diff --git a/internal/interactor/deployment.go b/internal/interactor/deployment.go
index 3e23e004..99fb2568 100644
--- a/internal/interactor/deployment.go
+++ b/internal/interactor/deployment.go
@@ -273,6 +273,35 @@ func (i *DeploymentInteractor) CreateDeploymentStatus(ctx context.Context, ds *e
 	return ds, nil
 }
 
+// CompareCommitsFromLastestDeployment returns the changed commit from the last deployment.
+// If there is no last deployment, an empty slice is returned.
+func (i *DeploymentInteractor) CompareCommitsFromLastestDeployment(ctx context.Context, r *ent.Repo, d *ent.Deployment, options *ListOptions) ([]*extent.Commit, error) {
+	if d.Status == deployment.StatusWaiting {
+		i.log.Info("The deployment is waiting, it doesn't have an SHA to compare.")
+		return []*extent.Commit{}, nil
+	}
+
+	last, err := i.store.FindPrevSuccessDeployment(ctx, d)
+	if e.HasErrorCode(err, e.ErrorCodeEntityNotFound) {
+		i.log.Info("The lastes deployment is not found. It returns an empty commit slice.")
+		return []*extent.Commit{}, nil
+	} else if err != nil {
+		i.log.Error("Failed to find the last success deployment.")
+		return nil, err
+	}
+
+	// TODO: Handling the not-found error.
+	u := ctx.Value(KeyUser).(*ent.User)
+
+	commits, _, err := i.scm.CompareCommits(ctx, u, r, last.Sha, d.Sha, options)
+	if err != nil {
+		i.log.Sugar().Errorf("Failed to compare %s ... %s.", last.Sha, d.Sha)
+		return nil, err
+	}
+
+	return commits, nil
+}
+
 func (i *DeploymentInteractor) runClosingInactiveDeployment(stop <-chan struct{}) {
 	ctx := context.Background()
 
diff --git a/internal/interactor/global.go b/internal/interactor/global.go
new file mode 100644
index 00000000..bd6ea9c3
--- /dev/null
+++ b/internal/interactor/global.go
@@ -0,0 +1,8 @@
+package interactor
+
+// ContextKey is used for context access.
+type ContextKey int
+
+const (
+	KeyUser ContextKey = iota
+)
diff --git a/internal/server/api/v1/repos/deployment_change.go b/internal/server/api/v1/repos/deployment_change.go
index f34d995e..5b644791 100644
--- a/internal/server/api/v1/repos/deployment_change.go
+++ b/internal/server/api/v1/repos/deployment_change.go
@@ -2,7 +2,6 @@ package repos
 
 import (
 	"context"
-	"fmt"
 	"net/http"
 	"strconv"
 
@@ -12,14 +11,10 @@ import (
 	i "github.com/gitploy-io/gitploy/internal/interactor"
 	gb "github.com/gitploy-io/gitploy/internal/server/global"
 	"github.com/gitploy-io/gitploy/model/ent"
-	"github.com/gitploy-io/gitploy/model/ent/deployment"
-	"github.com/gitploy-io/gitploy/model/extent"
 	"github.com/gitploy-io/gitploy/pkg/e"
 )
 
 func (s *DeploymentAPI) ListChanges(c *gin.Context) {
-	ctx := c.Request.Context()
-
 	var (
 		number  int
 		page    int
@@ -51,36 +46,16 @@ func (s *DeploymentAPI) ListChanges(c *gin.Context) {
 	vr, _ := c.Get(KeyRepo)
 	re := vr.(*ent.Repo)
 
