Basic Makefile and infrastructure to support dist tarballs.

Borrowing slightly from git.git, derive a VERSION-FILE
from the current state of user's git working directory.
The VERSION is derived relative to the latest git annotated
tag object (using git-describe) and includable either in
shell scripts or in Makefiles.

The basic 'make dist' target generates a .tar.gz and a .zip
file named by the detected version.

Also include a basic clean target and dummy test target.

Signed-off-by: Emil Sit <sit@emilsit.net>

GEN-VERSION-FILE

@@ -0,0 +1,38 @@
+#!/bin/sh
+# Based on git's GIT-VERSION-GEN.
+
+VF=VERSION-FILE
+DEF_VER=v2.2
+
+LF='
+'
+
+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="$VN-dirty" ;;
+	esac
+then
+	VN=$(echo "$VN" | sed -e 's/-/./g');
+else
+	VN="$DEF_VER"
+fi
+
+VN=$(expr "$VN" : v*'\(.*\)')
+
+if test -r $VF
+then
+	VC=$(sed -e 's/^VERSION=//' <$VF)
+else
+	VC=unset
+fi
+test "$VN" = "$VC" || {
+	echo >&2 "VERSION=$VN"
+	echo "VERSION=$VN" >$VF
+}
+
+