config.go

package buildah

import (
	"context"
	"encoding/json"
	"fmt"
	"os"
	"runtime"
	"strings"
	"time"

	"github.com/containerd/containerd/platforms"
	"github.com/containers/buildah/define"
	"github.com/containers/buildah/docker"
	"github.com/containers/common/pkg/util"
	"github.com/containers/image/v5/manifest"
	"github.com/containers/image/v5/pkg/compression"
	"github.com/containers/image/v5/transports"
	"github.com/containers/image/v5/types"
	"github.com/containers/storage/pkg/stringid"
	ociv1 "github.com/opencontainers/image-spec/specs-go/v1"
	"github.com/sirupsen/logrus"
)

// unmarshalConvertedConfig obtains the config blob of img valid for the wantedManifestMIMEType format
// (either as it exists, or converting the image if necessary), and unmarshals it into dest.
// NOTE: The MIME type is of the _manifest_, not of the _config_ that is returned.
func unmarshalConvertedConfig(ctx context.Context, dest interface{}, img types.Image, wantedManifestMIMEType string) error {
	_, actualManifestMIMEType, err := img.Manifest(ctx)
	if err != nil {
		return fmt.Errorf("error getting manifest MIME type for %q: %w", transports.ImageName(img.Reference()), err)
	}
	if wantedManifestMIMEType != actualManifestMIMEType {
		layerInfos := img.LayerInfos()
		for i := range layerInfos { // force the "compression" to gzip, which is supported by all of the formats we care about
			layerInfos[i].CompressionOperation = types.Compress
			layerInfos[i].CompressionAlgorithm = &compression.Gzip
		}
		updatedImg, err := img.UpdatedImage(ctx, types.ManifestUpdateOptions{
			LayerInfos: layerInfos,
		})
		if err != nil {
			return fmt.Errorf("resetting recorded compression for %q: %w", transports.ImageName(img.Reference()), err)
		}
		secondUpdatedImg, err := updatedImg.UpdatedImage(ctx, types.ManifestUpdateOptions{
			ManifestMIMEType: wantedManifestMIMEType,
		})
		if err != nil {
			return fmt.Errorf("error converting image %q from %q to %q: %w", transports.ImageName(img.Reference()), actualManifestMIMEType, wantedManifestMIMEType, err)
		}
		img = secondUpdatedImg
	}
	config, err := img.ConfigBlob(ctx)
	if err != nil {
		return fmt.Errorf("error reading %s config from %q: %w", wantedManifestMIMEType, transports.ImageName(img.Reference()), err)
	}
	if err := json.Unmarshal(config, dest); err != nil {
		return fmt.Errorf("error parsing %s configuration %q from %q: %w", wantedManifestMIMEType, string(config), transports.ImageName(img.Reference()), err)
	}
	return nil
}

func (b *Builder) initConfig(ctx context.Context, img types.Image, sys *types.SystemContext) error {
	if img != nil { // A pre-existing image, as opposed to a "FROM scratch" new one.
		rawManifest, manifestMIMEType, err := img.Manifest(ctx)
		if err != nil {
			return fmt.Errorf("error reading image manifest for %q: %w", transports.ImageName(img.Reference()), err)
		}
		rawConfig, err := img.ConfigBlob(ctx)
		if err != nil {
			return fmt.Errorf("error reading image configuration for %q: %w", transports.ImageName(img.Reference()), err)
		}
		b.Manifest = rawManifest
		b.Config = rawConfig

		dimage := docker.V2Image{}
		if err := unmarshalConvertedConfig(ctx, &dimage, img, manifest.DockerV2Schema2MediaType); err != nil {
			return err
		}
		b.Docker = dimage

		oimage := ociv1.Image{}
		if err := unmarshalConvertedConfig(ctx, &oimage, img, ociv1.MediaTypeImageManifest); err != nil {
			return err
		}
		b.OCIv1 = oimage

