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

1 files changed, 21 insertions, 0 deletions

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))
+}