protocol/packp: add reference update request encoder. (#147)

* add ReferenceUpdateRequest struct.
* add ReferenceUpdateRequest decoder.
* add ReferenceUpdateRequest encoder.

7 files changed, 759 insertions, 0 deletions

diff --git a/plumbing/protocol/packp/advrefs_decode.go b/plumbing/protocol/packp/advrefs_decode.go
index c8f8394..5926645 100644
--- a/plumbing/protocol/packp/advrefs_decode.go
+++ b/plumbing/protocol/packp/advrefs_decode.go
@@ -199,6 +199,7 @@ func decodeFirstRef(l *advRefsDecoder) decoderStateFn {
 func decodeCaps(p *advRefsDecoder) decoderStateFn {
 	if err := p.data.Capabilities.Decode(p.line); err != nil {
 		p.error("invalid capabilities: %s", err)
+		return nil
 	}
 
 	return decodeOtherRefs
diff --git a/plumbing/protocol/packp/common.go b/plumbing/protocol/packp/common.go
index 3d7786b..c8db931 100644
--- a/plumbing/protocol/packp/common.go
+++ b/plumbing/protocol/packp/common.go
@@ -15,6 +15,7 @@ var (
 	// common
 	sp  = []byte(" ")
 	eol = []byte("\n")
+	eq  = []byte{'='}
 
 	// advrefs
 	null       = []byte("\x00")
@@ -28,4 +29,7 @@ var (
 	deepenCommits   = []byte("deepen ")
 	deepenSince     = []byte("deepen-since ")
 	deepenReference = []byte("deepen-not ")
+
+	// updreq
+	shallowNoSp = []byte("shallow")
 )
diff --git a/plumbing/protocol/packp/updreq.go b/plumbing/protocol/packp/updreq.go
new file mode 100644
index 0000000..90d6e09
--- /dev/null
+++ b/plumbing/protocol/packp/updreq.go
@@ -0,0 +1,84 @@
+package packp
+
+import (
+	"errors"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/protocol/packp/capability"
+)
+
+var (
+	ErrEmptyCommands    = errors.New("commands cannot be empty")
+	ErrMalformedCommand = errors.New("malformed command")
+)
+
+// ReferenceUpdateRequest values represent reference upload requests.
+// Values from this type are not zero-value safe, use the New function instead.
+//
+// TODO: Add support for push-cert
+type ReferenceUpdateRequest struct {
+	Capabilities *capability.List
+	Commands     []*Command
+	Shallow      *plumbing.Hash
+}
+
+// New returns a pointer to a new ReferenceUpdateRequest value.
+func NewReferenceUpdateRequest() *ReferenceUpdateRequest {
+	return &ReferenceUpdateRequest{
+		Capabilities: capability.NewList(),
+		Commands:     nil,
+	}
+}
+
+func (r *ReferenceUpdateRequest) validate() error {
+	if len(r.Commands) == 0 {
+		return ErrEmptyCommands
+	}
+
+	for _, c := range r.Commands {
+		if err := c.validate(); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+type Action string
+
+const (
+	Create  Action = "create"
+	Update         = "update"
+	Delete         = "delete"
+	Invalid        = "invalid"
+)
+
+type Command struct {
+	Name string
+	Old  plumbing.Hash
+	New  plumbing.Hash
+}
+
+func (c *Command) Action() Action {
+	if c.Old == plumbing.ZeroHash && c.New == plumbing.ZeroHash {
+		return Invalid
+	}
+
+	if c.Old == plumbing.ZeroHash {
+		return Create
+	}
+
+	if c.New == plumbing.ZeroHash {
+		return Delete
+	}
+
+	return Update
+}
+
+func (c *Command) validate() error {
+	if c.Action() == Invalid {
+		return ErrMalformedCommand
+	}
+
+	return nil
+}
diff --git a/plumbing/protocol/packp/updreq_decode.go b/plumbing/protocol/packp/updreq_decode.go
new file mode 100644
index 0000000..0740871
--- /dev/null
+++ b/plumbing/protocol/packp/updreq_decode.go
@@ -0,0 +1,231 @@
+package packp
+
+import (
+	"bytes"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"io"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/format/pktline"
+)
+
+var (
+	shallowLineLength      = len(shallow) + hashSize
+	minCommandLength       = hashSize*2 + 2 + 1
+	minCommandAndCapsLenth = minCommandLength + 1
