difftree: simplify hash comparison with deprecated files modes

Difftree hash comparisson was quite complex because the hashes of
deprecated files were diferent from the hashes of regular files.  But
git's difftree really treat them as equal.

This patch fix this by making treenoder return the same hash for regular
files than for deprecated files; now the hash comparison function is
just a bytes.Equal call.

1 files changed, 17 insertions, 14 deletions

diff --git a/plumbing/object/difftree_test.go b/plumbing/object/difftree_test.go
index fa996c2..11f6b23 100644
--- a/plumbing/object/difftree_test.go
+++ b/plumbing/object/difftree_test.go
@@ -358,24 +358,27 @@ func (s *DiffTreeSuite) TestDiffTree(c *C) {
 }
 
 func (s *DiffTreeSuite) TestIssue279(c *C) {
-	// HashEqual should ignore files if the only change is from a 100664
-	// mode to a 100644 or vice versa.
-	from := &treeNoder{
-		hash: plumbing.NewHash("d08e895238bac36d8220586fdc28c27e1a7a76d3"),
+	// treeNoders should have the same hash when their mode is
+	// filemode.Deprecated and filemode.Regular.
+	a := &treeNoder{
+		hash: plumbing.NewHash("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"),
 		mode: filemode.Regular,
 	}
-	to := &treeNoder{
-		hash: plumbing.NewHash("d08e895238bac36d8220586fdc28c27e1a7a76d3"),
-		mode: filemode.Regular,
+	b := &treeNoder{
+		hash: plumbing.NewHash("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"),
+		mode: filemode.Deprecated,
 	}
-	c.Assert(hashEqual(from, to), Equals, true)
-	c.Assert(hashEqual(to, from), Equals, true)
+	c.Assert(a.Hash(), DeepEquals, b.Hash())
 
-	// but should detect if the contents of the file also changed.
-	to = &treeNoder{
-		hash: plumbing.NewHash("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"),
+	// yet, they should have different hashes if their contents change.
+	aa := &treeNoder{
+		hash: plumbing.NewHash("bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb"),
 		mode: filemode.Regular,
 	}
-	c.Assert(hashEqual(from, to), Equals, false)
-	c.Assert(hashEqual(to, from), Equals, false)
+	c.Assert(a.Hash(), Not(DeepEquals), aa.Hash())
+	bb := &treeNoder{
+		hash: plumbing.NewHash("bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb"),
+		mode: filemode.Deprecated,
+	}
+	c.Assert(b.Hash(), Not(DeepEquals), bb.Hash())
 }