1 files changed, 61 insertions, 2 deletions
diff --git a/clients/common.go b/clients/common.go
index fcbacf5..ce36dd1 100644
--- a/clients/common.go
+++ b/clients/common.go
@@ -1,10 +1,69 @@
+// Go-git needs the packfile and the refs of the repo. The
+// `NewGitUploadPackService` function returns an object that allows to
+// download them.
+//
+// Go-git supports HTTP and SSH (see `KnownProtocols`) for downloading
+// the packfile and the refs, but you can also install your own
+// protocols (see `InstallProtocol` below).
+//
+// Each protocol has its own implementation of
+// `NewGitUploadPackService`, but you should generally not use them
+// directly, use this package's `NewGitUploadPackService` instead.
 package clients
 
 import (
+	"fmt"
+	"net/url"
+
 	"gopkg.in/src-d/go-git.v2/clients/common"
 	"gopkg.in/src-d/go-git.v2/clients/http"
+	"gopkg.in/src-d/go-git.v2/clients/ssh"
 )
 
-func NewGitUploadPackService() common.GitUploadPackService {
-	return http.NewGitUploadPackService()
+// ServiceFromURLFunc defines a service returning function for a given
+// URL.
+type ServiceFromURLFunc func(url string) common.GitUploadPackService
+
+// DefaultProtocols are the protocols supported by default.
+// Wrapping is needed because you can not cast a function that
+// returns an implementation of an interface to a function that
+// returns the interface.
+var DefaultProtocols = map[string]ServiceFromURLFunc{
+	"http":  func(s string) common.GitUploadPackService { return http.NewGitUploadPackService(s) },
+	"https": func(s string) common.GitUploadPackService { return http.NewGitUploadPackService(s) },
+	"ssh":   func(s string) common.GitUploadPackService { return ssh.NewGitUploadPackService(s) },
+}
+
+// KnownProtocols holds the current set of known protocols. Initially
+// it gets its contents from `DefaultProtocols`. See `InstallProtocol`
+// below to add or modify this variable.
+var KnownProtocols = make(map[string]ServiceFromURLFunc, len(DefaultProtocols))
+
+func init() {
+	for k, v := range DefaultProtocols {
+		KnownProtocols[k] = v
+	}
+}
+
+// NewGitUploadPackService returns the appropiate upload pack service
+// among of the set of known protocols: HTTP, SSH. See `InstallProtocol`
+// to add or modify protocols.
+func NewGitUploadPackService(repoURL string) (common.GitUploadPackService, error) {
+	u, err := url.Parse(repoURL)
+	if err != nil {
+		return nil, fmt.Errorf("invalid url %q", repoURL)
+	}
+	srvFn, ok := KnownProtocols[u.Scheme]
+	if !ok {
+		return nil, fmt.Errorf("unsupported scheme %q", u.Scheme)
+	}
+	return srvFn(repoURL), nil
+}
+
+// InstallProtocol adds or modifies an existing protocol.
+func InstallProtocol(scheme string, serviceFn ServiceFromURLFunc) {
+	if serviceFn == nil {
+		panic("nil service")
+	}
+	KnownProtocols[scheme] = serviceFn
 }