I mean, I'd just put the reference to the head in the commit message, i. e. now the last commit is

test progress reporting f1af51e4

I'd add a line:

See unsquashed history at f1af51e4

In the final commit message

On Wed, 24 Nov 2021 at 23:50, Sergei Golubchik <serg@mariadb.org> wrote:

Hi, Nikita!

Sorry, I meant what did you mean by

> I would also embed a reference to the original unsquashed branch. It
> seems to me as a good idea in sense of helping the reader investigate
> the code

Regards,
Sergei
VP of MariaDB Server Engineering
and security@mariadb.org