transport: create Client interface (#132)

* plumbing: move plumbing/client package to plumbing/transport.

* transport: create Client interface.

* A Client can instantiate any client transport service.
* InstallProtocol installs a Client for a given protocol,
  instead of just a UploadPackService.
* A Client can open a session for fetch-pack or send-pack
  for a specific Endpoint.
* Adapt ssh and http clients to the new client interface.

* updated doc

19 files changed, 1828 insertions, 0 deletions

diff --git a/plumbing/transport/client/client.go b/plumbing/transport/client/client.go
new file mode 100644
index 0000000..5c6da05
--- /dev/null
+++ b/plumbing/transport/client/client.go
@@ -0,0 +1,32 @@
+package client
+
+import (
+	"fmt"
+
+	"gopkg.in/src-d/go-git.v4/plumbing/transport"
+	"gopkg.in/src-d/go-git.v4/plumbing/transport/http"
+	"gopkg.in/src-d/go-git.v4/plumbing/transport/ssh"
+)
+
+// Protocols are the protocols supported by default.
+var Protocols = map[string]transport.Client{
+	"http":  http.DefaultClient,
+	"https": http.DefaultClient,
+	"ssh":   ssh.DefaultClient,
+}
+
+// InstallProtocol adds or modifies an existing protocol.
+func InstallProtocol(scheme string, c transport.Client) {
+	Protocols[scheme] = c
+}
+
+// NewClient returns the appropriate client among of the set of known protocols:
+// HTTP, SSH. See `InstallProtocol` to add or modify protocols.
+func NewClient(endpoint transport.Endpoint) (transport.Client, error) {
+	f, ok := Protocols[endpoint.Scheme]
+	if !ok {
+		return nil, fmt.Errorf("unsupported scheme %q", endpoint.Scheme)
+	}
+
+	return f, nil
+}
diff --git a/plumbing/transport/client/client_test.go b/plumbing/transport/client/client_test.go
new file mode 100644
index 0000000..90bad57
--- /dev/null
+++ b/plumbing/transport/client/client_test.go
@@ -0,0 +1,73 @@
+package client
+
+import (
+	"fmt"
+	"net/http"
+	"testing"
+
+	"gopkg.in/src-d/go-git.v4/plumbing/transport"
+
+	. "gopkg.in/check.v1"
+)
+
+func Test(t *testing.T) { TestingT(t) }
+
+type ClientSuite struct{}
+
+var _ = Suite(&ClientSuite{})
+
+func (s *ClientSuite) TestNewClientHTTP(c *C) {
+	e, err := transport.NewEndpoint("http://github.com/src-d/go-git")
+	c.Assert(err, IsNil)
+
+	output, err := NewClient(e)
+	c.Assert(err, IsNil)
+	c.Assert(typeAsString(output), Equals, "*http.Client")
+
+	e, err = transport.NewEndpoint("https://github.com/src-d/go-git")
+	c.Assert(err, IsNil)
+
+	output, err = NewClient(e)
+	c.Assert(err, IsNil)
+	c.Assert(typeAsString(output), Equals, "*http.Client")
+}
+
+func (s *ClientSuite) TestNewClientSSH(c *C) {
+	e, err := transport.NewEndpoint("ssh://github.com/src-d/go-git")
+	c.Assert(err, IsNil)
+
+	output, err := NewClient(e)
+	c.Assert(err, IsNil)
+	c.Assert(typeAsString(output), Equals, "*ssh.Client")
+}
+
+func (s *ClientSuite) TestNewClientUnknown(c *C) {
+	e, err := transport.NewEndpoint("unknown://github.com/src-d/go-git")
+	c.Assert(err, IsNil)
+
+	_, err = NewClient(e)
+	c.Assert(err, NotNil)
+}
+
+func (s *ClientSuite) TestInstallProtocol(c *C) {
+	InstallProtocol("newscheme", &dummyClient{})
+	c.Assert(Protocols["newscheme"], NotNil)
+}
+
+type dummyClient struct {
+	*http.Client
+}
+
+func (*dummyClient) NewFetchPackSession(transport.Endpoint) (
+	transport.FetchPackSession, error) {
+	return nil, nil
+}
+
+func (*dummyClient) NewSendPackSession(transport.Endpoint) (
+	transport.SendPackSession, error) {
+	return nil, nil
+}
+
+func typeAsString(v interface{}) string {
+	return fmt.Sprintf("%T", v)
+}
diff --git a/plumbing/transport/client/example_test.go b/plumbing/transport/client/example_test.go
new file mode 100644
index 0000000..3e7a4f0
--- /dev/null
+++ b/plumbing/transport/client/example_test.go
@@ -0,0 +1,21 @@
+package client_test
+
+import (
+	"crypto/tls"
+	"net/http"
+
+	"gopkg.in/src-d/go-git.v4/plumbing/transport/client"
+	githttp "gopkg.in/src-d/go-git.v4/plumbing/transport/http"
+)
+
+func ExampleInstallProtocol() {
+	// Create custom net/http client that.
+	httpClient := &http.Client{
+		Transport: &http.Transport{
+			TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
+		},
+	}
+
+	// Install it as default client for https URLs.
+	client.InstallProtocol("https", githttp.NewClient(httpClient))
+}
diff --git a/plumbing/transport/common.go b/plumbing/transport/common.go
new file mode 100644
index 0000000..cc30564
--- /dev/null
+++ b/plumbing/transport/common.go
@@ -0,0 +1,121 @@
+// Package transport includes the implementation for different transport
+// protocols.
+//
+// `Client` can be used to fetch and send packfiles to a git server.
+// The `client` package provides higher level functions to instantiate the
+// appropiate `Client` based on the repository URL.
+//
+// Go-git supports HTTP and SSH (see `Protocols`), but you can also install
+// your own protocols (see the `client` package).
+//
+// Each protocol has its own implementation of `Client`, but you should
+// generally not use them directly, use `client.NewClient` instead.
+package transport
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"net/url"
+	"regexp"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+)
+
+var (
+	ErrRepositoryNotFound     = errors.New("repository not found")
+	ErrAuthorizationRequired  = errors.New("authorization required")
+	ErrEmptyUploadPackRequest = errors.New("empty git-upload-pack given")
+	ErrInvalidAuthMethod      = errors.New("invalid auth method")
+)
+
+const (
+	UploadPackServiceName = "git-upload-pack"
+)
+
+// Client can initiate git-fetch-pack and git-send-pack processes.
+type Client interface {
+	// NewFetchPackSession starts a git-fetch-pack session for an endpoint.
+	NewFetchPackSession(Endpoint) (FetchPackSession, error)
+	// NewSendPackSession starts a git-send-pack session for an endpoint.
+	NewSendPackSession(Endpoint) (SendPackSession, error)
+}
+
+type Session interface {
+	SetAuth(auth AuthMethod) error
+	io.Closer
+}
+
+type AuthMethod interface {
+	fmt.Stringer
+	Name() string
+}
+
+// FetchPackSession represents a git-fetch-pack session.
+// A git-fetch-pack session has two steps: reference discovery
+// (`AdvertisedReferences` function) and fetching pack (`FetchPack` function).
+// In that order.
+type FetchPackSession interface {
+	Session
+	// AdvertisedReferences retrieves the advertised references for a
+	// repository. It should be called before FetchPack, and it cannot be
+	// called after FetchPack.
+	AdvertisedReferences() (*UploadPackInfo, error)
+	// FetchPack takes a request and returns a reader for the packfile
+	// received from the server.
+	FetchPack(req *UploadPackRequest) (io.ReadCloser, error)
+}
+
+// FetchPackSession represents a git-send-pack session.
+// A git-send-pack session has two steps: reference discovery
+// (`AdvertisedReferences` function) and sending pack (`SendPack` function).
+// In that order.
+type SendPackSession interface {
+	Session
+	// AdvertisedReferences retrieves the advertised references for a
+	// repository. It should be called before FetchPack, and it cannot be
+	// called after FetchPack.
