git: implement upload-server-info. Fixes #731

This adds UpdateServerInfo along with a new go-git command to generate
info files to help git dumb http serve refs and their objects.
This also updates the docs to reflect this.

Docs: https://git-scm.com/docs/git-update-server-info
Fixes: https://github.com/go-git/go-git/issues/731

2 files changed, 35 insertions, 0 deletions

diff --git a/cli/go-git/main.go b/cli/go-git/main.go
index 97b8c3e..0a5ad2c 100644
--- a/cli/go-git/main.go
+++ b/cli/go-git/main.go
@@ -22,6 +22,7 @@ func main() {
 	}
 
 	parser := flags.NewNamedParser(bin, flags.Default)
+	parser.AddCommand("update-server-info", "", "", &CmdUpdateServerInfo{})
 	parser.AddCommand("receive-pack", "", "", &CmdReceivePack{})
 	parser.AddCommand("upload-pack", "", "", &CmdUploadPack{})
 	parser.AddCommand("version", "Show the version information.", "", &CmdVersion{})
diff --git a/cli/go-git/update_server_info.go b/cli/go-git/update_server_info.go
new file mode 100644
index 0000000..a7f3e3e
--- /dev/null
+++ b/cli/go-git/update_server_info.go
@@ -0,0 +1,34 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/go-git/go-git/v5"
+	"github.com/go-git/go-git/v5/plumbing/serverinfo"
+	"github.com/go-git/go-git/v5/storage/filesystem"
+)
+
+// CmdUpdateServerInfo command updates the server info files in the repository.
+// This is used by git http transport (dumb) to generate a list of available
+// refs for the repository. See:
+// https://git-scm.com/docs/git-update-server-info
+type CmdUpdateServerInfo struct {
+	cmd
+}
+
+// Usage returns the usage of the command.
+func (CmdUpdateServerInfo) Usage() string {
+	return fmt.Sprintf("within a git repository run: %s", os.Args[0])
+}
+
+// Execute runs the command.
+func (c *CmdUpdateServerInfo) Execute(args []string) error {
+	r, err := git.PlainOpen(".")
+	if err != nil {
+		return err
+	}
+
+	fs := r.Storer.(*filesystem.Storage).Filesystem()
+	return serverinfo.UpdateServerInfo(r.Storer, fs)
+}