+)
+
+var (
+	ErrEmpty                        = errors.New("empty update-request message")
+	errNoCommands                   = errors.New("unexpected EOF before any command")
+	errMissingCapabilitiesDelimiter = errors.New("capabilities delimiter not found")
+)
+
+func errMalformedRequest(reason string) error {
+	return fmt.Errorf("malformed request: %s", reason)
+}
+
+func errInvalidHashSize(got int) error {
+	return fmt.Errorf("invalid hash size: expected %d, got %d",
+		hashSize, got)
+}
+
+func errInvalidHash(err error) error {
+	return fmt.Errorf("invalid hash: %s", err.Error())
+}
+
+func errInvalidShallowLineLength(got int) error {
+	return errMalformedRequest(fmt.Sprintf(
+		"invalid shallow line length: expected %d, got %d",
+		shallowLineLength, got))
+}
+
+func errInvalidCommandCapabilitiesLineLength(got int) error {
+	return errMalformedRequest(fmt.Sprintf(
+		"invalid command and capabilities line length: expected at least %d, got %d",
+		minCommandAndCapsLenth, got))
+}
+
+func errInvalidCommandLineLength(got int) error {
+	return errMalformedRequest(fmt.Sprintf(
+		"invalid command line length: expected at least %d, got %d",
+		minCommandLength, got))
+}
+
+func errInvalidShallowObjId(err error) error {
+	return errMalformedRequest(
+		fmt.Sprintf("invalid shallow object id: %s", err.Error()))
+}
+
+func errInvalidOldObjId(err error) error {
+	return errMalformedRequest(
+		fmt.Sprintf("invalid old object id: %s", err.Error()))
+}
+
+func errInvalidNewObjId(err error) error {
+	return errMalformedRequest(
+		fmt.Sprintf("invalid new object id: %s", err.Error()))
+}
+
+func errMalformedCommand(err error) error {
+	return errMalformedRequest(fmt.Sprintf(
+		"malformed command: %s", err.Error()))
+}
+
+// Decode reads the next update-request message form the reader and wr
+func (req *ReferenceUpdateRequest) Decode(r io.Reader) error {
+	d := &updReqDecoder{s: pktline.NewScanner(r)}
+	return d.Decode(req)
+}
+
+type updReqDecoder struct {
+	s *pktline.Scanner
+	r *ReferenceUpdateRequest
+}
+
+func (d *updReqDecoder) Decode(r *ReferenceUpdateRequest) error {
+	d.r = r
+	funcs := []func() error{
+		d.scanLine,
+		d.decodeShallow,
+		d.decodeCommandAndCapabilities,
+		d.decodeCommands,
+		r.validate,
+	}
+
+	for _, f := range funcs {
+		if err := f(); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (d *updReqDecoder) scanLine() error {
+	if ok := d.s.Scan(); !ok {
+		return d.scanErrorOr(ErrEmpty)
+	}
+
+	return nil
+}
+
+func (d *updReqDecoder) decodeShallow() error {
+	b := d.s.Bytes()
+
+	if !bytes.HasPrefix(b, shallowNoSp) {
+		return nil
+	}
+
+	if len(b) != shallowLineLength {
+		return errInvalidShallowLineLength(len(b))
+	}
+
+	h, err := parseHash(string(b[len(shallow):]))
+	if err != nil {
+		return errInvalidShallowObjId(err)
+	}
+
+	if ok := d.s.Scan(); !ok {
+		return d.scanErrorOr(errNoCommands)
+	}
+
+	d.r.Shallow = &h
+
+	return nil
+}
+
+func (d *updReqDecoder) decodeCommands() error {
+	for {
+		b := d.s.Bytes()
+		if bytes.Equal(b, pktline.Flush) {
+			return nil
+		}
+
+		c, err := parseCommand(b)
+		if err != nil {
+			return err
+		}
+
+		d.r.Commands = append(d.r.Commands, c)
+
+		if ok := d.s.Scan(); !ok {
+			return d.s.Err()
+		}
+	}
+}
+
+func (d *updReqDecoder) decodeCommandAndCapabilities() error {
+	b := d.s.Bytes()
+	i := bytes.IndexByte(b, 0)
+	if i == -1 {
+		return errMissingCapabilitiesDelimiter
+	}
+
+	if len(b) < minCommandAndCapsLenth {
+		return errInvalidCommandCapabilitiesLineLength(len(b))
+	}
+
+	cmd, err := parseCommand(b[:i])
+	if err != nil {
+		return err
+	}
+
+	d.r.Commands = append(d.r.Commands, cmd)
+
