Re: extraclean and admin/grammars [was Re: Git master head build failure?]

[Eli Zaretskii]

> From: Tim Cross <theophilusx@gmail.com>
> Date: Sun, 4 Apr 2021 09:52:31 +1000
> Cc: Glenn Morris <rgm@gnu.org>, Lars Ingebrigtsen <larsi@gnus.org>,
>  Stefan Monnier <monnier@iro.umontreal.ca>,
>  Emacs developers <emacs-devel@gnu.org>
> 
> On Sun, 4 Apr 2021 at 01:15, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>  "make extraclean" is only needed when doing something very drastic,
>  like switching to a very different branch.  That is an extremely rare
>  (if not improbable) use case, so IMO having everyone pay for it is
>  unjustified.
> 
> I'm not sure that assumption is correct. You can run into this issue just 
> changing commits, not switching
> branches if that commit is old enough. For example, checking out the emacs-27 
> tag. I'm also not convinced
> moving between the last released version and the current development version 
> and back again is that
> unusual and the longer things go between the last release and current 
> development head, the larger the
> difference in commits and greater the potential for this sort of issue. 

It isn't an assumption: I'm doing all of the above all the time.

Switching between branches in Emacs is not recommended, because they
diverge very quickly.  If you must do that, "make extraclean" is the
way to go.