@@ -74,6 +74,10 @@ func NewSnapshotter(opt Opt) (snapshot.SnapshotterBase, error) {

 	return s, nil

 }

+func (s *snapshotter) Name() string {

+	return "default"

+}

+

 func (s *snapshotter) IdentityMapping() *idtools.IdentityMapping {

 	return nil

 }

@@ -27,7 +27,7 @@ github.com/imdario/mergo                            7c29201646fa3de8506f70121347

 golang.org/x/sync                                   e225da77a7e68af35c70ccbf71af2b83e6acac3c

 # buildkit

-github.com/moby/buildkit                            8818c67cff663befa7b70f21454e340f71616581

+github.com/moby/buildkit                            8c0fa8fdec187d8f259a349d2da16dc2dc5f144a # v0.5.0

 github.com/tonistiigi/fsutil                        3bbb99cdbd76619ab717299830c60f6f2a533a6b

 github.com/grpc-ecosystem/grpc-opentracing          8e809c8a86450a29b90dcc9efbf062d0fe6d9746

 github.com/opentracing/opentracing-go               1361b9cd60be79c4c3a7fa9841b3c132e40066a7

@@ -8,6 +8,7 @@ import (

 	"encoding/json"

 	"fmt"

 	"net"

+	"path"

 	"regexp"

 	"strconv"

 	"strings"

@@ -46,6 +47,7 @@ const (

 	keyOverrideCopyImage       = "override-copy-image" // remove after CopyOp implemented

 	keyNameContext             = "contextkey"

 	keyNameDockerfile          = "dockerfilekey"

+	keyContextSubDir           = "contextsubdir"

 )

 var httpPrefix = regexp.MustCompile("^https?://")

@@ -122,6 +124,8 @@ func Build(ctx context.Context, c client.Client) (*client.Result, error) {

 		dockerfile2llb.WithInternalName(name),

 	)

+	fileop := useFileOp(opts, &caps)

+

 	var buildContext *llb.State

 	isScratchContext := false

 	if st, ok := detectGitContext(opts[localNameContext]); ok {

@@ -157,7 +161,6 @@ func Build(ctx context.Context, c client.Client) (*client.Result, error) {

 			return nil, errors.Errorf("failed to read downloaded context")

 		}

 		if isArchive(dt) {

-			fileop := useFileOp(opts, &caps)

 			if fileop {

 				bc := llb.Scratch().File(llb.Copy(httpContext, "/context", "/", &llb.CopyInfo{

 					AttemptUnpack: true,

@@ -190,6 +193,12 @@ func Build(ctx context.Context, c client.Client) (*client.Result, error) {

 		}

 	}

+	if buildContext != nil {

+		if sub, ok := opts[keyContextSubDir]; ok {

+			buildContext = scopeToSubDir(buildContext, fileop, sub)

+		}

+	}

+

 	def, err := src.Marshal(marshalOpts...)

 	if err != nil {

 		return nil, errors.Wrapf(err, "failed to marshal local source")

@@ -561,3 +570,17 @@ func useFileOp(args map[string]string, caps *apicaps.CapSet) bool {

 	}

 	return enabled && caps != nil && caps.Supports(pb.CapFileBase) == nil

 }

+

+func scopeToSubDir(c *llb.State, fileop bool, dir string) *llb.State {

+	if fileop {

+		bc := llb.Scratch().File(llb.Copy(*c, dir, "/", &llb.CopyInfo{

+			CopyDirContentsOnly: true,

+		}))

+		return &bc

+	}

+	unpack := llb.Image(dockerfile2llb.DefaultCopyImage, dockerfile2llb.WithInternalName("helper image for file operations")).

+		Run(llb.Shlexf("copy %s/. /out/", path.Join("/src", dir)), llb.ReadonlyRootFS(), dockerfile2llb.WithInternalName("filtering build context"))

+	unpack.AddMount("/src", *c, llb.Readonly)

+	bc := unpack.AddMount("/out", llb.Scratch())

+	return &bc

+}

@@ -18,6 +18,7 @@ type Mountable interface {

 }

 type SnapshotterBase interface {

+	Name() string

 	Mounts(ctx context.Context, key string) (Mountable, error)

 	Prepare(ctx context.Context, key, parent string, opts ...snapshots.Opt) error

 	View(ctx context.Context, key, parent string, opts ...snapshots.Opt) (Mountable, error)

@@ -43,15 +44,20 @@ type Blobmapper interface {

 	SetBlob(ctx context.Context, key string, diffID, blob digest.Digest) error

 }

-func FromContainerdSnapshotter(s snapshots.Snapshotter, idmap *idtools.IdentityMapping) SnapshotterBase {

-	return &fromContainerd{Snapshotter: s, idmap: idmap}

+func FromContainerdSnapshotter(name string, s snapshots.Snapshotter, idmap *idtools.IdentityMapping) SnapshotterBase {

+	return &fromContainerd{name: name, Snapshotter: s, idmap: idmap}

 }

 type fromContainerd struct {

+	name string

 	snapshots.Snapshotter

 	idmap *idtools.IdentityMapping

 }

+func (s *fromContainerd) Name() string {

+	return s.name

+}

+

 func (s *fromContainerd) Mounts(ctx context.Context, key string) (Mountable, error) {

 	mounts, err := s.Snapshotter.Mounts(ctx, key)

 	if err != nil {