+	AdvertisedReferences() (*UploadPackInfo, error)
+	// UpdateReferences sends an update references request and returns a
+	// writer to be used for packfile writing.
+	//TODO: Complete signature.
+	SendPack() (io.WriteCloser, error)
+}
+
+type Endpoint url.URL
+
+var (
+	isSchemeRegExp   = regexp.MustCompile("^[^:]+://")
+	scpLikeUrlRegExp = regexp.MustCompile("^(?P<user>[^@]+@)?(?P<host>[^:]+):/?(?P<path>.+)$")
+)
+
+func NewEndpoint(endpoint string) (Endpoint, error) {
+	endpoint = transformSCPLikeIfNeeded(endpoint)
+
+	u, err := url.Parse(endpoint)
+	if err != nil {
+		return Endpoint{}, plumbing.NewPermanentError(err)
+	}
+
+	if !u.IsAbs() {
+		return Endpoint{}, plumbing.NewPermanentError(fmt.Errorf(
+			"invalid endpoint: %s", endpoint,
+		))
+	}
+
+	return Endpoint(*u), nil
+}
+
+func (e *Endpoint) String() string {
+	u := url.URL(*e)
+	return u.String()
+}
+
+func transformSCPLikeIfNeeded(endpoint string) string {
+	if !isSchemeRegExp.MatchString(endpoint) && scpLikeUrlRegExp.MatchString(endpoint) {
+		m := scpLikeUrlRegExp.FindStringSubmatch(endpoint)
+		return fmt.Sprintf("ssh://%s%s/%s", m[1], m[2], m[3])
+	}
+
+	return endpoint
+}
diff --git a/plumbing/transport/common_test.go b/plumbing/transport/common_test.go
new file mode 100644
index 0000000..9ca4459
--- /dev/null
+++ b/plumbing/transport/common_test.go
@@ -0,0 +1,31 @@
+package transport
+
+import (
+	"testing"
+
+	. "gopkg.in/check.v1"
+)
+
+func Test(t *testing.T) { TestingT(t) }
+
+type SuiteCommon struct{}
+
+var _ = Suite(&SuiteCommon{})
+
+func (s *SuiteCommon) TestNewEndpoint(c *C) {
+	e, err := NewEndpoint("ssh://git@github.com/user/repository.git")
+	c.Assert(err, IsNil)
+	c.Assert(e.String(), Equals, "ssh://git@github.com/user/repository.git")
+}
+
+func (s *SuiteCommon) TestNewEndpointSCPLike(c *C) {
+	e, err := NewEndpoint("git@github.com:user/repository.git")
+	c.Assert(err, IsNil)
+	c.Assert(e.String(), Equals, "ssh://git@github.com/user/repository.git")
+}
+
+func (s *SuiteCommon) TestNewEndpointWrongForgat(c *C) {
+	e, err := NewEndpoint("foo")
+	c.Assert(err, Not(IsNil))
+	c.Assert(e.Host, Equals, "")
+}
diff --git a/plumbing/transport/fetch_pack.go b/plumbing/transport/fetch_pack.go
new file mode 100644
index 0000000..3b2a39c
--- /dev/null
+++ b/plumbing/transport/fetch_pack.go
@@ -0,0 +1,156 @@
+package transport
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"strings"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/format/packp"
+	"gopkg.in/src-d/go-git.v4/plumbing/format/packp/advrefs"
+	"gopkg.in/src-d/go-git.v4/plumbing/format/packp/pktline"
+	"gopkg.in/src-d/go-git.v4/plumbing/storer"
+	"gopkg.in/src-d/go-git.v4/storage/memory"
+)
+
+//TODO: Replace this by advrefs.AdvRefs.
+type UploadPackInfo struct {
+	Capabilities *packp.Capabilities
+	Refs         memory.ReferenceStorage
+}
+
+func NewUploadPackInfo() *UploadPackInfo {
+	return &UploadPackInfo{
+		Capabilities: packp.NewCapabilities(),
+		Refs:         make(memory.ReferenceStorage, 0),
+	}
+}
+
+func (i *UploadPackInfo) Decode(r io.Reader) error {
+	d := advrefs.NewDecoder(r)
+	ar := advrefs.New()
+	if err := d.Decode(ar); err != nil {
+		if err == advrefs.ErrEmpty {
+			return plumbing.NewPermanentError(err)
+		}
+		return plumbing.NewUnexpectedError(err)
+	}
+
+	i.Capabilities = ar.Capabilities
+
+	if err := i.addRefs(ar); err != nil {
+		return plumbing.NewUnexpectedError(err)
+	}
+
+	return nil
+}
+
+func (i *UploadPackInfo) addRefs(ar *advrefs.AdvRefs) error {
+	for name, hash := range ar.References {
+		ref := plumbing.NewReferenceFromStrings(name, hash.String())
+		i.Refs.SetReference(ref)
+	}
+
+	return i.addSymbolicRefs(ar)
+}
+
+func (i *UploadPackInfo) addSymbolicRefs(ar *advrefs.AdvRefs) error {
+	if !hasSymrefs(ar) {
+		return nil
+	}
+
+	for _, symref := range ar.Capabilities.Get("symref").Values {
+		chunks := strings.Split(symref, ":")
+		if len(chunks) != 2 {
+			err := fmt.Errorf("bad number of `:` in symref value (%q)", symref)
+			return plumbing.NewUnexpectedError(err)
+		}
+		name := plumbing.ReferenceName(chunks[0])
+		target := plumbing.ReferenceName(chunks[1])
+		ref := plumbing.NewSymbolicReference(name, target)
+		i.Refs.SetReference(ref)
+	}
+
+	return nil
+}
+
+func hasSymrefs(ar *advrefs.AdvRefs) bool {
+	return ar.Capabilities.Supports("symref")
+}
+
+func (i *UploadPackInfo) Head() *plumbing.Reference {
+	ref, _ := storer.ResolveReference(i.Refs, plumbing.HEAD)
+	return ref
+}
+
+func (i *UploadPackInfo) String() string {
+	return string(i.Bytes())
+}
+
+func (i *UploadPackInfo) Bytes() []byte {
+	var buf bytes.Buffer
+	e := pktline.NewEncoder(&buf)
+
+	_ = e.EncodeString("# service=git-upload-pack\n")
+
+	// inserting a flush-pkt here violates the protocol spec, but some
+	// servers do it, like Github.com
+	e.Flush()
+
+	_ = e.Encodef("%s HEAD\x00%s\n", i.Head().Hash(), i.Capabilities.String())
+
+	for _, ref := range i.Refs {
+		if ref.Type() != plumbing.HashReference {
+			continue
+		}
+
+		_ = e.Encodef("%s %s\n", ref.Hash(), ref.Name())
+	}
+
+	e.Flush()
+
+	return buf.Bytes()
+}
+
+type UploadPackRequest struct {
+	Wants []plumbing.Hash
+	Haves []plumbing.Hash
+	Depth int
+}
+
+func (r *UploadPackRequest) Want(h ...plumbing.Hash) {
+	r.Wants = append(r.Wants, h...)
+}
+
+func (r *UploadPackRequest) Have(h ...plumbing.Hash) {
+	r.Haves = append(r.Haves, h...)
