Re: auto-save directory?

[hw <hw@adminart.net>]

On Sat, 2022-03-19 at 08:30 +0300, Jean Louis wrote:
> * hw <hw@adminart.net> [2022-03-19 07:07]:
> > 
> > Hi,
> > 
> > I'm wondering if there is a way to have emacs put all auto-save files
> > into a configurable directory.  We can set `tramp-auto-save-directory`,
> > but there doesn't seem an equivalent option for files that are not
> > remote.  I couldn't find one in either the documentation, nor the source.
> > 
> > I'd find it nicer to have all auto-save files in one place instead of
> > all over the place.  Is there such an option, and if there isn't, would
> > that be worth making a feature request?
> > ‘auto-save-file-name-transforms’
> > 
> 
> Evaluate this below to get into Info file:
> 
> (info "(emacs) Auto Save Files")
> 
>    The variable ‘auto-save-file-name-transforms’ allows a degree of
> control over the auto-save file name.  It lets you specify a series of
> regular expressions and replacements to transform the auto save file
> name.  The default value puts the auto-save files for remote files
> (*note Remote Files::) into the temporary file directory on the local
> machine.
> 
> On my side the variable ‘auto-save-file-name-transforms’ looks as
> this:
> 
> [INS] [DEL] List:
>             Regexp: \`/[^/]*:\([^/]*/\)*\([^/]*\)\'
>             Replacement: /home/data1/protected/tmp/\2
>             Uniquify: [Toggle]  on (non-nil)
> 
> 
> or as this:
> 
> auto-save-file-name-transforms ⇒ (("\\`/[^/]*:\\([^/]*/\\)*\\([^/]*\\)\\'" "/home/data1/protected/tmp/\\2" t))

Thanks!

When I let emacs evaluate above expression, it takes me to the info
node '18.6.1 Auto-Save Files' and doesn't tell me what might be
replaced by what.

Now the problem is that the regexp is kinda impossible to read and to
reasonably alter ...  It seems to match only file specifications
containing a colon and maybe other characters I would never
intentionally put into file names ...

Is there a stable database library like perls DBI for emacs, or can I
directly integrate perl into emacs?  If I save all auto-save files in
the same place, all information where they were originally edited gets
lost.  It might be nice if I could store some meta-information along
with the file in a database.