+	if err := d.r.Capabilities.Decode(b[i+1:]); err != nil {
+		return err
+	}
+
+	if err := d.scanLine(); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func parseCommand(b []byte) (*Command, error) {
+	if len(b) < minCommandLength {
+		return nil, errInvalidCommandLineLength(len(b))
+	}
+
+	var os, ns, n string
+	if _, err := fmt.Sscanf(string(b), "%s %s %s", &os, &ns, &n); err != nil {
+		return nil, errMalformedCommand(err)
+	}
+
+	oh, err := parseHash(os)
+	if err != nil {
+		return nil, errInvalidOldObjId(err)
+	}
+
+	nh, err := parseHash(ns)
+	if err != nil {
+		return nil, errInvalidNewObjId(err)
+	}
+
+	return &Command{Old: oh, New: nh, Name: n}, nil
+}
+
+func parseHash(s string) (plumbing.Hash, error) {
+	if len(s) != hashSize {
+		return plumbing.ZeroHash, errInvalidHashSize(len(s))
+	}
+
+	if _, err := hex.DecodeString(s); err != nil {
+		return plumbing.ZeroHash, errInvalidHash(err)
+	}
+
+	h := plumbing.NewHash(s)
+	return h, nil
+}
+
+func (d *updReqDecoder) scanErrorOr(origErr error) error {
+	if err := d.s.Err(); err != nil {
+		return err
+	}
+
+	return origErr
+}
diff --git a/plumbing/protocol/packp/updreq_decode_test.go b/plumbing/protocol/packp/updreq_decode_test.go
new file mode 100644
index 0000000..66d9180
--- /dev/null
+++ b/plumbing/protocol/packp/updreq_decode_test.go
@@ -0,0 +1,253 @@
+package packp
+
+import (
+	"bytes"
+	"io"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/format/pktline"
+
+	. "gopkg.in/check.v1"
+)
+
+type UpdReqDecodeSuite struct{}
+
+var _ = Suite(&UpdReqDecodeSuite{})
+
+func (s *UpdReqDecodeSuite) TestEmpty(c *C) {
+	r := NewReferenceUpdateRequest()
+	var buf bytes.Buffer
+	c.Assert(r.Decode(&buf), Equals, ErrEmpty)
+	c.Assert(r, DeepEquals, NewReferenceUpdateRequest())
+}
+
+func (s *UpdReqDecodeSuite) TestInvalidPktlines(c *C) {
+	r := NewReferenceUpdateRequest()
+	input := bytes.NewReader([]byte("xxxxxxxxxx"))
+	c.Assert(r.Decode(input), ErrorMatches, "invalid pkt-len found")
+}
+
+func (s *UpdReqDecodeSuite) TestInvalidShadow(c *C) {
+	payloads := []string{
+		"shallow",
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref\x00",
+		pktline.FlushString,
+	}
+	s.testDecoderErrorMatches(c, toPktLines(c, payloads), "^malformed request: invalid shallow line length: expected 48, got 7$")
+
+	payloads = []string{
+		"shallow ",
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref\x00",
+		pktline.FlushString,
+	}
+	s.testDecoderErrorMatches(c, toPktLines(c, payloads), "^malformed request: invalid shallow line length: expected 48, got 8$")
+
+	payloads = []string{
+		"shallow 1ecf0ef2c2dffb796033e5a02219af86ec65",
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref\x00",
+		pktline.FlushString,
+	}
+	s.testDecoderErrorMatches(c, toPktLines(c, payloads), "^malformed request: invalid shallow line length: expected 48, got 44$")
+
+	payloads = []string{
+		"shallow 1ecf0ef2c2dffb796033e5a02219af86ec6584e54",
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref\x00",
+		pktline.FlushString,
+	}
+	s.testDecoderErrorMatches(c, toPktLines(c, payloads), "^malformed request: invalid shallow line length: expected 48, got 49$")
+
+	payloads = []string{
+		"shallow 1ecf0ef2c2dffb796033e5a02219af86ec6584eu",
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref\x00",
+		pktline.FlushString,
+	}
+	s.testDecoderErrorMatches(c, toPktLines(c, payloads), "^malformed request: invalid shallow object id: invalid hash: .*")
+}
+
+func (s *UpdReqDecodeSuite) TestMalformedCommand(c *C) {
+	payloads := []string{
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5x2ecf0ef2c2dffb796033e5a02219af86ec6584e5xmyref\x00",
