Fix TreeWalk bug comparing DirCache and WorkingTree with ANY_DIFF

When comparing a DirCache and a WorkingTree using ANY_DIFF we
sometimes didn't recursive into a subtree of both sides gave us
zeroId() back for the identity of a subtree.  This happens when the
DirCache doesn't have a valid cache tree for the subtree, as then
it uses zeroId() for the ObjectId of the subtree, which then appears
to be equal to the zeroId() of the WorkingTreeIterator's subtree.

We work around this by adding a hasId() method that returns true
only if this iterator has a valid ObjectId.  The idEquals method
on TreeWalk than only performs a compare between two iterators if
both iterators have a valid id.

Change-Id: I695f7fafbeb452e8c0703a05c02921fae0822d3f
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/treewalk/TreeWalk.java b/org.eclipse.jgit/src/org/eclipse/jgit/treewalk/TreeWalk.java
index 16859646b6..992928bc43 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/treewalk/TreeWalk.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/treewalk/TreeWalk.java
@@ -683,8 +683,6 @@ public class TreeWalk {
 		final AbstractTreeIterator ch = currentHead;
 		final AbstractTreeIterator a = trees[nthA];
 		final AbstractTreeIterator b = trees[nthB];
-		if (a.matches == ch && b.matches == ch)
-			return a.idEqual(b);
 		if (a.matches != ch && b.matches != ch) {
 			// If neither tree matches the current path node then neither
 			// tree has this entry. In such case the ObjectId is zero(),
@@ -692,6 +690,10 @@ public class TreeWalk {
 			//
 			return true;
 		}
+		if (!a.hasId() || !b.hasId())
+			return false;
+		if (a.matches == ch && b.matches == ch)
+			return a.idEqual(b);
 		return false;
 	}