相当于补全当前buffer里已经出现过的word, 而不用预先定义abbrev.
默认绑定到了M-/, C-M-/, 前都被已经被我用掉了, 后者在terminal下按不出来:(
不过已经启用Auto Complete的同学是不需要这个了.
写这个只是记录一下dabbrev是怎么回事.
For example, if the buffer contains `does this follow ' and you type `f o M-/', the effect is to insert `follow' because that is the last word in the buffer that starts with `fo'. A numeric argument to `M-/' says to take the second, third, etc. distinct expansion found looking backward from point. Repeating `M-/' searches for an alternative expansion by looking farther back.