refactor parallel code

openos/which.lua

@@ -0,0 +1,25 @@
+local shell = require("shell")
+
+local args = shell.parse(...)
+if #args == 0 then
+  io.write("Usage: which <program>\n")
+  return 255
+end
+
+for i = 1, #args do
+  local result, reason = shell.resolve(args[i], "lua")
+  
+  if not result then
+    result = shell.getAlias(args[i])
+    if result then
+      result = args[i] .. ": aliased to " .. result
+    end
+  end
+
+  if result then
+    print(result)
+  else
+    io.stderr:write(args[i] .. ": " .. reason .. "\n")
+    return 1
+  end
+end