		if manifestMIMEType == ociv1.MediaTypeImageManifest {
			// Attempt to recover format-specific data from the manifest.
			v1Manifest := ociv1.Manifest{}
			if err := json.Unmarshal(b.Manifest, &v1Manifest); err != nil {
				return fmt.Errorf("error parsing OCI manifest %q: %w", string(b.Manifest), err)
			}
			for k, v := range v1Manifest.Annotations {
				// NOTE: do not override annotations that are
				// already set. Otherwise, we may erase
				// annotations such as the digest of the base
				// image.
				if value := b.ImageAnnotations[k]; value == "" {
					b.ImageAnnotations[k] = v
				}
			}
		}
	}

	b.setupLogger()
	b.fixupConfig(sys)
	return nil
}

func (b *Builder) fixupConfig(sys *types.SystemContext) {
	if b.Docker.Config != nil {
		// Prefer image-level settings over those from the container it was built from.
		b.Docker.ContainerConfig = *b.Docker.Config
	}
	b.Docker.Config = &b.Docker.ContainerConfig
	b.Docker.DockerVersion = ""
	now := time.Now().UTC()
	if b.Docker.Created.IsZero() {
		b.Docker.Created = now
	}
	if b.OCIv1.Created == nil || b.OCIv1.Created.IsZero() {
		b.OCIv1.Created = &now
	}
	if b.OS() == "" {
		if sys != nil && sys.OSChoice != "" {
			b.SetOS(sys.OSChoice)
		} else {
			b.SetOS(runtime.GOOS)
		}
	}
	if b.Architecture() == "" {
		if sys != nil && sys.ArchitectureChoice != "" {
			b.SetArchitecture(sys.ArchitectureChoice)
		} else {
			b.SetArchitecture(runtime.GOARCH)
		}
		// in case the arch string we started with was shorthand for a known arch+variant pair, normalize it
		ps := platforms.Normalize(ociv1.Platform{OS: b.OS(), Architecture: b.Architecture(), Variant: b.Variant()})
		b.SetArchitecture(ps.Architecture)
		b.SetVariant(ps.Variant)
	}
	if b.Format == define.Dockerv2ImageManifest && b.Hostname() == "" {
		b.SetHostname(stringid.TruncateID(stringid.GenerateRandomID()))
	}
}

func (b *Builder) setupLogger() {
	if b.Logger == nil {
		b.Logger = logrus.New()
		b.Logger.SetOutput(os.Stderr)
		b.Logger.SetLevel(logrus.GetLevel())
	}
}

// Annotations returns a set of key-value pairs from the image's manifest.
func (b *Builder) Annotations() map[string]string {
	return copyStringStringMap(b.ImageAnnotations)
}

// SetAnnotation adds or overwrites a key's value from the image's manifest.
// Note: this setting is not present in the Docker v2 image format, so it is
// discarded when writing images using Docker v2 formats.
func (b *Builder) SetAnnotation(key, value string) {
	if b.ImageAnnotations == nil {
		b.ImageAnnotations = map[string]string{}
	}
	b.ImageAnnotations[key] = value
}

// UnsetAnnotation removes a key and its value from the image's manifest, if
// it's present.
func (b *Builder) UnsetAnnotation(key string) {
	delete(b.ImageAnnotations, key)
}

// ClearAnnotations removes all keys and their values from the image's
// manifest.
func (b *Builder) ClearAnnotations() {
	b.ImageAnnotations = map[string]string{}
}

// CreatedBy returns a description of how this image was built.
func (b *Builder) CreatedBy() string {
	return b.ImageCreatedBy
}

// SetCreatedBy sets the description of how this image was built.
func (b *Builder) SetCreatedBy(how string) {
	b.ImageCreatedBy = how
}

// OS returns a name of the OS on which the container, or a container built
// using an image built from this container, is intended to be run.
func (b *Builder) OS() string {
	return b.OCIv1.OS
}

