capabilities: full integration (#151)

* format/pktline: fix readPayloadLen err handling

* protocol/pakp: UploadReq validation and creation of capabilities

* protocol/pakp: AdvRef tests

* protocol/pakp: capability.List.Delete

* protocol: filter unsupported capabilities

* remote capability negociation

* transport: UploadRequest validation

* requested changes

9 files changed, 393 insertions, 88 deletions

diff --git a/plumbing/protocol/packp/advrefs_test.go b/plumbing/protocol/packp/advrefs_test.go
index 1689938..52ddc5c 100644
--- a/plumbing/protocol/packp/advrefs_test.go
+++ b/plumbing/protocol/packp/advrefs_test.go
@@ -1,27 +1,89 @@
-package packp_test
+package packp
 
 import (
 	"bytes"
 	"fmt"
 	"io"
 	"strings"
-	"testing"
 
 	"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"
 	"gopkg.in/src-d/go-git.v4/plumbing/protocol/packp/capability"
 
 	. "gopkg.in/check.v1"
 )
 
-func Test(t *testing.T) { TestingT(t) }
+type AdvRefSuite struct{}
 
-type SuiteDecodeEncode struct{}
+var _ = Suite(&AdvRefSuite{})
 
-var _ = Suite(&SuiteDecodeEncode{})
+func (s *AdvRefSuite) TestAddReferenceSymbolic(c *C) {
+	ref := plumbing.NewSymbolicReference("foo", "bar")
 
-func (s *SuiteDecodeEncode) test(c *C, in []string, exp []string) {
+	a := NewAdvRefs()
+	err := a.AddReference(ref)
+	c.Assert(err, IsNil)
+
+	values := a.Capabilities.Get(capability.SymRef)
+	c.Assert(values, HasLen, 1)
+	c.Assert(values[0], Equals, "foo:bar")
+}
+
+func (s *AdvRefSuite) TestAddReferenceHash(c *C) {
+	ref := plumbing.NewHashReference("foo", plumbing.NewHash("5dc01c595e6c6ec9ccda4f6f69c131c0dd945f8c"))
+
+	a := NewAdvRefs()
+	err := a.AddReference(ref)
+	c.Assert(err, IsNil)
+
+	c.Assert(a.References, HasLen, 1)
+	c.Assert(a.References["foo"].String(), Equals, "5dc01c595e6c6ec9ccda4f6f69c131c0dd945f8c")
+}
+
+func (s *AdvRefSuite) TestAllReferences(c *C) {
+	hash := plumbing.NewHash("5dc01c595e6c6ec9ccda4f6f69c131c0dd945f8c")
+
+	a := NewAdvRefs()
+	err := a.AddReference(plumbing.NewSymbolicReference("foo", "bar"))
+	c.Assert(err, IsNil)
+	err = a.AddReference(plumbing.NewHashReference("bar", hash))
+	c.Assert(err, IsNil)
+
+	refs, err := a.AllReferences()
+	c.Assert(err, IsNil)
+
+	iter, err := refs.IterReferences()
+	c.Assert(err, IsNil)
+
+	var count int
+	iter.ForEach(func(ref *plumbing.Reference) error {
+		count++
+		switch ref.Name() {
+		case "bar":
+			c.Assert(ref.Hash(), Equals, hash)
+		case "foo":
+			c.Assert(ref.Target().String(), Equals, "bar")
+		}
+		return nil
+	})
+
+	c.Assert(count, Equals, 2)
+}
+
+func (s *AdvRefSuite) TestAllReferencesBadSymref(c *C) {
+	a := NewAdvRefs()
+	err := a.Capabilities.Set(capability.SymRef, "foo")
+	c.Assert(err, IsNil)
+
+	_, err = a.AllReferences()
+	c.Assert(err, NotNil)
+}
+
+type AdvRefsDecodeEncodeSuite struct{}
+
+var _ = Suite(&AdvRefsDecodeEncodeSuite{})
+
+func (s *AdvRefsDecodeEncodeSuite) test(c *C, in []string, exp []string) {
 	var err error
 	var input io.Reader
 	{
@@ -44,7 +106,7 @@ func (s *SuiteDecodeEncode) test(c *C, in []string, exp []string) {
 
 	var obtained []byte
 	{
-		ar := packp.NewAdvRefs()
+		ar := NewAdvRefs()
 		c.Assert(ar.Decode(input), IsNil)
 
 		var buf bytes.Buffer
@@ -56,7 +118,7 @@ func (s *SuiteDecodeEncode) test(c *C, in []string, exp []string) {
 	c.Assert(string(obtained), DeepEquals, string(expected))
 }
 
