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

[Sebastian Thiel <sebastian.thiel@icloud.com>]

On 13 Oct 2023, at 18:39, Junio C Hamano wrote:

> Come to think of it, we might be able to retrofit '!' without too
> much damage.  Something like "!unignored" is now a deprecated but
> still supported way to say "!!unignored", "!*precious" is new, and
> "\!anything" is a pathname that begins with '!'.

I don't know anything about statistics, and I don't which of the proposed
syntax thus far has the lowest probability of accidental breakage, possibly
in combination with the best possible usability.

However, I do like even more the idea to retro-fit `!` instead of having an
entirely new prefix, it seems more intuitive to me.

An apparent disadvantage would be that using `!` prefix with
backwards-compatibility will make any additional future modifier more
breaking. For instance `!*` is potentially ignoring an additional file
in old git, and another `!-` modifier is having the same effect.

Chances for this are probably low though, but if in doubt it would be possible
to check certain patterns against all files of the top-3.5TB of
GitHub repositories.

Using `!*` to signal precious files also seems like a less likely
path prefix than `!$` would be, but then again, it's just a guess
which most definitely doesn't have much bearing.

I personally also like this more than using special comments as 'modifier',
even though doing so would probably have the lowest probability for
accidentally ignoring files in old git.

Maybe it's time to choose one of the options with the possibility to validate
it for accidental exclusion of files against the top 3.5TB of
GitHub repositories to be more sure it?