Add rake task to install or upgrade gitlab-shell installation.

lib/tasks/gitlab/shell.rake

 namespace :gitlab do
   namespace :shell do
+    desc "GITLAB | Install or upgrade gitlab-shell"
+    task :install, [:tag, :repo] => :environment do |t, args|
+      warn_user_is_not_gitlab
+
+      args.with_defaults(tag: "v1.9.1", repo: "https://gitlab.com/gitlab-org/gitlab-shell.git")
+
+      user = Settings.gitlab.user
+      home_dir = Settings.gitlab.user_home
+      gitlab_url = Settings.gitlab.url
+      # gitlab-shell requires a / at the end of the url
+      gitlab_url += "/" unless gitlab_url.match(/\/$/)
+      target_dir = File.join(home_dir, "gitlab-shell")
+
+      # Clone if needed
+      unless File.directory?(target_dir)
+        sh "git clone '#{args.repo}' '#{target_dir}'"
+      end
+
+      # Make sure we're on the right tag
+      Dir.chdir(target_dir) do
+        sh "git fetch origin && git reset --hard $(git describe #{args.tag} || git describe origin/#{args.tag})"
+
+        redis_url = URI.parse(ENV['REDIS_URL'] || "redis://localhost:6379")
+
+        config = {
+          user: user,
+          gitlab_url: gitlab_url,
+          http_settings: {self_signed_cert: false},
+          repos_path: File.join(home_dir, "repositories"),
+          auth_file: File.join(home_dir, ".ssh", "authorized_keys"),
+          redis: {
+            bin: %x{which redis-cli}.chomp,
+            host: redis_url.host,
+            port: redis_url.port,
+            namespace: "resque:gitlab"
+          },
+          log_level: "INFO",
+          audit_usernames: false
+        }
+
+        # Generate config.yml based on existing gitlab settings
+        File.open("config.yml", "w+") {|f| f.puts config.to_yaml}
+
+        # Launch installation process
+        sh "bin/install"
+      end
+
+      # Required for debian packaging with PKGR: Setup .ssh/environment with
+      # the current PATH, so that the correct ruby version gets loaded
+      # Requires to set "PermitUserEnvironment yes" in sshd config (should not
+      # be an issue since it is more than likely that there are no "normal"
+      # user accounts on a gitlab server). The alternative is for the admin to
+      # install a ruby (1.9.3+) in the global path.
+      File.open(File.join(home_dir, ".ssh", "environment"), "w+") do |f|
+        f.puts "PATH=#{ENV['PATH']}"
+      end
+    end
+
     desc "GITLAB | Setup gitlab-shell"
     task setup: :environment do
       setup