object: fix Change.Files() method behavior (fix #317)

- If 'from' or 'to' are tree entries that aren't files, Files() method will return nil instead of object not found error.
- Added a test checking this using modules fixture.

1 files changed, 8 insertions, 0 deletions

diff --git a/plumbing/object/change.go b/plumbing/object/change.go
index d29836d..2f702e4 100644
--- a/plumbing/object/change.go
+++ b/plumbing/object/change.go
@@ -46,6 +46,10 @@ func (c *Change) Files() (from, to *File, err error) {
 
 	if action == merkletrie.Insert || action == merkletrie.Modify {
 		to, err = c.To.Tree.TreeEntryFile(&c.To.TreeEntry)
+		if !c.To.TreeEntry.Mode.IsFile() {
+			return nil, nil, nil
+		}
+
 		if err != nil {
 			return
 		}
@@ -53,6 +57,10 @@ func (c *Change) Files() (from, to *File, err error) {
 
 	if action == merkletrie.Delete || action == merkletrie.Modify {
 		from, err = c.From.Tree.TreeEntryFile(&c.From.TreeEntry)
+		if !c.From.TreeEntry.Mode.IsFile() {
+			return nil, nil, nil
+		}
+
 		if err != nil {
 			return
 		}