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

3 files changed, 126 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))
+}