Fix History rendering

There was the possibility that during history rendering we draw a lane
"trough" a passed commit. Vadim Dmitriev found that out in bug 335818. 
I added the needed check to that block of code where it was missing.

Bug: 335818
Change-Id: Ic944193b2aca55ff3eb0235d46afa60b7896aa0f
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>

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

@@ -141,6 +141,7 @@ public class PlotCommitList<L extends PlotLane> extends
 			}
 
 			currCommit.lane = c.lane;
+			handleBlockedLanes(index, currCommit, nChildren);
 		} else {
 			// More than one child, or our child is a merge.
 			// Use a different lane.
@@ -189,15 +190,27 @@ public class PlotCommitList<L extends PlotLane> extends
 			currCommit.lane = nextFreeLane();
 			activeLanes.add(currCommit.lane);
 
-			// take care: when connecting yourself to your child make sure that
+			handleBlockedLanes(index, currCommit, nChildren);
-			// you will not be located on a lane on which a passed commit is
+		}
-			// located on. Otherwise we would have to draw a line through a
+	}
-			// commit.
+
+	/**
+	 * when connecting a plotcommit to the child make sure that you will not be
+	 * located on a lane on which a passed commit is located on. Otherwise we
+	 * would have to draw a line through a commit.
+	 *
+	 * @param index
+	 * @param commit
+	 * @param nChildren
+	 */
+	private void handleBlockedLanes(final int index,
+			final PlotCommit<L> commit, final int nChildren) {
+		// take care:
 		int remaining = nChildren;
 		BitSet blockedPositions = new BitSet();
 		for (int r = index - 1; r >= 0; r--) {
 			final PlotCommit rObj = get(r);
-				if (currCommit.isChild(rObj)) {
+			if (commit.isChild(rObj)) {
 				if (--remaining == 0)
 					break;
 			}
@@ -205,11 +218,11 @@ public class PlotCommitList<L extends PlotLane> extends
 				PlotLane lane = rObj.getLane();
 				if (lane != null)
 					blockedPositions.set(lane.getPosition());
-					rObj.addPassingLane(currCommit.lane);
+				rObj.addPassingLane(commit.lane);
 			}
 		}
 		// Now let's check whether we have to reposition the lane
-			if (blockedPositions.get(currCommit.lane.getPosition())) {
+		if (blockedPositions.get(commit.lane.getPosition())) {
 			int newPos = -1;
 			for (Integer pos : freePositions)
 				if (!blockedPositions.get(pos)) {
@@ -218,9 +231,8 @@ public class PlotCommitList<L extends PlotLane> extends
 				}
 			if (newPos == -1)
 				newPos = positionsAllocated++;
-				freePositions.add(currCommit.lane.getPosition());
+			freePositions.add(commit.lane.getPosition());
-				currCommit.lane.position = newPos;
+			commit.lane.position = newPos;
-			}
 		}
 	}