"auto" for Kerberos, a history

[Douglas Bagnall]

On 20/08/20 6:53 pm, Stefan Metzmacher via samba-technical wrote:
> 
> yes means no fallback to NTLM,
> 
> Should we use "disabled", "if_available", "required"
> instead of "no", "auto", "yes"?
> 

I am a fan of "auto", as telling the tool "you decide".

It is nice for the user because there is a convention, and it is nice for
the toolmaker because there is no implicit guarantee about what decision
it will make.

There is considerable precedence for --foo=auto in command line culture.

The biggest cluster is --color=WHEN, where WHEN is conventionally
always|auto|never. This is shared by  ls, rustc, rpm, tc, grep, ip, git,
and dozens or hundreds or thousands of other tools.

While --color=WHEN's always/never is a different take than yes/no, yes/no
are usually also accepted:

  $ ls --color=maybe
  ls: invalid argument ‘maybe’ for ‘--color’
  Valid arguments are:
    - ‘always’, ‘yes’, ‘force’
    - ‘never’, ‘no’, ‘none’
    - ‘auto’, ‘tty’, ‘if-tty’
  Try 'ls --help' for more information.


A very brief search for other --foo=auto options reveals:

cp --reflink=auto --sparse=auto
xz --format=auto
flake8 -j auto
git log --decorate=auto
git format-patch --cover-letter=auto --numbered=auto --base=auto
etags --language=auto
gpg --trust-model=auto --tofu-default-policy=auto
valgrind --expensive-definedness-checks=auto
crash --kaslr=auto
grub-install --core-compress=auto
mount -t auto


Now, of course, I am not saying we want to follow gpg's human interface
guidelines, just that this pattern will have some resonance with users. If
the option is "if_available", people like me will be always forgetting the
exact term and whether it uses an underscore or a hyphen.

OK, so sorry for being late and somewhat bikesheddy. I don't object to new
more precise terms, but please let's not remove "auto". It is alright to
be vague, because it is SUPPOSED to be vague.

cheers,
Douglas