// SetOS sets the name of the OS on which the container, or a container built
// using an image built from this container, is intended to be run.
func (b *Builder) SetOS(os string) {
	b.OCIv1.OS = os
	b.Docker.OS = os
}

// OSVersion returns a version of the OS on which the container, or a container
// built using an image built from this container, is intended to be run.
func (b *Builder) OSVersion() string {
	return b.OCIv1.OSVersion
}

// SetOSVersion sets the version of the OS on which the container, or a
// container built using an image built from this container, is intended to be
// run.
func (b *Builder) SetOSVersion(version string) {
	b.OCIv1.OSVersion = version
	b.Docker.OSVersion = version
}

// OSFeatures returns a list of OS features which the container, or a container
// built using an image built from this container, depends on the OS supplying.
func (b *Builder) OSFeatures() []string {
	return copyStringSlice(b.OCIv1.OSFeatures)
}

// SetOSFeature adds a feature of the OS which the container, or a container
// built using an image built from this container, depends on the OS supplying.
func (b *Builder) SetOSFeature(feature string) {
	if !util.StringInSlice(feature, b.OCIv1.OSFeatures) {
		b.OCIv1.OSFeatures = append(b.OCIv1.OSFeatures, feature)
	}
	if !util.StringInSlice(feature, b.Docker.OSFeatures) {
		b.Docker.OSFeatures = append(b.Docker.OSFeatures, feature)
	}
}

// UnsetOSFeature removes a feature of the OS which the container, or a
// container built using an image built from this container, depends on the OS
// supplying.
func (b *Builder) UnsetOSFeature(feature string) {
	if util.StringInSlice(feature, b.OCIv1.OSFeatures) {
		features := make([]string, 0, len(b.OCIv1.OSFeatures))
		for _, f := range b.OCIv1.OSFeatures {
			if f != feature {
				features = append(features, f)
			}
		}
		b.OCIv1.OSFeatures = features
	}
	if util.StringInSlice(feature, b.Docker.OSFeatures) {
		features := make([]string, 0, len(b.Docker.OSFeatures))
		for _, f := range b.Docker.OSFeatures {
			if f != feature {
				features = append(features, f)
			}
		}
		b.Docker.OSFeatures = features
	}
}

// ClearOSFeatures clears the list of features of the OS which the container,
// or a container built using an image built from this container, depends on
// the OS supplying.
func (b *Builder) ClearOSFeatures() {
	b.OCIv1.OSFeatures = []string{}
	b.Docker.OSFeatures = []string{}
}

// Architecture returns a name of the architecture on which the container, or a
// container built using an image built from this container, is intended to be
// run.
func (b *Builder) Architecture() string {
	return b.OCIv1.Architecture
}

// SetArchitecture sets the name of the architecture on which the container, or
// a container built using an image built from this container, is intended to
// be run.
func (b *Builder) SetArchitecture(arch string) {
	b.OCIv1.Architecture = arch
	b.Docker.Architecture = arch
}

// Variant returns a name of the architecture variant on which the container,
// or a container built using an image built from this container, is intended
// to be run.
func (b *Builder) Variant() string {
	return b.OCIv1.Variant
}

// SetVariant sets the name of the architecture variant on which the container,
// or a container built using an image built from this container, is intended
// to be run.
func (b *Builder) SetVariant(variant string) {
	b.Docker.Variant = variant
	b.OCIv1.Variant = variant
}

// Maintainer returns contact information for the person who built the image.
func (b *Builder) Maintainer() string {
	return b.OCIv1.Author
}

// SetMaintainer sets contact information for the person who built the image.
func (b *Builder) SetMaintainer(who string) {
	b.OCIv1.Author = who
	b.Docker.Author = who
}

// User returns information about the user as whom the container, or a
// container built using an image built from this container, should be run.
func (b *Builder) User() string {
	return b.OCIv1.Config.User
}

