--- /dev/null
+--- a/src/OptionalConfiguration.hs
++++ b/src/OptionalConfiguration.hs
+@@ -31,2 +31,3 @@ import System.IO.Error ( catchIOError )
+ import MxList ( MxList(..) )
++import qualified Data.Semigroup as S
+
+@@ -59,2 +60,19 @@ merge_maybes (Just _) (Just y) = Just y
+
++instance S.Semigroup OptionalConfiguration where
++ cfg1 <> cfg2 =
++ OptionalConfiguration
++ (merge_maybes (database cfg1) (database cfg2))
++ (merge_maybes (domain_query cfg1) (domain_query cfg2))
++ all_excluded_mx
++ (merge_maybes (forward_query cfg1) (forward_query cfg2))
++ (merge_maybes (host cfg1) (host cfg2))
++ (merge_maybes (password cfg1) (password cfg2))
++ (merge_maybes (port cfg1) (port cfg2))
++ (merge_maybes (username cfg1) (username cfg2))
++ where
++ -- Use only the latter exclude_mx if there are any.
++ all_excluded_mx =
++ exclude_mx $ if (null (get_mxs $ exclude_mx cfg2))
++ then cfg1
++ else cfg2
+
--- /dev/null
+# Copyright 1999-2019 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=6
+
+# ebuild generated by hackport 0.4.4
+
+CABAL_FEATURES="bin test-suite"
+inherit haskell-cabal
+
+DESCRIPTION="List all remote forwards for mail accounts stored in a database"
+HOMEPAGE="http://hackage.haskell.org/package/list-remote-forwards"
+SRC_URI="https://hackage.haskell.org/package/${P}/${P}.tar.gz"
+
+LICENSE="GPL-3"
+SLOT="0"
+KEYWORDS="~amd64 ~x86"
+IUSE=""
+
+RESTRICT=test # Ambiguous packages: dns-3.0.2 resolv-0.1.1.1
+
+RDEPEND=""
+DEPEND="${RDEPEND}
+ >=dev-haskell/cabal-1.16.0
+ >=dev-haskell/cmdargs-0.10
+ >=dev-haskell/configurator-0.2
+ >=dev-haskell/dns-1.4
+ >=dev-haskell/hdbc-2.4
+ >=dev-haskell/hdbc-postgresql-2.3
+ >=dev-haskell/hdbc-sqlite3-2.3
+ >=dev-haskell/missingh-1.2
+ >=dev-haskell/tasty-0.8
+ >=dev-haskell/tasty-hunit-0.8
+ >=dev-haskell/tasty-quickcheck-0.8
+ >=dev-lang/ghc-7.6.1
+ test? ( >=dev-haskell/doctest-0.9
+ >=dev-haskell/filemanip-0.3.6 )
+"
+
+PATCHES=(
+ "${FILESDIR}"/${P}-ghc84.patch
+)
+
+src_install() {
+ haskell-cabal_src_install
+ doman "${S}/doc/man1/${PN}.1"
+}