Support for formatted overlayfs path spec when finding the root FS path

We're using snapshots in a CI set-up so that a Vagrant cluster can be built
once, then each push to the repository only checked as an incremental
update to the cluster. We copy each LXC VM to a master image, then re-create
the original names as snapshots.

This change corrects a method which assumes the LXC root path in the config
file is a simple directory name, which is only true for directory-backed
instances.

Conflicts:
	spec/unit/driver_spec.rb

lib/vagrant-lxc/driver.rb

@@ -45,7 +45,21 @@ module Vagrant
       end
 
       def rootfs_path
-        Pathname.new(config_string.match(/^lxc\.rootfs\s+=\s+(.+)$/)[1])
+        config_entry = config_string.match(/^lxc\.rootfs\s+=\s+(.+)$/)[1]
+        case config_entry
+        when /^overlayfs:/
+          # Split on colon (:), ignoring any colon escaped by an escape character ( \ )
+          # Pays attention to when the escape character is itself escaped.
+          fs_type, master_path, overlay_path = config_entry.split(/(?<!\\)(?:\\\\)*:/)
+          if overlay_path
+            Pathname.new(overlay_path)
+          else
+            # Malformed: fall back to prior behaviour
+            Pathname.new(config_entry)
+          end
+        else
+          Pathname.new(config_entry)
+        end
       end
 
       def mac_address

spec/unit/driver_spec.rb

@@ -176,16 +176,18 @@ describe Vagrant::LXC::Driver do
   end
 
   describe 'folder sharing' do
+    rootfs_path = Pathname('/path/to/rootfs')
+    
     let(:shared_folder)       { {guestpath: '/vagrant', hostpath: '/path/to/host/dir'} }
     let(:ro_rw_folder)        { {guestpath: '/vagrant/ro_rw', hostpath: '/path/to/host/dir', mount_options: ['ro', 'rw']} }
     let(:with_space_folder)   { {guestpath: '/tmp/with space', hostpath: '/path/with space'} }
     let(:folders)             { [shared_folder, ro_rw_folder, with_space_folder] }
-    let(:rootfs_path)         { Pathname('/path/to/rootfs') }
     let(:expected_guest_path) { "vagrant" }
     let(:sudo_wrapper)        { double(Vagrant::LXC::SudoWrapper, run: true) }
 
     subject { described_class.new('name', sudo_wrapper) }
 
+    describe "with fixed rootfs" do
       before do
         subject.stub(rootfs_path: rootfs_path, system: true)
         subject.share_folders(folders)
@@ -216,4 +218,61 @@ describe Vagrant::LXC::Driver do
         ]
       end
     end
+
+    describe "with directory-based LXC config" do
+      config_string = <<-ENDCONFIG.gsub(/^\s+/, '')
+        # Blah blah comment
+        lxc.mount.entry = proc proc proc nodev,noexec,nosuid 0 0
+        lxc.mount.entry = sysfs sys sysfs defaults  0 0
+        lxc.tty = 4
+        lxc.pts = 1024
+        lxc.rootfs = #{rootfs_path}
+        # VAGRANT-BEGIN
+        lxc.network.type=veth
+        lxc.network.name=eth1
+        # VAGRANT-END
+      ENDCONFIG
+      
+      before do
+        subject { described_class.new('name', sudo_wrapper) }
+        subject.stub(config_string: config_string)
+        subject.share_folders(folders)
+      end
+      
+      it 'adds a mount.entry to its local customizations' do
+        expect(subject.customizations).to include [
+          'mount.entry',
+          "#{shared_folder[:hostpath]} #{expected_guest_path} none bind 0 0"
+        ]
+      end
+    end
+
+    describe "with overlayfs-based LXC config" do
+      config_string = <<-ENDCONFIG.gsub(/^\s+/, '')
+        # Blah blah comment
+        lxc.mount.entry = proc proc proc nodev,noexec,nosuid 0 0
+        lxc.mount.entry = sysfs sys sysfs defaults  0 0
+        lxc.tty = 4
+        lxc.pts = 1024
+        lxc.rootfs = overlayfs:/path/to/master/directory:#{rootfs_path}
+        # VAGRANT-BEGIN
+        lxc.network.type=veth
+        lxc.network.name=eth1
+        # VAGRANT-END
+      ENDCONFIG
+
+      before do
+        subject { described_class.new('name', sudo_wrapper) }
+        subject.stub(config_string: config_string)
+        subject.share_folders(folders)
+      end
+
+      it 'adds a mount.entry to its local customizations' do
+        expect(subject.customizations).to include [
+          'mount.entry',
+          "#{shared_folder[:hostpath]} #{expected_guest_path} none bind 0 0"
+        ]
+      end
+    end
+  end
 end