-func (s *SuiteDecodeEncode) TestNoHead(c *C) {
+func (s *AdvRefsDecodeEncodeSuite) TestNoHead(c *C) {
 	input := []string{
 		"0000000000000000000000000000000000000000 capabilities^{}\x00",
 		pktline.FlushString,
@@ -70,7 +132,7 @@ func (s *SuiteDecodeEncode) TestNoHead(c *C) {
 	s.test(c, input, expected)
 }
 
-func (s *SuiteDecodeEncode) TestNoHeadSmart(c *C) {
+func (s *AdvRefsDecodeEncodeSuite) TestNoHeadSmart(c *C) {
 	input := []string{
 		"# service=git-upload-pack\n",
 		"0000000000000000000000000000000000000000 capabilities^{}\x00",
@@ -86,7 +148,7 @@ func (s *SuiteDecodeEncode) TestNoHeadSmart(c *C) {
 	s.test(c, input, expected)
 }
 
-func (s *SuiteDecodeEncode) TestNoHeadSmartBug(c *C) {
+func (s *AdvRefsDecodeEncodeSuite) TestNoHeadSmartBug(c *C) {
 	input := []string{
 		"# service=git-upload-pack\n",
 		pktline.FlushString,
@@ -104,7 +166,7 @@ func (s *SuiteDecodeEncode) TestNoHeadSmartBug(c *C) {
 	s.test(c, input, expected)
 }
 
-func (s *SuiteDecodeEncode) TestRefs(c *C) {
+func (s *AdvRefsDecodeEncodeSuite) TestRefs(c *C) {
 	input := []string{
 		"6ecf0ef2c2dffb796033e5a02219af86ec6584e5 HEAD\x00symref=HEAD:/refs/heads/master ofs-delta multi_ack",
 		"a6930aaee06755d1bdcfd943fbf614e4d92bb0c7 refs/heads/master",
@@ -124,7 +186,7 @@ func (s *SuiteDecodeEncode) TestRefs(c *C) {
 	s.test(c, input, expected)
 }
 
-func (s *SuiteDecodeEncode) TestPeeled(c *C) {
+func (s *AdvRefsDecodeEncodeSuite) TestPeeled(c *C) {
 	input := []string{
 		"6ecf0ef2c2dffb796033e5a02219af86ec6584e5 HEAD\x00symref=HEAD:/refs/heads/master ofs-delta multi_ack",
 		"7777777777777777777777777777777777777777 refs/tags/v2.6.12-tree\n",
@@ -148,7 +210,7 @@ func (s *SuiteDecodeEncode) TestPeeled(c *C) {
 	s.test(c, input, expected)
 }
 
-func (s *SuiteDecodeEncode) TestAll(c *C) {
+func (s *AdvRefsDecodeEncodeSuite) TestAll(c *C) {
 	input := []string{
 		"6ecf0ef2c2dffb796033e5a02219af86ec6584e5 HEAD\x00symref=HEAD:/refs/heads/master ofs-delta multi_ack\n",
 		"a6930aaee06755d1bdcfd943fbf614e4d92bb0c7 refs/heads/master\n",
@@ -176,7 +238,7 @@ func (s *SuiteDecodeEncode) TestAll(c *C) {
 	s.test(c, input, expected)
 }
 
-func (s *SuiteDecodeEncode) TestAllSmart(c *C) {
+func (s *AdvRefsDecodeEncodeSuite) TestAllSmart(c *C) {
 	input := []string{
 		"# service=git-upload-pack\n",
 		pktline.FlushString,
@@ -208,7 +270,7 @@ func (s *SuiteDecodeEncode) TestAllSmart(c *C) {
 	s.test(c, input, expected)
 }
 
