scripts: Enhance portability of cp_s

Eliminate bashisms; target the Bourne shell and a safer subset of POSIX
utilities.  Furthermore, properly handle pathnames with whitespace.

scripts/cp_s

@@ -1,19 +1,26 @@
-#!/bin/bash
-# This script emulates the cp -s command, which Mac OS doesn't support.
+#!/bin/sh
+# Emulate cp -s for systems without coreutils
 
-set -e
+if test -z "$1" || test -z "$2" ; then
+	echo "usage: ${0} srcdir destdir" >&2
+	exit 1
+fi
 
-pushd $1 > /dev/null
-SRCDIR=`pwd`
-DIRS=`find . -type d`
-FILES=`find . -type f`
-popd > /dev/null
+# Portability notes:
+# - Avoid set -e given its ambiguous interaction with subshells.
+# - Not all shells update $PWD as required by POSIX.
+#   Use the pwd builtin instead.
+# - Command substitution strips all trailing newlines.
+#   Preserve trailing newlines by appending a safety character and then
+#   removing it with parameter substitution, along with the newline
+#   appended by pwd itself.
 
-pushd $2 > /dev/null
-for i in $DIRS; do
-  mkdir -p $i
-done
-for i in $FILES; do
-  ln -f -s $SRCDIR/$i $i
-done
-popd > /dev/null
+mkdir -p "$2" &&
+destdir=`cd "$2" && pwd && echo x` &&
+destdir=${destdir%??} &&
+
+cd "$1" &&
+srcdir=`pwd && echo x` &&
+srcdir=${srcdir%??} &&
+find . -type d -exec mkdir -p "${destdir}/{}" \; &&
+find . -type f -exec ln -sf "${srcdir}/{}" "${destdir}/{}" \;