Re: [PATCH v3 01/13] parse-options: allow for hidden aliases

[Junio C Hamano <gitster@pobox.com>]

Kaartic Sivaraam <kaartic.sivaraam@gmail.com> writes:

>> Perhaps it doesn't make sense to add flags to OPT_ALIAS() at all?
>> ...
>
> Just some food for thought. There are a couple of other instances where 
> we are currently using OPT_ALIAS to represent the deprecated variant of 
> an option. They are:
>
>    1. `--recursive` is a deprecated alias of  `--recurse-submodule` in
>       `git clone`
>
>       cf. bb62e0a99f (clone: teach --recurse-submodules to optionally
>       take a pathspec, 2017-03-17) and 5c387428f1 (parse-options: don't
>       emit "ambiguous option" for aliases, 2019-04-29)
>
>    2.  `--negotiation-tip` is a deprecated alias of
>        `--negotiation-restrict` in `git fetch`
>
>        cf. 1a445fc60b (fetch: add --negotiation-restrict option,
>        2026-05-19)
>
>        Note: The documentation clarifies that --negotiation-restrict is
>        the preferred variant but does not mention about deprecation.
>
> Since they are not hidden, the deprecated variants still show up in the 
> help output of those commands. So, we appear to be doing fine with a 
> public alias so far. So, may be it is not a big deal if we expose the 
> deprecated option publicly?

The OPT_HIDDEN bit for an option indeed is a mechanism for
deprecation and it is not limited to alias.

When an option has a clearly better alternative, we would want to
eventually remove the old one and have everybody use the new one.
For that to happen, we need to let people know that the old thing is
on its way out, and "git cmd -h" is a good place to do so.  We do
not want to use OPT_HIDDEN in earlier half of the deprecation.
After sufficient time passes, there will be a lot of new users who
are equally unfamiliar with old and new options.  Telling them about
old way that is on its way out does not help them at all.  So at
some point, we want to start using OPT_HIDDEN for such options.

When nobody uses the old option, we can remove the entry from the
options[] array, or we can keep it and use it only to cause an error
message (i.e., "This option used to do something, but no longer. Do
not use it anymore").

If OPT_ALIAS() does not allow using OPT_HIDDEN, that is a bug in the
infrastructure.  It does not have to block a new topic that uses
OPT_ALIAS(), but we can leave a #leftoverbit mark to invite
interested parties to work on fixing it.

Thanks.