an exception erases source file

[s-trooper]

if target buffer is the same as source and the formatter throws an error, then the target and the source are empty and the original source will be lost.
to mitigate this problem there are a --force argument but this is by default false.

1. it is counter intuitive that per default the files are erased.
   could --force be set to true per default?
2. why an extra argument at all? i don't see any user case that should allows formatter to destroy source files.
   could --force argument be removed and the original source be kept in the exception case?

P.S: i will make PR for case 1. but honestly i would prefer 2.

[jindraivanek]

Agree with 2.

[nojaf]

I'm also in favor of 2.
Vote +1 for option 1, Hooray for option 2 and -1 if you don't agree.

[vasily-kirichenko]

Fixed via #268