diff --git a/do b/do
new file mode 100644
index 0000000..1a3c693
--- /dev/null
+++ b/do
@@ -0,0 +1,178 @@
+#!/bin/sh
+#
+# A minimal alternative to djb redo that doesn't support incremental builds.
+# For the full version, visit http://github.com/apenwarr/redo
+#
+# The author disclaims copyright to this source file and hereby places it in
+# the public domain. (2010 12 14)
+#
+
+# By default, no output coloring.
+green=""
+bold=""
+plain=""
+
+if [ -n "$TERM" -a "$TERM" != "dumb" ] && tty <&2 >/dev/null 2>&1; then
+	green="$(printf '\033[32m')"
+	bold="$(printf '\033[1m')"
+	plain="$(printf '\033[m')"
+fi
+
+_dirsplit()
+{
+	base=${1##*/}
+	dir=${1%"$base"}
+}
+
+dirname()
+(
+	_dirsplit "$1"
+	dir=${dir%/}
+	echo "${dir:-.}"
+)
+
+_dirsplit "$0"
+export REDO=$(cd "${dir:-.}" && echo "$PWD/$base")
+
+DO_TOP=
+if [ -z "$DO_BUILT" ]; then
+	DO_TOP=1
+	[ -n "$*" ] || set all  # only toplevel redo has a default target
+	export DO_BUILT="$PWD"/.do_built
+	: >>"$DO_BUILT"
+	echo "Removing previously built files..." >&2
+	sort -u "$DO_BUILT" | tee "$DO_BUILT.new" |
+	while read f; do printf "%s\0%s.did\0" "$f" "$f"; done |
+	xargs -0 rm -f 2>/dev/null
+	mv "$DO_BUILT.new" "$DO_BUILT"
+	DO_PATH="$DO_BUILT".dir
+	export PATH="$DO_PATH":"$PATH"
+	rm -rf "$DO_PATH"
+	mkdir "$DO_PATH"
+	for d in redo redo-ifchange; do
+		ln -s "$REDO" "$DO_PATH/$d";
+	done
+	[ -e /bin/true ] && TRUE=/bin/true || TRUE=/usr/bin/true
+	for d in redo-ifcreate redo-stamp redo-always; do
+		printf '#!/bin/sh\n' > "$DO_PATH/$d";
+		chmod a+x "$DO_PATH/$d";
+	done
+fi
+
+
+_find_dofile_pwd()
+{
+	dofile=default."$1".do
+	while :; do
+		dofile=default.${dofile#default.*.}
+		[ -e "$dofile" -o "$dofile" = default.do ] && break
+	done
+	ext=${dofile#default}
+	ext=${ext%.do}
+	base=${1%$ext}
+}
+
+
+_find_dofile()
+{
+	local prefix=
+	while :; do
+		_find_dofile_pwd "$1"
+		[ -e "$dofile" ] && break
+		[ "$PWD" = "/" ] && break
+		target=${PWD##*/}/"$target"
+		tmp=${PWD##*/}/"$tmp"
+		prefix=${PWD##*/}/"$prefix"
+		cd ..
+	done
+	base="$prefix""$base"
+}
+
+
+_run_dofile()
+{
+	export DO_DEPTH="$DO_DEPTH  "
+	export REDO_TARGET="$PWD"/"$target"
+	local line1
+	set -e
+	read line1 <"$PWD/$dofile" || true
+	cmd=${line1#"#!/"}
+	if [ "$cmd" != "$line1" ]; then
+		/$cmd "$PWD/$dofile" "$@" >"$tmp.tmp2"
+	else
+		:; . "$PWD/$dofile" >"$tmp.tmp2"
+	fi
+}
+
+
+_do()
+{
+	local dir="$1" target="$2" tmp="$3"
+	if [ ! -e "$target" ] || [ -d "$target" -a ! -e "$target.did" ]; then
+		printf '%sdo  %s%s%s%s\n' \
+			"$green" "$DO_DEPTH" "$bold" "$dir$target" "$plain" >&2
+		echo "$PWD/$target" >>"$DO_BUILT"
+		dofile="$target".do
+		base="$target"
+		ext=
+		[ -e "$target.do" ] || _find_dofile "$target"
+		if [ ! -e "$dofile" ]; then
+			echo "do: $target: no .do file" >&2
+			return 1
+		fi
+		[ ! -e "$DO_BUILT" ] || [ ! -d "$(dirname "$target")" ] ||
+		: >>"$target.did"
+		( _run_dofile "$target" "$base" "$tmp.tmp" )
+		rv="$?"
+		if [ $rv != 0 ]; then
+			printf "do: %s%s\n" "$DO_DEPTH" \
+				"$dir$target: got exit code $rv" >&2
+			rm -f "$tmp.tmp" "$tmp.tmp2" "$DO_BUILT"
+			return "$rv"
+		fi
+		mv "$tmp.tmp" "$target" 2>/dev/null ||
+		! test -s "$tmp.tmp2" ||
+		mv "$tmp.tmp2" "$target" 2>/dev/null
+		rm -f "$tmp.tmp2"
+	else
+		echo "do  $DO_DEPTH$target exists." >&2
+	fi
+}
+
+
+# Make corrections for directories that don't actually exist yet.
+_dir_shovel()
+{
+	local dir base
+	xdir="$1" xbase="$2" xbasetmp="$2"
+	while [ ! -d "$xdir" -a -n "$xdir" ]; do
+		_dirsplit "${xdir%/}"
+		xbasetmp=${base}__"$xbase"
+		xdir="$dir" xbase="$base"/"$xbase"
+		echo "xbasetmp='$xbasetmp'" >&2
+	done
+}
+
+
+_redo()
+{
+	set +e
+	for i in "$@"; do
+		_dirsplit "$i"
+		_dir_shovel "$dir" "$base"
+		dir="$xdir" base="$xbase" basetmp="$xbasetmp"
+		( cd "$dir" && _do "$dir" "$base" "$basetmp" )
+		[ "$?" = 0 ] || return 1
+	done
+}
+
+
+_redo "$@"
+[ "$?" = 0 ] || exit 1
+
+if [ -n "$DO_TOP" ]; then
+	echo "Removing stamp files..." >&2
+	[ ! -e "$DO_BUILT" ] ||
+	while read f; do printf "%s.did\0" "$f"; done <"$DO_BUILT" |
+	xargs -0 rm -f 2>/dev/null
+fi