Enable loading history until a given commit

This is needed to allow jumping to a selected commit when loading
history incrementally.

Change-Id: Id3b97d88d3b4b2d67561b11f8810cb88fe040823
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

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

@@ -0,0 +1,140 @@
+/*
+ * Copyright (C) 2012, Matthias Sohn <matthias.sohn@sap.com>
+ * 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 static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+
+import org.eclipse.jgit.api.Git;
+import org.eclipse.jgit.lib.Constants;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.RepositoryTestCase;
+import org.junit.Test;
+
+public class RevCommitListTest extends RepositoryTestCase {
+
+	private RevCommitList<RevCommit> list;
+
+	public void setup(int count) throws Exception {
+		Git git = new Git(db);
+		for (int i = 0; i < count; i++)
+			git.commit().setCommitter(committer).setAuthor(author)
+					.setMessage("commit " + i).call();
+		list = new RevCommitList<RevCommit>();
+		RevWalk w = new RevWalk(db);
+		w.markStart(w.lookupCommit(db.resolve(Constants.HEAD)));
+		list.source(w);
+	}
+
+	@Test
+	public void testFillToHighMark2() throws Exception {
+		setup(3);
+		list.fillTo(1);
+		assertEquals(2, list.size());
+		assertEquals("commit 2", list.get(0).getFullMessage());
+		assertEquals("commit 1", list.get(1).getFullMessage());
+		assertNull("commit 0 shouldn't be loaded", list.get(2));
+	}
+
+	@Test
+	public void testFillToHighMarkAll() throws Exception {
+		setup(3);
+		list.fillTo(2);
+		assertEquals(3, list.size());
+		assertEquals("commit 2", list.get(0).getFullMessage());
+		assertEquals("commit 0", list.get(2).getFullMessage());
+	}
+
+	@Test
+	public void testFillToHighMark4() throws Exception {
+		setup(3);
+		list.fillTo(3);
+		assertEquals(3, list.size());
+		assertEquals("commit 2", list.get(0).getFullMessage());
+		assertEquals("commit 0", list.get(2).getFullMessage());
+		assertNull("commit 3 can't be loaded", list.get(3));
+	}
+
+	@Test
+	public void testFillToHighMarkMulitpleBlocks() throws Exception {
+		setup(258);
+		list.fillTo(257);
+		assertEquals(258, list.size());
+	}
+
+	@Test
+	public void testFillToCommit() throws Exception {
+		setup(3);
+
+		RevWalk w = new RevWalk(db);
+		w.markStart(w.lookupCommit(db.resolve(Constants.HEAD)));
+
+		w.next();
+		RevCommit c = w.next();
+		assertNotNull("should have found 2. commit", c);
+
+		list.fillTo(c, 5);
+		assertEquals(2, list.size());
+		assertEquals("commit 1", list.get(1).getFullMessage());
+		assertNull(list.get(3));
+	}
+
+	@Test
+	public void testFillToUnknownCommit() throws Exception {
+		setup(258);
+		RevCommit c = new RevCommit(
+				ObjectId.fromString("9473095c4cb2f12aefe1db8a355fe3fafba42f67"));
+
+		list.fillTo(c, 300);
+		assertEquals("loading to unknown commit should load all commits", 258,
+				list.size());
+	}
+
+	@Test
+	public void testFillToNullCommit() throws Exception {
+		setup(3);
+		list.fillTo(null, 1);
+		assertNull(list.get(0));
+	}
+}

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

@@ -339,6 +339,72 @@ public class RevCommitList<E extends RevCommit> extends RevObjectList<E> {
 		}
 	}
 
+	/**
+	 * Ensures all commits until the given commit are loaded. The revision
+	 * walker specified by {@link #source(RevWalk)} is pumped until the
+	 * specified commit is loaded. Callers can test the final size of the list
+	 * by {@link #size()} to determine if the high water mark specified was met.
+	 * <p/>
+	 * @param commitToLoad
+	 *            commit the caller wants this list to contain when the fill
+	 *            operation is complete.
+	 * @param highMark
+	 *            maximum number of commits the caller wants this list to
+	 *            contain when the fill operation is complete. If highMark is 0
+	 *            the walk is pumped until the specified commit or the end of
+	 *            the walk is reached.
+	 * @throws IOException
+	 *             see {@link RevWalk#next()}
+	 * @throws IncorrectObjectTypeException
+	 *             see {@link RevWalk#next()}
+	 * @throws MissingObjectException
+	 *             see {@link RevWalk#next()}
+	 */
+	public void fillTo(final RevCommit commitToLoad, int highMark)
+			throws MissingObjectException, IncorrectObjectTypeException,
+			IOException {
+		if (walker == null || commitToLoad == null
+				|| (highMark > 0 && size > highMark))
+			return;
+
+		RevCommit c = walker.next();
+		if (c == null) {
+			walker = null;
+			return;
+		}
+		enter(size, (E) c);
+		add((E) c);
+
+		while ((highMark == 0 || size <= highMark) && !c.equals(commitToLoad)) {
+			int index = size;
+			Block s = contents;
+			while (index >> s.shift >= BLOCK_SIZE) {
+				s = new Block(s.shift + BLOCK_SHIFT);
+				s.contents[0] = contents;
+				contents = s;
+			}
+			while (s.shift > 0) {
+				final int i = index >> s.shift;
+				index -= i << s.shift;
+				if (s.contents[i] == null)
+					s.contents[i] = new Block(s.shift - BLOCK_SHIFT);
+				s = (Block) s.contents[i];
+			}
+
+			final Object[] dst = s.contents;
+			while ((highMark == 0 || size <= highMark) && index < BLOCK_SIZE
+					&& !c.equals(commitToLoad)) {
+				c = walker.next();
+				if (c == null) {
+					walker = null;
+					return;
+				}
+				enter(size++, (E) c);
+				dst[index++] = c;
+			}
+		}
+	}
+
 	/**
 	 * Optional callback invoked when commits enter the list by fillTo.
 	 * <p>