+		pktline.FlushString,
+	}
+	s.testDecoderErrorMatches(c, toPktLines(c, payloads), "^malformed request: malformed command: EOF$")
+
+	payloads = []string{
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref\x00",
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5x2ecf0ef2c2dffb796033e5a02219af86ec6584e5xmyref",
+		pktline.FlushString,
+	}
+	s.testDecoderErrorMatches(c, toPktLines(c, payloads), "^malformed request: malformed command: EOF$")
+}
+
+func (s *UpdReqDecodeSuite) TestInvalidCommandInvalidHash(c *C) {
+	payloads := []string{
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref\x00",
+		pktline.FlushString,
+	}
+	s.testDecoderErrorMatches(c, toPktLines(c, payloads), "^malformed request: invalid old object id: invalid hash size: expected 40, got 39$")
+
+	payloads = []string{
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e myref\x00",
+		pktline.FlushString,
+	}
+	s.testDecoderErrorMatches(c, toPktLines(c, payloads), "^malformed request: invalid new object id: invalid hash size: expected 40, got 39$")
+
+	payloads = []string{
+		"1ecf0ef2c2dffb796033e5a02219af86e 2ecf0ef2c2dffb796033e5a02219af86ec6 m\x00",
+		pktline.FlushString,
+	}
+	s.testDecoderErrorMatches(c, toPktLines(c, payloads), "^malformed request: invalid command and capabilities line length: expected at least 84, got 72$")
+
+	payloads = []string{
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584eu 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref\x00",
+		pktline.FlushString,
+	}
+	s.testDecoderErrorMatches(c, toPktLines(c, payloads), "^malformed request: invalid old object id: invalid hash: .*$")
+
+	payloads = []string{
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584eu myref\x00",
+		pktline.FlushString,
+	}
+	s.testDecoderErrorMatches(c, toPktLines(c, payloads), "^malformed request: invalid new object id: invalid hash: .*$")
+}
+
+func (s *UpdReqDecodeSuite) TestInvalidCommandMissingNullDelimiter(c *C) {
+	payloads := []string{
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref",
+		pktline.FlushString,
+	}
+	s.testDecoderErrorMatches(c, toPktLines(c, payloads), "capabilities delimiter not found")
+}
+
+func (s *UpdReqDecodeSuite) TestInvalidCommandMissingName(c *C) {
+	payloads := []string{
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e5\x00",
+		pktline.FlushString,
+	}
+	s.testDecoderErrorMatches(c, toPktLines(c, payloads), "^malformed request: invalid command and capabilities line length: expected at least 84, got 82$")
+
+	payloads = []string{
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 \x00",
+		pktline.FlushString,
+	}
+	s.testDecoderErrorMatches(c, toPktLines(c, payloads), "^malformed request: invalid command and capabilities line length: expected at least 84, got 83$")
+
+	payloads = []string{
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref\x00",
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e5",
+		pktline.FlushString,
+	}
+	s.testDecoderErrorMatches(c, toPktLines(c, payloads), "^malformed request: invalid command line length: expected at least 83, got 81$")
+
+	payloads = []string{
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref\x00",
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 ",
+		pktline.FlushString,
+	}
+	s.testDecoderErrorMatches(c, toPktLines(c, payloads), "^malformed request: invalid command line length: expected at least 83, got 82$")
+}
+
+func (s *UpdReqDecodeSuite) TestOneUpdateCommand(c *C) {
+	hash1 := plumbing.NewHash("1ecf0ef2c2dffb796033e5a02219af86ec6584e5")
+	hash2 := plumbing.NewHash("2ecf0ef2c2dffb796033e5a02219af86ec6584e5")
+	name := "myref"
+
