bug#70996: project-find-file defaults

[Juri Linkov <juri@linkov.net>]

>> But the problem is that in this case it drops the current file name
>> as the default value that is also useful in many cases.
>> Fortunately, the minibuffer supports a list of default values,
>> like in the following patch:
>
> This seems like a good idea, except it reverses the priority: previously,
> if file-at-point was present, it would be the default, not the current file
> name.

I mentioned in the log message that this change was intentional.

> So how about this?

The reason of this change to make the first item of the M-n list
more deterministic:

1. when there is no thing-at-point, then the first item will be
   buffer-file-name;

2. and also when there is a thing-at-point, the first item
   will remain buffer-file-name.

Otherwise, it was too unpredictable: after typing 'M-n RET'
to use buffer-file-name, it often did a wrong thing
when point happened to stay in a thing-at-point.