This commit fixes some style issues noticed after #1345 was merged.

This adds missing docstrings to the new interface methods and changes the way
TaskSpec is passed so it can't be mutated.

pkg/apis/pipeline/v1alpha1/build_gcs_resource.go

@@ -143,7 +143,7 @@ func (s *BuildGCSResource) GetInputTaskModifier(ts *TaskSpec, sourcePath string)
 			Args:    args,
 		}}}
 
-	volumes, err := getStorageVolumeSpec(s, ts)
+	volumes, err := getStorageVolumeSpec(s, *ts)
 	if err != nil {
 		return nil, err
 	}

pkg/apis/pipeline/v1alpha1/cloud_event_resource.go

@@ -78,10 +78,12 @@ func (s *CloudEventResource) Replacements() map[string]string {
 	}
 }
 
+// GetInputTaskModifier returns the TaskModifier to be used when this resource is an input.
 func (s *CloudEventResource) GetInputTaskModifier(_ *TaskSpec, _ string) (TaskModifier, error) {
 	return &InternalTaskModifier{}, nil
 }
 
+// GetOutputTaskModifier returns a No-op TaskModifier.
 func (s *CloudEventResource) GetOutputTaskModifier(_ *TaskSpec, _ string) (TaskModifier, error) {
 	return &InternalTaskModifier{}, nil
 }

pkg/apis/pipeline/v1alpha1/cluster_resource.go

@@ -142,10 +142,12 @@ func (s ClusterResource) String() string {
 	return string(json)
 }
 
+// GetOutputTaskModifier returns a No-op TaskModifier.
 func (s *ClusterResource) GetOutputTaskModifier(_ *TaskSpec, _ string) (TaskModifier, error) {
 	return &InternalTaskModifier{}, nil
 }
 
+// GetInputTaskModifier returns the TaskModifier to be used when this resource is an input.
 func (s *ClusterResource) GetInputTaskModifier(ts *TaskSpec, path string) (TaskModifier, error) {
 	var envVars []corev1.EnvVar
 	for _, sec := range s.Secrets {

pkg/apis/pipeline/v1alpha1/gcs_resource.go

@@ -97,6 +97,7 @@ func (s *GCSResource) Replacements() map[string]string {
 	}
 }
 
+// GetOutputTaskModifier returns the TaskModifier to be used when this resource is an output.
 func (s *GCSResource) GetOutputTaskModifier(ts *TaskSpec, path string) (TaskModifier, error) {
 	var args []string
 	if s.TypeDir {
@@ -116,7 +117,7 @@ func (s *GCSResource) GetOutputTaskModifier(ts *TaskSpec, path string) (TaskModi
 		Env:          envVars},
 	}
 
-	volumes, err := getStorageVolumeSpec(s, ts)
+	volumes, err := getStorageVolumeSpec(s, *ts)
 	if err != nil {
 		return nil, err
 	}
@@ -127,6 +128,7 @@ func (s *GCSResource) GetOutputTaskModifier(ts *TaskSpec, path string) (TaskModi
 	}, nil
 }
 
+// GetInputTaskModifier returns the TaskModifier to be used when this resource is an input.
 func (s *GCSResource) GetInputTaskModifier(ts *TaskSpec, path string) (TaskModifier, error) {
 	if path == "" {
 		return nil, xerrors.Errorf("GCSResource: Expect Destination Directory param to be set %s", s.Name)
@@ -150,7 +152,7 @@ func (s *GCSResource) GetInputTaskModifier(ts *TaskSpec, path string) (TaskModif
 			VolumeMounts: secretVolumeMount,
 		}}}
 
-	volumes, err := getStorageVolumeSpec(s, ts)
+	volumes, err := getStorageVolumeSpec(s, *ts)
 	if err != nil {
 		return nil, err
 	}

pkg/apis/pipeline/v1alpha1/git_resource.go

@@ -95,6 +95,7 @@ func (s *GitResource) Replacements() map[string]string {
 	}
 }
 
