bug#66317: Project mode-line

[Juri Linkov]

>> There is another problem: calling 'project-name' while evaluating
>> 'mode-line-format' often changes the coding system mode-line indicator
>> from U (utf-8) to raw-text during saving the current buffer.
>>
>> Here is a backtrace:
>>
>> - project-name
>> - project--value-in-dir (that uses with-temp-buffer)
>> - hack-dir-local-variables-non-file-buffer
>> - hack-local-variables-apply
>>
>> Then in the last function the coding system is broken
>> in two different ways:
>>
>> 1. by 'hack-one-local-variable' in `emacs -Q`
>
> How and where?
>
>> 2. by (run-hooks 'hack-local-variables-hook)
>>    in buffers where flyspell-mode is enabled
>>    'flyspell-hack-local-variables-hook' breaks
>>    the coding system too.
>
> Why?

The bug occurs when multiple lines are displayed in the echo area.
Then '(:eval (project-mode-line-format)) is called twice.
At the end of the first call 'buffer-file-coding-system'
is still correct: utf-8.  But at the beginning of the
second call it's already wrong: raw-text.

I guess it was a mistake to allow specifying the project name
in .dir-locals.el.  A better place would be in ~/.emacs.d/projects.