1 files changed, 51 insertions, 0 deletions
diff --git a/storage/transactional/shallow.go b/storage/transactional/shallow.go
new file mode 100644
index 0000000..bedc325
--- /dev/null
+++ b/storage/transactional/shallow.go
@@ -0,0 +1,51 @@
+package transactional
+
+import (
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/storer"
+)
+
+// ShallowStorage implements the storer.ShallowStorer for the transactional package.
+type ShallowStorage struct {
+	storer.ShallowStorer
+	temporal storer.ShallowStorer
+}
+
+// NewShallowStorage returns a new ShallowStorage based on a base storer and
+// a temporal storer.
+func NewShallowStorage(base, temporal storer.ShallowStorer) *ShallowStorage {
+	return &ShallowStorage{
+		ShallowStorer: base,
+		temporal:      temporal,
+	}
+}
+
+// SetShallow honors the storer.ShallowStorer interface.
+func (s *ShallowStorage) SetShallow(commits []plumbing.Hash) error {
+	return s.temporal.SetShallow(commits)
+}
+
+// Shallow honors the storer.ShallowStorer interface.
+func (s *ShallowStorage) Shallow() ([]plumbing.Hash, error) {
+	shallow, err := s.temporal.Shallow()
+	if err != nil {
+		return nil, err
+	}
+
+	if len(shallow) != 0 {
+		return shallow, nil
+	}
+
+	return s.ShallowStorer.Shallow()
+}
+
+// Commit it copies the shallow information of the temporal storage into the
+// base storage.
+func (s *ShallowStorage) Commit() error {
+	commits, err := s.temporal.Shallow()
+	if err != nil || len(commits) == 0 {
+		return err
+	}
+
+	return s.ShallowStorer.SetShallow(commits)
+}