+}
+
+func (r *UploadPackRequest) String() string {
+	b, _ := ioutil.ReadAll(r.Reader())
+	return string(b)
+}
+
+func (r *UploadPackRequest) Reader() *strings.Reader {
+	var buf bytes.Buffer
+	e := pktline.NewEncoder(&buf)
+
+	for _, want := range r.Wants {
+		_ = e.Encodef("want %s\n", want)
+	}
+
+	for _, have := range r.Haves {
+		_ = e.Encodef("have %s\n", have)
+	}
+
+	if r.Depth != 0 {
+		_ = e.Encodef("deepen %d\n", r.Depth)
+	}
+
+	_ = e.Flush()
+	_ = e.EncodeString("done\n")
+
+	return strings.NewReader(buf.String())
+}
diff --git a/plumbing/transport/fetch_pack_test.go b/plumbing/transport/fetch_pack_test.go
new file mode 100644
index 0000000..7a7f86f
--- /dev/null
+++ b/plumbing/transport/fetch_pack_test.go
@@ -0,0 +1,96 @@
+package transport
+
+import (
+	"bytes"
+	"encoding/base64"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+
+	. "gopkg.in/check.v1"
+)
+
+type UploadPackSuite struct{}
+
+var _ = Suite(&UploadPackSuite{})
+
+const UploadPackInfoFixture = "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"
+
+func (s *UploadPackSuite) TestUploadPackInfo(c *C) {
+	b, _ := base64.StdEncoding.DecodeString(UploadPackInfoFixture)
+
+	i := NewUploadPackInfo()
+	err := i.Decode(bytes.NewBuffer(b))
+	c.Assert(err, IsNil)
+
+	name := i.Capabilities.SymbolicReference("HEAD")
+	c.Assert(name, Equals, "refs/heads/master")
+	c.Assert(i.Refs, HasLen, 4)
+
+	ref := i.Refs[plumbing.ReferenceName(name)]
+	c.Assert(ref, NotNil)
+	c.Assert(ref.Hash().String(), Equals, "6ecf0ef2c2dffb796033e5a02219af86ec6584e5")
+
+	ref = i.Refs[plumbing.HEAD]
+	c.Assert(ref, NotNil)
+	c.Assert(ref.Target(), Equals, plumbing.ReferenceName(name))
+}
+
+const UploadPackInfoNoHEADFixture = "MDAxZSMgc2VydmljZT1naXQtdXBsb2FkLXBhY2sKMDAwMDAwYmNkN2UxZmVlMjYxMjM0YmIzYTQzYzA5NmY1NTg3NDhhNTY5ZDc5ZWZmIHJlZnMvaGVhZHMvdjQAbXVsdGlfYWNrIHRoaW4tcGFjayBzaWRlLWJhbmQgc2lkZS1iYW5kLTY0ayBvZnMtZGVsdGEgc2hhbGxvdyBuby1wcm9ncmVzcyBpbmNsdWRlLXRhZyBtdWx0aV9hY2tfZGV0YWlsZWQgbm8tZG9uZSBhZ2VudD1naXQvMS45LjEKMDAwMA=="
+
+func (s *UploadPackSuite) TestUploadPackInfoNoHEAD(c *C) {
+	b, _ := base64.StdEncoding.DecodeString(UploadPackInfoNoHEADFixture)
+
+	i := NewUploadPackInfo()
+	err := i.Decode(bytes.NewBuffer(b))
+	c.Assert(err, IsNil)
+
+	name := i.Capabilities.SymbolicReference("HEAD")
+	c.Assert(name, Equals, "")
+	c.Assert(i.Refs, HasLen, 1)
+
+	ref := i.Refs["refs/heads/v4"]
+	c.Assert(ref, NotNil)
+	c.Assert(ref.Hash().String(), Equals, "d7e1fee261234bb3a43c096f558748a569d79eff")
+}
+
+func (s *UploadPackSuite) TestUploadPackInfoEmpty(c *C) {
+	b := bytes.NewBuffer(nil)
+
+	i := NewUploadPackInfo()
+	err := i.Decode(b)
+	c.Assert(err, ErrorMatches, "permanent.*empty.*")
+}
+
+func (s *UploadPackSuite) TestUploadPackEncode(c *C) {
+	info := NewUploadPackInfo()
+	info.Capabilities.Add("symref", "HEAD:refs/heads/master")
+
+	ref := plumbing.ReferenceName("refs/heads/master")
+	hash := plumbing.NewHash("6ecf0ef2c2dffb796033e5a02219af86ec6584e5")
+	info.Refs = map[plumbing.ReferenceName]*plumbing.Reference{
+		plumbing.HEAD: plumbing.NewSymbolicReference(plumbing.HEAD, ref),
+		ref:           plumbing.NewHashReference(ref, hash),
+	}
+
+	c.Assert(info.Head(), NotNil)
+	c.Assert(info.String(), Equals,
+		"001e# service=git-upload-pack\n"+
+			"000000506ecf0ef2c2dffb796033e5a02219af86ec6584e5 HEAD\x00symref=HEAD:refs/heads/master\n"+
+			"003f6ecf0ef2c2dffb796033e5a02219af86ec6584e5 refs/heads/master\n"+
+			"0000",
+	)
+}
+
+func (s *UploadPackSuite) TestUploadPackRequest(c *C) {
+	r := &UploadPackRequest{}
+	r.Want(plumbing.NewHash("d82f291cde9987322c8a0c81a325e1ba6159684c"))
+	r.Want(plumbing.NewHash("2b41ef280fdb67a9b250678686a0c3e03b0a9989"))
+	r.Have(plumbing.NewHash("6ecf0ef2c2dffb796033e5a02219af86ec6584e5"))
+
+	c.Assert(r.String(), Equals,
+		"0032want d82f291cde9987322c8a0c81a325e1ba6159684c\n"+
+			"0032want 2b41ef280fdb67a9b250678686a0c3e03b0a9989\n"+
+			"0032have 6ecf0ef2c2dffb796033e5a02219af86ec6584e5\n0000"+
+			"0009done\n",
+	)
+}
diff --git a/plumbing/transport/http/common.go b/plumbing/transport/http/common.go
new file mode 100644
index 0000000..038c469
--- /dev/null
+++ b/plumbing/transport/http/common.go
@@ -0,0 +1,155 @@
+// Package http implements a HTTP client for go-git.
+package http
+
+import (
+	"fmt"
+	"net/http"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/transport"
+)
+
+type Client struct {
+	c *http.Client
+}
+
+var DefaultClient = NewClient(nil)
+
+// NewClient creates a new client with a custom net/http client.
+// See `InstallProtocol` to install and override default http client.
+// Unless a properly initialized client is given, it will fall back into
+// `http.DefaultClient`.
