On Thu, Dec 10, 2020 at 11:17:01PM -0800, Junio C Hamano wrote:

You want to let the user express: "I do not want to choose either
rebase or merge.  I want 'pull' to fail when it needs to deal with
non-ff history.  But I do not need to be told about command line
option and configuration every time."

I said I don't (I view that disabling half the "git pull" just a
safe fallback behaviour until the user chooses between merge and
rebase), but if we wanted to offer it as a valid choice to users, we
can do so.  We just make it possible to squelch the latter two parts
of the three-part message---you leave pull.rebase unconfigured and
squelch the latter two parts of the message, and you got the "stop
me, I do not merge or rebase, but don't even tell me how to further
configure" already.

FWIW, I would be such a user who would want to squelch the error but
keep the ff-only behavior (and have been doing so for years via
pull.ff=only).

I primarily use "git pull" only with branches where I am tracking
upstream work, but don't have any of my own (e.g., if I do all of my
work on topic branches, I may still keep a "master" branch that mirrors
"origin/master", and use "git checkout master && git pull" to
fast-forward it).

So I think this is a valuable thing to have. And it does work just fine
already, without pull.mode. The reasons to care about pull.mode (IMHO)
are mostly about explaining it:

  - it isn't respected with rebase. So if you set pull.rebase=true, now
    pull.ff=only does nothing. This is arguably confusing, though I
    doubt it comes up much in practice.

  - having a single tri-state of merge/rebase/error for "what do I do
    when pulling a non-fast-forward merge" is conceptually simple and
    easy to explain.

So I like pull.mode in that sense. But it is also weighed against the
fact that we'd still have to support pull.rebase, and we'd still have to
support pull.ff, and explain how those interact with pull.mode (and I
think any new error in this area must be squelched by those existing
variables, or it would be a regression for people who already picked
their default long ago).

But there is an established way used in this project when we allow
squelching overly-helpful help messages, and we can apply it here as
well.  That way:

 - unconfigured folks would get all the three parts of the messages,
   just like the current system.

 - if you tell rebase or merge, you do not see any.

 - if you do not choose between rebase or merge, you can still
   squelch the latter two by setting advice.pullNonFF to false.

The last one is "keep the more dangerous half of 'git pull' disabled,
without getting told how to enable it over and over", which is what
you want to be able to specify.

Using advice.* to squelch the advice would be fine with me, provided it
was _also_ squelched by the existing config options.

Which I think is where your thinking is ending up.

-Peff