utils: merkletrie support for symlinks

2 files changed, 54 insertions, 6 deletions

diff --git a/utils/merkletrie/filesystem/node.go b/utils/merkletrie/filesystem/node.go
index 5461bd3..a8f3b86 100644
--- a/utils/merkletrie/filesystem/node.go
+++ b/utils/merkletrie/filesystem/node.go
@@ -136,25 +136,54 @@ func (n *node) calculateHash(path string, file os.FileInfo) ([]byte, error) {
 		return make([]byte, 24), nil
 	}
 
-	f, err := n.fs.Open(path)
+	var hash plumbing.Hash
+	var err error
+	if file.Mode()&os.ModeSymlink != 0 {
+		hash, err = n.doCalculateHashForSymlink(path, file)
+	} else {
+		hash, err = n.doCalculateHashForRegular(path, file)
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	mode, err := filemode.NewFromOSFileMode(file.Mode())
 	if err != nil {
 		return nil, err
 	}
 
+	return append(hash[:], mode.Bytes()...), nil
+}
+
+func (n *node) doCalculateHashForRegular(path string, file os.FileInfo) (plumbing.Hash, error) {
+	f, err := n.fs.Open(path)
+	if err != nil {
+		return plumbing.ZeroHash, err
+	}
+
 	defer f.Close()
 
 	h := plumbing.NewHasher(plumbing.BlobObject, file.Size())
 	if _, err := io.Copy(h, f); err != nil {
-		return nil, err
+		return plumbing.ZeroHash, err
 	}
 
-	mode, err := filemode.NewFromOSFileMode(file.Mode())
+	return h.Sum(), nil
+}
+
+func (n *node) doCalculateHashForSymlink(path string, file os.FileInfo) (plumbing.Hash, error) {
+	target, err := n.fs.Readlink(path)
 	if err != nil {
-		return nil, err
+		return plumbing.ZeroHash, err
 	}
 
-	hash := h.Sum()
-	return append(hash[:], mode.Bytes()...), nil
+	h := plumbing.NewHasher(plumbing.BlobObject, file.Size())
+	if _, err := h.Write([]byte(target)); err != nil {
+		return plumbing.ZeroHash, err
+	}
+
+	return h.Sum(), nil
 }
 
 func (n *node) String() string {
diff --git a/utils/merkletrie/filesystem/node_test.go b/utils/merkletrie/filesystem/node_test.go
index a383716..bf1178a 100644
--- a/utils/merkletrie/filesystem/node_test.go
+++ b/utils/merkletrie/filesystem/node_test.go
@@ -25,11 +25,13 @@ func (s *NoderSuite) TestDiff(c *C) {
 	WriteFile(fsA, "foo", []byte("foo"), 0644)
 	WriteFile(fsA, "qux/bar", []byte("foo"), 0644)
 	WriteFile(fsA, "qux/qux", []byte("foo"), 0644)
+	fsA.Symlink("foo", "bar")
 
 	fsB := memfs.New()
 	WriteFile(fsB, "foo", []byte("foo"), 0644)
 	WriteFile(fsB, "qux/bar", []byte("foo"), 0644)
 	WriteFile(fsB, "qux/qux", []byte("foo"), 0644)
+	fsB.Symlink("foo", "bar")
 
 	ch, err := merkletrie.DiffTree(
 		NewRootNode(fsA, nil),
@@ -41,6 +43,23 @@ func (s *NoderSuite) TestDiff(c *C) {
 	c.Assert(ch, HasLen, 0)
 }
 
+func (s *NoderSuite) TestDiffChangeLink(c *C) {
+	fsA := memfs.New()
+	fsA.Symlink("qux", "foo")
+
+	fsB := memfs.New()
+	fsB.Symlink("bar", "foo")
+
+	ch, err := merkletrie.DiffTree(
+		NewRootNode(fsA, nil),
+		NewRootNode(fsB, nil),
+		IsEquals,
+	)
+
+	c.Assert(err, IsNil)
+	c.Assert(ch, HasLen, 1)
+}
+
 func (s *NoderSuite) TestDiffChangeContent(c *C) {
 	fsA := memfs.New()
 	WriteFile(fsA, "foo", []byte("foo"), 0644)