+func NewClient(c *http.Client) transport.Client {
+	if c == nil {
+		return &Client{http.DefaultClient}
+	}
+
+	return &Client{
+		c: c,
+	}
+}
+
+func (c *Client) NewFetchPackSession(ep transport.Endpoint) (
+	transport.FetchPackSession, error) {
+
+	return newFetchPackSession(c.c, ep), nil
+}
+
+func (c *Client) NewSendPackSession(ep transport.Endpoint) (
+	transport.SendPackSession, error) {
+
+	return newSendPackSession(c.c, ep), nil
+}
+
+type session struct {
+	auth     AuthMethod
+	client   *http.Client
+	endpoint transport.Endpoint
+}
+
+func (s *session) SetAuth(auth transport.AuthMethod) error {
+	a, ok := auth.(AuthMethod)
+	if !ok {
+		return transport.ErrInvalidAuthMethod
+	}
+
+	s.auth = a
+	return nil
+}
+
+func (*session) Close() error {
+	return nil
+}
+
+func (s *session) applyAuthToRequest(req *http.Request) {
+	if s.auth == nil {
+		return
+	}
+
+	s.auth.setAuth(req)
+}
+
+// AuthMethod is concrete implementation of common.AuthMethod for HTTP services
+type AuthMethod interface {
+	transport.AuthMethod
+	setAuth(r *http.Request)
+}
+
+func basicAuthFromEndpoint(ep transport.Endpoint) *BasicAuth {
+	info := ep.User
+	if info == nil {
+		return nil
+	}
+
+	p, ok := info.Password()
+	if !ok {
+		return nil
+	}
+
+	u := info.Username()
+	return NewBasicAuth(u, p)
+}
+
+// BasicAuth represent a HTTP basic auth
+type BasicAuth struct {
+	username, password string
+}
+
+// NewBasicAuth returns a basicAuth base on the given user and password
+func NewBasicAuth(username, password string) *BasicAuth {
+	return &BasicAuth{username, password}
+}
+
+func (a *BasicAuth) setAuth(r *http.Request) {
+	if a == nil {
+		return
+	}
+
+	r.SetBasicAuth(a.username, a.password)
+}
+
+// Name is name of the auth
+func (a *BasicAuth) Name() string {
+	return "http-basic-auth"
+}
+
+func (a *BasicAuth) String() string {
+	masked := "*******"
+	if a.password == "" {
+		masked = "<empty>"
+	}
+
+	return fmt.Sprintf("%s - %s:%s", a.Name(), a.username, masked)
+}
+
+// Err is a dedicated error to return errors based on status code
+type Err struct {
+	Response *http.Response
+}
+
+// NewErr returns a new Err based on a http response
+func NewErr(r *http.Response) error {
+	if r.StatusCode >= http.StatusOK && r.StatusCode < http.StatusMultipleChoices {
+		return nil
+	}
+
+	switch r.StatusCode {
+	case http.StatusUnauthorized:
+		return transport.ErrAuthorizationRequired
+	case http.StatusNotFound:
+		return transport.ErrRepositoryNotFound
+	}
+
+	return plumbing.NewUnexpectedError(&Err{r})
+}
+
+// StatusCode returns the status code of the response
+func (e *Err) StatusCode() int {
+	return e.Response.StatusCode
+}
+
+func (e *Err) Error() string {
+	return fmt.Sprintf("unexpected requesting %q status code: %d",
+		e.Response.Request.URL, e.Response.StatusCode,
+	)
+}
diff --git a/plumbing/transport/http/common_test.go b/plumbing/transport/http/common_test.go
new file mode 100644
index 0000000..1d09fba
--- /dev/null
+++ b/plumbing/transport/http/common_test.go
@@ -0,0 +1,89 @@
+package http
+
+import (
+	"crypto/tls"
+	"net/http"
+	"testing"
+
+	"gopkg.in/src-d/go-git.v4/plumbing/transport"
+
+	. "gopkg.in/check.v1"
+)
+
+func Test(t *testing.T) { TestingT(t) }
+
+type ClientSuite struct {
+	Endpoint transport.Endpoint
+}
+
+var _ = Suite(&ClientSuite{})
+
+func (s *ClientSuite) SetUpSuite(c *C) {
+	var err error
+	s.Endpoint, err = transport.NewEndpoint("https://github.com/git-fixtures/basic")
+	c.Assert(err, IsNil)
+}
+
+func (s *FetchPackSuite) TestNewClient(c *C) {
+	roundTripper := &http.Transport{TLSClientConfig: &tls.Config{InsecureSkipVerify: true}}
+	client := &http.Client{Transport: roundTripper}
+	r := NewClient(client).(*Client)
+
+	c.Assert(r.c, Equals, client)
+}
+
+func (s *ClientSuite) TestNewBasicAuth(c *C) {
+	a := NewBasicAuth("foo", "qux")
+
+	c.Assert(a.Name(), Equals, "http-basic-auth")
+	c.Assert(a.String(), Equals, "http-basic-auth - foo:*******")
+}
+
+func (s *ClientSuite) TestNewErrOK(c *C) {
+	res := &http.Response{StatusCode: http.StatusOK}
+	err := NewErr(res)
+	c.Assert(err, IsNil)
+}
+
+func (s *ClientSuite) TestNewErrUnauthorized(c *C) {
+	s.testNewHTTPError(c, http.StatusUnauthorized, "authorization required")
+}
+
+func (s *ClientSuite) TestNewErrNotFound(c *C) {
+	s.testNewHTTPError(c, http.StatusNotFound, "repository not found")
+}
+
+func (s *ClientSuite) TestNewHTTPError40x(c *C) {
+	s.testNewHTTPError(c, http.StatusPaymentRequired, "unexpected client error.*")
+}
+
+func (s *ClientSuite) testNewHTTPError(c *C, code int, msg string) {
+	req, _ := http.NewRequest("GET", "foo", nil)
+	res := &http.Response{
+		StatusCode: code,
+		Request:    req,
+	}
+
+	err := NewErr(res)
+	c.Assert(err, NotNil)
+	c.Assert(err, ErrorMatches, msg)
+}
+
+func (s *ClientSuite) TestSetAuth(c *C) {
+	auth := &BasicAuth{}
+	r, err := DefaultClient.NewFetchPackSession(s.Endpoint)
+	c.Assert(err, IsNil)
+	r.SetAuth(auth)
+	c.Assert(auth, Equals, r.(*fetchPackSession).auth)
+}
+
+type mockAuth struct{}
+
+func (*mockAuth) Name() string   { return "" }
+func (*mockAuth) String() string { return "" }
+
+func (s *ClientSuite) TestSetAuthWrongType(c *C) {
+	r, err := DefaultClient.NewFetchPackSession(s.Endpoint)
+	c.Assert(err, IsNil)
+	c.Assert(r.SetAuth(&mockAuth{}), Equals, transport.ErrInvalidAuthMethod)
+}
diff --git a/plumbing/transport/http/fetch_pack.go b/plumbing/transport/http/fetch_pack.go
new file mode 100644
index 0000000..0c32672
--- /dev/null
+++ b/plumbing/transport/http/fetch_pack.go
@@ -0,0 +1,155 @@
+package http
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/format/packp/pktline"
+	"gopkg.in/src-d/go-git.v4/plumbing/transport"
+)
+
+type fetchPackSession struct {
+	*session
+}
+
+func newFetchPackSession(c *http.Client,
+	ep transport.Endpoint) transport.FetchPackSession {
+
+	return &fetchPackSession{
+		session: &session{
+			auth:     basicAuthFromEndpoint(ep),
+			client:   c,
+			endpoint: ep,
+		},
+	}
+}
+
+func (s *fetchPackSession) AdvertisedReferences() (*transport.UploadPackInfo,
+	error) {
+
+	url := fmt.Sprintf(
+		"%s/info/refs?service=%s",
+		s.endpoint.String(), transport.UploadPackServiceName,
+	)
+
+	req, err := http.NewRequest(http.MethodGet, url, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	s.applyAuthToRequest(req)
+	s.applyHeadersToRequest(req, nil)
+	res, err := s.client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+
+	defer res.Body.Close()
+	if res.StatusCode == http.StatusUnauthorized {
+		return nil, transport.ErrAuthorizationRequired
+	}
+
+	i := transport.NewUploadPackInfo()
+	return i, i.Decode(res.Body)
+}
+
+func (s *fetchPackSession) FetchPack(r *transport.UploadPackRequest) (io.ReadCloser, error) {
+	url := fmt.Sprintf(
+		"%s/%s",
+		s.endpoint.String(), transport.UploadPackServiceName,
+	)
+
+	res, err := s.doRequest("POST", url, r.Reader())
+	if err != nil {
+		return nil, err
+	}
+
+	reader := newBufferedReadCloser(res.Body)
+	if _, err := reader.Peek(1); err != nil {
+		if err == io.ErrUnexpectedEOF {
+			return nil, transport.ErrEmptyUploadPackRequest
+		}
+
+		return nil, err
+	}
+
+	if err := discardResponseInfo(reader); err != nil {
+		return nil, err
+	}
+
+	return reader, nil
+}
+
+// Close does nothing.
