Directory reorg: move code into redo/, generate binaries in bin/.

It's time to start preparing for a version of redo that doesn't work
unless we build it first (because it will rely on C modules, and
eventually be rewritten in C altogether).

To get rolling, remove the old-style symlinks to the main programs, and
rename those programs from redo-*.py to redo/cmd_*.py.  We'll also move
all library functions into the redo/ dir, which is a more python-style
naming convention.

Previously, install.do was generating wrappers for installing in
/usr/bin, which extend sys.path and then import+run the right file.
This made "installed" redo work quite differently from running redo
inside its source tree.  Instead, let's always generate the wrappers in
bin/, and not make anything executable except those wrappers.

Since we're generating wrappers anyway, let's actually auto-detect the
right version of python for the running system; distros can't seem to
agree on what to call their python2 binaries (sigh). We'll fill in the
right #! shebang lines.  Since we're doing that, we can stop using
/usr/bin/env, which will a) make things slightly faster, and b) let us
use "python -S", which tells python not to load a bunch of extra crap
we're not using, thus improving startup times.

Annoyingly, we now have to build redo using minimal/do, then run the
tests using bin/redo.  To make this less annoying, we add a toplevel
./do script that knows the right steps, and a Makefile (whee!) for
people who are used to typing 'make' and 'make test' and 'make clean'.

do

@@ -0,0 +1,83 @@
+#!/bin/sh
+#
+# Bootstrap script, so we can build and test redo using (mostly) redo.
+# Before redo is available, we have to use minimal/do to build it.  After
+# that, we switch to real redo.
+#
+# NOTE: Don't use this as a model for your own redo projects!  It's friendly
+# to provide a 'do' script at the top of your project for people who haven't
+# installed redo, but that script is usually just a copy of minimal/do,
+# because your project probably doesn't have the same bootstrap problem that
+# redo itself does.
+#
+
+die() {
+	echo "$0:" "$@" >&2
+	exit 42
+}
+
+usage() {
+	echo "Usage: $0 [redo-args...] <target>" >&2
+	echo "   where valid targets are: build all test install clean" >&2
+	echo "   and redo-args are optional args for redo, like -j10, -x" >&2
+	exit 10
+}
+
+mydir=$(dirname "$0")
+cd "$mydir" || die "can't find self in dir: $mydir"
+
+args=
+while [ "$1" != "${1#-}" ]; do
+	args="$args $1"
+	shift
+done
+
+if [ "$#" -gt 1 ]; then
+	usage
+fi
+
+if [ -n "$args" -a "$#" -lt 1 ]; then
+	usage
+fi
+
+if [ "$#" -lt 1 ]; then
+	# if no extra args given, use a default target
+	target=all
+else
+	target=$1
+fi
+
+
+build() {
+	./minimal/do -c bin/all || die "failed to compile redo."
+	bin/redo bin/all || die "redo failed self test."
+}
+
+clean() {
+	./minimal/do -c clean || die "failed to clean."
+	rm -rf .redo .do_built .do_built.dir
+}
+
+case $target in
+	build)
+		build
+		;;
+	all|install)
+		build && bin/redo $args "$target"
+		;;
+	test)
+		# Test both redo and minimal/do
+		build
+		PATH=$PWD/redo:$PATH minimal/do test || die "minimal/do test failed"
+		clean
+		build
+		bin/redo $args test || die "redo test failed"
+		;;
+	clean)
+		clean
+		;;
+	*)
+		echo "$0: unknown target '$target'" >&2
+		exit 11
+		;;
+esac