Rewrite update-po target, so that it works less like a shell script and more

like a makefile with real dependencies.

Instead of overwriting the old po file, write the new one to .po.new.  This is
less annoying and integrates better with the NLS web site.

Also, we can now merge languages that don't have a po file yet, by merging
against all other po files of that language, to pick up recurring translations
automatically.  This previously only worked when a po file already existed.

doc/src/sgml/nls.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/nls.sgml,v 1.16 2007/02/01 00:28:17 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/nls.sgml,v 1.17 2009/01/09 10:54:07 petere Exp $ -->
 
 <chapter id="nls">
  <chapterinfo>
@@ -200,9 +200,8 @@ gmake update-po
     which will create a new blank message catalog file (the pot file
     you started with) and will merge it with the existing PO files.
     If the merge algorithm is not sure about a particular message it
-    marks it <quote>fuzzy</quote> as explained above.  For the case
-    where something went really wrong, the old PO file is saved with a
-    <filename>.po.old</filename> extension.
+    marks it <quote>fuzzy</quote> as explained above.  The new PO file
+    is saved with a <filename>.po.new</filename> extension.
    </para>
   </sect2>
 

src/nls-global.mk

-# $PostgreSQL: pgsql/src/nls-global.mk,v 1.16 2009/01/02 15:15:42 petere Exp $
+# $PostgreSQL: pgsql/src/nls-global.mk,v 1.17 2009/01/09 10:54:08 petere Exp $
 
 # Common rules for Native Language Support (NLS)
 #
@@ -80,7 +80,7 @@ uninstall-po:
 
 clean-po:
 	$(if $(MO_FILES),rm -f $(MO_FILES))
-	@$(if $(PO_FILES),rm -f $(addsuffix .old, $(PO_FILES)))
+	@$(if $(wildcard po/*.po.new),rm -f po/*.po.new)
 	rm -f po/$(CATALOG_NAME).pot
 
 
@@ -93,26 +93,31 @@ maintainer-check-po: $(PO_FILES)
 init-po: po/$(CATALOG_NAME).pot
 
 
-define merge-lang
-@printf 'merging $(1) '
-@if $(MSGMERGE) $(srcdir)/po/$(1).po $< -o po/$(1).po.new $(addprefix --compendium=,$(shell find $(top_srcdir) -name $(1).po -printf '%p ')); \
-then \
-    mv $(srcdir)/po/$(1).po po/$(1).po.old; \
-    mv po/$(1).po.new $(srcdir)/po/$(1).po; \
-else \
-    echo "msgmerge for $(1) failed"; \
-    rm -f po/$(1).po.new; \
-fi
-
-endef
-
-update-po: po/$(CATALOG_NAME).pot
-ifdef MSGMERGE
-	$(foreach lang,$(LANGUAGES),$(call merge-lang,$(lang)))
+# For performance reasons, only calculate these when the user actually
+# requested update-po or a specific file.
+ifneq (,$(filter update-po %.po.new,$(MAKECMDGOALS)))
+ALL_LANGUAGES := $(shell find $(top_srcdir) -name '*.po' -printf '%f\n' | sort -u | sed 's/\.po$$//')
+all_compendia := $(shell find $(top_srcdir) -name '*.po' -printf '%p ')
 else
-	@echo "You don't have 'msgmerge'." ; exit 1
+ALL_LANGUAGES = $(AVAIL_LANGUAGES)
+all_compendia = FORCE
+FORCE:
+endif
+
+ifdef WANTED_LANGUAGES
+ALL_LANGUAGES := $(filter $(WANTED_LANGUAGES), $(ALL_LANGUAGES))
 endif
 
+update-po: $(ALL_LANGUAGES:%=po/%.po.new)
+
+$(AVAIL_LANGUAGES:%=po/%.po.new): po/%.po.new: po/%.po po/$(CATALOG_NAME).pot $(all_compendia)
+	$(MSGMERGE) $(word 1, $^) $(word 2,$^) -o $@ $(addprefix --compendium=,$(filter %/$*.po,$(wordlist 3,$(words $^),$^)))
+
+# For languages not yet available, merge against empty file, to pick
+# up translations from the compendia.
+po/%.po.new: po/$(CATALOG_NAME).pot $(all_compendia)
+	$(MSGMERGE) /dev/null $(word 1,$^) -o $@ $(addprefix --compendium=,$(filter %/$*.po,$(wordlist 2,$(words $^),$^)))
+
 
 all: all-po
 install: install-po