Add Version file and associated scripts

When building from source, it is desired that we embed the version
string into the resulting binaries so that we can determine exactly what
version of the sources were used.

This change adds a Version file, which always holds the latest release
version, and a configure.version script, which tries to get the version
information from Git, before falling back to using the version embedded
in the above file. The generated configure script will then have the
version embedded within it, which will then create the BUILD_VERSION
definition in config.h. Applications can then use this definition as
needed.

Makefile.am

@@ -83,6 +83,8 @@ EXTRA_DIST += \
 	LICENSE \
 	README.md \
 	config.rpath \
+	configure.version \
+	Version \
 	gettext.h \
 	usb-ids.h \
 	po/README.md

Version

@@ -0,0 +1 @@
+0.2.3

configure.ac

@@ -4,7 +4,7 @@
 #
 # SPDX-License-Identifier: GPL-2.0-only WITH Classpath-exception-2.0
 
-AC_INIT([x52pro-linux], [0.2.3], [nirenjan@gmail.com])
+AC_INIT([x52pro-linux], [m4_esyscmd_s([cat ./Version])], [nirenjan@gmail.com])
 AC_CONFIG_MACRO_DIR([m4])
 AM_INIT_AUTOMAKE([-Wall foreign subdir-objects])
 AC_REQUIRE_AUX_FILE([tap-driver.sh])
@@ -26,6 +26,8 @@ AX_GCC_FUNC_ATTRIBUTE([format])
 AX_GCC_FUNC_ATTRIBUTE([noreturn])
 AC_C_TYPEOF
 
+AC_DEFINE([BUILD_VERSION], ["m4_esyscmd([./configure.version])"], [Build version])
+
 AC_MSG_NOTICE([Detected host OS is ${host_os}])
 build_linux=no
 # Detect target system

configure.version

@@ -0,0 +1,34 @@
+#!/bin/sh
+# Use the Git version if Git is available, otherwise fallback to Version
+
+top_srcdir="${1-.}"
+test -d "${top_srcdir}" || { \
+    echo "FATAL: Could not change to top_srcdir '$1'" >&2 ; \
+    exit 1 ; \
+}
+
+version="${top_srcdir}/Version"
+
+# Use GIT_DIR if set
+if ! test -n "${GIT_DIR}"
+then
+    GIT_DIR="${top_srcdir}/.git"
+    export GIT_DIR
+fi
+
+if test -d "${GIT_DIR}"
+then
+    # Change tags like vX.Y.Z to X.Y.Z
+    DESCRIBE=$(git describe --dirty 2>/dev/null)
+fi
+
+if test ! -n "${DESCRIBE}"
+then
+    DESCRIBE="unknown-version"
+    if test -f "${version}"
+    then
+        DESCRIBE="v$(cat "${version}")"
+    fi
+fi
+
+printf "%s" "${DESCRIBE}"