Fix po entry flag text representation (#105)

Format multiple flags into a commma separated single line.
Without this change, at least `msgcat` command, which is one of gettexts
commands only loads last flag and the rest are ignored.

---------

Co-authored-by: Sutou Kouhei <[email protected]>

Author: ynojima

lib/gettext/po_entry.rb

@@ -428,11 +428,12 @@ def format_reference_comment
       end
 
       def format_flag_comment
-        formatted_flags = String.new
-        @entry.flags.each do |flag|
-          formatted_flags << format_comment(FLAG_MARK, flag)
+        if @entry.flags.empty?
+          String.new
+        else
+          joined_flags = @entry.flags.join(", ")
+          format_comment(FLAG_MARK, joined_flags)
         end
-        formatted_flags
       end
 
       def format_previous_comment

test/test_po_entry.rb

@@ -344,6 +344,20 @@ def test_flag
       assert_equal(expected_po, entry.to_s)
     end
 
+    def test_multiple_flags
+      entry = GetText::POEntry.new(:normal)
+      entry.msgid = "msgid"
+      entry.msgstr = "msgstr"
+      entry.flags = ["It's the flag.", "fuzzy"]
+
+      expected_po = <<-EOP
+#, It's the flag., fuzzy
+msgid "msgid"
+msgstr "msgstr"
+EOP
+      assert_equal(expected_po, entry.to_s)
+    end
+
     def test_previous
       entry = GetText::POEntry.new(:normal)
       entry.msgid = "msgid"