+func (s *fetchPackSession) Close() error {
+	return nil
+}
+
+func discardResponseInfo(r io.Reader) error {
+	s := pktline.NewScanner(r)
+	for s.Scan() {
+		if bytes.Equal(s.Bytes(), []byte{'N', 'A', 'K', '\n'}) {
+			break
+		}
+	}
+
+	return s.Err()
+}
+
+func (s *fetchPackSession) doRequest(method, url string, content *strings.Reader) (*http.Response, error) {
+	var body io.Reader
+	if content != nil {
+		body = content
+	}
+
+	req, err := http.NewRequest(method, url, body)
+	if err != nil {
+		return nil, plumbing.NewPermanentError(err)
+	}
+
+	s.applyHeadersToRequest(req, content)
+	s.applyAuthToRequest(req)
+
+	res, err := s.client.Do(req)
+	if err != nil {
+		return nil, plumbing.NewUnexpectedError(err)
+	}
+
+	if err := NewErr(res); err != nil {
+		_ = res.Body.Close()
+		return nil, err
+	}
+
+	return res, nil
+}
+
+func (s *fetchPackSession) applyHeadersToRequest(req *http.Request, content *strings.Reader) {
+	req.Header.Add("User-Agent", "git/1.0")
+	req.Header.Add("Host", "github.com")
+
+	if content == nil {
+		req.Header.Add("Accept", "*/*")
+	} else {
+		req.Header.Add("Accept", "application/x-git-upload-pack-result")
+		req.Header.Add("Content-Type", "application/x-git-upload-pack-request")
+		req.Header.Add("Content-Length", string(content.Len()))
+	}
+}
+
+type bufferedReadCloser struct {
+	*bufio.Reader
+	closer io.Closer
+}
+
+func newBufferedReadCloser(r io.ReadCloser) *bufferedReadCloser {
+	return &bufferedReadCloser{bufio.NewReader(r), r}
+}
+
+func (r *bufferedReadCloser) Close() error {
+	return r.closer.Close()
+}
diff --git a/plumbing/transport/http/fetch_pack_test.go b/plumbing/transport/http/fetch_pack_test.go
new file mode 100644
index 0000000..5ec9991
--- /dev/null
+++ b/plumbing/transport/http/fetch_pack_test.go
@@ -0,0 +1,122 @@
+package http
+
+import (
+	"fmt"
+	"io/ioutil"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/transport"
+
+	. "gopkg.in/check.v1"
+)
+
+type FetchPackSuite struct {
+	Endpoint transport.Endpoint
+}
+
+var _ = Suite(&FetchPackSuite{})
+
+func (s *FetchPackSuite) SetUpSuite(c *C) {
+	fmt.Println("SetUpSuite\n")
+	var err error
+	s.Endpoint, err = transport.NewEndpoint("https://github.com/git-fixtures/basic")
+	c.Assert(err, IsNil)
+}
+
+func (s *FetchPackSuite) TestInfoEmpty(c *C) {
+	endpoint, _ := transport.NewEndpoint("https://github.com/git-fixture/empty")
+	r, err := DefaultClient.NewFetchPackSession(endpoint)
+	c.Assert(err, IsNil)
+	info, err := r.AdvertisedReferences()
+	c.Assert(err, Equals, transport.ErrAuthorizationRequired)
+	c.Assert(info, IsNil)
+}
+
+//TODO: Test this error with HTTP BasicAuth too.
+func (s *FetchPackSuite) TestInfoNotExists(c *C) {
+	endpoint, _ := transport.NewEndpoint("https://github.com/git-fixture/not-exists")
+	r, err := DefaultClient.NewFetchPackSession(endpoint)
+	c.Assert(err, IsNil)
+	info, err := r.AdvertisedReferences()
+	c.Assert(err, Equals, transport.ErrAuthorizationRequired)
+	c.Assert(info, IsNil)
+}
+
+func (s *FetchPackSuite) TestDefaultBranch(c *C) {
+	r, err := DefaultClient.NewFetchPackSession(s.Endpoint)
+	c.Assert(err, IsNil)
+	info, err := r.AdvertisedReferences()
+	c.Assert(err, IsNil)
+	c.Assert(info.Capabilities.SymbolicReference("HEAD"), Equals, "refs/heads/master")
+}
+
+func (s *FetchPackSuite) TestCapabilities(c *C) {
+	r, err := DefaultClient.NewFetchPackSession(s.Endpoint)
+	c.Assert(err, IsNil)
+	info, err := r.AdvertisedReferences()
+	c.Assert(err, IsNil)
+	c.Assert(info.Capabilities.Get("agent").Values, HasLen, 1)
+}
+
+func (s *FetchPackSuite) TestFullFetchPack(c *C) {
+	r, err := DefaultClient.NewFetchPackSession(s.Endpoint)
+	c.Assert(err, IsNil)
+
+	info, err := r.AdvertisedReferences()
+	c.Assert(err, IsNil)
+	c.Assert(info, NotNil)
+
+	req := &transport.UploadPackRequest{}
+	req.Want(plumbing.NewHash("6ecf0ef2c2dffb796033e5a02219af86ec6584e5"))
+
+	reader, err := r.FetchPack(req)
+	c.Assert(err, IsNil)
+
+	b, err := ioutil.ReadAll(reader)
+	c.Assert(err, IsNil)
+	c.Assert(b, HasLen, 85374)
+}
+
+func (s *FetchPackSuite) TestFetchPack(c *C) {
+	r, err := DefaultClient.NewFetchPackSession(s.Endpoint)
+	c.Assert(err, IsNil)
+
+	req := &transport.UploadPackRequest{}
+	req.Want(plumbing.NewHash("6ecf0ef2c2dffb796033e5a02219af86ec6584e5"))
+
+	reader, err := r.FetchPack(req)
+	c.Assert(err, IsNil)
+
+	b, err := ioutil.ReadAll(reader)
+	c.Assert(err, IsNil)
+	c.Assert(b, HasLen, 85374)
+}
+
+func (s *FetchPackSuite) TestFetchPackNoChanges(c *C) {
+	r, err := DefaultClient.NewFetchPackSession(s.Endpoint)
+	c.Assert(err, IsNil)
+
+	req := &transport.UploadPackRequest{}
+	req.Want(plumbing.NewHash("6ecf0ef2c2dffb796033e5a02219af86ec6584e5"))
+	req.Have(plumbing.NewHash("6ecf0ef2c2dffb796033e5a02219af86ec6584e5"))
+
+	reader, err := r.FetchPack(req)
+	c.Assert(err, Equals, transport.ErrEmptyUploadPackRequest)
+	c.Assert(reader, IsNil)
+}
+
+func (s *FetchPackSuite) TestFetchPackMulti(c *C) {
+	r, err := DefaultClient.NewFetchPackSession(s.Endpoint)
+	c.Assert(err, IsNil)
+
+	req := &transport.UploadPackRequest{}
+	req.Want(plumbing.NewHash("6ecf0ef2c2dffb796033e5a02219af86ec6584e5"))
+	req.Want(plumbing.NewHash("e8d3ffab552895c19b9fcf7aa264d277cde33881"))
+
+	reader, err := r.FetchPack(req)
+	c.Assert(err, IsNil)
+
+	b, err := ioutil.ReadAll(reader)
+	c.Assert(err, IsNil)
+	c.Assert(b, HasLen, 85585)
+}
diff --git a/plumbing/transport/http/send_pack.go b/plumbing/transport/http/send_pack.go
new file mode 100644
index 0000000..39be95c
--- /dev/null
+++ b/plumbing/transport/http/send_pack.go
@@ -0,0 +1,29 @@
+package http
+
+import (
+	"errors"
+	"io"
+	"net/http"
+
+	"gopkg.in/src-d/go-git.v4/plumbing/transport"
+)
+
+var errSendPackNotSupported = errors.New("send-pack not supported yet")
+
+type sendPackSession struct{
+	*session
+}
+
+func newSendPackSession(c *http.Client, ep transport.Endpoint) transport.SendPackSession {
+	return &sendPackSession{&session{}}
+}
+
+func (s *sendPackSession) AdvertisedReferences() (*transport.UploadPackInfo,
+	error) {
+
+	return nil, errSendPackNotSupported
+}
+
+func (s *sendPackSession) SendPack() (io.WriteCloser, error) {
+	return nil, errSendPackNotSupported
+}
diff --git a/plumbing/transport/ssh/auth_method.go b/plumbing/transport/ssh/auth_method.go
new file mode 100644
index 0000000..9c3d6f3
--- /dev/null
+++ b/plumbing/transport/ssh/auth_method.go
@@ -0,0 +1,157 @@
+package ssh
+
+import (
+	"fmt"
+	"net"
+	"os"
+
+	"golang.org/x/crypto/ssh"
+	"golang.org/x/crypto/ssh/agent"
+)
+
+// AuthMethod is the interface all auth methods for the ssh client
+// must implement. The clientConfig method returns the ssh client
+// configuration needed to establish an ssh connection.