-func (s *SuiteDecodeEncode) TestAllSmartBug(c *C) {
+func (s *AdvRefsDecodeEncodeSuite) TestAllSmartBug(c *C) {
 	input := []string{
 		"# service=git-upload-pack\n",
 		pktline.FlushString,
@@ -254,7 +316,7 @@ func ExampleDecoder_Decode() {
 	input := strings.NewReader(raw)
 
 	// Decode the input into a newly allocated AdvRefs value.
-	ar := packp.NewAdvRefs()
+	ar := NewAdvRefs()
 	_ = ar.Decode(input) // error check ignored for brevity
 
 	// Do something interesting with the AdvRefs, e.g. print its contents.
@@ -270,7 +332,7 @@ func ExampleDecoder_Decode() {
 
 func ExampleEncoder_Encode() {
 	// Create an AdvRefs with the contents you want...
-	ar := packp.NewAdvRefs()
+	ar := NewAdvRefs()
 
 	// ...add a hash for the HEAD...
 	head := plumbing.NewHash("1111111111111111111111111111111111111111")
diff --git a/plumbing/protocol/packp/capability/list.go b/plumbing/protocol/packp/capability/list.go
index ff8d4a4..7197d36 100644
--- a/plumbing/protocol/packp/capability/list.go
+++ b/plumbing/protocol/packp/capability/list.go
@@ -145,6 +145,23 @@ func (l *List) Supports(capability Capability) bool {
 	return ok
 }
 
+// Delete deletes a capability from the List
+func (l *List) Delete(capability Capability) {
+	if !l.Supports(capability) {
+		return
+	}
+
+	delete(l.m, capability)
+	for i, c := range l.sort {
+		if c != string(capability) {
+			continue
+		}
+
+		l.sort = append(l.sort[:i], l.sort[i+1:]...)
+		return
+	}
+}
+
 // String generates the capabilities strings, the capabilities are sorted in
 // insertion order
 func (l *List) String() string {
diff --git a/plumbing/protocol/packp/capability/list_test.go b/plumbing/protocol/packp/capability/list_test.go
index eeb3173..d6aac16 100644
--- a/plumbing/protocol/packp/capability/list_test.go
+++ b/plumbing/protocol/packp/capability/list_test.go
@@ -97,6 +97,22 @@ func (s *SuiteCapabilities) TestGetEmpty(c *check.C) {
 	c.Assert(cap.Get(Agent), check.HasLen, 0)
 }
 
+func (s *SuiteCapabilities) TestDelete(c *check.C) {
+	cap := NewList()
+	cap.Delete(SymRef)
+
+	err := cap.Add(Sideband)
+	c.Assert(err, check.IsNil)
+	err = cap.Set(SymRef, "bar")
+	c.Assert(err, check.IsNil)
+	err = cap.Set(Sideband64k)
+	c.Assert(err, check.IsNil)
+
+	cap.Delete(SymRef)
+
+	c.Assert(cap.String(), check.Equals, "side-band side-band-64k")
+}
+
 func (s *SuiteCapabilities) TestAdd(c *check.C) {
 	cap := NewList()
 	err := cap.Add(SymRef, "foo", "qux")
diff --git a/plumbing/protocol/packp/ulreq.go b/plumbing/protocol/packp/ulreq.go
index be68b26..254e85e 100644
--- a/plumbing/protocol/packp/ulreq.go
+++ b/plumbing/protocol/packp/ulreq.go
@@ -1,12 +1,15 @@
 package packp
 
 import (
+	"fmt"
 	"time"
 
 	"gopkg.in/src-d/go-git.v4/plumbing"
 	"gopkg.in/src-d/go-git.v4/plumbing/protocol/packp/capability"
 )
 
+const DefaultAgent = "go-git/4.x"
+
 // UploadRequest values represent the information transmitted on a
 // upload-request message.  Values from this type are not zero-value
 // safe, use the New function instead.
@@ -41,10 +44,9 @@ type DepthReference string
 
 func (d DepthReference) isDepth() {}
 
-// NewUploadRequest returns a pointer to a new UlReq value, ready to be used.  It has
-// no capabilities, wants or shallows and an infinite depth.  Please
-// note that to encode an upload-request it has to have at least one
-// wanted hash.
+// NewUploadRequest returns a pointer to a new UploadRequest value, ready to be
+// used. It has no capabilities, wants or shallows and an infinite depth. Please
+// note that to encode an upload-request it has to have at least one wanted hash.
 func NewUploadRequest() *UploadRequest {
 	return &UploadRequest{
 		Capabilities: capability.NewList(),
@@ -54,7 +56,96 @@ func NewUploadRequest() *UploadRequest {
 	}
 }
 
