Re: [RFC] Define "precious" attribute and support it in `git clean`

From: Sebastian Thiel <sebastian.thiel@icloud.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: Elijah Newren <newren@gmail.com>,
	Josh Triplett <josh@joshtriplett.org>,
	git@vger.kernel.org
Subject: Re: [RFC] Define "precious" attribute and support it in `git clean`
Date: Mon, 16 Oct 2023 08:02:25 +0200	[thread overview]
Message-ID: <1EE716BB-C8D5-4543-A5BE-EB8518151077@icloud.com> (raw)
In-Reply-To: <xmqqmswjsv8c.fsf@gitster.g>

Thanks a lot, that makes perfect sense!

Thanks to Elijah we may also have discovered why the idea of precious files
didn't get implemented last time it came up: it's too much work to make
all portions of the code aware.

I don't know if this time will be different as I can only offer to implement
the syntax adjustment, whatever that might be (possibly after validating
the candidate against a corpus of repositories), along with the update
to `git clean` so it leaves precious files alone by default and a new flag
to also remove precious files.

Maybe that already is something worth having, but I can also imagine
that ideally there is a plan for retrofitting other portions of git as
well along with the resources to actually do it.

On 15 Oct 2023, at 18:31, Junio C Hamano wrote:

> Sebastian Thiel <sebastian.thiel@icloud.com> writes:
>
>> A particularly interesting question brought up here also was the question
>> of what's more important: untracked files, or precious files? Are they
>> effectively treated the same, or is there a difference?
>
> Think of it this way.  There are two orthogonal axes.
>
>  (1) Are you a candidate to be tracked, even though you are not
>      tracked right now?
>
>  (2) Should you be kept and make an operation fail that wants to
>      remove you to make room?
>
> For untracked files, both are "Yes".  As we already saw in the long
> discussion, precious files are "not to be added and not to be
> clobbered", so you'd answer "No" and "Yes" [*].
>
> In other words, both are equally protected from getting cloberred.
>
>     Side note: for completeness, for ignored files, the answers are
>     "No", and "No".  The introduction of "precious" class makes a
>     combination "No-Yes" that hasn't been possible so far.
>
> Elijah, thanks for doing a very good job of creating a catalog of
> kludges we accumulated over the years for the lack of proper support
> for the precious paths.  I think they should be kept for backward
> compatibility, but for new users they should not have to learn any
> of them once we have the support for precious paths.