// SetUser sets information about the user as whom the container, or a
// container built using an image built from this container, should be run.
// Acceptable forms are a user name or ID, optionally followed by a colon and a
// group name or ID.
func (b *Builder) SetUser(spec string) {
	b.OCIv1.Config.User = spec
	b.Docker.Config.User = spec
}

// OnBuild returns the OnBuild value from the container.
func (b *Builder) OnBuild() []string {
	return copyStringSlice(b.Docker.Config.OnBuild)
}

// ClearOnBuild removes all values from the OnBuild structure
func (b *Builder) ClearOnBuild() {
	b.Docker.Config.OnBuild = []string{}
}

// SetOnBuild sets a trigger instruction to be executed when the image is used
// as the base of another image.
// Note: this setting is not present in the OCIv1 image format, so it is
// discarded when writing images using OCIv1 formats.
func (b *Builder) SetOnBuild(onBuild string) {
	if onBuild != "" && b.Format != define.Dockerv2ImageManifest {
		b.Logger.Warnf("ONBUILD is not supported for OCI image format, %s will be ignored. Must use `docker` format", onBuild)
	}
	b.Docker.Config.OnBuild = append(b.Docker.Config.OnBuild, onBuild)
}

// WorkDir returns the default working directory for running commands in the
// container, or in a container built using an image built from this container.
func (b *Builder) WorkDir() string {
	return b.OCIv1.Config.WorkingDir
}

// SetWorkDir sets the location of the default working directory for running
// commands in the container, or in a container built using an image built from
// this container.
func (b *Builder) SetWorkDir(there string) {
	b.OCIv1.Config.WorkingDir = there
	b.Docker.Config.WorkingDir = there
}

// Shell returns the default shell for running commands in the
// container, or in a container built using an image built from this container.
func (b *Builder) Shell() []string {
	return copyStringSlice(b.Docker.Config.Shell)
}

// SetShell sets the default shell for running
// commands in the container, or in a container built using an image built from
// this container.
// Note: this setting is not present in the OCIv1 image format, so it is
// discarded when writing images using OCIv1 formats.
func (b *Builder) SetShell(shell []string) {
	if len(shell) > 0 && b.Format != define.Dockerv2ImageManifest {
		b.Logger.Warnf("SHELL is not supported for OCI image format, %s will be ignored. Must use `docker` format", shell)
	}

	b.Docker.Config.Shell = copyStringSlice(shell)
}

// Env returns a list of key-value pairs to be set when running commands in the
// container, or in a container built using an image built from this container.
func (b *Builder) Env() []string {
	return copyStringSlice(b.OCIv1.Config.Env)
}

// SetEnv adds or overwrites a value to the set of environment strings which
// should be set when running commands in the container, or in a container
// built using an image built from this container.
func (b *Builder) SetEnv(k string, v string) {
	reset := func(s *[]string) {
		n := []string{}
		for i := range *s {
			if !strings.HasPrefix((*s)[i], k+"=") {
				n = append(n, (*s)[i])
			}
		}
		n = append(n, k+"="+v)
		*s = n
	}
	reset(&b.OCIv1.Config.Env)
	reset(&b.Docker.Config.Env)
}

// UnsetEnv removes a value from the set of environment strings which should be
// set when running commands in this container, or in a container built using
// an image built from this container.
func (b *Builder) UnsetEnv(k string) {
	unset := func(s *[]string) {
		n := []string{}
		for i := range *s {
			if !strings.HasPrefix((*s)[i], k+"=") {
				n = append(n, (*s)[i])
			}
		}
		*s = n
	}
	unset(&b.OCIv1.Config.Env)
	unset(&b.Docker.Config.Env)
}

// ClearEnv removes all values from the set of environment strings which should
// be set when running commands in this container, or in a container built
// using an image built from this container.
func (b *Builder) ClearEnv() {
	b.OCIv1.Config.Env = []string{}
	b.Docker.Config.Env = []string{}
}

