Query references by multiple prefixes

Support multiple prefixes when querying references to allow
implementor to minimize number of RPC calls.

Change-Id: I5f822fd7eaf9756b44750080d3056de138b64f4a
Signed-off-by: Minh Thai <mthai@google.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/RefTest.java

@@ -333,4 +333,17 @@ public class RefTest extends SampleDataRepositoryTestCase {
 		assertEquals(1, refs.size());
 		checkContainsRef(refs, db.exactRef("refs/heads/prefix/a"));
 	}
+
+	@Test
+	public void testGetRefsByPrefixes() throws IOException {
+		List<Ref> refs = db.getRefDatabase().getRefsByPrefix();
+		assertEquals(0, refs.size());
+
+		refs = db.getRefDatabase().getRefsByPrefix("refs/heads/p",
+				"refs/tags/A");
+		assertEquals(3, refs.size());
+		checkContainsRef(refs, db.exactRef("refs/heads/pa"));
+		checkContainsRef(refs, db.exactRef("refs/heads/prefix/a"));
+		checkContainsRef(refs, db.exactRef("refs/tags/A"));
+	}
 }

org.eclipse.jgit/src/org/eclipse/jgit/lib/RefDatabase.java

@@ -414,6 +414,31 @@ public abstract class RefDatabase {
 		return Collections.unmodifiableList(result);
 	}
 
+	/**
+	 * Returns refs whose names start with one of the given prefixes.
+	 * <p>
+	 * The default implementation uses {@link #getRefsByPrefix(String)}.
+	 * Implementors of {@link RefDatabase} should override this method directly
+	 * if a better implementation is possible.
+	 *
+	 * @param prefixes
+	 *            strings that names of refs should start with.
+	 * @return immutable list of refs whose names start with one of
+	 *         {@code prefixes}.  Refs can be unsorted and may contain
+	 *         duplicates if the prefixes overlap.
+	 * @throws java.io.IOException
+	 *             the reference space cannot be accessed.
+	 * @since 5.1
+	 */
+	@NonNull
+	public List<Ref> getRefsByPrefix(String... prefixes) throws IOException {
+		List<Ref> result = new ArrayList<>();
+		for (String prefix : prefixes) {
+			result.addAll(getRefsByPrefix(prefix));
+		}
+		return Collections.unmodifiableList(result);
+	}
+
 	/**
 	 * Check if any refs exist in the ref database.
 	 * <p>