GIT-VERSION-GEN, as modified by Pat Notz: http://stackoverflow.com/questions/514188/how-would-you-include-the-current-commit-id-in-a-git-projects-files/514668#514668

VERSION-GEN

#!/bin/sh

# Tag revisions like this:
# $ git tag -a -m "Version 0.2" v0.2 HEAD

VF=VERSION-FILE
DEFAULT_VERSION=UNKNOWN

LF='
'

# First see if there is a version file (included in release tarballs),
# then try git-describe, then default.
if test -d .git -o -f .git &&
	VN=$(git describe --abbrev=4 HEAD 2>/dev/null) &&
	case "$VN" in
	*$LF*) (exit 1) ;;
	v[0-9]*)
		git update-index -q --refresh
		test -z "$(git diff-index --name-only HEAD --)" ||
		VN="$VN-mod" ;;
	esac
then
        continue
	#VN=$(echo "$VN" | sed -e 's/-/./g');
else
	VN="$DEFAULT_VERSION"
fi

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

# Show the version to the user via stderr
echo >&2 "version: $VN"

# Parse the existing VERSION-FILE 
if test -r $VF
then
	VC=$(sed -e 's/^version: //' <$VF)
else
	VC=unset
fi

# If version has changed, update VERSION-FILE
test "$VN" = "$VC" || {
	echo "version: $VN" >$VF
	echo >&2 "($VF updated)"
}