i18n: avoid substitution of PYFILES at runtime for readability of output

This substitution decreases readability of "make update-pot" output,
because PYFILES consists of many files.

This patch makes "make update-pot" show "find mercurial hgext doc
-name '*.py'" instead of many *.py files at runtime.

Makefile

@@ -9,7 +9,8 b' PYTHON=python'
 $(eval HGROOT := $(shell pwd))
 HGPYTHONS ?= $(HGROOT)/build/pythons
 PURE=
-PYFILES:=$(shell find mercurial hgext doc -name '*.py')
+PYFILESCMD=find mercurial hgext doc -name '*.py'
+PYFILES:=$(shell $(PYFILESCMD))
 DOCFILES=mercurial/help/*.txt
 export LANGUAGE=C
 export LC_ALL=C
@@ -145,7 +146,7 b' i18n/hg.pot: $(PYFILES) $(DOCFILES) i18n'
         # parse them even though they are not marked for translation.
         # Extracting with an explicit encoding of ISO-8859-1 will make
         # xgettext "parse" and ignore them.
-	echo $(PYFILES) | xargs \
+	$(PYFILESCMD) | xargs \
 	  xgettext --package-name "Mercurial" \
 	  --msgid-bugs-address "<[e-mail]>" \
 	  --copyright-holder "Matt Mackall <[e-mail]> and others" \