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, 59 insertions, 0 deletions

diff --git a/plumbing/transport/server/loader.go b/plumbing/transport/server/loader.go
new file mode 100644
index 0000000..55bcf1d
--- /dev/null
+++ b/plumbing/transport/server/loader.go
@@ -0,0 +1,59 @@
+package server
+
+import (
+	"gopkg.in/src-d/go-git.v4/plumbing/storer"
+	"gopkg.in/src-d/go-git.v4/plumbing/transport"
+	"gopkg.in/src-d/go-git.v4/storage/filesystem"
+
+	"srcd.works/go-billy.v1"
+	"srcd.works/go-billy.v1/os"
+)
+
+// DefaultLoader is a filesystem loader ignoring host and resolving paths to /.
+var DefaultLoader = NewFilesystemLoader(os.New("/"))
+
+// Loader loads repository's storer.Storer based on an optional host and a path.
+type Loader interface {
+	// Load loads a storer.Storer given a transport.Endpoint.
+	// Returns transport.ErrRepositoryNotFound if the repository does not
+	// exist.
+	Load(ep transport.Endpoint) (storer.Storer, error)
+}
+
+type fsLoader struct {
+	base billy.Filesystem
+}
+
+// NewFilesystemLoader creates a Loader that ignores host and resolves paths
+// with a given base filesystem.
+func NewFilesystemLoader(base billy.Filesystem) Loader {
+	return &fsLoader{base}
+}
+
+// Load looks up the endpoint's path in the base file system and returns a
+// storer for it. Returns transport.ErrRepositoryNotFound if a repository does
+// not exist in the given path.
+func (l *fsLoader) Load(ep transport.Endpoint) (storer.Storer, error) {
+	fs := l.base.Dir(ep.Path)
+	if _, err := fs.Stat("config"); err != nil {
+		return nil, transport.ErrRepositoryNotFound
+	}
+
+	return filesystem.NewStorage(fs)
+}
+
+// MapLoader is a Loader that uses a lookup map of storer.Storer by
+// transport.Endpoint.
+type MapLoader map[transport.Endpoint]storer.Storer
+
+// Load returns a storer.Storer for given a transport.Endpoint by looking it up
+// in the map. Returns transport.ErrRepositoryNotFound if the endpoint does not
+// exist.
+func (l MapLoader) Load(ep transport.Endpoint) (storer.Storer, error) {
+	s, ok := l[ep]
+	if !ok {
+		return nil, transport.ErrRepositoryNotFound
+	}
+
+	return s, nil
+}