Re: [PATCH 1/1] Introduce "precious" file concept

From: Duy Nguyen <pclouds@gmail.com>
Date: Feb 20, 2019, 01:35 UTC
Message-ID: <CACsJy8Dq9_uFofs40XwjLkmiBNWXCpic96W1MK_tjLQyaF0+BA@mail.gmail.com>
In-Reply-To: <xmqq8syb3b3j.fsf@gitster-ct.c.googlers.com>

On Wed, Feb 20, 2019 at 1:08 AM Junio C Hamano <gitster@pobox.com> wrote:

Show 37 quoted lines

>
> Duy Nguyen <pclouds@gmail.com> writes:
>
> > On Sun, Feb 17, 2019 at 2:36 AM Ævar Arnfjörð Bjarmason
> > <avarab@gmail.com> wrote:
> >>
> >>
> >> On Sat, Feb 16 2019, Nguyễn Thái Ngọc Duy wrote:
> >>
> >> [Re-CC some people involved the last time around]
> >>
> >> > A new attribute "precious" is added to indicate that certain files
> >> > have valuable content and should not be easily discarded even if they
> >> > are ignored or untracked.
> >> >
> >> > So far there are one part of Git that are made aware of precious
> >> > files: "git clean" will leave precious files alone.
> >>
> >> Thanks for bringing this up again. There were also some patches recently
> >> to save away clobbered files, do you/anyone else have any end goal in
> >> mind here that combines this & that, or some other thing I may not have
> >> kept up with?
> >
> > I assume you mean the clobbering untracked files by merge/checkout.
> > Those files will be backed up [1] if backup-log is implemented. Even
> > files deleted by "git clean" could be saved but that might go a little
> > too far.
>
> I agree with Ævar that it is a very good idea to ask what the
> endgame should look like.  I would have expected that, with an
> introduction of new "ignored but unexpendable" class of file
> (i.e. "precious" here), operations such as merge and checkout will
> be updated to keep them in situations where we would remove "ignored
> and expendable" files (i.e. "ignored").  And it is perfectly OK if
> the very first introduction of the "precious" support begins only
> with a single operation, such as "clean", as long as the end-goal is
> clear.

I think the sticking point is how to deal with the surprise factor and "precious" will not help at all in this aspect. In my mind there are three classes

 - total expectation, i know i want git to not touch some files, i
tell git so (e.g. with "precious")

 - surprises sometimes, but in known classes. This is the main use
case of backup log, where I may accidentally do "git commit
-amsomething" after carefully preparing the index. Saving overwritten
files by merge/checkout could be done here as an alternative to
"garbage" attribute.

Show 6 quoted lines

> I personally do not believe in "backup log"; if we can screw up and
> can fail to stop an operation that must avoid losing info, then we
> can screw up the same way and fail to design and implement "backup"
> to save info before an operation loses it.  If we do a good job in
> supporting "precious" in various operations, we can rely less on
> "backup log" and still be safe ;-)

and this is the third class, something completely unexpected. Yes backup-log can't help here, but I don't think "precious" can either. And I have no good proposal for this case.

-- 
Duy