+	expected := NewReferenceUpdateRequest()
+	expected.Commands = []*Command{
+		{Name: name, Old: hash1, New: hash2},
+	}
+
+	payloads := []string{
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref\x00",
+		pktline.FlushString,
+	}
+
+	c.Assert(s.testDecodeOK(c, payloads), DeepEquals, expected)
+}
+
+func (s *UpdReqDecodeSuite) TestMultipleCommands(c *C) {
+	hash1 := plumbing.NewHash("1ecf0ef2c2dffb796033e5a02219af86ec6584e5")
+	hash2 := plumbing.NewHash("2ecf0ef2c2dffb796033e5a02219af86ec6584e5")
+
+	expected := NewReferenceUpdateRequest()
+	expected.Commands = []*Command{
+		{Name: "myref1", Old: hash1, New: hash2},
+		{Name: "myref2", Old: plumbing.ZeroHash, New: hash2},
+		{Name: "myref3", Old: hash1, New: plumbing.ZeroHash},
+	}
+
+	payloads := []string{
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref1\x00",
+		"0000000000000000000000000000000000000000 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref2",
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 0000000000000000000000000000000000000000 myref3",
+		pktline.FlushString,
+	}
+
+	c.Assert(s.testDecodeOK(c, payloads).Commands, DeepEquals, expected.Commands)
+	c.Assert(s.testDecodeOK(c, payloads).Shallow, DeepEquals, expected.Shallow)
+	c.Assert(s.testDecodeOK(c, payloads).Capabilities, DeepEquals, expected.Capabilities)
+	c.Assert(s.testDecodeOK(c, payloads), DeepEquals, expected)
+}
+
+func (s *UpdReqDecodeSuite) TestMultipleCommandsAndCapabilities(c *C) {
+	hash1 := plumbing.NewHash("1ecf0ef2c2dffb796033e5a02219af86ec6584e5")
+	hash2 := plumbing.NewHash("2ecf0ef2c2dffb796033e5a02219af86ec6584e5")
+
+	expected := NewReferenceUpdateRequest()
+	expected.Commands = []*Command{
+		{Name: "myref1", Old: hash1, New: hash2},
+		{Name: "myref2", Old: plumbing.ZeroHash, New: hash2},
+		{Name: "myref3", Old: hash1, New: plumbing.ZeroHash},
+	}
+	expected.Capabilities.Add("shallow")
+
+	payloads := []string{
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref1\x00shallow",
+		"0000000000000000000000000000000000000000 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref2",
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 0000000000000000000000000000000000000000 myref3",
+		pktline.FlushString,
+	}
+
+	c.Assert(s.testDecodeOK(c, payloads), DeepEquals, expected)
+}
+
+func (s *UpdReqDecodeSuite) TestMultipleCommandsAndCapabilitiesShallow(c *C) {
+	hash1 := plumbing.NewHash("1ecf0ef2c2dffb796033e5a02219af86ec6584e5")
+	hash2 := plumbing.NewHash("2ecf0ef2c2dffb796033e5a02219af86ec6584e5")
+
+	expected := NewReferenceUpdateRequest()
+	expected.Commands = []*Command{
+		{Name: "myref1", Old: hash1, New: hash2},
+		{Name: "myref2", Old: plumbing.ZeroHash, New: hash2},
+		{Name: "myref3", Old: hash1, New: plumbing.ZeroHash},
+	}
+	expected.Capabilities.Add("shallow")
+	expected.Shallow = &hash1
+
+	payloads := []string{
+		"shallow 1ecf0ef2c2dffb796033e5a02219af86ec6584e5",
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref1\x00shallow",
+		"0000000000000000000000000000000000000000 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref2",
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 0000000000000000000000000000000000000000 myref3",
+		pktline.FlushString,
+	}
+
+	c.Assert(s.testDecodeOK(c, payloads), DeepEquals, expected)
+}
+
+func (s *UpdReqDecodeSuite) testDecoderErrorMatches(c *C, input io.Reader, pattern string) {
+	r := NewReferenceUpdateRequest()
+	c.Assert(r.Decode(input), ErrorMatches, pattern)
+}
+
+func (s *UpdReqDecodeSuite) testDecodeOK(c *C, payloads []string) *ReferenceUpdateRequest {
+	var buf bytes.Buffer
+	e := pktline.NewEncoder(&buf)
+	err := e.EncodeString(payloads...)