-// Want adds a hash reference to the 'wants' list.
-func (r *UploadRequest) Want(h ...plumbing.Hash) {
-	r.Wants = append(r.Wants, h...)
+// NewUploadRequestFromCapabilities returns a pointer to a new UploadRequest
+// value, the request capabilities are filled with the most optiomal ones, based
+// on the adv value (advertaised capabilities), the UploadRequest generated it
+// has no wants or shallows and an infinite depth.
+func NewUploadRequestFromCapabilities(adv *capability.List) *UploadRequest {
+	r := NewUploadRequest()
+
+	if adv.Supports(capability.MultiACKDetailed) {
+		r.Capabilities.Set(capability.MultiACKDetailed)
+	} else if adv.Supports(capability.MultiACK) {
+		r.Capabilities.Set(capability.MultiACK)
+	}
+
+	if adv.Supports(capability.ThinPack) {
+		r.Capabilities.Set(capability.ThinPack)
+	}
+
+	if adv.Supports(capability.OFSDelta) {
+		r.Capabilities.Set(capability.OFSDelta)
+	}
+
+	if adv.Supports(capability.Agent) {
+		r.Capabilities.Set(capability.Agent, DefaultAgent)
+	}
+
+	return r
+}
+
+// Validate validates the content of UploadRequest, following the next rules:
+//   - Wants MUST have at least one reference
+//   - capability.Shallow MUST be present if Shallows is not empty
+//   - is a non-zero DepthCommits is given capability.Shallow MUST be present
+//   - is a DepthSince is given capability.Shallow MUST be present
+//   - is a DepthReference is given capability.DeepenNot MUST be present
+//   - MUST contain only maximum of one of capability.Sideband and capability.Sideband64k
+//   - MUST contain only maximum of one of capability.MultiACK and capability.MultiACKDetailed
+func (r *UploadRequest) Validate() error {
+	if len(r.Wants) == 0 {
+		return fmt.Errorf("want can't be empty")
+	}
+
+	if err := r.validateRequiredCapabilities(); err != nil {
+		return err
+	}
+
+	if err := r.validateConflictCapabilities(); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (r *UploadRequest) validateRequiredCapabilities() error {
+	msg := "missing capability %s"
+
+	if len(r.Shallows) != 0 && !r.Capabilities.Supports(capability.Shallow) {
+		return fmt.Errorf(msg, capability.Shallow)
+	}
+
+	switch r.Depth.(type) {
+	case DepthCommits:
+		if r.Depth != DepthCommits(0) {
+			if !r.Capabilities.Supports(capability.Shallow) {
+				return fmt.Errorf(msg, capability.Shallow)
+			}
+		}
+	case DepthSince:
+		if !r.Capabilities.Supports(capability.DeepenSince) {
+			return fmt.Errorf(msg, capability.DeepenSince)
+		}
+	case DepthReference:
+		if !r.Capabilities.Supports(capability.DeepenNot) {
+			return fmt.Errorf(msg, capability.DeepenNot)
+		}
+	}
+
+	return nil
+}
+
+func (r *UploadRequest) validateConflictCapabilities() error {
+	msg := "capabilities %s and %s are mutually exclusive"
+	if r.Capabilities.Supports(capability.Sideband) &&
+		r.Capabilities.Supports(capability.Sideband64k) {
+		return fmt.Errorf(msg, capability.Sideband, capability.Sideband64k)
+	}
+
+	if r.Capabilities.Supports(capability.MultiACK) &&
+		r.Capabilities.Supports(capability.MultiACKDetailed) {
+		return fmt.Errorf(msg, capability.MultiACK, capability.MultiACKDetailed)
+	}
+
+	return nil
 }
diff --git a/plumbing/protocol/packp/ulreq_decode_test.go b/plumbing/protocol/packp/ulreq_decode_test.go
index e7d9d7c6..82a4e1f 100644
--- a/plumbing/protocol/packp/ulreq_decode_test.go
+++ b/plumbing/protocol/packp/ulreq_decode_test.go
@@ -8,9 +8,9 @@ import (
 
