Start work on porting diff kitten

tools/cmd/diff/main.go

@@ -0,0 +1,19 @@
+// License: GPLv3 Copyright: 2023, Kovid Goyal, <kovid at kovidgoyal.net>
+
+package diff
+
+import (
+	"fmt"
+
+	"kitty/tools/cli"
+)
+
+var _ = fmt.Print
+
+func main(_ *cli.Command, opts *Options, args []string) (rc int, err error) {
+	return
+}
+
+func EntryPoint(parent *cli.Command) {
+	create_cmd(parent, main)
+}