providers/docker: ability to specify build dir synced folder opts [GH-3727]

CHANGELOG.md

@@ -8,6 +8,8 @@ IMPROVEMENTS:
       RDP client. [GH-3686]
   - providers/docker: `build_args` config to specify extra args for
       `docker build`. [GH-3684]
+  - providers/docker: Can specify options for the build dir synced
+      folder when a host VM is in use. [GH-3727]
   - synced\_folders/nfs: Can tell Vagrant not to handle exporting
       by setting `nfs_export: false` [GH-3636]
 

plugins/providers/docker/action/host_machine_build_dir.rb

@@ -32,7 +32,7 @@ module VagrantPlugins
           options       = {
             docker__ignore: true,
             docker__exact: true,
-          }
+          }.merge(machine.provider_config.host_vm_build_dir_options || {})
           machine.config.vm.synced_folder(build_dir, new_build_dir, options)
 
           # Set the build dir to be the correct one

plugins/providers/docker/config.rb

@@ -44,6 +44,11 @@ module VagrantPlugins
       # provisioning, etc.
       attr_accessor :has_ssh
 
+      # Options for the build dir synced folder if a host VM is in use.
+      #
+      # @return [Hash]
+      attr_accessor :host_vm_build_dir_options
+
       # The name for the container. This must be unique for all containers
       # on the proxy machine if it is made.
       #
@@ -87,6 +92,7 @@ module VagrantPlugins
         @expose     = []
         @force_host_vm = UNSET_VALUE
         @has_ssh    = UNSET_VALUE
+        @host_vm_build_dir_options = UNSET_VALUE
         @image      = UNSET_VALUE
         @name       = UNSET_VALUE
         @links      = []
@@ -147,6 +153,10 @@ module VagrantPlugins
         @vagrant_machine = nil if @vagrant_machine == UNSET_VALUE
         @vagrant_vagrantfile = nil if @vagrant_vagrantfile == UNSET_VALUE
 
+        if @host_vm_build_dir_options == UNSET_VALUE
+          @host_vm_build_dir_options = nil
+        end
+
         # The machine name must be a symbol
         @vagrant_machine = @vagrant_machine.to_sym if @vagrant_machine
 

test/unit/plugins/providers/docker/config_test.rb

@@ -43,6 +43,7 @@ describe VagrantPlugins::DockerProvider::Config do
     its(:cmd) { should eq([]) }
     its(:env) { should eq({}) }
     its(:force_host_vm) { should be_false }
+    its(:host_vm_build_dir_options) { should be_nil }
     its(:image) { should be_nil }
     its(:name) { should be_nil }
     its(:privileged) { should be_false }

website/docs/source/v2/docker/configuration.html.md

@@ -44,6 +44,10 @@ you may set. A complete reference is shown below.
     the container. This allows `vagrant ssh` to work, provisioners, etc.
     This defaults to false.
 
+  * `host_vm_build_dir_options` (hash) - Synced folder options for the
+    `build_dir`, since the build directory is synced using a synced folder
+    if a host VM is in use.
+
   * `name` (string) - Name of the container. Note that this has to be unique
     across all containers on the host VM. By default Vagrant will generate
     some random name.