chore: Significantly restructure folder layout

This moves the various projects from "type-based" folders (such as
"services" or "tools") into more appropriate semantic folders (such as
"nix", "ops" or "web").

Deprecated projects (nixcon-demo & gotest) which only existed for
testing/demonstration purposes have been removed.

(Note: *all* builds are broken with this commit)

ops/sync-gcsr/main.go

@@ -0,0 +1,92 @@
+// 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/transport/http"
+)
+
+func EnvOr(key, def string) string {
+	v := os.Getenv(key)
+	if v == "" {
+		return def
+	}
+
+	return v
+}
+
+func updateRepo(repo *git.Repository, tree *git.Worktree, opts *git.PullOptions) error {
+	err := tree.Pull(opts)
+	if err == git.NoErrAlreadyUpToDate {
+		// nothing to do ...
+		return nil
+	} else if err != nil {
+		return err
+	}
+
+	log.Println("Updated local repository mirror")
+	return nil
+}
+
+func main() {
+	var dest = EnvOr("SYNC_DEST", "/git/depot")
+	var project = EnvOr("SYNC_PROJECT", "tazjins-infrastructure")
+	var repo = EnvOr("SYNC_REPO", "depot")
+	var user = os.Getenv("SYNC_USER")
+	var pass = os.Getenv("SYNC_PASS")
+
+	log.Printf("Syncing repository '%s/%s' to destination '%s'", project, repo, dest)
+
+	var cloneOpts = git.CloneOptions{
+		URL: fmt.Sprintf("https://source.developers.google.com/p/%s/r/%s", project, repo),
+	}
+
+	if user != "" && pass != "" {
+		cloneOpts.Auth = &http.BasicAuth{
+			Username: user,
+			Password: pass,
+		}
+		log.Println("Enabling basic authentication as user", user)
+	}
+
+	action := "clone"
+	handle, err := git.PlainClone(dest, false, &cloneOpts)
+
+	if err == git.ErrRepositoryAlreadyExists {
+		log.Println("Repository has already been cloned!")
+		handle, err = git.PlainOpen(dest)
+		action = "open"
+	}
+
+	if err != nil {
+		log.Fatalf("Failed to %s repository: %s", action, err)
+	} else {
+		log.Println("Initiating update loop")
+	}
+
+	tree, err := handle.Worktree()
+	if err != nil {
+		log.Fatalln("Failed to open repository worktree:", err)
+	}
+
+	pullOpts := git.PullOptions{
+		Auth:  cloneOpts.Auth,
+		Force: true,
+	}
+
+	for {
+		if err = updateRepo(handle, tree, &pullOpts); err != nil {
+			log.Fatalf("Failed to pull updated repository: %s", err)
+		}
+		time.Sleep(30 * time.Second) //  TODO(tazjin): Config option for pull interval?
+	}
+}