# File lib/gettext/tools/msgcat.rb, line 74
        def merge(po)
          po.each do |entry|
            if entry.msgid == :last
              next unless @config.output_obsolete_entries?
            end
            id = [entry.msgctxt, entry.msgid]
            if @output_po.has_key?(*id)
              merged_entry = merge_entry(@output_po[*id], entry)
            else
              merged_entry = entry
            end
            next unless merged_entry
            if merged_entry.header?
              update_po_revision_date!(merged_entry)
              remove_header_fields!(merged_entry)
            end
            @output_po[*id] = merged_entry
          end
        end