1AC_DEFUN([AX_DETECT_GIT_HEAD], [
2	AC_SUBST(GIT_HEAD_ID)
3	AC_SUBST(GIT_HEAD)
4	AC_SUBST(GIT_HEAD_VERSION)
5	if test -f $srcdir/.git/HEAD; then
6		GIT_HEAD="$srcdir/.git/index"
7		GIT_REPO="$srcdir/.git"
8		GIT_HEAD_ID=`GIT_DIR=$GIT_REPO git describe`
9	elif test -f $srcdir/GIT_HEAD_ID; then
10		GIT_HEAD_ID=`cat $srcdir/GIT_HEAD_ID`
11	else
12		mysrcdir=`(cd $srcdir; pwd)`
13		head=`basename $mysrcdir | sed -e 's/.*-//'`
14		head2=`echo $head | sed -e 's/[^0-9a-f]//'`
15		head3=`echo $head2 | sed -e 's/........................................//'`
16		if test "x$head3" = "x" -a "x$head" = "x$head2"; then
17			GIT_HEAD_ID="$head"
18		else
19			GIT_HEAD_ID="UNKNOWN"
20		fi
21	fi
22	if test -z "$GIT_REPO" ; then
23		GIT_HEAD_VERSION="$GIT_HEAD_ID"
24	else
25	    GIT_HEAD_VERSION="\`GIT_DIR=$GIT_REPO git describe\`"
26	fi
27])
28