bug#41572: 28.0.50; [PATCH] Support plain project marked with file .emacs-project

[Zihao Zhu <cjpeople2013@gmail.com>]

Besides Perforce, Darcs and Fossil aren't supported yet. If we have 
plain project, we don't have to fiddle around with different sorts of VC.

A more netrual suggestion: We can make project-find-functions a 
defcustom first.


On 2020/5/29 上午3:58, Dmitry Gutov wrote:
> On 28.05.2020 18:46, Zihao Zhu wrote:
>> If I have a project.el based plugin,  and I wanna use them in a 
>> directory not under VC. Add an mark to force project.el work is 
>> easier than modify the source of plugin or initialize VC system.
>
> The problem with that, is that next time we'll get a report that these 
> projects are too slow. Or that people who added .emacs-project file in 
> the middle of a VC repository suddenly get significantly worse file 
> listing performance, without expecting it.
>
> So we'd have to add caching to the file list, and then some 
> invalidation, probably. And I'm not a fan of having manual 
> invalidation commands.
>
> That's why I'm wary of adding such a separate project type by default, 
> especially when the initial proposal doesn't add any of the advanced 
> features described above, or explains how they won't be necessary.
>
> But opinions welcome.
>
>> And this  can also be used as a side solution to use project.el in 
>> unsupported VCed project in Emacs (AFAIK, P4(Perforce) is not 
>> supported by vc.el).
>
> Perhaps we could add Perforce support to project-vc instead?
>
> There was a vc-p4 packages somewhere out there. But if it's entirely 
> dead, we could add such support to project--vc-list-files directly.
>
> Or, better yet, release it as a project-p4 package on GNU ELPA.
>
> That all depends, of course, on whether the p4 command line utility 
> also has the means to quickly list repository files and add ignores.
>
>> IMO, a plain project is like a transient project.
>
> One difference is, nobody really expects much from "transient" 
> projects. And this type of project is only applied when the directory 
> is not covered by any other kind of project.