Convert 4 spaces to 2 spaces in Sublime Text

4spaces_to_2spaces.sublime-macro

[
  {
		"args": null,
		"command": "select_all"
	},
	{
		"args":
		{
			"set_translate_tabs": true
		},
		"command": "unexpand_tabs"
	},
	{
		"args": {
			"setting": "tab_size",
			"value": 2
		},
		"command": "set_setting"
	},
	{
		"args":
		{
			"set_translate_tabs": true
		},
		"command": "expand_tabs"
	}
]

Default (OSX).sublime-keymap

[
  { "keys": ["super+shift+alt+s"], "command": "run_macro_file", "args" : {"file" : "Packages/User/4spaces_to_2spaces.sublime-macro"} }
]