Re: [PATCH] rebase, cherry-pick, revert: only run from toplevel

From: Elijah Newren <newren@gmail.com>
Date: Sep 1, 2021, 04:43 UTC
Message-ID: <CABPp-BGkQTBBR_D-3EJPY-ONVYY4jjbEE4zA40n_oiz2DCrHgA@mail.gmail.com>
In-Reply-To: <YS7rl8ynKD0fAerG@nand.local>

On Tue, Aug 31, 2021 at 7:55 PM Taylor Blau <me@ttaylorr.com> wrote:

Show 27 quoted lines

>
> On Tue, Aug 31, 2021 at 01:14:55PM -0700, Elijah Newren wrote:
> > > Now I have spent zero time looking into actually coding this, so it may
> > > turn out to be much trickier than I am suggesting. But this seems like a
> > > much more fruitful direction, where we can protect users in cases where
> > > they benefit (and give them sensible and actionable error messages),
> > > without bothering people in the majority of cases where their cwd
> > > doesn't go away.
> >
> > Ooh, this sounds intriguing to me...but what if we changed that rule
> > slightly and just decided to never make the cwd go away?  Currently,
> > the checkout code removes directories if they have no tracked or
> > untracked or ignored files left, i.e. if they're empty.  What if we
> > decide to only have remove_scheduled_dirs() remove directories that
> > are empty AND they are not the current working directory?
>
> Hmm. My first thought after reading this is that it would cause
> surprising behavior for anybody who had 'git add --all' in their 'rebase
> -x' script. But would it?
>
> I.e., imagine somebody doing an in-place sed in a rebase and then `git
> add --all`-ing the result at each point in history. If the directory
> they were in ever went away, then the *next* revision would add that
> directory right back.
>
> That behavior seems somewhat surprising to me, or at least I could
> imagine it being surprising to users.

I'm not following. `git add --all` doesn't add empty directories, so I don't see how my proposed change would cause any problems in such a case; nothing would be added back.

> Another thought is what should happen when the current directory goes
> away and then comes back as a file? We wouldn't be able to checkout that
> file, I don't think, so it might be a dead end.

I'm not following this either. Peff's original suggestion was to error out only when we knew it could cause problems, in particular when the working directory would be removed. Here I've shifted the way the problem is viewed by just not removing the working directory, but the end result is the same -- it errors out when the removal was needed. Given that erroring out is exactly what we wanted for a case like this, why does that make it a dead end?