+type AuthMethod interface {
+	clientConfig() *ssh.ClientConfig
+}
+
+// The names of the AuthMethod implementations. To be returned by the
+// Name() method. Most git servers only allow PublicKeysName and
+// PublicKeysCallbackName.
+const (
+	KeyboardInteractiveName = "ssh-keyboard-interactive"
+	PasswordName            = "ssh-password"
+	PasswordCallbackName    = "ssh-password-callback"
+	PublicKeysName          = "ssh-public-keys"
+	PublicKeysCallbackName  = "ssh-public-key-callback"
+)
+
+// KeyboardInteractive implements AuthMethod by using a
+// prompt/response sequence controlled by the server.
+type KeyboardInteractive struct {
+	User      string
+	Challenge ssh.KeyboardInteractiveChallenge
+}
+
+func (a *KeyboardInteractive) Name() string {
+	return KeyboardInteractiveName
+}
+
+func (a *KeyboardInteractive) String() string {
+	return fmt.Sprintf("user: %s, name: %s", a.User, a.Name())
+}
+
+func (a *KeyboardInteractive) clientConfig() *ssh.ClientConfig {
+	return &ssh.ClientConfig{
+		User: a.User,
+		Auth: []ssh.AuthMethod{ssh.KeyboardInteractiveChallenge(a.Challenge)},
+	}
+}
+
+// Password implements AuthMethod by using the given password.
+type Password struct {
+	User string
+	Pass string
+}
+
+func (a *Password) Name() string {
+	return PasswordName
+}
+
+func (a *Password) String() string {
+	return fmt.Sprintf("user: %s, name: %s", a.User, a.Name())
+}
+
+func (a *Password) clientConfig() *ssh.ClientConfig {
+	return &ssh.ClientConfig{
+		User: a.User,
+		Auth: []ssh.AuthMethod{ssh.Password(a.Pass)},
+	}
+}
+
+// PasswordCallback implements AuthMethod by using a callback
+// to fetch the password.
+type PasswordCallback struct {
+	User     string
+	Callback func() (pass string, err error)
+}
+
+func (a *PasswordCallback) Name() string {
+	return PasswordCallbackName
+}
+
+func (a *PasswordCallback) String() string {
+	return fmt.Sprintf("user: %s, name: %s", a.User, a.Name())
+}
+
+func (a *PasswordCallback) clientConfig() *ssh.ClientConfig {
+	return &ssh.ClientConfig{
+		User: a.User,
+		Auth: []ssh.AuthMethod{ssh.PasswordCallback(a.Callback)},
+	}
+}
+
+// PublicKeys implements AuthMethod by using the given
+// key pairs.
+type PublicKeys struct {
+	User   string
+	Signer ssh.Signer
+}
+
+func (a *PublicKeys) Name() string {
+	return PublicKeysName
+}
+
+func (a *PublicKeys) String() string {
+	return fmt.Sprintf("user: %s, name: %s", a.User, a.Name())
+}
+
+func (a *PublicKeys) clientConfig() *ssh.ClientConfig {
+	return &ssh.ClientConfig{
+		User: a.User,
+		Auth: []ssh.AuthMethod{ssh.PublicKeys(a.Signer)},
+	}
+}
+
+// PublicKeysCallback implements AuthMethod by asking a
+// ssh.agent.Agent to act as a signer.
+type PublicKeysCallback struct {
+	User     string
+	Callback func() (signers []ssh.Signer, err error)
+}
+
+func (a *PublicKeysCallback) Name() string {
+	return PublicKeysCallbackName
+}
+
+func (a *PublicKeysCallback) String() string {
+	return fmt.Sprintf("user: %s, name: %s", a.User, a.Name())
+}
+
+func (a *PublicKeysCallback) clientConfig() *ssh.ClientConfig {
+	return &ssh.ClientConfig{
+		User: a.User,
+		Auth: []ssh.AuthMethod{ssh.PublicKeysCallback(a.Callback)},
+	}
+}
+
+const DefaultSSHUsername = "git"
+
+// Opens a pipe with the ssh agent and uses the pipe
+// as the implementer of the public key callback function.
+func NewSSHAgentAuth(user string) (*PublicKeysCallback, error) {
+	if user == "" {
+		user = DefaultSSHUsername
+	}
+
+	pipe, err := net.Dial("unix", os.Getenv("SSH_AUTH_SOCK"))
+	if err != nil {
+		return nil, err
+	}
+
+	return &PublicKeysCallback{
+		User:     user,
+		Callback: agent.NewClient(pipe).Signers,
+	}, nil
+}
diff --git a/plumbing/transport/ssh/auth_method_test.go b/plumbing/transport/ssh/auth_method_test.go
new file mode 100644
index 0000000..f9e7dec
--- /dev/null
+++ b/plumbing/transport/ssh/auth_method_test.go
@@ -0,0 +1,91 @@
+package ssh
+
+import (
+	"fmt"
+
+	. "gopkg.in/check.v1"
+)
+
+type SuiteCommon struct{}
+
+var _ = Suite(&SuiteCommon{})
+
+func (s *SuiteCommon) TestKeyboardInteractiveName(c *C) {
+	a := &KeyboardInteractive{
+		User:      "test",
+		Challenge: nil,
+	}
+	c.Assert(a.Name(), Equals, KeyboardInteractiveName)
+}
+
+func (s *SuiteCommon) TestKeyboardInteractiveString(c *C) {
+	a := &KeyboardInteractive{
+		User:      "test",
+		Challenge: nil,
+	}
+	c.Assert(a.String(), Equals, fmt.Sprintf("user: test, name: %s", KeyboardInteractiveName))
+}
+
+func (s *SuiteCommon) TestPasswordName(c *C) {
+	a := &Password{
+		User: "test",
+		Pass: "",
+	}
+	c.Assert(a.Name(), Equals, PasswordName)
+}
+
+func (s *SuiteCommon) TestPasswordString(c *C) {
+	a := &Password{
+		User: "test",
+		Pass: "",
+	}
+	c.Assert(a.String(), Equals, fmt.Sprintf("user: test, name: %s", PasswordName))
+}
+
+func (s *SuiteCommon) TestPasswordCallbackName(c *C) {
+	a := &PasswordCallback{
+		User:     "test",
+		Callback: nil,
+	}
+	c.Assert(a.Name(), Equals, PasswordCallbackName)
+}
+
+func (s *SuiteCommon) TestPasswordCallbackString(c *C) {
+	a := &PasswordCallback{
+		User:     "test",
+		Callback: nil,
+	}
+	c.Assert(a.String(), Equals, fmt.Sprintf("user: test, name: %s", PasswordCallbackName))
+}
+
+func (s *SuiteCommon) TestPublicKeysName(c *C) {
+	a := &PublicKeys{
+		User:   "test",
+		Signer: nil,
+	}
+	c.Assert(a.Name(), Equals, PublicKeysName)
+}
+
+func (s *SuiteCommon) TestPublicKeysString(c *C) {
+	a := &PublicKeys{
+		User:   "test",
+		Signer: nil,
+	}
+	c.Assert(a.String(), Equals, fmt.Sprintf("user: test, name: %s", PublicKeysName))
+}
+
+func (s *SuiteCommon) TestPublicKeysCallbackName(c *C) {
+	a := &PublicKeysCallback{
+		User:     "test",
+		Callback: nil,
+	}
+	c.Assert(a.Name(), Equals, PublicKeysCallbackName)
+}
+
+func (s *SuiteCommon) TestPublicKeysCallbackString(c *C) {
+	a := &PublicKeysCallback{
+		User:     "test",
+		Callback: nil,
+	}
+	c.Assert(a.String(), Equals, fmt.Sprintf("user: test, name: %s", PublicKeysCallbackName))
+}
diff --git a/plumbing/transport/ssh/common.go b/plumbing/transport/ssh/common.go
new file mode 100644
index 0000000..6f0f3d4
--- /dev/null
+++ b/plumbing/transport/ssh/common.go
@@ -0,0 +1,151 @@
+package ssh
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"strings"
+
+	"gopkg.in/src-d/go-git.v4/plumbing/transport"
+
+	"golang.org/x/crypto/ssh"
+)
+
+// New errors introduced by this package.