+	c.Assert(err, IsNil)
+
+	r := NewReferenceUpdateRequest()
+	c.Assert(r.Decode(&buf), IsNil)
+
+	return r
+}
diff --git a/plumbing/protocol/packp/updreq_encode.go b/plumbing/protocol/packp/updreq_encode.go
new file mode 100644
index 0000000..b2b7944
--- /dev/null
+++ b/plumbing/protocol/packp/updreq_encode.go
@@ -0,0 +1,67 @@
+package packp
+
+import (
+	"fmt"
+	"io"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/format/pktline"
+	"gopkg.in/src-d/go-git.v4/plumbing/protocol/packp/capability"
+)
+
+var (
+	zeroHashString = plumbing.ZeroHash.String()
+)
+
+// Encode writes the ReferenceUpdateRequest encoding to the stream.
+func (r *ReferenceUpdateRequest) Encode(w io.Writer) error {
+	if err := r.validate(); err != nil {
+		return err
+	}
+
+	e := pktline.NewEncoder(w)
+
+	if err := r.encodeShallow(e, r.Shallow); err != nil {
+		return err
+	}
+
+	if err := r.encodeCommands(e, r.Commands, r.Capabilities); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (r *ReferenceUpdateRequest) encodeShallow(e *pktline.Encoder,
+	h *plumbing.Hash) error {
+
+	if h == nil {
+		return nil
+	}
+
+	objId := []byte(h.String())
+	return e.Encodef("%s%s", shallow, objId)
+}
+
+func (r *ReferenceUpdateRequest) encodeCommands(e *pktline.Encoder,
+	cmds []*Command, cap *capability.List) error {
+
+	if err := e.Encodef("%s\x00%s",
+		formatCommand(cmds[0]), cap.String()); err != nil {
+		return err
+	}
+
+	for _, cmd := range cmds[1:] {
+		if err := e.Encodef(formatCommand(cmd)); err != nil {
+			return err
+		}
+	}
+
+	return e.Flush()
+}
+
+func formatCommand(cmd *Command) string {
+	o := cmd.Old.String()
+	n := cmd.New.String()
+	return fmt.Sprintf("%s %s %s", o, n, cmd.Name)
+}
diff --git a/plumbing/protocol/packp/updreq_encode_test.go b/plumbing/protocol/packp/updreq_encode_test.go
new file mode 100644
index 0000000..47958fd
--- /dev/null
+++ b/plumbing/protocol/packp/updreq_encode_test.go
@@ -0,0 +1,119 @@
+package packp
+
+import (
+	"bytes"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/format/pktline"
+
+	. "gopkg.in/check.v1"
+)
+
+type UpdReqEncodeSuite struct{}
+
+var _ = Suite(&UpdReqEncodeSuite{})
+
+func (s *UpdReqEncodeSuite) testEncode(c *C, input *ReferenceUpdateRequest,
+	expected []byte) {
+
+	var buf bytes.Buffer
+	c.Assert(input.Encode(&buf), IsNil)
+	obtained := buf.Bytes()
+
+	comment := Commentf("\nobtained = %s\nexpected = %s\n", string(obtained), string(expected))
+	c.Assert(obtained, DeepEquals, expected, comment)
+}
+
+func (s *UpdReqEncodeSuite) TestZeroValue(c *C) {
+	r := &ReferenceUpdateRequest{}
+	var buf bytes.Buffer
+	c.Assert(r.Encode(&buf), Equals, ErrEmptyCommands)
+
+	r = NewReferenceUpdateRequest()
+	c.Assert(r.Encode(&buf), Equals, ErrEmptyCommands)
+}
+
+func (s *UpdReqEncodeSuite) TestOneUpdateCommand(c *C) {
+	hash1 := plumbing.NewHash("1ecf0ef2c2dffb796033e5a02219af86ec6584e5")
