Generate version string

This grabs code from GNU ease.js.

* .gitignore (build-aux/): Ignore all but `vergen'.
* build-aux/vergen: Add file  copied from GNU ease.js.
* configure.ac: Use it.

.gitignore

@@ -1,5 +1,6 @@
 # generated by autotools
-build-aux/
+build-aux/*
+!build-aux/vergen
 aclocal.m4
 autom4te.cache
 configure

build-aux/vergen

@@ -0,0 +1,38 @@
+#!/bin/sh
+# Generates version string
+#
+#  Copyright (C) 2012, 2013, 2014 Free Software Foundation, Inc.
+#
+#  This file is part of GNU ease.js.
+#
+#  This program is free software: you can redistribute it and/or modify
+#  it under the terms of the GNU General Public License as published by
+#  the Free Software Foundation, either version 3 of the License, or
+#  (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+##
+
+# for distributions
+if [ -s version ]; then
+  cat version
+  exit
+fi
+
+git rev-parse --show-toplevel >/dev/null 2>&1 || {
+  echo 'fatal: git repository is not available'
+}
+
+version="$( git describe --match='[0-9]\.*' --abbrev=7 HEAD 2>/dev/null )"
+git update-index -q --refresh
+verstr="${version:-0.0.0}"
+test -z "$( git diff-index --name-only HEAD)" || verstr="$verstr-dirty"
+
+echo -n "$verstr"
+

configure.ac

@@ -18,10 +18,26 @@
 #  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ##
 
-AC_INIT([shspec], [0.0.1-dev], [mtg@gnu.org])
+# version string is dynamically generated
+m4_define([ver], m4_esyscmd(build-aux/vergen))
+m4_if(ver, [], [m4_exit(1)])
+
+AC_INIT([shspec], [ver], [mtg@gnu.org])
 AC_CONFIG_AUX_DIR([build-aux])
 AM_INIT_AUTOMAKE([foreign])
 
+# provide more granular version numbers based on the version string, using
+# the format MAJOR.MINOR.REV[-SUFFIX], where SUFFIX can itself contain
+# dashes (and often will)
+m4_define([ver_split],
+  m4_split(
+    patsubst(AC_PACKAGE_VERSION, [^\([^-]+\)-], [\1.]),
+    [\.]))
+AC_SUBST(MAJOR, m4_argn(1, ver_split))
+AC_SUBST(MINOR, m4_argn(2, ver_split))
+AC_SUBST(REV, m4_argn(3, ver_split))
+AC_SUBST(SUFFIX, m4_argn(4, ver_split))
+
 AC_CHECK_PROGS(XXD, [xxd])
 test "$XXD" || AC_MSG_ERROR([missing xxd])