Sublime text2空格替换tab键

如图想换几个空格就敲几个空格键

{ "keys": ["tab"], "command": "insert_best_completion", "args": {"default": "\t", "exact": true} },
{ "keys": ["tab"], "command": "insert_best_completion", "args": {"default": "    ", "exact": false},
"context":
[
{ "key": "setting.tab_completion", "operator": "equal", "operand": true }
]
},
{ "keys": ["tab"], "command": "reindent", "context":
[
{ "key": "setting.auto_indent", "operator": "equal", "operand": "    " },
{ "key": "selection_empty", "operator": "equal", "operand": true, "match_all": true },
{ "key": "preceding_text", "operator": "regex_match", "operand": "^$", "match_all": true },
{ "key": "following_text", "operator": "regex_match", "operand": "^$", "match_all": true }
]
},