[PATCH v2 11/17] build: define RELEASE_YEAR with AC_SUBST

Rather than reading it dynamically from the ChangeLog -- that,
remember, is only a dummy in a Git checkout!  To avoid risking
the definition to get out-of-sync, let's enhance the maintainer
target 'update-copyright' to update it automatically (the same
way it's done in the Automake build system).

* configure.ac (RELEASE_YEAR): New AC_SUBST'd variable.
* cfg.mk (update-release-year): New maintainer-specific target
to automatically update the value of that variable.
(update-copyright): Depend on the new target.
* bin/local.mk (RELEASE_YEAR): Drop definition.
(edit): Simplify quoting of $(RELEASE_YEAR).
* lib/Makefile.am (RELEASE_YEAR): Drop definition.
(m4sugar/version.m4): Simplify quoting of $(RELEASE_YEAR).

Signed-off-by: Stefano Lattarini <[email protected]>
---
 bin/local.mk    |  6 +-----
 cfg.mk          | 12 ++++++++++++
 configure.ac    |  5 +++++
 lib/Makefile.am |  6 +-----
 4 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/bin/local.mk b/bin/local.mk
index 57983f8..ff7b2cf 100644
--- a/bin/local.mk
+++ b/bin/local.mk
@@ -38,10 +38,6 @@ EXTRA_DIST += \
 # Files that should be removed, but which Automake does not know.
 MOSTLYCLEANFILES += $(bin_SCRIPTS) bin/autoconf.in bin/*.tmp
 
-# Get the release year from ChangeLog.
-RELEASE_YEAR = \
-  `sed 's/^\([0-9][0-9][0-9][0-9]\).*/\1/;q' $(top_srcdir)/ChangeLog`
-
 ## ------------- ##
 ## The scripts.  ##
 ## ------------- ##
@@ -60,7 +56,7 @@ edit = sed \
 	-e 's|@M4_DEBUGFILE[@]|$(M4_DEBUGFILE)|g' \
 	-e 's|@M4_GNU[@]|$(M4_GNU)|g' \
 	-e 's|@AWK[@]|$(AWK)|g' \
-	-e 's|@RELEASE_YEAR[@]|'$(RELEASE_YEAR)'|g' \
+	-e 's|@RELEASE_YEAR[@]|$(RELEASE_YEAR)|g' \
 	-e 's|@VERSION[@]|$(VERSION)|g' \
 	-e 's|@PACKAGE_NAME[@]|$(PACKAGE_NAME)|g' \
 	-e 's|@configure_input[@]|Generated from [email protected]; do not edit by hand.|g'
diff --git a/cfg.mk b/cfg.mk
index a57196e..980eab9 100644
--- a/cfg.mk
+++ b/cfg.mk
@@ -123,6 +123,18 @@ update-copyright-env = \
   UPDATE_COPYRIGHT_USE_INTERVALS=1 \
   UPDATE_COPYRIGHT_MAX_LINE_LENGTH=72
 
+update-copyright: update-release-year
+update-release-year:
+	$(AM_V_GEN):; \
+	if test -n "$$UPDATE_COPYRIGHT_YEAR"; then \
+	   current_year=$$UPDATE_COPYRIGHT_YEAR; \
+	else \
+	  current_year=`date +%Y` && test -n "$$current_year" \
+	    || { echo "$@: cannot get current year" >&2; exit 1; }; \
+	fi; \
+	sed -i "/^RELEASE_YEAR=/s/=.*$$/=$$current_year/" configure.ac
+.PHONY: update-release-year
+
 # Prevent incorrect NEWS edits.
 old_NEWS_hash = 8532b4ed4fb456eb71071a5cf8c258d4
 
diff --git a/configure.ac b/configure.ac
index b3f3fa9..91f6a74 100644
--- a/configure.ac
+++ b/configure.ac
@@ -27,6 +27,11 @@ AC_CONFIG_AUX_DIR([build-aux])
 
 AM_INIT_AUTOMAKE([1.11 dist-xz readme-alpha no-texinfo.tex std-options])
 
+# Keep this on a line of its own, since it must be found and processed
+# by the 'update-release-year' rule in our Makefile.
+RELEASE_YEAR=2013
+AC_SUBST([RELEASE_YEAR])
+
 AB_INIT
 
 # We use '/bin/sh -n script' to check that there are no syntax errors
diff --git a/lib/Makefile.am b/lib/Makefile.am
index 1004622..2b4c494 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -162,10 +162,6 @@ nodist_m4sugarlib_DATA = \
 
 CLEANFILES += $(nodist_m4sugarlib_DATA)
 
-# Get the release year from ../ChangeLog.
-RELEASE_YEAR = \
-  `sed 's/^\([0-9][0-9][0-9][0-9]\).*/\1/;q' $(top_srcdir)/ChangeLog`
-
 # The ':;' in the second line of the recipe works around a redirected
 # compound command bash exit status bug.
 m4sugar/version.m4: Makefile
@@ -182,7 +178,7 @@ m4sugar/version.m4: Makefile
 	  echo 'm4_define([m4_PACKAGE_STRING],    [$(PACKAGE_STRING)])' && \
 	  echo 'm4_define([m4_PACKAGE_BUGREPORT], [$(PACKAGE_BUGREPORT)])' && \
 	  echo 'm4_define([m4_PACKAGE_URL],       [$(PACKAGE_URL)])' && \
-	  echo 'm4_define([m4_PACKAGE_YEAR],      ['$(RELEASE_YEAR)'])'; \
+	  echo 'm4_define([m4_PACKAGE_YEAR],      [$(RELEASE_YEAR)])'; \
 	} > $@-t
 	mv $@-t $@
 
-- 
1.8.3.rc0.19.g7e6a0cc