clean up openwrt version handling, use a separate script that is executed at the beginning of the build process, fix revision checking with git

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@9723 3c298f89-4303-0410-b956-a3cf2f4a3e73

scripts/getver.sh

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+export LANG=C
+[ -n "$TOPDIR" ] && cd $TOPDIR
+
+try_version() {
+	[ -f version ] || return 1
+	REV="$(cat version)"
+	[ -n "$REV" ]
+}
+
+try_svn() {
+	[ -d .svn ] || return 1
+	REV="$(svn info | awk '/^Revision:/ { print $2 }')"
+	REV="${REV:+r$REV}"
+	[ -n "$REV" ]
+}
+
+try_git() {
+	[ -d .git ] || return 1
+	REV="$(git-log | grep -m 1 git-svn-id | awk '{ gsub(/.*@/, "", $2); print $2 }')"
+	REV="${REV:+r$REV}"
+	[ -n "$REV" ]
+}
+
+try_version || try_svn || try_git || REV="unknown"
+echo "$REV"