Add RevWalkUtils with count(start, end) method

It returns the number of commits that are in start and not in end.
Useful for calculating how much a branch is ahead of another one.

Change-Id: I09f7d9b049beea417da7ff32c9f8bf0d4ed46a7f
Signed-off-by: Robin Stocker <robin@nibor.org>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/revwalk/RevWalkUtilsCountTest.java

@@ -0,0 +1,103 @@
+/*
+ * Copyright (C) 2011, Robin Stocker <robin@nibor.org>
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.eclipse.jgit.revwalk;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class RevWalkUtilsCountTest extends RevWalkTestCase {
+
+	@Test
+	public void shouldWorkForNormalCase() throws Exception {
+		final RevCommit a = commit();
+		final RevCommit b = commit(a);
+
+		assertEquals(1, count(b, a));
+	}
+
+	@Test
+	public void shouldReturnZeroOnSameCommit() throws Exception {
+		final RevCommit c1 = commit(commit(commit()));
+		assertEquals(0, count(c1, c1));
+	}
+
+	@Test
+	public void shouldReturnZeroWhenMergedInto() throws Exception {
+		final RevCommit a = commit();
+		final RevCommit b = commit(a);
+
+		assertEquals(0, count(a, b));
+	}
+
+	@Test
+	public void shouldWorkWithMerges() throws Exception {
+		final RevCommit a = commit();
+		final RevCommit b1 = commit(a);
+		final RevCommit b2 = commit(a);
+		final RevCommit c = commit(b1, b2);
+
+		assertEquals(3, count(c, a));
+	}
+
+	@Test
+	public void shouldWorkWithoutCommonAncestor() throws Exception {
+		final RevCommit a1 = commit();
+		final RevCommit a2 = commit();
+		final RevCommit b = commit(a1);
+
+		assertEquals(2, count(b, a2));
+	}
+
+	@Test
+	public void shouldWorkWithZeroAsEnd() throws Exception {
+		final RevCommit c = commit(commit());
+
+		assertEquals(2, count(c, null));
+	}
+
+	private int count(RevCommit start, RevCommit end) throws Exception {
+		return RevWalkUtils.count(rw, start, end);
+	}
+}

org.eclipse.jgit/src/org/eclipse/jgit/revwalk/RevWalkUtils.java

@@ -0,0 +1,96 @@
+/*
+ * Copyright (C) 2011, Robin Stocker <robin@nibor.org>
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.eclipse.jgit.revwalk;
+
+import java.io.IOException;
+
+import org.eclipse.jgit.errors.IncorrectObjectTypeException;
+import org.eclipse.jgit.errors.MissingObjectException;
+
+/**
+ * Utility methods for {@link RevWalk}.
+ */
+public final class RevWalkUtils {
+
+	private RevWalkUtils() {
+		// Utility class
+	}
+
+	/**
+	 * Count the number of commits that are reachable from <code>start</code>
+	 * until a commit that is reachable from <code>end</code> is encountered. In
+	 * other words, count the number of commits that are in <code>start</code>,
+	 * but not in <code>end</code>.
+	 * <p>
+	 * Note that this method calls {@link RevWalk#reset()} at the beginning.
+	 * Also note that the existing rev filter on the walk is left as-is, so be
+	 * sure to set the right rev filter before calling this method.
+	 *
+	 * @param walk
+	 *            the rev walk to use
+	 * @param start
+	 *            the commit to start counting from
+	 * @param end
+	 *            the commit where counting should end, or null if counting
+	 *            should be done until there are no more commits
+	 *
+	 * @return the number of commits
+	 * @throws MissingObjectException
+	 * @throws IncorrectObjectTypeException
+	 * @throws IOException
+	 */
+	public static int count(final RevWalk walk, final RevCommit start,
+			final RevCommit end) throws MissingObjectException,
+			IncorrectObjectTypeException, IOException {
+		walk.reset();
+		walk.markStart(start);
+		if (end != null)
+			walk.markUninteresting(end);
+
+		int count = 0;
+		for (RevCommit c = walk.next(); c != null; c = walk.next())
+			count++;
+		return count;
+	}
+}