Update Rakefile to generate debian/changelog.

`rake changelog` and a commit should be run after each `hg tag`.

Rakefile

@@ -50,3 +50,118 @@ end
 
 desc "Remove all build targets, binaries and temporary files"
 maketask :clean
+
+# If you've made a commit, the changelog needs redoing
+file "debian/changelog" => ".hg/last-message.txt" do
+  latesttag_cmd = "hg log -l1 --template '{latesttag}'"
+  latesttag = `#{latesttag_cmd}`.strip
+  log_cmd = "hg log -r #{latesttag}:0 --style xml"
+  projname = "flexnbd"
+
+  File.open("debian/changelog", "w") do |changelog|
+    IO.popen( log_cmd, "r" ) do |io|
+      listener = HGChangelog::Listener.new changelog, projname
+      REXML::Document.parse_stream io, listener
+      io.close
+    end
+  end
+end
+task :changelog => "debian/changelog"
+
+BEGIN {
+  require 'rexml/document'
+  require 'date'
+  require 'erb'
+
+  module HGChangelog
+    class ChangelogEntry
+      attr_accessor :email
+      attr_accessor :author_name
+      attr_accessor :date
+      def initialize(projname, tag, rev)
+        @projname = projname
+        @tag = tag
+        @rev = rev
+        @lines = []
+      end
+
+      def close( stream )
+        stream.write self.to_s
+      end
+
+      def <<( msg )
+        @lines << msg
+      end
+
+      def to_s
+        template = <<-TEMPLATE
+<%= @projname %> (<%= @tag %>-<%= @rev %>) stable; urgency=low
+
+<% for  line in @lines -%>
+  * <%= line.split("\n").first.strip %>
+<% end  -%>
+
+ -- <%= @author_name %> <<%= @email %>>  <%= render_date %>
+
+        TEMPLATE
+
+        ERB.new(template, nil, "-").result(binding)
+      end
+
+      def render_date
+        DateTime.parse(@date).rfc2822
+      end
+
+    end # class ChangelogEntry
+
+
+    class Listener
+      def initialize out, projname
+        @out = out
+        @projname = projname
+      end
+
+      def method_missing(sym,*args,&blk)
+      end
+
+      def tag_start( name, attrs )
+        case name
+        when "logentry"
+          @rev = attrs['revision']
+        when "author"
+          @email = attrs['email']
+        when "tag"
+          @entry.close @out if @entry
+          @tagged = true
+        end
+      end
+
+      def tag_end( name )
+        case name
+        when "logentry"
+          if @tagged
+            @entry.email = @email
+            @entry.author_name = @author_name
+            @entry.date = @date
+          end
+          @entry << @message if @message !~ /Added tag.*for changeset/
+                                                          @tagged = false
+          when "author"
+            @author_name = @text
+          when "tag"
+            @entry = ChangelogEntry.new @projname, @text, @rev
+          when "msg"
+            @message = @text
+          when "date"
+            @date = @text
+          when "log"
+            @entry.close @out
+          end
+        end
+
+        def text( text )
+          @text = text
+        end
+      end # class Listener
+    end # module HGChangelog
+}