eclipse.jgit.lib.Sets;
 import org.junit.Test;
 
 public class StatusCommandTest extends RepositoryTestCase {