Added --previous flag to msgmerge command used by makemessages

Also took the opportunity to slightly refactor gettext options
so as to ease customization by subclassing the command.
Thanks Michal Čihař for the report and initial patch.

django/core/management/commands/makemessages.py

@@ -80,14 +80,8 @@ def process(self, command, domain):
                 '--keyword=ngettext_lazy:1,2',
                 '--keyword=pgettext:1c,2',
                 '--keyword=npgettext:1c,2,3',
-                '--from-code=UTF-8',
-                '--add-comments=Translators',
                 '--output=-'
-            ]
-            if command.wrap:
-                args.append(command.wrap)
-            if command.location:
-                args.append(command.location)
+            ] + command.xgettext_options
             args.append(work_file)
         elif domain == 'django' and (file_ext == '.py' or file_ext in command.extensions):
             thefile = self.file
@@ -115,14 +109,8 @@ def process(self, command, domain):
                 '--keyword=npgettext:1c,2,3',
                 '--keyword=pgettext_lazy:1c,2',
                 '--keyword=npgettext_lazy:1c,2,3',
-                '--from-code=UTF-8',
-                '--add-comments=Translators',
                 '--output=-'
-            ]
-            if command.wrap:
-                args.append(command.wrap)
-            if command.location:
-                args.append(command.location)
+            ] + command.xgettext_options
             args.append(work_file)
         else:
             return
@@ -206,6 +194,11 @@ class Command(NoArgsCommand):
     requires_system_checks = False
     leave_locale_alone = True
 
+    msgmerge_options = ['-q', '--previous']
+    msguniq_options = ['--to-code=utf-8']
+    msgattrib_options = ['--no-obsolete']
+    xgettext_options = ['--from-code=UTF-8', '--add-comments=Translators']
+
     def handle_noargs(self, *args, **options):
         locale = options.get('locale')
         self.domain = options.get('domain')
@@ -217,8 +210,19 @@ def handle_noargs(self, *args, **options):
         if options.get('use_default_ignore_patterns'):
             ignore_patterns += ['CVS', '.*', '*~', '*.pyc']
         self.ignore_patterns = list(set(ignore_patterns))
-        self.wrap = '--no-wrap' if options.get('no_wrap') else ''
-        self.location = '--no-location' if options.get('no_location') else ''
+
+        # Avoid messing with mutable class variables
+        if options.get('no_wrap'):
+            self.msgmerge_options = self.msgmerge_options[:] + ['--no-wrap']
+            self.msguniq_options = self.msguniq_options[:] + ['--no-wrap']
+            self.msgattrib_options = self.msgattrib_options[:] + ['--no-wrap']
+            self.xgettext_options = self.xgettext_options[:] + ['--no-wrap']
+        if options.get('no_location'):
+            self.msgmerge_options = self.msgmerge_options[:] + ['--no-location']
+            self.msguniq_options = self.msguniq_options[:] + ['--no-location']
+            self.msgattrib_options = self.msgattrib_options[:] + ['--no-location']
+            self.xgettext_options = self.xgettext_options[:] + ['--no-location']
+
         self.no_obsolete = options.get('no_obsolete')
         self.keep_pot = options.get('keep_pot')
 
@@ -307,12 +311,7 @@ def build_potfiles(self):
             potfile = os.path.join(path, '%s.pot' % str(self.domain))
             if not os.path.exists(potfile):
                 continue
-            args = ['msguniq', '--to-code=utf-8']
-            if self.wrap:
-                args.append(self.wrap)
-            if self.location:
-                args.append(self.location)
-            args.append(potfile)
+            args = ['msguniq'] + self.msguniq_options + [potfile]
             msgs, errors, status = popen_wrapper(args)
             if errors:
                 if status != STATUS_OK:
@@ -389,12 +388,7 @@ def write_po_file(self, potfile, locale):
         pofile = os.path.join(basedir, '%s.po' % str(self.domain))
 
         if os.path.exists(pofile):
-            args = ['msgmerge', '-q']
-            if self.wrap:
-                args.append(self.wrap)
-            if self.location:
-                args.append(self.location)
-            args.extend([pofile, potfile])
+            args = ['msgmerge'] + self.msgmerge_options + [pofile, potfile]
             msgs, errors, status = popen_wrapper(args)
             if errors:
                 if status != STATUS_OK:
@@ -413,12 +407,7 @@ def write_po_file(self, potfile, locale):
             fp.write(msgs)
 
         if self.no_obsolete:
-            args = ['msgattrib', '-o', pofile, '--no-obsolete']
-            if self.wrap:
-                args.append(self.wrap)
-            if self.location:
-                args.append(self.location)
-            args.append(pofile)
+            args = ['msgattrib'] + self.msgattrib_options + ['-o', pofile, pofile]
             msgs, errors, status = popen_wrapper(args)
             if errors:
                 if status != STATUS_OK:

docs/ref/django-admin.txt

@@ -569,6 +569,11 @@ Example usage::
 
     Added the ability to specify multiple locales.
 
+.. versionchanged:: 1.7
+
+    Added the ``--previous`` option to the ``msgmerge`` command when merging
+    with existing po files.
+
 .. django-admin-option:: --domain
 
 Use the ``--domain`` or ``-d`` option to change the domain of the messages files.

docs/releases/1.7.txt

@@ -572,6 +572,10 @@ Internationalization
   app or project message file. See :ref:`how-to-create-language-files` for
   details.
 
+* The :djadmin:`makemessages` command now always adds the ``--previous``
+  command line flag to the ``msgmerge`` command, keeping previously translated
+  strings in po files for fuzzy strings.
+
 * The following settings to adjust the language cookie options were introduced:
   :setting:`LANGUAGE_COOKIE_AGE`, :setting:`LANGUAGE_COOKIE_DOMAIN`
   and :setting:`LANGUAGE_COOKIE_PATH`.