dpkg -l emacs-snapshot returns:

Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-==============-===========================================-============-========================================
ii emacs-snapshot 2:20221017+emacs-28.2-159651-geff4a4f49a7-1 amd64 GNU Emacs editor (with GTK+ GUI support)

emacs-repository-version is nil.

Many thanks for your help,

Geoff

On Fri, 21 Oct 2022 at 08:41, Dima Kogan <dima@secretsauce.net> wrote:

>> It is unclear from which commit of the Emacs Git repository was this
>> built. AFAIR, there were some problems in this area fixed lately on
>> master, so perhaps try with the current master branch.
>
> I'm also copying in Dima Kogan, the maintainer of the Debian packages
> on secretsauce.net in case he has anything to add.

The package version contains the git hash: "dpkg -l emacs-snapshot" will
pinpoint the revision.