// Cmd returns the default command, or command parameters if an Entrypoint is
// set, to use when running a container built from an image built from this
// container.
func (b *Builder) Cmd() []string {
	return copyStringSlice(b.OCIv1.Config.Cmd)
}

// SetCmd sets the default command, or command parameters if an Entrypoint is
// set, to use when running a container built from an image built from this
// container.
func (b *Builder) SetCmd(cmd []string) {
	b.OCIv1.Config.Cmd = copyStringSlice(cmd)
	b.Docker.Config.Cmd = copyStringSlice(cmd)
}

// Entrypoint returns the command to be run for containers built from images
// built from this container.
func (b *Builder) Entrypoint() []string {
	if len(b.OCIv1.Config.Entrypoint) > 0 {
		return copyStringSlice(b.OCIv1.Config.Entrypoint)
	}
	return nil
}

// SetEntrypoint sets the command to be run for in containers built from images
// built from this container.
func (b *Builder) SetEntrypoint(ep []string) {
	b.OCIv1.Config.Entrypoint = copyStringSlice(ep)
	b.Docker.Config.Entrypoint = copyStringSlice(ep)
}

// Labels returns a set of key-value pairs from the image's runtime
// configuration.
func (b *Builder) Labels() map[string]string {
	return copyStringStringMap(b.OCIv1.Config.Labels)
}

// SetLabel adds or overwrites a key's value from the image's runtime
// configuration.
func (b *Builder) SetLabel(k string, v string) {
	if b.OCIv1.Config.Labels == nil {
		b.OCIv1.Config.Labels = map[string]string{}
	}
	b.OCIv1.Config.Labels[k] = v
	if b.Docker.Config.Labels == nil {
		b.Docker.Config.Labels = map[string]string{}
	}
	b.Docker.Config.Labels[k] = v
}

// UnsetLabel removes a key and its value from the image's runtime
// configuration, if it's present.
func (b *Builder) UnsetLabel(k string) {
	delete(b.OCIv1.Config.Labels, k)
	delete(b.Docker.Config.Labels, k)
}

// ClearLabels removes all keys and their values from the image's runtime
// configuration.
func (b *Builder) ClearLabels() {
	b.OCIv1.Config.Labels = map[string]string{}
	b.Docker.Config.Labels = map[string]string{}
}

// Ports returns the set of ports which should be exposed when a container
// based on an image built from this container is run.
func (b *Builder) Ports() []string {
	p := []string{}
	for k := range b.OCIv1.Config.ExposedPorts {
		p = append(p, k)
	}
	return p
}

// SetPort adds or overwrites an exported port in the set of ports which should
// be exposed when a container based on an image built from this container is
// run.
func (b *Builder) SetPort(p string) {
	if b.OCIv1.Config.ExposedPorts == nil {
		b.OCIv1.Config.ExposedPorts = map[string]struct{}{}
	}
	b.OCIv1.Config.ExposedPorts[p] = struct{}{}
	if b.Docker.Config.ExposedPorts == nil {
		b.Docker.Config.ExposedPorts = make(docker.PortSet)
	}
	b.Docker.Config.ExposedPorts[docker.Port(p)] = struct{}{}
}

// UnsetPort removes an exposed port from the set of ports which should be
// exposed when a container based on an image built from this container is run.
func (b *Builder) UnsetPort(p string) {
	delete(b.OCIv1.Config.ExposedPorts, p)
	delete(b.Docker.Config.ExposedPorts, docker.Port(p))
}

// ClearPorts empties the set of ports which should be exposed when a container
// based on an image built from this container is run.
func (b *Builder) ClearPorts() {
	b.OCIv1.Config.ExposedPorts = map[string]struct{}{}
	b.Docker.Config.ExposedPorts = docker.PortSet{}
}

