Fix PlotCommit for commits with duplicate parents

JGit allows to create commits which have duplicate parents: e.g. a
commit X has first parent Y and second parent Y. Such commits are not
handled correctly by PlotCommit leading to wrong display of the history
in EGit. In such cases there is a never ending passing line drawn beside
all commits younger than the commit with duplicate parents. This commit
fixes this by explicitly checking for duplicate parents.

In a different commit we should fix JGit not to create commits with
duplicate parents. I think native git also doesn't allow such commits,
although history display in native git (gitk, git log --graph) is not
damaged by such commits.

Change-Id: Ie3019ef613a507023958bea27b1badc3b8950279

1 files changed, 7 insertions, 3 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/revplot/PlotCommit.java b/org.eclipse.jgit/src/org/eclipse/jgit/revplot/PlotCommit.java
index 40e6aba11e..4a413c306a 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/revplot/PlotCommit.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/revplot/PlotCommit.java
@@ -100,9 +100,13 @@ public class PlotCommit<L extends PlotLane> extends RevCommit {
 		final int cnt = children.length;
 		if (cnt == 0)
 			children = new PlotCommit[] { c };
-		else if (cnt == 1)
-			children = new PlotCommit[] { children[0], c };
-		else {
+		else if (cnt == 1) {
+			if (!c.getId().equals(children[0].getId()))
+				children = new PlotCommit[] { children[0], c };
+		} else {
+			for (PlotCommit pc : children)
+				if (c.getId().equals(pc.getId()))
+					return;
 			final PlotCommit[] n = new PlotCommit[cnt + 1];
 			System.arraycopy(children, 0, n, 0, cnt);
 			n[cnt] = c;