 	"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"
 
 	. "gopkg.in/check.v1"
-	"gopkg.in/src-d/go-git.v4/plumbing/protocol/packp/capability"
 )
 
 type UlReqDecodeSuite struct{}
diff --git a/plumbing/protocol/packp/ulreq_test.go b/plumbing/protocol/packp/ulreq_test.go
index 5e9e978..53626ee 100644
--- a/plumbing/protocol/packp/ulreq_test.go
+++ b/plumbing/protocol/packp/ulreq_test.go
@@ -9,8 +9,109 @@ import (
 	"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"
+
+	. "gopkg.in/check.v1"
 )
 
+type UlReqSuite struct{}
+
+var _ = Suite(&UlReqSuite{})
+
+func (s *UlReqSuite) TestNewUploadRequestFromCapabilities(c *C) {
+	cap := capability.NewList()
+	cap.Set(capability.Sideband)
+	cap.Set(capability.Sideband64k)
+	cap.Set(capability.MultiACK)
+	cap.Set(capability.MultiACKDetailed)
+	cap.Set(capability.ThinPack)
+	cap.Set(capability.OFSDelta)
+	cap.Set(capability.Agent, "foo")
+
+	r := NewUploadRequestFromCapabilities(cap)
+	c.Assert(r.Capabilities.String(), Equals,
+		"multi_ack_detailed thin-pack ofs-delta agent=go-git/4.x",
+	)
+}
+
+func (s *UlReqSuite) TestValidateWants(c *C) {
+	r := NewUploadRequest()
+	err := r.Validate()
+	c.Assert(err, NotNil)
+
+	r.Wants = append(r.Wants, plumbing.NewHash("1111111111111111111111111111111111111111"))
+	err = r.Validate()
+	c.Assert(err, IsNil)
+}
+
+func (s *UlReqSuite) TestValidateShallows(c *C) {
+	r := NewUploadRequest()
+	r.Wants = append(r.Wants, plumbing.NewHash("1111111111111111111111111111111111111111"))
+	r.Shallows = append(r.Shallows, plumbing.NewHash("2222222222222222222222222222222222222222"))
+	err := r.Validate()
+	c.Assert(err, NotNil)
+
+	r.Capabilities.Set(capability.Shallow)
+	err = r.Validate()
+	c.Assert(err, IsNil)
+}
+
+func (s *UlReqSuite) TestValidateDepthCommits(c *C) {
+	r := NewUploadRequest()
+	r.Wants = append(r.Wants, plumbing.NewHash("1111111111111111111111111111111111111111"))
+	r.Depth = DepthCommits(42)
+
+	err := r.Validate()
+	c.Assert(err, NotNil)
+
+	r.Capabilities.Set(capability.Shallow)
+	err = r.Validate()
+	c.Assert(err, IsNil)
+}
+
+func (s *UlReqSuite) TestValidateDepthReference(c *C) {
+	r := NewUploadRequest()
+	r.Wants = append(r.Wants, plumbing.NewHash("1111111111111111111111111111111111111111"))
+	r.Depth = DepthReference("1111111111111111111111111111111111111111")
+
+	err := r.Validate()
+	c.Assert(err, NotNil)
+
+	r.Capabilities.Set(capability.DeepenNot)
+	err = r.Validate()
+	c.Assert(err, IsNil)
+}
+
+func (s *UlReqSuite) TestValidateDepthSince(c *C) {
+	r := NewUploadRequest()
+	r.Wants = append(r.Wants, plumbing.NewHash("1111111111111111111111111111111111111111"))
+	r.Depth = DepthSince(time.Now())
+
+	err := r.Validate()
+	c.Assert(err, NotNil)
+
+	r.Capabilities.Set(capability.DeepenSince)
+	err = r.Validate()
+	c.Assert(err, IsNil)
+}
+
+func (s *UlReqSuite) TestValidateConflictSideband(c *C) {
+	r := NewUploadRequest()
+	r.Wants = append(r.Wants, plumbing.NewHash("1111111111111111111111111111111111111111"))
+	r.Capabilities.Set(capability.Sideband)
+	r.Capabilities.Set(capability.Sideband64k)
+	err := r.Validate()
+	c.Assert(err, NotNil)
+}
+
+func (s *UlReqSuite) TestValidateConflictMultiACK(c *C) {
+	r := NewUploadRequest()
+	r.Wants = append(r.Wants, plumbing.NewHash("1111111111111111111111111111111111111111"))
+	r.Capabilities.Set(capability.MultiACK)
+	r.Capabilities.Set(capability.MultiACKDetailed)
+	err := r.Validate()
+	c.Assert(err, NotNil)
+}
+
 func ExampleUlReqEncoder_Encode() {
 	// Create an empty UlReq with the contents you want...
 	ur := NewUploadRequest()
diff --git a/plumbing/protocol/packp/upload_pack_request_test.go b/plumbing/protocol/packp/upload_pack_request_test.go
deleted file mode 100644
index f321736..0000000
--- a/plumbing/protocol/packp/upload_pack_request_test.go
+++ /dev/null
@@ -1,33 +0,0 @@
-package packp
-
-import (
-	"gopkg.in/src-d/go-git.v4/plumbing"
-
-	. "gopkg.in/check.v1"
-)
-
-type UploadPackRequestSuite struct{}
-
-var _ = Suite(&UploadPackRequestSuite{})
-
-func (s *UploadPackRequestSuite) TestUploadPackRequest_IsEmpty(c *C) {
-	r := NewUploadPackRequest()
-	r.Want(plumbing.NewHash("d82f291cde9987322c8a0c81a325e1ba6159684c"))
-	r.Want(plumbing.NewHash("2b41ef280fdb67a9b250678686a0c3e03b0a9989"))
-	r.Have(plumbing.NewHash("6ecf0ef2c2dffb796033e5a02219af86ec6584e5"))
-
-	c.Assert(r.IsEmpty(), Equals, false)
-
-	r = NewUploadPackRequest()
-	r.Want(plumbing.NewHash("d82f291cde9987322c8a0c81a325e1ba6159684c"))
-	r.Want(plumbing.NewHash("2b41ef280fdb67a9b250678686a0c3e03b0a9989"))
-	r.Have(plumbing.NewHash("d82f291cde9987322c8a0c81a325e1ba6159684c"))
-
-	c.Assert(r.IsEmpty(), Equals, false)
-
-	r = NewUploadPackRequest()
-	r.Want(plumbing.NewHash("d82f291cde9987322c8a0c81a325e1ba6159684c"))
-	r.Have(plumbing.NewHash("d82f291cde9987322c8a0c81a325e1ba6159684c"))
-
-	c.Assert(r.IsEmpty(), Equals, true)
-}
diff --git a/plumbing/protocol/packp/upload_pack_request.go b/plumbing/protocol/packp/uppackreq.go
index 42033b1..2b1cb84 100644
--- a/plumbing/protocol/packp/upload_pack_request.go
+++ b/plumbing/protocol/packp/uppackreq.go
@@ -6,37 +6,9 @@ import (
 
