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.

4 files changed, 128 insertions, 0 deletions

diff --git a/cli/go-git/main.go b/cli/go-git/main.go
new file mode 100644
index 0000000..97b8c3e
--- /dev/null
+++ b/cli/go-git/main.go
@@ -0,0 +1,41 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+
+	"github.com/jessevdk/go-flags"
+)
+
+const (
+	bin            = "go-git"
+	receivePackBin = "git-receive-pack"
+	uploadPackBin  = "git-upload-pack"
+)
+
+func main() {
+	switch filepath.Base(os.Args[0]) {
+	case receivePackBin:
+		os.Args = append([]string{"git", "receive-pack"}, os.Args[1:]...)
+	case uploadPackBin:
+		os.Args = append([]string{"git", "upload-pack"}, os.Args[1:]...)
+	}
+
+	parser := flags.NewNamedParser(bin, flags.Default)
+	parser.AddCommand("receive-pack", "", "", &CmdReceivePack{})
+	parser.AddCommand("upload-pack", "", "", &CmdUploadPack{})
+	parser.AddCommand("version", "Show the version information.", "", &CmdVersion{})
+
+	_, err := parser.Parse()
+	if err != nil {
+		if e, ok := err.(*flags.Error); ok && e.Type == flags.ErrCommandRequired {
+			parser.WriteHelp(os.Stdout)
+		}
+
+		os.Exit(1)
+	}
+}
+
+type cmd struct {
+	Verbose bool `short:"v" description:"Activates the verbose mode"`
+}
diff --git a/cli/go-git/receive_pack.go b/cli/go-git/receive_pack.go
new file mode 100644
index 0000000..0f96a28
--- /dev/null
+++ b/cli/go-git/receive_pack.go
@@ -0,0 +1,36 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"gopkg.in/src-d/go-git.v4/plumbing/transport/file"
+)
+
+type CmdReceivePack struct {
+	cmd
+
+	Args struct {
+		GitDir string `positional-arg-name:"git-dir" required:"true"`
+	} `positional-args:"yes"`
+}
+
+func (CmdReceivePack) Usage() string {
+	//TODO: git-receive-pack returns error code 129 if arguments are invalid.
+	return fmt.Sprintf("usage: %s <git-dir>", os.Args[0])
+}
+
+func (c *CmdReceivePack) Execute(args []string) error {
+	gitDir, err := filepath.Abs(c.Args.GitDir)
+	if err != nil {
+		return err
+	}
+
+	if err := file.ServeReceivePack(gitDir); err != nil {
+		fmt.Fprintln(os.Stderr, "ERR:", err)
+		os.Exit(128)
+	}
+
+	return nil
+}
diff --git a/cli/go-git/upload_pack.go b/cli/go-git/upload_pack.go
new file mode 100644
index 0000000..c45fe48
--- /dev/null
+++ b/cli/go-git/upload_pack.go
@@ -0,0 +1,37 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"gopkg.in/src-d/go-git.v4/plumbing/transport/file"
+)
+
+//TODO: usage: git upload-pack [--strict] [--timeout=<n>] <dir>
+type CmdUploadPack struct {
+	cmd
+
+	Args struct {
+		GitDir string `positional-arg-name:"git-dir" required:"true"`
+	} `positional-args:"yes"`
+}
+
+func (CmdUploadPack) Usage() string {
+	//TODO: git-upload-pack returns error code 129 if arguments are invalid.
+	return fmt.Sprintf("usage: %s <git-dir>", os.Args[0])
+}
+
+func (c *CmdUploadPack) Execute(args []string) error {
+	gitDir, err := filepath.Abs(c.Args.GitDir)
+	if err != nil {
+		return err
+	}
+
+	if err := file.ServeUploadPack(gitDir); err != nil {
+		fmt.Fprintln(os.Stderr, "ERR:", err)
+		os.Exit(128)
+	}
+
+	return nil
+}
diff --git a/cli/go-git/version.go b/cli/go-git/version.go
new file mode 100644
index 0000000..b0e773d
--- /dev/null
+++ b/cli/go-git/version.go
@@ -0,0 +1,14 @@
+package main
+
+import "fmt"
+
+var version string
+var build string
+
+type CmdVersion struct{}
+
+func (c *CmdVersion) Execute(args []string) error {
+	fmt.Printf("%s (%s) - build %s\n", bin, version, build)
+
+	return nil
+}