Add a resolve_host_path capability for bsd and darwin hosts

For bsd the resolve_host_path capability is a no-op. For darwin
hosts, if firmlinks are defined on the system, paths will be properly
resolved to real path.

plugins/hosts/bsd/cap/path.rb

@@ -0,0 +1,11 @@
+module VagrantPlugins
+  module HostBSD
+    module Cap
+      class Path
+        def self.resolve_host_path(env, path)
+          path
+        end
+      end
+    end
+  end
+end

plugins/hosts/bsd/plugin.rb

@@ -36,6 +36,11 @@ module VagrantPlugins
         Cap::NFS
       end
 
+      host_capability("bsd", "resolve_host_path") do
+        require_relative "cap/path"
+        Cap::Path
+      end
+
       host_capability("bsd", "set_ssh_key_permissions") do
         require_relative "cap/ssh"
         Cap::SSH

plugins/hosts/darwin/cap/path.rb

@@ -0,0 +1,58 @@
+module VagrantPlugins
+  module HostDarwin
+    module Cap
+      class Path
+        @@logger = Log4r::Logger.new("vagrant::host::darwin::path")
+
+        FIRMLINK_DEFS = "/usr/share/firmlinks".freeze
+        FIRMLINK_DATA_PATH = "/System/Volumes/Data".freeze
+
+        # Resolve the given host path to the actual
+        # usable system path by detecting firmlinks
+        # if available on the current system
+        #
+        # @param [String] path Host system path
+        # @return [String] resolved path
+        def self.resolve_host_path(env, path)
+          path = File.expand_path(path)
+          firmlink = firmlink_map.detect do |mount_path, data_path|
+            path.start_with?(mount_path)
+          end
+          return path if firmlink.nil?
+          current_prefix, new_suffix = firmlink
+          new_prefix = File.join(FIRMLINK_DATA_PATH, new_suffix)
+          new_path = path.sub(current_prefix, new_prefix)
+          @@logger.debug("Resolved given path `#{path}` to `#{new_path}`")
+          new_path
+        end
+
+        # Generate mapping of firmlinks if available on the host
+        #
+        # @return [Hash<String,String>]
+        def self.firmlink_map
+          if !@firmlink_map
+            return @firmlink_map = {} if !File.exist?(FIRMLINK_DEFS)
+            begin
+              @firmlink_map = Hash[
+                File.readlines(FIRMLINK_DEFS).map { |d|
+                  d.strip.split(/\s+/, 2)
+                }
+              ]
+            rescue => err
+              @@logger.warn("Failed to parse firmlink definitions: #{err}")
+              @firmlink_map = {}
+            end
+          end
+          @firmlink_map
+        end
+
+        # @private
+        # Reset the cached values for capability. This is not considered a public
+        # API and should only be used for testing.
+        def self.reset!
+          instance_variables.each(&method(:remove_instance_variable))
+        end
+      end
+    end
+  end
+end

plugins/hosts/darwin/plugin.rb

@@ -16,6 +16,11 @@ module VagrantPlugins
         Cap::ProviderInstallVirtualBox
       end
 
+      host_capability("darwin", "resolve_host_path") do
+        require_relative "cap/path"
+        Cap::Path
+      end
+
       host_capability("darwin", "rdp_client") do
         require_relative "cap/rdp"
         Cap::RDP