bug#48747: 28.0.50; add project-name generic

[Dmitry Gutov <dgutov@yandex.ru>]

Hi Stephen,

On 30.05.2021 20:38, Stephen Leake wrote:
> In project.el, add a 'project-name' cl-defgeneric, to be used in prompts
> and other situations where the user is asked to identify a project.
> 
> It must return a string, which is nominally unique among the user's
> various projects.
> 
> The default could be 'project-root'.

Would you like to attach a patch that includes the places where we would 
use the new method?

project-prefixed-buffer-name?

I was also thinking project-prompt-project-dir, but we use absolute 
directory names there, so it seems difficult to incorporate, even if we 
agree to rename and update the docstring: the default implementation of 
'project-name' will supposedly be the base name of the root dir, and 
those are not always unique and easy to recognize.

Or, if the default impl returns the absolute directory name, we couldn't 
use it in project-prefixed-buffer-name.