git-commit-vandalism/GIT-VERSION-GEN

#!/bin/sh

GVF=GIT-VERSION-FILE
DEF_VER=v1.5.0.GIT

LF='
'

# First try git-describe, then see if there is a version file
# (included in release tarballs), then default
if VN=$(git describe --abbrev=4 HEAD 2>/dev/null) &&
   case "$VN" in
   *$LF*) (exit 1) ;;
   v[0-9]*) : happy ;;
   esac
then
	VN=$(echo "$VN" | sed -e 's/-/./g');
elif test -f version
then
	VN=$(cat version) || VN="$DEF_VER"
else
	VN="$DEF_VER"
fi

VN=$(expr "$VN" : v*'\(.*\)')

dirty=$(sh -c 'git diff-index --name-only HEAD' 2>/dev/null) || dirty=
case "$dirty" in
'')
	;;
*)
	VN="$VN-dirty" ;;
esac

if test -r $GVF
then
	VC=$(sed -e 's/^GIT_VERSION = //' <$GVF)
else
	VC=unset
fi
test "$VN" = "$VC" || {
	echo >&2 "GIT_VERSION = $VN"
	echo "GIT_VERSION = $VN" >$GVF
}