+// GetInputTaskModifier returns the TaskModifier to be used when this resource is an input.
 func (s *GitResource) GetInputTaskModifier(_ *TaskSpec, path string) (TaskModifier, error) {
 	args := []string{"-url", s.URL,
 		"-revision", s.Revision,
@@ -116,6 +117,7 @@ func (s *GitResource) GetInputTaskModifier(_ *TaskSpec, path string) (TaskModifi
 	}, nil
 }
 
+// GetOutputTaskModifier returns a No-op TaskModifier.
 func (s *GitResource) GetOutputTaskModifier(_ *TaskSpec, _ string) (TaskModifier, error) {
 	return &InternalTaskModifier{}, nil
 }

pkg/apis/pipeline/v1alpha1/image_resource.go

@@ -74,10 +74,12 @@ func (s *ImageResource) Replacements() map[string]string {
 	}
 }
 
+// GetInputTaskModifier returns the TaskModifier to be used when this resource is an input.
 func (s *ImageResource) GetInputTaskModifier(_ *TaskSpec, _ string) (TaskModifier, error) {
 	return &InternalTaskModifier{}, nil
 }
 
+// GetOutputTaskModifier returns a No-op TaskModifier.
 func (s *ImageResource) GetOutputTaskModifier(_ *TaskSpec, _ string) (TaskModifier, error) {
 	return &InternalTaskModifier{}, nil
 }

pkg/apis/pipeline/v1alpha1/pull_request_resource.go

@@ -93,12 +93,14 @@ func (s *PullRequestResource) Replacements() map[string]string {
 	}
 }
 
+// GetInputTaskModifier returns the TaskModifier to be used when this resource is an input.
 func (s *PullRequestResource) GetInputTaskModifier(ts *TaskSpec, sourcePath string) (TaskModifier, error) {
 	return &InternalTaskModifier{
 		StepsToPrepend: s.getSteps("download", sourcePath),
 	}, nil
 }
 
+// GetOutputTaskModifier returns a No-op TaskModifier.
 func (s *PullRequestResource) GetOutputTaskModifier(ts *TaskSpec, sourcePath string) (TaskModifier, error) {
 	return &InternalTaskModifier{
 		StepsToAppend: s.getSteps("upload", sourcePath),

pkg/apis/pipeline/v1alpha1/resource_types.go

@@ -67,24 +67,29 @@ type TaskModifier interface {
 	GetVolumes() []v1.Volume
 }
 
+// InternalTaskModifier implements TaskModifier for resources that are built-in to Tekton Pipelines.
 type InternalTaskModifier struct {
 	StepsToPrepend []Step
 	StepsToAppend  []Step
 	Volumes        []v1.Volume
 }
 
+// GetStepsToPrepend returns a set of Steps to prepend to the Task.
 func (tm *InternalTaskModifier) GetStepsToPrepend() []Step {
 	return tm.StepsToPrepend
 }
 
+// GetStepsToPrepend returns a set of Steps to append to the Task.
 func (tm *InternalTaskModifier) GetStepsToAppend() []Step {
 	return tm.StepsToAppend
 }
 
+// GetVolumes returns a set of Volumes to prepend to the Task pod.
 func (tm *InternalTaskModifier) GetVolumes() []v1.Volume {
 	return tm.Volumes
 }
 
+// ApplyTaskModifier applies a modifier to the task by appending and prepending steps and volumes.
 func ApplyTaskModifier(ts *TaskSpec, tm TaskModifier) {
 	steps := tm.GetStepsToPrepend()
 	ts.Steps = append(steps, ts.Steps...)

pkg/apis/pipeline/v1alpha1/storage_resource.go

@@ -58,7 +58,7 @@ func NewStorageResource(r *PipelineResource) (PipelineStorageResourceInterface,
 	return nil, xerrors.Errorf("StoreResource: Cannot create a storage resource without type %s in spec", r.Name)
 }
 
-func getStorageVolumeSpec(s PipelineStorageResourceInterface, spec *TaskSpec) ([]corev1.Volume, error) {
+func getStorageVolumeSpec(s PipelineStorageResourceInterface, spec TaskSpec) ([]corev1.Volume, error) {
 	var storageVol []corev1.Volume
 	mountedSecrets := map[string]string{}