 	"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"
 )
 
-// UploadHaves is a message to signal the references that a client has in a
-// upload-pack. Do not use this directly. Use UploadPackRequest request instead.
-type UploadHaves struct {
-	Haves []plumbing.Hash
-}
-
-// Encode encodes the UploadHaves into the Writer.
-func (u *UploadHaves) Encode(w io.Writer) error {
-	e := pktline.NewEncoder(w)
-	for _, have := range u.Haves {
-		if err := e.Encodef("have %s\n", have); err != nil {
-			return fmt.Errorf("sending haves for %q: %s", have, err)
-		}
-	}
-
-	if len(u.Haves) != 0 {
-		if err := e.Flush(); err != nil {
-			return fmt.Errorf("sending flush-pkt after haves: %s", err)
-		}
-	}
-
-	return nil
-}
-
-// Have adds a hash reference to the 'haves' list.
-func (r *UploadHaves) Have(h ...plumbing.Hash) {
-	r.Haves = append(r.Haves, h...)
-}
-
 // UploadPackRequest represents a upload-pack request.
 // Zero-value is not safe, use NewUploadPackRequest instead.
 type UploadPackRequest struct {
@@ -52,6 +24,19 @@ func NewUploadPackRequest() *UploadPackRequest {
 	}
 }
 