+	ctx := context.WithValue(c.Request.Context(), i.KeyUser, u)
+
 	d, err := s.i.FindDeploymentOfRepoByNumber(ctx, re, number)
 	if err != nil {
-		s.log.Check(gb.GetZapLogLevel(err), "Failed to find the deployments.").Write(zap.Error(err))
-		gb.ResponseWithError(c, err)
-		return
-	}
-
-	ld, err := s.i.FindPrevSuccessDeployment(ctx, d)
-	if e.HasErrorCode(err, e.ErrorCodeEntityNotFound) {
-		s.log.Debug("The previous deployment is not found.")
-		gb.Response(c, http.StatusOK, []*extent.Commit{})
-		return
-	} else if err != nil {
-		s.log.Check(gb.GetZapLogLevel(err), "Failed to find the deployments.").Write(zap.Error(err))
+		s.log.Warn("Failed to find the deployment.", zap.Error(err))
 		gb.ResponseWithError(c, err)
 		return
 	}
 
-	// Get SHA when the status of deployment is waiting.
-	sha := d.Sha
-	if sha == "" {
-		sha, err = s.getCommitSha(ctx, u, re, d.Type, d.Ref)
-		if err != nil {
-			s.log.Check(gb.GetZapLogLevel(err), "It has failed to get the commit SHA.").Write(zap.Error(err))
-			gb.ResponseWithError(c, err)
-			return
-		}
-	}
-
-	commits, _, err := s.i.CompareCommits(ctx, u, re, ld.Sha, sha, &i.ListOptions{
+	commits, err := s.i.CompareCommitsFromLastestDeployment(ctx, re, d, &i.ListOptions{
 		Page:    page,
 		PerPage: perPage,
 	})
@@ -90,33 +65,6 @@ func (s *DeploymentAPI) ListChanges(c *gin.Context) {
 		return
 	}
 
+	s.log.Info("Get the changed commits for the deployment.", zap.Int("number", number))
 	gb.Response(c, http.StatusOK, commits)
 }
-
-func (s *DeploymentAPI) getCommitSha(ctx context.Context, u *ent.User, re *ent.Repo, typ deployment.Type, ref string) (string, error) {
-	switch typ {
-	case deployment.TypeCommit:
-		c, err := s.i.GetCommit(ctx, u, re, ref)
-		if err != nil {
-			return "", err
-		}
-
-		return c.SHA, nil
-	case deployment.TypeBranch:
-		b, err := s.i.GetBranch(ctx, u, re, ref)
-		if err != nil {
-			return "", err
-		}
-
-		return b.CommitSHA, nil
-	case deployment.TypeTag:
-		t, err := s.i.GetTag(ctx, u, re, ref)
-		if err != nil {
-			return "", err
-		}
-
-		return t.CommitSHA, nil
-	default:
-		return "", fmt.Errorf("Type must be one of commit, branch, tag.")
-	}
-}
diff --git a/internal/server/api/v1/repos/deployment_change_test.go b/internal/server/api/v1/repos/deployment_change_test.go
index c59083f1..0e2fb022 100644
--- a/internal/server/api/v1/repos/deployment_change_test.go
+++ b/internal/server/api/v1/repos/deployment_change_test.go
@@ -55,21 +55,12 @@ func TestDeploymentAPI_ListChanges(t *testing.T) {
 
 		m.
 			EXPECT().
-			FindPrevSuccessDeployment(ctx, any).
-			Return(&ent.Deployment{
-				ID:     5,
-				Sha:    base,
-				Status: deployment.StatusSuccess,
-			}, nil)
-
-		m.
-			EXPECT().
-			CompareCommits(ctx, any, any, base, head, gomock.Any()).
+			CompareCommitsFromLastestDeployment(ctx, any, gomock.AssignableToTypeOf(&ent.Deployment{}), any).
 			Return([]*extent.Commit{
 				{
 					SHA: head,
 				},
-			}, []*extent.CommitFile{}, nil)
+			}, nil)
 
