autogen.sh: update package version when necessary

Force update of PACKAGE_VERSION from "git describe" when necessary.

autogen.sh

@@ -4,6 +4,19 @@
 srcdir=`dirname "$0"`
 [ -z "$srcdir" ] || cd "$srcdir"
 
+# sed program
+SED=${SED-sed}
+
+# Check whether the version needs to be updated from git infos
+if [ -d ".git" ] && [ -d "autom4te.cache" ]; then
+  git_describe=`git describe 2>/dev/null || echo devel`
+  for f in autom4te.cache/output.*; do
+    [ -f "$f" ] || continue
+    pkg_ver=`${SED} -n "s/^PACKAGE_VERSION='\(.*\)'\$/\1/p" "$f"`
+    [ "x$pkg_ver" = "x$git_describe" ] || rm -rf "autom4te.cache"
+  done
+fi
+
 echo "Generating configure files... may take a while."
 
 autoreconf --install --force && \