add dockercli backend

docker ruby api based backend does not support all connection
types, such as ssh

lib/specinfra/backend.rb

@@ -5,6 +5,7 @@
 require 'specinfra/backend/powershell/command'
 require 'specinfra/backend/cmd'
 require 'specinfra/backend/docker'
+require 'specinfra/backend/dockercli'
 require 'specinfra/backend/lxc'
 require 'specinfra/backend/lxd'
 require 'specinfra/backend/winrm'

lib/specinfra/backend/dockercli.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+module Specinfra
+  module Backend
+    # Docker command line transport
+    class Dockercli < Exec
+      def build_command(cmd)
+        docker_cmd = %w[docker exec]
+        docker_cmd << '--interactive' if get_config(:interactive_shell)
+        docker_cmd << '--tty' if get_config(:request_pty)
+        docker_cmd << instance
+        (docker_cmd << super(cmd)).join(' ')
+      end
+
+      def send_file(from, to)
+        to = Pathname.new(to).dirname.to_s if File.directory?(from)
+        cmd = %W[docker cp #{from} #{instance}:#{to}]
+        spawn_command(cmd.join(' '))
+      end
+
+      def send_directory(from, to)
+        send_file(from, to)
+      end
+
+      private
+
+      def instance
+        raise 'Please specify docker_container' unless (container = get_config(:docker_container))
+
+        container
+      end
+    end
+  end
+end

lib/specinfra/configuration.rb

@@ -25,6 +25,7 @@ class << self
         :request_pty,
         :ssh_options,
         :ssh_without_env,
+        :docker_container,
         :dockerfile_finalizer,
         :telnet_options,
         :jail_name,

spec/backend/dockercli/build_command_spec.rb

@@ -0,0 +1,118 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'shellwords'
+
+describe Specinfra::Backend::Dockercli do
+  let(:interactive_shell) { false }
+  let(:login_shell) { false }
+  let(:request_pty) { false }
+  let(:shell) { '/bin/sh' }
+  let(:docker_container) { 'instance' }
+  let(:path) { nil }
+  let(:docker_exec) do
+    cmd = %w[docker exec]
+    cmd << '--interactive' if interactive_shell
+    cmd << '--tty' if request_pty
+    cmd << docker_container
+    cmd << "env PATH=\"#{path}\"" if path
+    cmd << shell.shellescape
+    cmd << '-i' if interactive_shell
+    cmd << '-l' if login_shell
+    cmd << '-c'
+    cmd.join(' ')
+  end
+
+  before(:each) do
+    set :backend, :dockercli
+    RSpec.configure do |c|
+      c.request_pty = request_pty
+      c.interactive_shell = interactive_shell
+      c.docker_container = docker_container
+      c.path = path
+    end
+  end
+
+  after(:each) do
+    Specinfra::Backend::Dockercli.clear
+  end
+
+  describe '#build_command' do
+    context 'without required docker_container set' do
+      let(:docker_container) { nil }
+      it {
+        expect { subject.build_command('true') }.to raise_error(RuntimeError, /docker_container/)
+      }
+    end
+
+    context 'with simple command' do
+      it 'should escape spaces' do
+        expect(subject.build_command('test -f /etc/passwd')).to eq "#{docker_exec} test\\ -f\\ /etc/passwd"
+      end
+    end
+
+    context 'with complex command' do
+      it 'should escape special chars' do
+        expect(subject.build_command('test ! -f /etc/selinux/config || (getenforce | grep -i -- disabled && grep -i -- ^SELINUX=disabled$ /etc/selinux/config)'))
+          .to eq "#{docker_exec} test\\ \\!\\ -f\\ /etc/selinux/config\\ \\|\\|\\ \\(getenforce\\ \\|\\ grep\\ -i\\ --\\ disabled\\ \\&\\&\\ grep\\ -i\\ --\\ \\^SELINUX\\=disabled\\$\\ /etc/selinux/config\\)"
+      end
+
+      it 'should escape quotes' do
+        if Gem::Version.new(RUBY_VERSION.dup) < Gem::Version.new('2.7')
+          expect(subject.build_command(%Q(find /etc/apt/ -name \*.list | xargs grep -o -E "^deb +[\\"']?http://ppa.launchpad.net/gluster/glusterfs-3.7"))).to eq("#{docker_exec} find\\ /etc/apt/\\ -name\\ \\*.list\\ \\|\\ xargs\\ grep\\ -o\\ -E\\ \\\"\\^deb\\ \\+\\[\\\\\\\"\\'\\]\\?http://ppa.launchpad.net/gluster/glusterfs-3.7\\\"")
+        else
+          # Since Ruby 2.7, `+` is not escaped.
+          expect(subject.build_command(%Q(find /etc/apt/ -name \*.list | xargs grep -o -E "^deb +[\\"']?http://ppa.launchpad.net/gluster/glusterfs-3.7"))).to eq("#{docker_exec} find\\ /etc/apt/\\ -name\\ \\*.list\\ \\|\\ xargs\\ grep\\ -o\\ -E\\ \\\"\\^deb\\ +\\[\\\\\\\"\\'\\]\\?http://ppa.launchpad.net/gluster/glusterfs-3.7\\\"")
+        end
+      end
+    end
+
+    context 'with custom shell' do
+      let(:shell) { '/usr/local/bin/tcsh' }
+
+      it 'should use custom shell' do
+        expect(subject.build_command('test -f /etc/passwd')).to eq "#{docker_exec} test\\ -f\\ /etc/passwd"
+      end
+    end
+
+    context 'with custom shell that needs escaping' do
+      let(:shell) { '/usr/test & spec/bin/sh' }
+
+      it 'should use custom shell' do
+        expect(subject.build_command('test -f /etc/passwd')).to eq "#{docker_exec} test\\ -f\\ /etc/passwd"
+      end
+    end
+
+    context 'with an interactive shell' do
+      let(:interactive_shell) { true }
+
+      it 'should emulate an interactive shell' do
+        expect(subject.build_command('test -f /etc/passwd')).to eq "#{docker_exec} test\\ -f\\ /etc/passwd"
+      end
+    end
+
+    context 'with an login shell' do
+      let(:login_shell) { true }
+
+      it 'should emulate an login shell' do
+        expect(subject.build_command('test -f /etc/passwd')).to eq "#{docker_exec} test\\ -f\\ /etc/passwd"
+      end
+    end
+
+    context 'with custom path' do
+      let(:path) { '/opt/bin:/opt/foo/bin:$PATH' }
+
+      it 'should use custom path' do
+        expect(subject.build_command('test -f /etc/passwd')).to eq "#{docker_exec} test\\ -f\\ /etc/passwd"
+      end
+    end
+
+    context 'with custom path that needs escaping' do
+      let(:path) { '/opt/bin:/opt/test & spec/bin:$PATH' }
+
+      it 'should use custom path' do
+        expect(subject.build_command('test -f /etc/passwd')).to eq "#{docker_exec} test\\ -f\\ /etc/passwd"
+      end
+    end
+  end
+end