 		// Ready the router to handle it.
 		gin.SetMode(gin.ReleaseMode)
diff --git a/internal/server/api/v1/repos/interface.go b/internal/server/api/v1/repos/interface.go
index fbf86191..f5d85482 100644
--- a/internal/server/api/v1/repos/interface.go
+++ b/internal/server/api/v1/repos/interface.go
@@ -32,6 +32,7 @@ type (
 		DeployToRemote(ctx context.Context, u *ent.User, r *ent.Repo, d *ent.Deployment, env *extent.Env) (*ent.Deployment, error)
 		GetConfig(ctx context.Context, u *ent.User, r *ent.Repo) (*extent.Config, error)
 		GetEvaluatedConfig(ctx context.Context, u *ent.User, r *ent.Repo, v *extent.EvalValues) (*extent.Config, error)
+		CompareCommitsFromLastestDeployment(ctx context.Context, r *ent.Repo, d *ent.Deployment, options *i.ListOptions) ([]*extent.Commit, error)
 
 		ListDeploymentStatuses(ctx context.Context, d *ent.Deployment) ([]*ent.DeploymentStatus, error)
 		CreateRemoteDeploymentStatus(ctx context.Context, u *ent.User, r *ent.Repo, d *ent.Deployment, ds *extent.RemoteDeploymentStatus) (*extent.RemoteDeploymentStatus, error)
diff --git a/internal/server/api/v1/repos/mock/interactor.go b/internal/server/api/v1/repos/mock/interactor.go
index 142e711d..da81979b 100644
--- a/internal/server/api/v1/repos/mock/interactor.go
+++ b/internal/server/api/v1/repos/mock/interactor.go
@@ -68,6 +68,21 @@ func (mr *MockInteractorMockRecorder) CompareCommits(ctx, u, r, base, head, opt
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "CompareCommits", reflect.TypeOf((*MockInteractor)(nil).CompareCommits), ctx, u, r, base, head, opt)
 }
 
+// CompareCommitsFromLastestDeployment mocks base method.
+func (m *MockInteractor) CompareCommitsFromLastestDeployment(ctx context.Context, r *ent.Repo, d *ent.Deployment, options *interactor.ListOptions) ([]*extent.Commit, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "CompareCommitsFromLastestDeployment", ctx, r, d, options)
+	ret0, _ := ret[0].([]*extent.Commit)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// CompareCommitsFromLastestDeployment indicates an expected call of CompareCommitsFromLastestDeployment.
+func (mr *MockInteractorMockRecorder) CompareCommitsFromLastestDeployment(ctx, r, d, options interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "CompareCommitsFromLastestDeployment", reflect.TypeOf((*MockInteractor)(nil).CompareCommitsFromLastestDeployment), ctx, r, d, options)
+}
+
 // CreateLock mocks base method.
 func (m *MockInteractor) CreateLock(ctx context.Context, l *ent.Lock) (*ent.Lock, error) {
 	m.ctrl.T.Helper()
diff --git a/pkg/e/code.go b/pkg/e/code.go
index 4ef65a54..7f4fe53e 100644
--- a/pkg/e/code.go
+++ b/pkg/e/code.go
@@ -77,6 +77,16 @@ func NewError(code ErrorCode, wrap error) *Error {
 	}
 }
 
+// TODO: Migrate the other functions which
+// constructs an error into this function.
+func NError(code ErrorCode, message string) *Error {
+	return &Error{
+		Code:     code,
+		Message:  GetMessage(code),
+		httpCode: mapHTTPCode(code),
+	}
+}
+
 func NewErrorWithMessage(code ErrorCode, message string, wrap error) *Error {
 	return &Error{
 		Code:     code,
@@ -105,14 +115,20 @@ func (e *Error) GetHTTPCode() int {
 }
 
 // SetHTTPCode sets the HTTP code manually.
-func (e *Error) SetHTTPCode(code int) {
+func (e *Error) SetHTTPCode(code int) *Error {
 	e.httpCode = code
+	return e
 }
 
 func (e *Error) Unwrap() error {
 	return e.Wrap
 }
 
+func (e *Error) SetWrap(wrap error) *Error {
+	e.Wrap = wrap
+	return e
+}
+
 func mapHTTPCode(code ErrorCode) int {
 	httpCode, ok := httpCodes[code]
 	if !ok {