Update git-diff-script.

This uses the fixed rev-parse to allow passing diff options to the
underlying diff command.  For example:

    $ git diff -r HEAD

shows the output in raw-diff format, and

    $ git diff -p -R HEAD | git apply

generates a patch to go back from your working tree to HEAD commit
(i.e. an expensive way to say "git checkout -f HEAD").

At the same time, it accidentally removes the use of shell arrays.

Signed-off-by: Junio C Hamano <junkio@cox.net>

git-diff-script

@@ -1,23 +1,35 @@
 #!/bin/sh
-rev=($(git-rev-parse --revs-only "$@")) || exit
-flags=($(git-rev-parse --no-revs --flags "$@"))
-files=($(git-rev-parse --no-revs --no-flags "$@"))
-case "${#rev[*]}" in
-0)
-	git-diff-files -M -p "$@";;
-1)
-	git-diff-cache -M -p "$@";;
-2)
-	case "${rev[1]}" in
-	^?*)
-		begin=$(echo "${rev[1]}" | tr -d '^')
-		end="${rev[0]}" ;;
-	*)
-		begin="${rev[0]}"
-		end="${rev[1]}"	;;
-	esac
-	git-diff-tree -M -p $flags $begin $end $files;;
+#
+# Copyright (c) 2005 Linus Torvalds
+# Copyright (c) 2005 Junio C Hamano
+
+rev=$(git-rev-parse --revs-only --no-flags --sq "$@") || exit
+flags=$(git-rev-parse --no-revs --flags --sq "$@")
+files=$(git-rev-parse --no-revs --no-flags --sq "$@")
+
+: ${flags:="'-M' '-p'"}
+
+case "$rev" in
+?*' '?*' '?*)
+	die "I don't understand"
+	;;
+?*' '^?*)
+	begin=$(expr "$rev" : '.*^.\([0-9a-f]*\).*') &&
+	end=$(expr "$rev" : '.\([0-9a-f]*\). .*') || exit
+	cmd="git-diff-tree $flags $begin $end $files"
+	;;
+?*' '?*)
+	cmd="git-diff-tree $flags $rev $files"
+	;;
+?*' ')
+	cmd="git-diff-cache $flags $rev $files"
+	;;
+'')
+	cmd="git-diff-files $flags $files"
+	;;
 *)
-	echo "I don't understand"
-	exit 1;;
+	die "I don't understand $*"
+	;;
 esac
+
+eval "$cmd"