2 files changed, 139 insertions, 0 deletions
diff --git a/ops/sync-gcsr/default.nix b/ops/sync-gcsr/default.nix
new file mode 100644
index 000000000000..114ff221bed1
--- /dev/null
+++ b/ops/sync-gcsr/default.nix
@@ -0,0 +1,10 @@
+{ pkgs, ... }:
+
+pkgs.buildGo.program {
+  name = "sync-gcsr";
+  srcs = [ ./main.go ];
+
+  deps = with pkgs.third_party; map (p: p.gopkg) [
+    gopkgs."gopkg.in".src-d.go-git
+  ];
+}
diff --git a/ops/sync-gcsr/main.go b/ops/sync-gcsr/main.go
new file mode 100644
index 000000000000..a02f6d552730
--- /dev/null
+++ b/ops/sync-gcsr/main.go
@@ -0,0 +1,129 @@
+// Copyright 2019 Google LLC.
+// SPDX-License-Identifier: Apache-2.0
+//
+// sync-gcsr implements a small utility that periodically mirrors a
+// remote Google Cloud Source Repository to a local file path.
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"time"
+
+	git "gopkg.in/src-d/go-git.v4"
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/transport/http"
+)
+
+func EnvOr(key, def string) string {
+	v := os.Getenv(key)
+	if v == "" {
+		return def
+	}
+
+	return v
+}
+
+// ensure that all remote branches exist locally & are up to date.
+func updateBranches(auth *http.BasicAuth, repo *git.Repository) error {
+	origin, err := repo.Remote("origin")
+	if err != nil {
+		return err
+	}
+
+	refs, err := origin.List(&git.ListOptions{
+		Auth: auth,
+	})
+	if err != nil {
+		return err
+	}
+
+	for _, ref := range refs {
+		if !ref.Name().IsBranch() || ref.Type() != plumbing.HashReference {
+			continue
+		}
+
+		branch := plumbing.NewHashReference(
+			plumbing.NewBranchReferenceName(ref.Name().Short()),
+			ref.Hash(),
+		)
+
+		err := repo.Storer.SetReference(branch)
+		if err != nil {
+			return err
+		}
+		log.Println("Updated branch", ref.Name().String())
+	}
+
+	return nil
+}
+
+func updateRepo(auth *http.BasicAuth, repo *git.Repository, opts *git.FetchOptions) error {
+	err := repo.Fetch(opts)
+
+	if err == git.NoErrAlreadyUpToDate {
+		// nothing to do ...
+		return nil
+	} else if err != nil {
+		return err
+	}
+
+	log.Println("Fetched updates from remote, updating local branches")
+	return updateBranches(auth, repo)
+}
+
+func cloneRepo(dest, project, repo string, auth *http.BasicAuth) (*git.Repository, error) {
+	var cloneOpts = git.CloneOptions{
+		Auth: auth,
+		URL:  fmt.Sprintf("https://source.developers.google.com/p/%s/r/%s", project, repo),
+	}
+
+	handle, err := git.PlainClone(dest, true, &cloneOpts)
+
+	if err == git.ErrRepositoryAlreadyExists {
+		handle, err = git.PlainOpen(dest)
+	}
+
+	return handle, updateBranches(auth, handle)
+}
+
+func main() {
+	dest := EnvOr("SYNC_DEST", "/git/depot")
+	project := EnvOr("SYNC_PROJECT", "tazjins-infrastructure")
+	repo := EnvOr("SYNC_REPO", "depot")
+	user := os.Getenv("SYNC_USER")
+	pass := os.Getenv("SYNC_PASS")
+
+	log.Printf("Syncing repository '%s/%s' to destination '%s'", project, repo, dest)
+
+	var auth *http.BasicAuth
+	if user != "" && pass != "" {
+		auth = &http.BasicAuth{
+			Username: user,
+			Password: pass,
+		}
+		log.Println("Enabling basic authentication as user", user)
+	}
+
+	handle, err := cloneRepo(dest, project, repo, auth)
+
+	if err != nil {
+		log.Fatalf("Failed to clone repository: %s", err)
+	} else {
+		log.Println("Initiating update loop")
+	}
+
+	fetchOpts := git.FetchOptions{
+		Auth:  auth,
+		Force: true,
+	}
+
+	for {
+		if err = updateRepo(auth, handle, &fetchOpts); err != nil {
+			log.Fatalf("Failed to pull updated repository: %s", err)
+		}
+
+		time.Sleep(10 * time.Second)
+	}
+}