Miscellaneous tweaks to OpenOS (#2636)

* Parse Lua REPL inputs with an implicit "return "

If an input does not start with a leading "=", this will parse the input
with "return " appended and, if that fails, will parse as a normal
statement.

This allows for normal expressions to be entered into the repl (such as
`2 + 2`) but does mean the parse errors for malformed inputs are
confusing. For instance, `3 + ` will error at '3' rather than '<eof>'.

* Do not insert into history if a duplicate

This mimics the behaviour of shells such as bash or zsh, where
whitespace-only lines are not entered into history, nor are ones equal
to the previous input. This makes history navigation slightly easier.

src/main/resources/assets/opencomputers/loot/openos/lib/core/lua_shell.lua

@@ -101,7 +101,10 @@ while tty.isAvailable() do
   if string.sub(command, 1, 1) == "=" then
     code, reason = load("return " .. string.sub(command, 2), "=stdin", "t", env)
   else
-    code, reason = load(command, "=stdin", "t", env)
+    code, reason = load("return " .. command, "=stdin", "t", env)
+    if not code then
+      code, reason = load(command, "=stdin", "t", env)
+    end
   end
   if code then
     local result = table.pack(xpcall(code, debug.traceback))

src/main/resources/assets/opencomputers/loot/openos/lib/tty.lua

@@ -32,11 +32,11 @@ function tty.key_down_handler(handler, cursor, char, code)
   elseif code == keys.enter or code == keys.numpadenter then
     cursor:move(math.huge)
     cursor:draw("\n")
-    if #data > 0 then
+    if data:find("%S") and data ~= handler[1] then
       table.insert(handler, 1, data)
       handler[(tonumber(os.getenv("HISTSIZE")) or 10)+1]=nil
-      handler[0]=nil
     end
+    handler[0]=nil
     return nil, data .. "\n"
   elseif code == keys.up or code == keys.down then
     local ni = handler.index + (code == keys.up and 1 or -1)