// Volumes returns a list of filesystem locations which should be mounted from
// outside of the container when a container built from an image built from
// this container is run.
func (b *Builder) Volumes() []string {
	v := []string{}
	for k := range b.OCIv1.Config.Volumes {
		v = append(v, k)
	}
	if len(v) > 0 {
		return v
	}
	return nil
}

// CheckVolume returns True if the location exists in the image's list of locations
// which should be mounted from outside of the container when a container
// based on an image built from this container is run

func (b *Builder) CheckVolume(v string) bool {
	_, OCIv1Volume := b.OCIv1.Config.Volumes[v]
	_, DockerVolume := b.Docker.Config.Volumes[v]
	return OCIv1Volume || DockerVolume
}

// AddVolume adds a location to the image's list of locations which should be
// mounted from outside of the container when a container based on an image
// built from this container is run.
func (b *Builder) AddVolume(v string) {
	if b.OCIv1.Config.Volumes == nil {
		b.OCIv1.Config.Volumes = map[string]struct{}{}
	}
	b.OCIv1.Config.Volumes[v] = struct{}{}
	if b.Docker.Config.Volumes == nil {
		b.Docker.Config.Volumes = map[string]struct{}{}
	}
	b.Docker.Config.Volumes[v] = struct{}{}
}

// RemoveVolume removes a location from the list of locations which should be
// mounted from outside of the container when a container based on an image
// built from this container is run.
func (b *Builder) RemoveVolume(v string) {
	delete(b.OCIv1.Config.Volumes, v)
	delete(b.Docker.Config.Volumes, v)
}

// ClearVolumes removes all locations from the image's list of locations which
// should be mounted from outside of the container when a container based on an
// image built from this container is run.
func (b *Builder) ClearVolumes() {
	b.OCIv1.Config.Volumes = map[string]struct{}{}
	b.Docker.Config.Volumes = map[string]struct{}{}
}

// Hostname returns the hostname which will be set in the container and in
// containers built using images built from the container.
func (b *Builder) Hostname() string {
	return b.Docker.Config.Hostname
}

// SetHostname sets the hostname which will be set in the container and in
// containers built using images built from the container.
// Note: this setting is not present in the OCIv1 image format, so it is
// discarded when writing images using OCIv1 formats.
func (b *Builder) SetHostname(name string) {
	b.Docker.Config.Hostname = name
}

// Domainname returns the domainname which will be set in the container and in
// containers built using images built from the container.
func (b *Builder) Domainname() string {
	return b.Docker.Config.Domainname
}

// SetDomainname sets the domainname which will be set in the container and in
// containers built using images built from the container.
// Note: this setting is not present in the OCIv1 image format, so it is
// discarded when writing images using OCIv1 formats.
func (b *Builder) SetDomainname(name string) {
	if name != "" && b.Format != define.Dockerv2ImageManifest {
		b.Logger.Warnf("DOMAINNAME is not supported for OCI image format, domainname %s will be ignored. Must use `docker` format", name)
	}
	b.Docker.Config.Domainname = name
}

// SetDefaultMountsFilePath sets the mounts file path for testing purposes
func (b *Builder) SetDefaultMountsFilePath(path string) {
	b.DefaultMountsFilePath = path
}

// Comment returns the comment which will be set in the container and in
// containers built using images built from the container
func (b *Builder) Comment() string {
	return b.Docker.Comment
}

// SetComment sets the comment which will be set in the container and in
// containers built using images built from the container.
// Note: this setting is not present in the OCIv1 image format, so it is
// discarded when writing images using OCIv1 formats.
func (b *Builder) SetComment(comment string) {
	if comment != "" && b.Format != define.Dockerv2ImageManifest {
		logrus.Warnf("COMMENT is not supported for OCI image format, comment %s will be ignored. Must use `docker` format", comment)
	}
	b.Docker.Comment = comment
}

// HistoryComment returns the comment which will be used in the history item
// which will describe the latest layer when we commit an image.
func (b *Builder) HistoryComment() string {
	return b.ImageHistoryComment
}

