1 files changed, 121 insertions, 0 deletions
diff --git a/plumbing/difftree/change.go b/plumbing/difftree/change.go
new file mode 100644
index 0000000..c636577
--- /dev/null
+++ b/plumbing/difftree/change.go
@@ -0,0 +1,121 @@
+package difftree
+
+import (
+	"bytes"
+	"fmt"
+	"strings"
+
+	"srcd.works/go-git.v4/plumbing/object"
+	"srcd.works/go-git.v4/utils/merkletrie"
+)
+
+// Change values represent a detected change between two git trees.  For
+// modifications, From is the original status of the node and To is its
+// final status.  For insertions, From is the zero value and for
+// deletions To is the zero value.
+type Change struct {
+	From ChangeEntry
+	To   ChangeEntry
+}
+
+var empty = ChangeEntry{}
+
+// Action returns the kind of action represented by the change, an
+// insertion, a deletion or a modification.
+func (c *Change) Action() (merkletrie.Action, error) {
+	if c.From == empty && c.To == empty {
+		return merkletrie.Action(0),
+			fmt.Errorf("malformed change: empty from and to")
+	}
+	if c.From == empty {
+		return merkletrie.Insert, nil
+	}
+	if c.To == empty {
+		return merkletrie.Delete, nil
+	}
+
+	return merkletrie.Modify, nil
+}
+
+// Files return the files before and after a change.
+// For insertions from will be nil. For deletions to will be nil.
+func (c *Change) Files() (from, to *object.File, err error) {
+	action, err := c.Action()
+	if err != nil {
+		return
+	}
+
+	if action == merkletrie.Insert || action == merkletrie.Modify {
+		to, err = c.To.Tree.TreeEntryFile(&c.To.TreeEntry)
+		if err != nil {
+			return
+		}
+	}
+
+	if action == merkletrie.Delete || action == merkletrie.Modify {
+		from, err = c.From.Tree.TreeEntryFile(&c.From.TreeEntry)
+		if err != nil {
+			return
+		}
+	}
+
+	return
+}
+
+func (c *Change) String() string {
+	action, err := c.Action()
+	if err != nil {
+		return fmt.Sprintf("malformed change")
+	}
+
+	return fmt.Sprintf("<Action: %s, Path: %s>", action, c.name())
+}
+
+func (c *Change) name() string {
+	if c.From != empty {
+		return c.From.Name
+	}
+
+	return c.To.Name
+}
+
+// ChangeEntry values represent a node that has suffered a change.
+type ChangeEntry struct {
+	// Full path of the node using "/" as separator.
+	Name string
+	// Parent tree of the node that has changed.
+	Tree *object.Tree
+	// The entry of the node.
+	TreeEntry object.TreeEntry
+}
+
+// Changes represents a collection of changes between two git trees.
+// Implements sort.Interface lexicographically over the path of the
+// changed files.
+type Changes []*Change
+
+func (c Changes) Len() int {
+	return len(c)
+}
+
+func (c Changes) Swap(i, j int) {
+	c[i], c[j] = c[j], c[i]
+}
+
+func (c Changes) Less(i, j int) bool {
+	return strings.Compare(c[i].name(), c[j].name()) < 0
+}
+
+func (c Changes) String() string {
+	var buffer bytes.Buffer
+	buffer.WriteString("[")
+	comma := ""
+	for _, v := range c {
+		buffer.WriteString(comma)
+		buffer.WriteString(v.String())
+		comma = ", "
+	}
+	buffer.WriteString("]")
+
+	return buffer.String()
+}