bug#20322: 25.0.50; indent-tabs-mode should default to nil

[Dmitry Gutov]

On 12/30/2015 09:18 PM, John Wiegley wrote:

> The longer we wait? This has the default (according to Git) since at least
> 1991, or 25 years now. Probably much longer, since that commit is just there
> to begin the Git history.

The question is, do we believe it'll have to be changed eventually. If 
not now, then maybe in 10-20 years' time.

> What about the needs of existing users who'll become confused by our changing
> such an established default on them?

What's so confusing about it? They'll see the new behavior (or read 
NEWS), look it up, and customize one variable, if they really want to. 
Unlike new users, they might know the variable already, and they 
certainly know how to customize.

We do change defaults from time to time. Maybe usually not 25-year-old 
defaults, but there are not that many of them left anyway.

> When did pleasing the expectations of new
> users become a driving force for these types of changes?

You're saying this like making the barrier of entry low is a bad thing.

I also want 'emacs -Q' to behave better, and I want to be more 
comfortable in recommending Emacs to other people.

> We can also expect
> new users to learn how Emacs does things, too.

indent-tabs-mode is not "how". It's "what" Emacs does, for predominantly 
historical reasons. Learning about it isn't going to be gratifying, 
unlike many other aspects of Emacs.

> What I would *like* is for tabs to insert spaces. But a change like this
> affects far more people than just the target audience. We need an excellent
> reason to do this.

We don't actually know how many people it's going to be a problem for, 
do we? For all we know, most of the existing users already use spaces 
(the third-party community has standardized on them). And some fraction 
will be indifferent to the change.

There must also be some fraction of users who are not aware of this 
variable, who "mess up" indentation when they edit some existing code 
bases. Statistically speaking, we'll be doing them a favor as well.

Should we poll Reddit users? Only asking on the mailing lists, I'm 
afraid, would unfairly skew the results in favor of _real_ old-timers.

If it were up to me, we'd try changing the default during the 
development cycle of Emacs 26, and see how many complaints we get.