// SetHistoryComment sets the comment which will be used in the history item
// which will describe the latest layer when we commit an image.
func (b *Builder) SetHistoryComment(comment string) {
	b.ImageHistoryComment = comment
}

// StopSignal returns the signal which will be set in the container and in
// containers built using images built from the container
func (b *Builder) StopSignal() string {
	return b.Docker.Config.StopSignal
}

// SetStopSignal sets the signal which will be set in the container and in
// containers built using images built from the container.
func (b *Builder) SetStopSignal(stopSignal string) {
	b.OCIv1.Config.StopSignal = stopSignal
	b.Docker.Config.StopSignal = stopSignal
}

// Healthcheck returns information that recommends how a container engine
// should check if a running container is "healthy".
func (b *Builder) Healthcheck() *docker.HealthConfig {
	if b.Docker.Config.Healthcheck == nil {
		return nil
	}
	return &docker.HealthConfig{
		Test:        copyStringSlice(b.Docker.Config.Healthcheck.Test),
		Interval:    b.Docker.Config.Healthcheck.Interval,
		Timeout:     b.Docker.Config.Healthcheck.Timeout,
		StartPeriod: b.Docker.Config.Healthcheck.StartPeriod,
		Retries:     b.Docker.Config.Healthcheck.Retries,
	}
}

// SetHealthcheck sets recommended commands to run in order to verify that a
// running container based on this image is "healthy", along with information
// specifying how often that test should be run, and how many times the test
// should fail before the container should be considered unhealthy.
// Note: this setting is not present in the OCIv1 image format, so it is
// discarded when writing images using OCIv1 formats.
func (b *Builder) SetHealthcheck(config *docker.HealthConfig) {
	b.Docker.Config.Healthcheck = nil
	if config != nil {
		if b.Format != define.Dockerv2ImageManifest {
			b.Logger.Warnf("HEALTHCHECK is not supported for OCI image format and will be ignored. Must use `docker` format")
		}
		b.Docker.Config.Healthcheck = &docker.HealthConfig{
			Test:        copyStringSlice(config.Test),
			Interval:    config.Interval,
			Timeout:     config.Timeout,
			StartPeriod: config.StartPeriod,
			Retries:     config.Retries,
		}
	}
}

// AddPrependedEmptyLayer adds an item to the history that we'll create when
// committing the image, after any history we inherit from the base image, but
// before the history item that we'll use to describe the new layer that we're
// adding.
func (b *Builder) AddPrependedEmptyLayer(created *time.Time, createdBy, author, comment string) {
	if created != nil {
		copiedTimestamp := *created
		created = &copiedTimestamp
	}
	b.PrependedEmptyLayers = append(b.PrependedEmptyLayers, ociv1.History{
		Created:    created,
		CreatedBy:  createdBy,
		Author:     author,
		Comment:    comment,
		EmptyLayer: true,
	})
}

// ClearPrependedEmptyLayers clears the list of history entries that we'll add
// to the committed image before the entry for the layer that we're adding.
func (b *Builder) ClearPrependedEmptyLayers() {
	b.PrependedEmptyLayers = nil
}

// AddAppendedEmptyLayer adds an item to the history that we'll create when
// committing the image, after the history item that we'll use to describe the
// new layer that we're adding.
func (b *Builder) AddAppendedEmptyLayer(created *time.Time, createdBy, author, comment string) {
	if created != nil {
		copiedTimestamp := *created
		created = &copiedTimestamp
	}
	b.AppendedEmptyLayers = append(b.AppendedEmptyLayers, ociv1.History{
		Created:    created,
		CreatedBy:  createdBy,
		Author:     author,
		Comment:    comment,
		EmptyLayer: true,
	})
}

// ClearAppendedEmptyLayers clears the list of history entries that we'll add
// to the committed image after the entry for the layer that we're adding.
func (b *Builder) ClearAppendedEmptyLayers() {
	b.AppendedEmptyLayers = nil
}