[PATCH v2] 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.
---

This is version 2 of id:1390689800-16654-1-git-send-email-tomi.ollila@iki.fi

in case of IS_GIT = yes, the contents of file VERSION is compared what
git describe returns and if this differs then VERSION file is updated.

 Makefile.local | 10 +++++++++-

diff --git a/Makefile.local b/Makefile.local
index c85e09c..96f39be 100644
--- a/Makefile.local
+++ b/Makefile.local
@@ -21,7 +21,8 @@ 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=`exec 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 +70,11 @@ 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) > version
+
 $(TAR_FILE):
 	if git tag -v $(VERSION) >/dev/null 2>&1; then \
            ref=$(VERSION); \
@@ -280,6 +286,8 @@ 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 $@
 
-- 
1.8.4.2