[Xfce-i18n] Usage of msgmerge

[Pjotr]

@Nick: neither the man pages of msgmerge nor a Google query, sufficed
to let me see the light concerning the use of msgmerge. The man is
your friend, they say, but unfortunately not mine, not now....

So: could you please help me out by supplying an example command,
where "stable.po" is the fully translated stable package, and
"master.po" is the largely untranslated development package in master?
In other words, what is the msgmerge command to transfer the
translations from "stable.po" to "master.po"?