bug#34911: 26.1; doc about lock file names

[Eli Zaretskii <eliz@gnu.org>]

> Date: Tue, 19 Mar 2019 07:54:48 -0700 (PDT)
> From: Drew Adams <drew.adams@oracle.com>
> Cc: 34911@debbugs.gnu.org
> 
> > > I don't see documented anywhere what a lock file name looks like.
> > > I looked through both the Emacs manual and the Elisp manual.  Did I miss
> > > it somehow, or is it defined/described nowhere?
> > 
> > It is described in the node "File Locks" in the ELisp manual.
> 
> I started there.  I see nothing in that node that says
> what the name looks like.  I'm using Emacs 26.  Did
> someone perhaps add a description of it since that
> release?

Yes, as I wrote in a followup message, this information is now present
in what will be Emacs 26.2.

> The default value is "^\\.?#\\|^\\.$\\|^\\.\\.$".
> 
> \\.?# matches only the first char of an auto-save file
> name, and the first two chars of a lock file name.  It
> does not match the full name, requiring it to end with
> `#'.  That means that (1) it cannot be used as is for,
> say, font-locking such a (complete) name, and (2) as
> it is now, it can falsely identify files that are not
> auto-save or lock files.

Then maybe we need to change the default value, but that's a separate
issue.  AFAIU, the bug report was about documentation.

> Also, please add a doc string for `dired-omit-regexp',
> referring to `dired-omit-files' (where this missing doc
> will hopefully be added) and `dired-omit-extensions', as
> is done for `dired-mark-omitted', for example.

Another separate issue, unrelated to file locks, AFAIU.

> Does this clarify what I meant by "the default value only
> approximately matches auto-save files (and lock files?)"?

Yes, but I don't necessarily see that as a problem.