make: templatize Debian build target a la e63dfbbdbd07

.hgignore

@@ -30,6 +30,7 b' build'
 contrib/chg/chg
 contrib/hgsh/hgsh
 contrib/vagrant/.vagrant
+contrib/docker/debian-*
 contrib/docker/ubuntu-*
 dist
 packages

Makefile

@@ -196,7 +196,10 b' deb:'
 ppa:
 	contrib/builddeb --source-only
 
-docker-debian-jessie:
+contrib/docker/debian-%: contrib/docker/debian.template
+	sed "s/__CODENAME__/$*/" $< > $@
+
+docker-debian-jessie: contrib/docker/debian-jessie
 	mkdir -p packages/debian-jessie
 	contrib/dockerdeb debian jessie
 

contrib/docker/debian.template

@@ -1,4 +1,4 b''
-FROM debian:jessie
+FROM debian:__CODENAME__
 RUN apt-get update && apt-get install -y \
   build-essential \
   debhelper \