fix(preview): never preview binary files

[vegerot]

I think this is a bug fix instead of a new feature. The reason for this is that the current behavior overrides user choice of FZF_PREVIEW_COMMAND. No matter what preview command they provide, we never run it on binary files. However, if the user supplies no preview command, then we'll run it through bat which produces an error. This sounds like a mistake.

This commit makes the behavior when no preview command is supplied the same as the behavior when a preview command is given.

Before:

After:

[junegunn]

Do you prefer the "After:" output with mime types?

I didn't pay much attention to this because I was fine with the error message from bat, or maybe I even preferred it because it clearly showed the [bat warning] with color highlighting.

[junegunn]

We could maybe improve the output for binary files

[warning] foobar300 is a binary file
- info
- more info

[vegerot]

I didn't pay much attention to this because I was fine with the error message from bat,

Good point. Either way the current behavior is inconsistent. I agree with the suggestion in your second message.