Make inter-release --version output more useful.

Now, each unofficial build has a version "number" like 2.61a-19-58dd,
which indicates that it is built using the 19th change set
(in _some_ repository) following the "v2.61a" tag, and that 58dd
is a prefix of the commit SHA1.
* build-aux/git-version-gen: New file.
* configure.ac: Run it to set the version.
(AM_INIT_AUTOMAKE): Don't check NEWS here.
* Makefile.am (dist-hook): Arrange so that .version appears only
in distribution tarballs, never in a checked-out repository.
* .gitignore: Add .version here, too.  Just in case.
* tests/Makefile.am ($(srcdir)/package.m4): Depend on Makefile,
not configure.ac, now that the version number changes automatically.

Ensure that $(VERSION) is up to date for dist-related targets.
* GNUmakefile: Arrange to rerun autoconf, if the version reported by
git-version-gen doesn't match $(VERSION), but only for dist targets.

1 files changed, 14 insertions, 0 deletions

diff --git a/GNUmakefile b/GNUmakefile
index 7a1b0d2b..30fdcc42 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -39,6 +39,20 @@ ifeq ($(have-Makefile),yes)
 export TAR_OPTIONS = --owner=0 --group=0 --numeric-owner
 
 include Makefile
+
+# Ensure that $(VERSION) is up to date for dist-related targets, but not
+# for others: rerunning autoconf and recompiling everything isn't cheap.
+ifeq (0,$(MAKELEVEL))
+  _is-dist-target = $(filter dist% alpha beta major,$(MAKECMDGOALS))
+  ifneq (,$(_is-dist-target))
+    _curr-ver := $(shell build-aux/git-version-gen .version)
+    ifneq ($(_curr-ver),$(VERSION))
+      $(info INFO: rerunning autoconf for new version string: $(_curr-ver))
+      dummy := $(shell rm -rf autom4te.cache; $(AUTOCONF))
+    endif
+  endif
+endif
+
 include $(srcdir)/Makefile.cfg
 include $(srcdir)/Makefile.maint