oups! .pot is for Template, so it was the right extension

.gitattributes

@@ -250,7 +250,7 @@ bureau/locales/es_VE/LC_MESSAGES/manual.po -text
 bureau/locales/es_VE/LC_MESSAGES/messages.po -text
 bureau/locales/fr_FR/LC_MESSAGES/manual.po -text
 bureau/locales/fr_FR/LC_MESSAGES/messages.po -text
-bureau/locales/manual.po -text
+bureau/locales/manual.pot -text
 bureau/locales/messages.pot -text
 bureau/style.css -text
 debian/.cvsignore -text

bureau/locales/Makefile

@@ -1,12 +1,12 @@
-all: messages.po */LC_MESSAGES/messages.po */LC_MESSAGES/manual.po
+all: messages.pot */LC_MESSAGES/messages.po */LC_MESSAGES/manual.po
 
 
 messages.po: ../*/*.php
 	touch $@
 	xgettext --force-po --omit-header --keyword=__ --keyword=_  -L PHP --from-code iso-8859-1 -j $^
 
-%/LC_MESSAGES/messages.po: messages.po
+%/LC_MESSAGES/messages.po: messages.pot
 	msgmerge -v -U $@ $^
 
-%/LC_MESSAGES/manual.po: manual.po
+%/LC_MESSAGES/manual.po: manual.pot
 	msgmerge -v -U $@ $^