PlotCommitList: Close plot lanes at root commits

Bug: 443006
Change-Id: I40b1eb044fa2d9e6c5d4b956c17e32ca6c1bd39f
Signed-off-by: Konrad Kügler <swamblumat-eclipsebugs@yahoo.de>

org.eclipse.jgit.test/tst/org/eclipse/jgit/revplot/PlotCommitListTest.java

@@ -668,4 +668,42 @@ public class PlotCommitListTest extends RevWalkTestCase {
 				new PlotLane[] { laneB }, test.current.passingLanes);
 		test.noMoreCommits();
 	}
+
+	@Test
+	public void testTwoRoots1() throws Exception {
+		final RevCommit a = commit();
+		final RevCommit b = commit();
+
+		PlotWalk pw = new PlotWalk(db);
+		pw.markStart(pw.lookupCommit(a));
+		pw.markStart(pw.lookupCommit(b));
+		PlotCommitList<PlotLane> pcl = new PlotCommitList<PlotLane>();
+		pcl.source(pw);
+		pcl.fillTo(Integer.MAX_VALUE);
+
+		CommitListAssert test = new CommitListAssert(pcl);
+		test.commit(b).lanePos(0);
+		test.commit(a).lanePos(0);
+		test.noMoreCommits();
+	}
+
+	@Test
+	public void testTwoRoots2() throws Exception {
+		final RevCommit a = commit();
+		final RevCommit b1 = commit();
+		final RevCommit b2 = commit(b1);
+
+		PlotWalk pw = new PlotWalk(db);
+		pw.markStart(pw.lookupCommit(a));
+		pw.markStart(pw.lookupCommit(b2));
+		PlotCommitList<PlotLane> pcl = new PlotCommitList<PlotLane>();
+		pcl.source(pw);
+		pcl.fillTo(Integer.MAX_VALUE);
+
+		CommitListAssert test = new CommitListAssert(pcl);
+		test.commit(b2).lanePos(0);
+		test.commit(b1).lanePos(0);
+		test.commit(a).lanePos(0);
+		test.noMoreCommits();
+	}
 }

org.eclipse.jgit/src/org/eclipse/jgit/revplot/PlotCommitList.java

@@ -128,11 +128,8 @@ public class PlotCommitList<L extends PlotLane> extends
 		final int nChildren = currCommit.getChildCount();
 		if (nChildren == 0) {
 			currCommit.lane = nextFreeLane();
-			continueActiveLanes(currCommit);
-			return;
-		}
-
-		if (nChildren == 1 && currCommit.children[0].getParentCount() < 2) {
+		} else if (nChildren == 1
+				&& currCommit.children[0].getParentCount() < 2) {
 			// Only one child, child has only us as their parent.
 			// Stay in the same lane as the child.
 
@@ -195,7 +192,10 @@ public class PlotCommitList<L extends PlotLane> extends
 					closeLane(c.lane);
 			}
 		}
+
 		continueActiveLanes(currCommit);
+		if (currCommit.getParentCount() == 0)
+			closeLane(currCommit.lane);
 	}
 
 	private void continueActiveLanes(final PlotCommit currCommit) {