Jonathan Nieder [off-list ref] writes:

In other words, I think the commit message needs a bit more detail about
the use case, to say why omitting those tags is useful.  The use case
is probably sane but it is not explained.  A side effect (and my main
motivation) is that this would make it crystal clear to people looking
at the patch in history that it is talking about tags that are part of
"master"'s history, not tags pointing elsewhere.

I agree that it is unclear "having no tags, not even the harmless
and usually useful ones that point at the history of the branch of
interest" is the point of this new feature from the documentation
and log message.  

Responding to your other message, I do not think this new feature
should be tied to --single-branch; I think having the tags to mark
commits in the branch's history (while not fetching other tags
irrelevant to the branch's history) is usually what users would
want.

quoted

Before this the only way of doing this was either by manually tweaking
the config in a fresh repository:

Usually commit messages refer to the state of things without some
patch using the present tense --- e.g. "Without this patch, this
--no-tags option can be emulated by (1) manually tweaking the config
in a fresh repository, or (2) by setting tagOpt=--no-tags after
cloning and deleting any existing tags".

Thanks--I'll use this myself when responding to patches from other
people.  I recall getting irritated while reading some patches and
couldn't pinpoint why they were irritating, and now I realize that
it was because they said "Previously Git did X." and somesuch.