[PATCH v4] build: write VERSION file containing $(VERSION) string

[Tomi Ollila <tomi.ollila@iki.fi>]

This version file will be as prerequisite to the target files
that use the version info for some purpose, like printing
it to the user to examine. The contents of the VERSION file
is seldom read by the build system itself as the $(VERSION)
variable has the same information.
---

ctested also with:
       mv .git .x
       make
       cat VERSION version
       mv .x .git
       make
       cat VERSION version

 Makefile.local | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/Makefile.local b/Makefile.local
index 174506c..65c91cb 100644
--- a/Makefile.local
+++ b/Makefile.local
@@ -21,7 +21,13 @@ endif
 VERSION:=$(shell cat ${srcdir}/version)
 ifeq ($(filter release release-message pre-release update-versions,$(MAKECMDGOALS)),)
 ifeq ($(IS_GIT),yes)
-VERSION:=$(shell git describe --match '[0-9.]*'|sed -e s/_/~/ -e s/-/+/ -e s/-/~/)
+# Also write VERSION file in case its contents differ from $(VERSION)
+VERSION:=$(shell\
+	gv=`git describe --match '[0-9.]*'|sed -e s/_/~/ -e s/-/+/ -e s/-/~/`;\
+	test -f VERSION || touch VERSION;\
+	read fv < VERSION;\
+	test x"$$fv" = x"$$gv" || echo "$$gv" > VERSION;\
+	echo "$$gv")
 endif
 endif
 
@@ -69,6 +75,11 @@ ifeq ($(shell cat .first-build-message 2>/dev/null),)
 endif
 endif
 
+# Depend (also) on 'version' file. In case of ifeq ($(IS_GIT),yes)
+# this file may already have been updated.
+VERSION: version
+	echo $(VERSION) > $@
+
 $(TAR_FILE):
 	if git tag -v $(VERSION) >/dev/null 2>&1; then \
            ref=$(VERSION); \
@@ -280,6 +291,8 @@ notmuch_client_srcs =		\
 
 notmuch_client_modules = $(notmuch_client_srcs:.c=.o)
 
+notmuch.o: VERSION
+
 notmuch: $(notmuch_client_modules) lib/libnotmuch.a util/libutil.a parse-time-string/libparse-time-string.a
 	$(call quiet,CXX $(CFLAGS)) $^ $(FINAL_LIBNOTMUCH_LDFLAGS) -o $@
 
@@ -318,7 +331,7 @@ install-desktop:
 	desktop-file-install --mode 0644 --dir "$(DESTDIR)$(desktop_dir)" notmuch.desktop
 
 SRCS  := $(SRCS) $(notmuch_client_srcs)
-CLEAN := $(CLEAN) notmuch notmuch-shared $(notmuch_client_modules) notmuch.elc
+CLEAN := $(CLEAN) VERSION notmuch notmuch-shared $(notmuch_client_modules)
 
 DISTCLEAN := $(DISTCLEAN) .first-build-message Makefile.config
 
-- 
1.8.4.2