+var (
+	ErrAdvertistedReferencesAlreadyCalled = errors.New("cannot call AdvertisedReference twice")
+	ErrAlreadyConnected                   = errors.New("ssh session already created")
+	ErrAuthRequired                       = errors.New("cannot connect: auth required")
+	ErrNotConnected                       = errors.New("not connected")
+	ErrUploadPackAnswerFormat             = errors.New("git-upload-pack bad answer format")
+	ErrUnsupportedVCS                     = errors.New("only git is supported")
+	ErrUnsupportedRepo                    = errors.New("only github.com is supported")
+)
+
+type Client struct{}
+
+var DefaultClient = NewClient()
+
+func NewClient() transport.Client {
+	return &Client{}
+}
+
+func (c *Client) NewFetchPackSession(ep transport.Endpoint) (
+	transport.FetchPackSession, error) {
+
+	return newFetchPackSession(ep)
+}
+
+func (c *Client) NewSendPackSession(ep transport.Endpoint) (
+	transport.SendPackSession, error) {
+
+	return newSendPackSession(ep)
+}
+
+type session struct {
+	connected   bool
+	endpoint    transport.Endpoint
+	client      *ssh.Client
+	session     *ssh.Session
+	stdin       io.WriteCloser
+	stdout      io.Reader
+	sessionDone chan error
+	auth        AuthMethod
+}
+
+func (s *session) SetAuth(auth transport.AuthMethod) error {
+	a, ok := auth.(AuthMethod)
+	if !ok {
+		return transport.ErrInvalidAuthMethod
+	}
+
+	s.auth = a
+	return nil
+}
+
+// Close closes the SSH session.
+func (s *session) Close() error {
+	if !s.connected {
+		return nil
+	}
+
+	s.connected = false
+	return s.client.Close()
+}
+
+// ensureConnected connects to the SSH server, unless a AuthMethod was set with
+// SetAuth method, by default uses an auth method based on PublicKeysCallback,
+// it connects to a SSH agent, using the address stored in the SSH_AUTH_SOCK
+// environment var.
+func (s *session) connect() error {
+	if s.connected {
+		return ErrAlreadyConnected
+	}
+
+	if err := s.setAuthFromEndpoint(); err != nil {
+		return err
+	}
+
+	var err error
+	s.client, err = ssh.Dial("tcp", s.getHostWithPort(), s.auth.clientConfig())
+	if err != nil {
+		return err
+	}
+
+	if err := s.openSSHSession(); err != nil {
+		_ = s.client.Close()
+		return err
+	}
+
+	s.connected = true
+	return nil
+}
+
+func (s *session) getHostWithPort() string {
+	host := s.endpoint.Host
+	if strings.Index(s.endpoint.Host, ":") == -1 {
+		host += ":22"
+	}
+
+	return host
+}
+
+func (s *session) setAuthFromEndpoint() error {
+	var u string
+	if info := s.endpoint.User; info != nil {
+		u = info.Username()
+	}
+
+	var err error
+	s.auth, err = NewSSHAgentAuth(u)
+	return err
+}
+
+func (s *session) openSSHSession() error {
+	var err error
+	s.session, err = s.client.NewSession()
+	if err != nil {
+		return fmt.Errorf("cannot open SSH session: %s", err)
+	}
+
+	s.stdin, err = s.session.StdinPipe()
+	if err != nil {
+		return fmt.Errorf("cannot pipe remote stdin: %s", err)
+	}
+
+	s.stdout, err = s.session.StdoutPipe()
+	if err != nil {
+		return fmt.Errorf("cannot pipe remote stdout: %s", err)
+	}
+
+	return nil
+}
+
+func (s *session) runCommand(cmd string) chan error {
+	done := make(chan error)
+	go func() {
+		done <- s.session.Run(cmd)
+	}()
+
+	return done
+}
diff --git a/plumbing/transport/ssh/common_test.go b/plumbing/transport/ssh/common_test.go
new file mode 100644
index 0000000..ac4d03e
--- /dev/null
+++ b/plumbing/transport/ssh/common_test.go
@@ -0,0 +1,17 @@
+package ssh
+
+import (
+	"testing"
+
+	. "gopkg.in/check.v1"
+)
+
+func Test(t *testing.T) { TestingT(t) }
+
+type ClientSuite struct{}
+
+var _ = Suite(&ClientSuite{})
+
+func (s *ClientSuite) TestNewClient(c *C) {
+	c.Assert(DefaultClient, DeepEquals, NewClient())
+}
diff --git a/plumbing/transport/ssh/fetch_pack.go b/plumbing/transport/ssh/fetch_pack.go
new file mode 100644
index 0000000..bda4edf
--- /dev/null
+++ b/plumbing/transport/ssh/fetch_pack.go
@@ -0,0 +1,202 @@
+// Package ssh implements a ssh client for go-git.
+package ssh
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+
+	"gopkg.in/src-d/go-git.v4/plumbing/format/packp/pktline"
+	"gopkg.in/src-d/go-git.v4/plumbing/format/packp/ulreq"
+	"gopkg.in/src-d/go-git.v4/plumbing/transport"
+
+	"golang.org/x/crypto/ssh"
+)
+
+type fetchPackSession struct {
+	*session
+	cmdRun     bool
+	advRefsRun bool
+	done       chan error
+}
+
+func newFetchPackSession(ep transport.Endpoint) (*fetchPackSession, error) {
+	s := &fetchPackSession{
+		session: &session{
+			endpoint: ep,
+		},
+	}
+	if err := s.connect(); err != nil {
+		return nil, err
+	}
+
+	return s, nil
+}
+
+func (s *fetchPackSession) AdvertisedReferences() (*transport.UploadPackInfo, error) {
+	if s.advRefsRun {
+		return nil, ErrAdvertistedReferencesAlreadyCalled
+	}
+
+	if err := s.ensureRunCommand(); err != nil {
+		return nil, err
+	}
+
+	defer func() { s.advRefsRun = true }()
+
+	i := transport.NewUploadPackInfo()
+	return i, i.Decode(s.stdout)
+}
+
+// FetchPack returns a packfile for a given upload request.
+// Closing the returned reader will close the SSH session.
+func (s *fetchPackSession) FetchPack(req *transport.UploadPackRequest) (
+	io.ReadCloser, error) {
+
+	if !s.advRefsRun {
+		if _, err := s.AdvertisedReferences(); err != nil {
+			return nil, err
+		}
+	}
+
+	if err := fetchPack(s.stdin, s.stdout, req); err != nil {
+		return nil, err
+	}
+
+	return &fetchSession{
+		Reader:  s.stdout,
+		session: s.session.session,
+		done:    s.done,
+	}, nil
+}
+
+func (s *fetchPackSession) ensureRunCommand() error {
+	if s.cmdRun {
+		return nil
+	}
+
+	s.cmdRun = true
+	s.done = s.runCommand(s.getCommand())
+	return nil
+}
+
+type fetchSession struct {
+	io.Reader
+	session *ssh.Session
+	done    <-chan error
+}
+
+// Close closes the session and collects the output state of the remote
+// SSH command.
+//
+// If both the remote command and the closing of the session completes
+// susccessfully it returns nil.
+//
+// If the remote command completes unsuccessfully or is interrupted by a
+// signal, it returns the corresponding *ExitError.
+//
+// Otherwise, if clossing the SSH session fails it returns the close
+// error.  Closing the session when the other has already close it is
+// not cosidered an error.
