Fix misbehavior of msgmerge --for-msgfmt

This fixes build errors in packages with empty .po files:
https://gitlab.gnome.org/GNOME/gcr/issues/25
https://github.com/p11-glue/p11-kit/issues/238

gettext-msgmerge-for-msgfmt.patch

@@ -0,0 +1,82 @@
+From 2336451ed68d91ff4b5ae1acbc1eca30e47a86a9 Mon Sep 17 00:00:00 2001
+From: Bruno Haible <bruno@clisp.org>
+Date: Sun, 19 May 2019 13:10:06 +0200
+Subject: [PATCH] msgmerge: Fix behaviour of --for-msgfmt on PO files with no
+ translations.
+
+Reported by Don Lawrence <dlawrence@iecok.com>
+in <https://lists.freedesktop.org/archives/p11-glue/2019-May/000700.html>
+via Daiki Ueno
+in <https://lists.gnu.org/archive/html/bug-gettext/2019-05/msg00124.html>.
+
+* gettext-tools/src/msgmerge.c (main): Treat force_po like true if for_msgfmt
+is true.
+* gettext-tools/tests/msgmerge-26: Add test of PO file with no translations.
+---
+ gettext-tools/src/msgmerge.c    |  4 ++--
+ gettext-tools/tests/msgmerge-26 | 36 ++++++++++++++++++++++++++++++---
+ 2 files changed, 35 insertions(+), 5 deletions(-)
+
+diff --git a/gettext-tools/src/msgmerge.c b/gettext-tools/src/msgmerge.c
+index cd762c029..92c9b7a8e 100644
+--- a/gettext-tools/src/msgmerge.c
++++ b/gettext-tools/src/msgmerge.c
+@@ -520,8 +520,8 @@ There is NO WARRANTY, to the extent permitted by law.\n\
+   else
+     {
+       /* Write the merged message list out.  */
+-      msgdomain_list_print (result, output_file, output_syntax, force_po,
+-                            false);
++      msgdomain_list_print (result, output_file, output_syntax,
++                            for_msgfmt || force_po, false);
+     }
+ 
+   exit (EXIT_SUCCESS);
+diff --git a/gettext-tools/tests/msgmerge-26 b/gettext-tools/tests/msgmerge-26
+index cd3862e33..b86f7a073 100755
+--- a/gettext-tools/tests/msgmerge-26
++++ b/gettext-tools/tests/msgmerge-26
+@@ -73,7 +73,37 @@ msgstr "Papaya"
+ EOF
+ 
+ : ${DIFF=diff}
+-${DIFF} mm-test26.ok mm-test26.out
+-result=$?
++${DIFF} mm-test26.ok mm-test26.out || Exit 1
+ 
+-exit $result
++# Test with a PO file that has no translated messages.
++
++cat <<\EOF > mm-test26a.in1
++msgid ""
++msgstr ""
++"Content-Type: text/plain; charset=UTF-8\n"
++
++msgid "Hello world"
++msgstr "Hallo Welt"
++EOF
++
++cat <<\EOF > mm-test26a.in2
++msgid ""
++msgstr ""
++"Content-Type: text/plain; charset=ASCII\n"
++
++msgid "Hello, world!"
++msgstr ""
++EOF
++
++: ${MSGMERGE=msgmerge}
++${MSGMERGE} --for-msgfmt -o mm-test26a.tmp mm-test26a.in1 mm-test26a.in2 \
++    || Exit 1
++LC_ALL=C tr -d '\r' < mm-test26a.tmp > mm-test26a.out || Exit 1
++
++cat <<\EOF > mm-test26a.ok
++msgid ""
++msgstr "Content-Type: text/plain; charset=UTF-8\n"
++EOF
++
++: ${DIFF=diff}
++${DIFF} mm-test26a.ok mm-test26a.out || Exit 1
+-- 
+2.21.0
+

gettext.spec

@@ -7,7 +7,7 @@
 Summary: GNU libraries and utilities for producing multi-lingual messages
 Name: gettext
 Version: %{tarversion}
-Release: 1%{?dist}
+Release: 2%{?dist}
 # The following are licensed under LGPLv2+:
 # - libintl and its headers
 # - libasprintf and its headers
@@ -27,6 +27,8 @@ Source: https://ftp.gnu.org/pub/gnu/gettext/%{name}-%{version}.tar.xz
 Source2: msghack.py
 Source3: msghack.1
 
+Patch1: gettext-msgmerge-for-msgfmt.patch
+
 # for bootstrapping
 # BuildRequires: autoconf >= 2.62
 # BuildRequires: automake
@@ -394,6 +396,9 @@ make check LIBUNISTRING=-lunistring
 %{_mandir}/man1/msghack.1*
 
 %changelog
+* Tue Aug 20 2019 Daiki Ueno <dueno@redhat.com> - 0.20.1-2
+- Fix misbehavior of msgmerge --for-msgfmt
+
 * Fri Aug  9 2019 Jerry James <loganjerry@gmail.com> - 0.20.1-1
 - update to 0.20.1 release, all patches upstreamed
 - add GFDL to License fields due to info files