cap: add sshfs_get_absolute_path guest capability

lib/vagrant-sshfs/cap/guest/linux/sshfs_get_absolute_path.rb

@@ -0,0 +1,25 @@
+module VagrantPlugins
+  module GuestLinux
+    module Cap
+      class SSHFSGetAbsolutePath
+        def self.sshfs_get_absolute_path(machine, path)
+          abs_path = ""
+          machine.communicate.execute("readlink -f #{path}") do |type, data|
+            if type == :stdout
+              abs_path = data
+            end
+          end
+
+          if ! abs_path
+            # If no real absolute path was detected then error out
+            error_class = VagrantPlugins::SyncedFolderSSHFS::Errors::SSHFSGetAbsolutePathFailed
+            raise error_class, path: path
+          end
+
+          # Chomp the string so that any trailing newlines are killed
+          return abs_path.chomp
+        end
+      end
+    end
+  end
+end

lib/vagrant-sshfs/errors.rb

@@ -33,6 +33,10 @@ class SSHFSNotInstalledInGuest < SSHFSError
       class SSHFSExeNotAvailable < SSHFSError
         error_key(:exe_not_in_host)
       end
+
+      class SSHFSGetAbsolutePathFailed < SSHFSError
+        error_key(:get_absolute_path_failed)
+      end
     end
   end
 end

lib/vagrant-sshfs/plugin.rb

@@ -65,6 +65,11 @@ class Plugin < Vagrant.plugin("2")
         VagrantPlugins::GuestLinux::Cap::MountSSHFS
       end
 
+      guest_capability("linux", "sshfs_get_absolute_path") do
+        require_relative "cap/guest/linux/sshfs_get_absolute_path"
+        VagrantPlugins::GuestLinux::Cap::SSHFSGetAbsolutePath
+      end
+
       guest_capability("redhat", "sshfs_installed") do
         require_relative "cap/guest/redhat/sshfs_client"
         VagrantPlugins::GuestRedHat::Cap::SSHFSClient

locales/synced_folder_sshfs.yml

@@ -35,6 +35,8 @@ en:
           try again.
         sshfs_not_in_guest: |-
           The necessary SSHFS software is not installed in the guest. 
+        get_absolute_path_failed: |-
+          Could not get the absolute path of the folder within the guest '%{path}'
         install_failed_arch: |-
           The install of the sshfs client software failed. On Arch this is most likely
           because the package lists are not up to date [1] and partial upgrades are not