Make SetAuthKeys action aware of previous keys

Because SSHAuthorizedKeyring needs them at the time of write to
know if file should be written or not. Slightly related to
#320

src/lib/y2users/linux/set_auth_keys_action.rb

@@ -33,21 +33,29 @@ class SetAuthKeysAction < Action
       # Constructor
       #
       # @see Action
-      def initialize(user, commit_config = nil)
+      # @param user [User] user to perform the action
+      # @param commit_config [CommitConfig, nil] optional configuration for the commit
+      # @param previous_keys [Array<String>, nil] optional collection holding previous keys, if any
+      def initialize(user, commit_config = nil, previous_keys = nil)
         textdomain "users"
 
-        super
+        super(user, commit_config)
+        @previous_keys = previous_keys || []
       end
 
     private
 
+      attr_accessor :previous_keys
+
       alias_method :user, :action_element
 
       # @see Action#run_action
       #
       # Issues are generated when the authorized keys cannot be set.
       def run_action
-        Yast::Users::SSHAuthorizedKeyring.new(user.home, user.authorized_keys).write_keys
+        keyring = Yast::Users::SSHAuthorizedKeyring.new(user.home.path, previous_keys)
+        keyring.add_keys(user.authorized_keys)
+        keyring.write_keys
         true
       rescue Yast::Users::SSHAuthorizedKeyring::PathError => e
         issues << Y2Issues::Issue.new(

test/lib/y2users/linux/set_auth_keys_action_test.rb

@@ -34,17 +34,19 @@
     it "calls SSHAuthorizedKeyring#write_keys" do
       obj = double
       expect(obj).to receive(:write_keys)
-      expect(Yast::Users::SSHAuthorizedKeyring).to receive(:new).with(user.home, ["test"])
+      expect(obj).to receive(:add_keys).with(["test"])
+      expect(Yast::Users::SSHAuthorizedKeyring).to receive(:new).with("/home/test", [])
         .and_return(obj)
 
       subject.perform
     end
 
     it "returns result without success and with issues if cmd failed" do
       obj = double
+      expect(obj).to receive(:add_keys).with(["test"])
       expect(obj).to receive(:write_keys)
-        .and_raise(Yast::Users::SSHAuthorizedKeyring::PathError, user.home)
-      expect(Yast::Users::SSHAuthorizedKeyring).to receive(:new).with(user.home, ["test"])
+        .and_raise(Yast::Users::SSHAuthorizedKeyring::PathError, "/home/test")
+      expect(Yast::Users::SSHAuthorizedKeyring).to receive(:new).with("/home/test", [])
         .and_return(obj)
 
       result = action.perform