+	hash2 := plumbing.NewHash("2ecf0ef2c2dffb796033e5a02219af86ec6584e5")
+	name := "myref"
+
+	r := NewReferenceUpdateRequest()
+	r.Commands = []*Command{
+		{Name: name, Old: hash1, New: hash2},
+	}
+
+	expected := pktlines(c,
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref\x00",
+		pktline.FlushString,
+	)
+
+	s.testEncode(c, r, expected)
+}
+
+func (s *UpdReqEncodeSuite) TestMultipleCommands(c *C) {
+	hash1 := plumbing.NewHash("1ecf0ef2c2dffb796033e5a02219af86ec6584e5")
+	hash2 := plumbing.NewHash("2ecf0ef2c2dffb796033e5a02219af86ec6584e5")
+
+	r := NewReferenceUpdateRequest()
+	r.Commands = []*Command{
+		{Name: "myref1", Old: hash1, New: hash2},
+		{Name: "myref2", Old: plumbing.ZeroHash, New: hash2},
+		{Name: "myref3", Old: hash1, New: plumbing.ZeroHash},
+	}
+
+	expected := pktlines(c,
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref1\x00",
+		"0000000000000000000000000000000000000000 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref2",
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 0000000000000000000000000000000000000000 myref3",
+		pktline.FlushString,
+	)
+
+	s.testEncode(c, r, expected)
+}
+
+func (s *UpdReqEncodeSuite) TestMultipleCommandsAndCapabilities(c *C) {
+	hash1 := plumbing.NewHash("1ecf0ef2c2dffb796033e5a02219af86ec6584e5")
+	hash2 := plumbing.NewHash("2ecf0ef2c2dffb796033e5a02219af86ec6584e5")
+
+	r := NewReferenceUpdateRequest()
+	r.Commands = []*Command{
+		{Name: "myref1", Old: hash1, New: hash2},
+		{Name: "myref2", Old: plumbing.ZeroHash, New: hash2},
+		{Name: "myref3", Old: hash1, New: plumbing.ZeroHash},
+	}
+	r.Capabilities.Add("shallow")
+
+	expected := pktlines(c,
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref1\x00shallow",
+		"0000000000000000000000000000000000000000 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref2",
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 0000000000000000000000000000000000000000 myref3",
+		pktline.FlushString,
+	)
+
+	s.testEncode(c, r, expected)
+}
+
+func (s *UpdReqEncodeSuite) TestMultipleCommandsAndCapabilitiesShallow(c *C) {
+	hash1 := plumbing.NewHash("1ecf0ef2c2dffb796033e5a02219af86ec6584e5")
+	hash2 := plumbing.NewHash("2ecf0ef2c2dffb796033e5a02219af86ec6584e5")
+
+	r := NewReferenceUpdateRequest()
+	r.Commands = []*Command{
+		{Name: "myref1", Old: hash1, New: hash2},
+		{Name: "myref2", Old: plumbing.ZeroHash, New: hash2},
+		{Name: "myref3", Old: hash1, New: plumbing.ZeroHash},
+	}
+	r.Capabilities.Add("shallow")
+	r.Shallow = &hash1
+
+	expected := pktlines(c,
+		"shallow 1ecf0ef2c2dffb796033e5a02219af86ec6584e5",
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref1\x00shallow",
+		"0000000000000000000000000000000000000000 2ecf0ef2c2dffb796033e5a02219af86ec6584e5 myref2",
+		"1ecf0ef2c2dffb796033e5a02219af86ec6584e5 0000000000000000000000000000000000000000 myref3",
+		pktline.FlushString,
+	)
+
+	s.testEncode(c, r, expected)
+}