server: add git server implementation (#190)

* server: add generic server implementation (transport-independent),
  both for git-upload-pack and git-receive-pack.
* server: move internal functions to internal/common.
* cli: add git-receive-pack and git-upload-pack implementations.
* format/packfile: add UpdateObjectStorage function, extracted from
  Remote.
* transport: implement tranport RPC-like, only with git-upload-pack and
  git-receive-pack methods. Client renamed to Transport.
* storer: add storer.Storer interface.
* protocol/packp: add UploadPackResponse constructor with packfile.
* protocol/packp: fix UploadPackResponse encoding, add tests.
* protocol/packp/capability: implement All.

1 files changed, 174 insertions, 0 deletions

diff --git a/plumbing/transport/http/upload_pack.go b/plumbing/transport/http/upload_pack.go
new file mode 100644
index 0000000..26257f5
--- /dev/null
+++ b/plumbing/transport/http/upload_pack.go
@@ -0,0 +1,174 @@
+package http
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"net/http"
+	"strconv"
+
+	"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/transport"
+	"gopkg.in/src-d/go-git.v4/plumbing/transport/internal/common"
+	"gopkg.in/src-d/go-git.v4/utils/ioutil"
+)
+
+type upSession struct {
+	*session
+}
+
+func newUploadPackSession(c *http.Client,
+	ep transport.Endpoint) transport.UploadPackSession {
+
+	return &upSession{
+		session: &session{
+			auth:     basicAuthFromEndpoint(ep),
+			client:   c,
+			endpoint: ep,
+		},
+	}
+}
+
+func (s *upSession) AdvertisedReferences() (*packp.AdvRefs, error) {
+	if s.advRefs != nil {
+		return s.advRefs, nil
+	}
+
+	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
+	}
+
+	ar := packp.NewAdvRefs()
+	if err := ar.Decode(res.Body); err != nil {
+		if err == packp.ErrEmptyAdvRefs {
+			err = transport.ErrEmptyRemoteRepository
+		}
+
+		return nil, err
+	}
+
+	transport.FilterUnsupportedCapabilities(ar.Capabilities)
+	s.advRefs = ar
+	return ar, nil
+}
+
+func (s *upSession) UploadPack(req *packp.UploadPackRequest) (*packp.UploadPackResponse, error) {
+	if req.IsEmpty() {
+		return nil, transport.ErrEmptyUploadPackRequest
+	}
+
+	if err := req.Validate(); err != nil {
+		return nil, err
+	}
+
+	url := fmt.Sprintf(
+		"%s/%s",
+		s.endpoint.String(), transport.UploadPackServiceName,
+	)
+
+	content, err := uploadPackRequestToReader(req)
+	if err != nil {
+		return nil, err
+	}
+
+	res, err := s.doRequest(http.MethodPost, url, content)
+	if err != nil {
+		return nil, err
+	}
+
+	r, err := ioutil.NonEmptyReader(res.Body)
+	if err != nil {
+		if err == ioutil.ErrEmptyReader || err == io.ErrUnexpectedEOF {
+			return nil, transport.ErrEmptyUploadPackRequest
+		}
+
+		return nil, err
+	}
+
+	rc := ioutil.NewReadCloser(r, res.Body)
+	return common.DecodeUploadPackResponse(rc, req)
+}
+
+// Close does nothing.
+func (s *upSession) Close() error {
+	return nil
+}
+
+func (s *upSession) doRequest(method, url string, content *bytes.Buffer) (*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
+}
+
+// it requires a bytes.Buffer, because we need to know the length
+func (s *upSession) applyHeadersToRequest(req *http.Request, content *bytes.Buffer) {
+	req.Header.Add("User-Agent", "git/1.0")
+	req.Header.Add("Host", s.endpoint.Host)
+
+	if content == nil {
+		req.Header.Add("Accept", "*/*")
+		return
+	}
+
+	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", strconv.Itoa(content.Len()))
+}
+
+func uploadPackRequestToReader(req *packp.UploadPackRequest) (*bytes.Buffer, error) {
+	buf := bytes.NewBuffer(nil)
+	e := pktline.NewEncoder(buf)
+
+	if err := req.UploadRequest.Encode(buf); err != nil {
+		return nil, fmt.Errorf("sending upload-req message: %s", err)
+	}
+
+	if err := req.UploadHaves.Encode(buf); err != nil {
+		return nil, fmt.Errorf("sending haves message: %s", err)
+	}
+
+	_ = e.EncodeString("done\n")
+	return buf, nil
+}