4 files changed, 41 insertions, 1 deletions
diff --git a/entity/dag/interface.go b/entity/dag/interface.go
index 613f60e6..80abaced 100644
--- a/entity/dag/interface.go
+++ b/entity/dag/interface.go
@@ -25,6 +25,10 @@ type Interface[SnapT Snapshot, OpT Operation] interface {
 	// Commit writes the staging area in Git and move the operations to the packs
 	Commit(repo repository.ClockedRepo) error
 
+	// CommitAsNeeded execute a Commit only if necessary. This function is useful to avoid getting an error if the Entity
+	// is already in sync with the repository.
+	CommitAsNeeded(repo repository.ClockedRepo) error
+
 	// FirstOp lookup for the very first operation of the Entity.
 	FirstOp() OpT
 
@@ -32,7 +36,7 @@ type Interface[SnapT Snapshot, OpT Operation] interface {
 	// For a valid Entity, should never be nil
 	LastOp() OpT
 
-	// Compile a bug in an easily usable snapshot
+	// Compile an Entity in an easily usable snapshot
 	Compile() SnapT
 
 	// CreateLamportTime return the Lamport time of creation
diff --git a/entity/dag/operation.go b/entity/dag/operation.go
index 1a778878..1b891aeb 100644
--- a/entity/dag/operation.go
+++ b/entity/dag/operation.go
@@ -63,6 +63,13 @@ type Operation interface {
 	setExtraMetadataImmutable(key string, value string)
 }
 
+type OperationWithApply[SnapT Snapshot] interface {
+	Operation
+
+	// Apply the operation to a Snapshot to create the final state
+	Apply(snapshot SnapT)
+}
+
 // OperationWithFiles is an optional extension for an Operation that has files dependency, stored in git.
 type OperationWithFiles interface {
 	// GetFiles return the files needed by this operation
diff --git a/entity/err.go b/entity/err.go
index 408e27b4..9d7c266e 100644
--- a/entity/err.go
+++ b/entity/err.go
@@ -5,6 +5,23 @@ import (
 	"strings"
 )
 
+type ErrNotFound struct {
+	typename string
+}
+
+func NewErrNotFound(typename string) *ErrNotFound {
+	return &ErrNotFound{typename: typename}
+}
+
+func (e ErrNotFound) Error() string {
+	return fmt.Sprintf("%s doesn't exist", e.typename)
+}
+
+func IsErrNotFound(err error) bool {
+	_, ok := err.(*ErrNotFound)
+	return ok
+}
+
 type ErrMultipleMatch struct {
 	entityType string
 	Matching   []Id
diff --git a/entity/interface.go b/entity/interface.go
index fb4735e4..656d4dc6 100644
--- a/entity/interface.go
+++ b/entity/interface.go
@@ -10,3 +10,15 @@ type Interface interface {
 	// It is acceptable to use such a hash and keep mutating that data as long as Id() is not called.
 	Id() Id
 }
+
+// type Commitable interface {
+// 	Interface
+// 	NeedCommit() bool
+// 	CommitAsNeeded(repo repository.ClockedRepo) error
+// 	Commit(repo repository.ClockedRepo) error
+// }
+
+//
+// type Operation interface {
+//
+// }