Bug#908291: developers-reference, section 5.11.4: Add a note on versioning scheme when reverting an NMU

[Joseph Herlant <herlantj@gmail.com>]

Source: developers-reference
Severity: wishlist
Tags: patch

Dear Maintainer,

The Developer's reference explains a lot about NMUs and corresponding version
scheme but it does not explain the naming convention to use when you have to
revert an NMU that brings a new upstream version.
Lintian has a check about it (https://lintian.debian.org/tags/epoch-changed-
but-upstream-version-did-not-go-backwards.html), so it seems the format is
wildly accepted.
So maybe a not about it here would be a good thing.

I took the liberty to provide a patch via a MR:
https://salsa.debian.org/debian/developers-reference/merge_requests/4

Let me know if adding that paragraph would be ok and if the wording is correct.
I'm not sure on how to handle the po files. Let me know if I can help on that
too.

Thanks
Joseph