Added makefile for maintaining translations as PO files

languages/Makefile

@@ -0,0 +1,58 @@
+# Maintain translations for web2py as gettext po files to make life
+# easier for translators.
+#
+# These rules assume the en-us.py file is generated from source and
+# contain every translatable string in the application.  It further
+# ignore the default.py and plural-*.py files, because I do not know
+# how to best handle them as po files.
+#
+# Too migrate once from py to po files, run this:
+#   make migrate oztree.pot pofiles clean
+#
+# To generate py files for use when building, run
+#   make
+#
+# To see translation status, run
+#   make stats
+#
+# You need a version of Translation Toolkit where
+# https://github.com/translate/translate/issues/3254 is fixed, for
+# example the version from Debian.
+
+TRANSLATIONS = ar ca cs de es fr-ca fr hi hu id it my-mm my nl \
+	pl pt-br pt ro ru sk sv tr uk zh-cn zh-tw zh
+
+POFILES = $(TRANSLATIONS:=.po)
+PYFILES = $(TRANSLATIONS:=.py)
+
+all: $(PYFILES)
+
+pyfiles: $(PYFILES)
+pofiles: $(POFILES)
+
+oztree.pot: en-us.py
+	web2py2po -P -i en-us.py -o oztree.pot
+
+$(POFILES): oztree.pot
+	msgmerge $@ oztree.pot -o $@.new && mv $@.new $@
+
+.po.py:
+	po2web2py -i $^ -o $@
+
+clean:
+	$(RM) $(PYFILES)
+
+stats:
+	for f in $(POFILES); do \
+	  printf "%-15s " $$f; msgfmt --output /dev/null --statistics $$f; \
+	done
+
+# This target should only be used once, when starting to maintain
+# translations as PO files.
+migrate:
+	for f in $(PYFILES); do \
+	  echo web2py2po -P -i $$f -o $${f%.py}.po ; \
+	  web2py2po -P -i $$f -o $${f%.py}.po ; \
+	done
+
+.SUFFIXES: .po .py .pot