Add a simple "./debian/rules generate" to build debian/control.

This is ugly and annoying but alternatives are storing generated files
in version control, or manually maintaining pesky little details.
The control file will be part of the .diff.gz.

debian/rules

@@ -1,7 +1,31 @@
 #!/usr/bin/make -f
 # -*- mode: makefile; coding: utf-8 -*-
 
+ifeq ($(wildcard debian/control),)
+ifeq ($(DEB_AUTO_UPDATE_DEBIAN_CONTROL),)
+advice_about_control := yes
+endif
+endif
+
+ifeq ($(advice_about_control),yes)
+advice-on-debian-control %::
+	@echo "It seems you are building from pristine source and"
+	@echo "debian/control is missing. It will be autogenerated"
+	@echo "if you say:"
+	@echo
+	@echo "  ./debian/rules generate"
+	@echo
+	@exit 1
+else
+
 DEB_PYTHON_SYSTEM := pysupport
 
 include /usr/share/cdbs/1/rules/debhelper.mk
 include /usr/share/cdbs/1/class/python-distutils.mk
+endif
+
+
+generate::
+#	I wish this was atomic
+	cp debian/control.in debian/control
+	fakeroot env DEB_AUTO_UPDATE_DEBIAN_CONTROL=1 ./debian/rules clean