add write method for branch (#109)

internal/store/refs.go

@@ -42,6 +42,21 @@ func (b *branch) loadHash(rootGoitPath string) error {
 	return nil
 }
 
+func (b *branch) write(rootGoitPath string) error {
+	branchPath := filepath.Join(rootGoitPath, "refs", "heads", b.Name)
+	f, err := os.Create(branchPath)
+	if err != nil {
+		return fmt.Errorf("fail to create %s: %w", branchPath, err)
+	}
+	defer f.Close()
+
+	if _, err := f.WriteString(b.hash.String()); err != nil {
+		return fmt.Errorf("fail to write hash(%s): %w", b.hash, err)
+	}
+
+	return nil
+}
+
 type Refs struct {
 	Heads []*branch
 }
@@ -94,14 +109,8 @@ func (r *Refs) AddBranch(rootGoitPath, newBranchName string, newBranchHash sha.S
 	r.Heads = append(r.Heads, b)
 
 	// write file
-	branchPath := filepath.Join(rootGoitPath, "refs", "heads", newBranchName)
-	f, err := os.Create(branchPath)
-	if err != nil {
-		return err
-	}
-	defer f.Close()
-	if _, err := f.WriteString(newBranchHash.String()); err != nil {
-		return err
+	if err := b.write(rootGoitPath); err != nil {
+		return fmt.Errorf("fail to write branch: %w", err)
 	}
 
 	// sort heads
@@ -203,15 +212,9 @@ func (r *Refs) UpdateBranchHash(rootGoitPath, branchName string, newHash sha.SHA
 	branch := r.Heads[n]
 	branch.hash = newHash
 
-	branchPath := filepath.Join(rootGoitPath, "refs", "heads", branchName)
-	f, err := os.Create(branchPath)
-	if err != nil {
-		return fmt.Errorf("fail to create %s: %w", branchPath, err)
-	}
-	defer f.Close()
-
-	if _, err := f.WriteString(newHash.String()); err != nil {
-		return fmt.Errorf("fail to write hash: %w", err)
+	// write file
+	if err := branch.write(rootGoitPath); err != nil {
+		return fmt.Errorf("fail to write branch: %w", err)
 	}
 
 	return nil