3 files changed, 84 insertions, 0 deletions
diff --git a/entity/doc.go b/entity/doc.go
new file mode 100644
index 00000000..4682d545
--- /dev/null
+++ b/entity/doc.go
@@ -0,0 +1,8 @@
+// Package entity contains the base common code to define an entity stored
+// in a chain of git objects, supporting actions like Push, Pull and Merge.
+package entity
+
+// TODO: Bug and Identity are very similar, right ? I expect that this package
+// will eventually hold the common code to define an entity and the related
+// helpers, errors and so on. When this work is done, it will become easier
+// to add new entities, for example to support pull requests.
diff --git a/entity/interface.go b/entity/interface.go
new file mode 100644
index 00000000..62b92a58
--- /dev/null
+++ b/entity/interface.go
@@ -0,0 +1,8 @@
+package entity
+
+type Interface interface {
+	// Id return the Entity identifier
+	Id() string
+	// HumanId return the Entity identifier truncated for human consumption
+	HumanId() string
+}
diff --git a/entity/merge.go b/entity/merge.go
new file mode 100644
index 00000000..544f2168
--- /dev/null
+++ b/entity/merge.go
@@ -0,0 +1,68 @@
+package entity
+
+import "fmt"
+
+// MergeStatus represent the result of a merge operation of an entity
+type MergeStatus int
+
+const (
+	_ MergeStatus = iota
+	MergeStatusNew
+	MergeStatusInvalid
+	MergeStatusUpdated
+	MergeStatusNothing
+)
+
+type MergeResult struct {
+	// Err is set when a terminal error occur in the process
+	Err error
+
+	Id     string
+	Status MergeStatus
+
+	// Only set for invalid status
+	Reason string
+
+	// Not set for invalid status
+	Entity Interface
+}
+
+func (mr MergeResult) String() string {
+	switch mr.Status {
+	case MergeStatusNew:
+		return "new"
+	case MergeStatusInvalid:
+		return fmt.Sprintf("invalid data: %s", mr.Reason)
+	case MergeStatusUpdated:
+		return "updated"
+	case MergeStatusNothing:
+		return "nothing to do"
+	default:
+		panic("unknown merge status")
+	}
+}
+
+func NewMergeError(err error, id string) MergeResult {
+	return MergeResult{
+		Err: err,
+		Id:  id,
+	}
+}
+
+func NewMergeStatus(status MergeStatus, id string, entity Interface) MergeResult {
+	return MergeResult{
+		Id:     id,
+		Status: status,
+
+		// Entity is not set for an invalid merge result
+		Entity: entity,
+	}
+}
+
+func NewMergeInvalidStatus(id string, reason string) MergeResult {
+	return MergeResult{
+		Id:     id,
+		Status: MergeStatusInvalid,
+		Reason: reason,
+	}
+}