+func (f *fetchSession) Close() (err error) {
+	if err := <-f.done; err != nil {
+		return err
+	}
+
+	if err := f.session.Close(); err != nil && err != io.EOF {
+		return err
+	}
+
+	return nil
+}
+
+func (s *fetchPackSession) getCommand() string {
+	directory := s.endpoint.Path
+	directory = directory[1:]
+
+	return fmt.Sprintf("git-upload-pack '%s'", directory)
+}
+
+var (
+	nak = []byte("NAK")
+	eol = []byte("\n")
+)
+
+// FetchPack implements the git-fetch-pack protocol.
+//
+// TODO support multi_ack mode
+// TODO support multi_ack_detailed mode
+// TODO support acks for common objects
+// TODO build a proper state machine for all these processing options
+func fetchPack(w io.WriteCloser, r io.Reader,
+	req *transport.UploadPackRequest) error {
+
+	if err := sendUlReq(w, req); err != nil {
+		return fmt.Errorf("sending upload-req message: %s", err)
+	}
+
+	if err := sendHaves(w, req); err != nil {
+		return fmt.Errorf("sending haves message: %s", err)
+	}
+
+	if err := sendDone(w); err != nil {
+		return fmt.Errorf("sending done message: %s", err)
+	}
+
+	if err := w.Close(); err != nil {
+		return fmt.Errorf("closing input: %s", err)
+	}
+
+	if err := readNAK(r); err != nil {
+		return fmt.Errorf("reading NAK: %s", err)
+	}
+
+	return nil
+}
+
+func sendUlReq(w io.Writer, req *transport.UploadPackRequest) error {
+	ur := ulreq.New()
+	ur.Wants = req.Wants
+	ur.Depth = ulreq.DepthCommits(req.Depth)
+	e := ulreq.NewEncoder(w)
+
+	return e.Encode(ur)
+}
+
+func sendHaves(w io.Writer, req *transport.UploadPackRequest) error {
+	e := pktline.NewEncoder(w)
+	for _, have := range req.Haves {
+		if err := e.Encodef("have %s\n", have); err != nil {
+			return fmt.Errorf("sending haves for %q: %s", have, err)
+		}
+	}
+
+	if len(req.Haves) != 0 {
+		if err := e.Flush(); err != nil {
+			return fmt.Errorf("sending flush-pkt after haves: %s", err)
+		}
+	}
+
+	return nil
+}
+
+func sendDone(w io.Writer) error {
+	e := pktline.NewEncoder(w)
+
+	return e.Encodef("done\n")
+}
+
+func readNAK(r io.Reader) error {
+	s := pktline.NewScanner(r)
+	if !s.Scan() {
+		return s.Err()
+	}
+
+	b := s.Bytes()
+	b = bytes.TrimSuffix(b, eol)
+	if !bytes.Equal(b, nak) {
+		return fmt.Errorf("expecting NAK, found %q instead", string(b))
+	}
+
+	return nil
+}
diff --git a/plumbing/transport/ssh/fetch_pack_test.go b/plumbing/transport/ssh/fetch_pack_test.go
new file mode 100644
index 0000000..3d62e57
--- /dev/null
+++ b/plumbing/transport/ssh/fetch_pack_test.go
@@ -0,0 +1,100 @@
+package ssh
+
+import (
+	"io/ioutil"
+	"os"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/transport"
+
+	. "gopkg.in/check.v1"
+)
+
+type FetchPackSuite struct {
+	Endpoint transport.Endpoint
+}
+
+var _ = Suite(&FetchPackSuite{})
+
+func (s *FetchPackSuite) SetUpSuite(c *C) {
+	var err error
+	s.Endpoint, err = transport.NewEndpoint("git@github.com:git-fixtures/basic.git")
+	c.Assert(err, IsNil)
+
+	if os.Getenv("SSH_AUTH_SOCK") == "" {
+		c.Skip("SSH_AUTH_SOCK is not set")
+	}
+}
+
+func (s *FetchPackSuite) TestDefaultBranch(c *C) {
+	r, err := DefaultClient.NewFetchPackSession(s.Endpoint)
+	c.Assert(err, IsNil)
+	defer func() { c.Assert(r.Close(), IsNil) }()
+
+	info, err := r.AdvertisedReferences()
+	c.Assert(err, IsNil)
+	c.Assert(info.Capabilities.SymbolicReference("HEAD"), Equals, "refs/heads/master")
+}
+
+func (s *FetchPackSuite) TestCapabilities(c *C) {
+	r, err := DefaultClient.NewFetchPackSession(s.Endpoint)
+	c.Assert(err, IsNil)
+	defer func() { c.Assert(r.Close(), IsNil) }()
+
+	info, err := r.AdvertisedReferences()
+	c.Assert(err, IsNil)
+	c.Assert(info.Capabilities.Get("agent").Values, HasLen, 1)
+}
+
+func (s *FetchPackSuite) TestFullFetchPack(c *C) {
+	r, err := DefaultClient.NewFetchPackSession(s.Endpoint)
+	c.Assert(err, IsNil)
+	defer func() { c.Assert(r.Close(), IsNil) }()
+
+	_, err = r.AdvertisedReferences()
+	c.Assert(err, IsNil)
+
+	req := &transport.UploadPackRequest{}
+	req.Want(plumbing.NewHash("6ecf0ef2c2dffb796033e5a02219af86ec6584e5"))
+	req.Want(plumbing.NewHash("e8d3ffab552895c19b9fcf7aa264d277cde33881"))
+	reader, err := r.FetchPack(req)
+	c.Assert(err, IsNil)
+
+	defer func() { c.Assert(reader.Close(), IsNil) }()
+
+	b, err := ioutil.ReadAll(reader)
+	c.Assert(err, IsNil)
+	c.Check(len(b), Equals, 85585)
+}
+
+func (s *FetchPackSuite) TestFetchPack(c *C) {
+	r, err := DefaultClient.NewFetchPackSession(s.Endpoint)
+	c.Assert(err, IsNil)
+	defer func() { c.Assert(r.Close(), IsNil) }()
+
+	req := &transport.UploadPackRequest{}
+	req.Want(plumbing.NewHash("6ecf0ef2c2dffb796033e5a02219af86ec6584e5"))
+	req.Want(plumbing.NewHash("e8d3ffab552895c19b9fcf7aa264d277cde33881"))
+	reader, err := r.FetchPack(req)
+	c.Assert(err, IsNil)
+	defer func() { c.Assert(reader.Close(), IsNil) }()
+
+	b, err := ioutil.ReadAll(reader)
+	c.Assert(err, IsNil)
+	c.Check(len(b), Equals, 85585)
+}
+
+func (s *FetchPackSuite) TestFetchError(c *C) {
+	r, err := DefaultClient.NewFetchPackSession(s.Endpoint)
+	c.Assert(err, IsNil)
+	defer func() { c.Assert(r.Close(), IsNil) }()
+
+	req := &transport.UploadPackRequest{}
+	req.Want(plumbing.NewHash("1111111111111111111111111111111111111111"))
+
+	reader, err := r.FetchPack(req)
+	c.Assert(err, IsNil)
+
+	err = reader.Close()
+	c.Assert(err, Not(IsNil))
+}
diff --git a/plumbing/transport/ssh/send_pack.go b/plumbing/transport/ssh/send_pack.go
new file mode 100644
index 0000000..afe7510
--- /dev/null
+++ b/plumbing/transport/ssh/send_pack.go
@@ -0,0 +1,30 @@
+package ssh
+
+import (
+	"errors"
+	"io"
+
+	"gopkg.in/src-d/go-git.v4/plumbing/transport"
+)
+
+var errSendPackNotSupported = errors.New("send-pack not supported yet")
+
+type sendPackSession struct {
+	*session
+}
+
+func newSendPackSession(ep transport.Endpoint) (transport.SendPackSession,
+	error) {
+
+	return &sendPackSession{&session{}}, nil
+}
+
+func (s *sendPackSession) AdvertisedReferences() (*transport.UploadPackInfo,
+	error) {
+
+	return nil, errSendPackNotSupported
+}
+
+func (s *sendPackSession) SendPack() (io.WriteCloser, error) {
+	return nil, errSendPackNotSupported
+}