Hi all,

since I personally asked that question and investigated a bit the subject,
here is some information that could be probably useful to someone else:

http://stackoverflow.com/questions/13457203/how-to-add-the-signed-off-by-field-in-the-git-patch
http://stackoverflow.com/questions/1962094/what-is-the-sign-off-feature-in-git-for
http://stackoverflow.com/questions/15015894/git-add-signed-off-by-line-using-format-signoff-not-working
http://git-scm.com/docs/git-format-patch (CONFIGURATION section)

Personally I've chosen to add
[format]
        signOff = true
to git.config file.

--
Dmitry.