+// NewUploadPackRequestFromCapabilities creates a new UploadPackRequest and
+// returns a pointer. The request capabilities are filled with the most optiomal
+// ones, based on the adv value (advertaised capabilities), the UploadPackRequest
+// it has no wants, haves or shallows and an infinite depth
+func NewUploadPackRequestFromCapabilities(adv *capability.List) *UploadPackRequest {
+	return &UploadPackRequest{
+		UploadHaves:   &UploadHaves{},
+		UploadRequest: NewUploadRequestFromCapabilities(adv),
+	}
+}
+
+// IsEmpty a request if empty if Haves are contained in the Wants, or if Wants
+// length is zero
 func (r *UploadPackRequest) IsEmpty() bool {
 	return isSubset(r.Wants, r.Haves)
 }
@@ -73,3 +58,27 @@ func isSubset(needle []plumbing.Hash, haystack []plumbing.Hash) bool {
 
 	return true
 }
+
+// UploadHaves is a message to signal the references that a client has in a
+// upload-pack. Do not use this directly. Use UploadPackRequest request instead.
+type UploadHaves struct {
+	Haves []plumbing.Hash
+}
+
+// Encode encodes the UploadHaves into the Writer.
+func (u *UploadHaves) Encode(w io.Writer) error {
+	e := pktline.NewEncoder(w)
+	for _, have := range u.Haves {
+		if err := e.Encodef("have %s\n", have); err != nil {
+			return fmt.Errorf("sending haves for %q: %s", have, err)
+		}
+	}
+
+	if len(u.Haves) != 0 {
+		if err := e.Flush(); err != nil {
+			return fmt.Errorf("sending flush-pkt after haves: %s", err)
+		}
+	}
+
+	return nil
+}
diff --git a/plumbing/protocol/packp/uppackreq_test.go b/plumbing/protocol/packp/uppackreq_test.go
new file mode 100644
index 0000000..75b75b4
--- /dev/null
+++ b/plumbing/protocol/packp/uppackreq_test.go
@@ -0,0 +1,42 @@
+package packp
+
+import (
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/protocol/packp/capability"
+
+	. "gopkg.in/check.v1"
+)
+
+type UploadPackRequestSuite struct{}
+
+var _ = Suite(&UploadPackRequestSuite{})
+
+func (s *UploadPackRequestSuite) TestNewUploadPackRequestFromCapabilities(c *C) {
+	cap := capability.NewList()
+	cap.Set(capability.Agent, "foo")
+
+	r := NewUploadPackRequestFromCapabilities(cap)
+	c.Assert(r.Capabilities.String(), Equals, "agent=go-git/4.x")
+}
+
+func (s *UploadPackRequestSuite) TestIsEmpty(c *C) {
+	r := NewUploadPackRequest()
+	r.Wants = append(r.Wants, plumbing.NewHash("d82f291cde9987322c8a0c81a325e1ba6159684c"))
+	r.Wants = append(r.Wants, plumbing.NewHash("2b41ef280fdb67a9b250678686a0c3e03b0a9989"))
+	r.Haves = append(r.Haves, plumbing.NewHash("6ecf0ef2c2dffb796033e5a02219af86ec6584e5"))
+
+	c.Assert(r.IsEmpty(), Equals, false)
+
+	r = NewUploadPackRequest()
+	r.Wants = append(r.Wants, plumbing.NewHash("d82f291cde9987322c8a0c81a325e1ba6159684c"))
+	r.Wants = append(r.Wants, plumbing.NewHash("2b41ef280fdb67a9b250678686a0c3e03b0a9989"))
+	r.Haves = append(r.Haves, plumbing.NewHash("d82f291cde9987322c8a0c81a325e1ba6159684c"))
+
+	c.Assert(r.IsEmpty(), Equals, false)
+
+	r = NewUploadPackRequest()
+	r.Wants = append(r.Wants, plumbing.NewHash("d82f291cde9987322c8a0c81a325e1ba6159684c"))
+	r.Haves = append(r.Haves, plumbing.NewHash("d82f291cde9987322c8a0c81a325e1ba6159684c"))
+
+	c.Assert(r.IsEmpty(), Equals, true)
+}