Re: [PATCH v2 0/1] Make 'git commit' not accidentally lose staged content

[Jacob Keller <jacob.keller@gmail.com>]

On Mon, Sep 17, 2018 at 11:15 AM Jeff King <peff@peff.net> wrote:
>
> On Mon, Sep 17, 2018 at 07:29:26PM +0200, Duy Nguyen wrote:
>
> > > On the other hand, if I am keeping some change that should never be
> > > in a commit in the working tree file, and building the contents in
> > > the index using "add -p" to incrementally, it would be the same
> > > disaster as you are trying to prevent if I by mistake did a whole
> > > path 'add', even if I catch myself doing so before running 'commit'
> > > i.e.
> > >
> > >         edit X
> > >         git add -p X
> > >         git diff --cached X
> > >         git diff X
> > >         ... repeat the above number of times ...
> > >         git add X ;# OOPS!
> > >         git add . ;# OOPS! even worse!
> > >
> > > Even though this does not involve "git commit -a" or "git commit X",
> > > an unrecoverable damage that requires redoing the manual work is
> > > already done.
> >
> > I don't see a good way to get to recover this situation. I could go
> > back to the "index log" idea, where we keep a log of index changes (or
> > just "interesting" changes). That way there's no behavior change at
> > all. The user who accidentally updates/deletes something can always
> > retrieve the old content back (assuming that they realize quickly
> > since we can't keep very long log).
>
> FWIW, I like that approach much better, since:
>
>   1. It does not bother or restrict anybody in their workflow; instead,
>      they pay the complexity price only when they know they have made a
>      mistake.
>
>   2. It covers many more cases (e.g., just doing the wrong thing via
>      "add -p").
>

I also think this is a better approach for the same reasons.

> A naive index log would be pretty cheap in CPU, at least for POSIX-ish
> systems. You could just hard link "index" to "index.N" before renaming
> "index.lock" over "index". But I guess if you have a gigantic index,
> that's less appealing. So maybe storing the equivalent of a "--raw" diff
> between the two index states would make more sense (and after all, you
> don't really need the stat-cache or cache-tree). It would cost more to
> reconstruct the index on the fly, but then the point is that you would
> create these logs a lot more than you access them.
>
> > I've been thinking about allowing to undo worktree changes too (e.g.
> > accidental "git reset --hard") and this log can cover it as well.
>
> I like that, too. It's a little more costly just because it may involve
> object-db writes, but I think in most cases it would be fine. I almost
> always "git stash" away discarded changes these days instead of "git
> reset --hard", because it effectively provides this kind of log.
>

Obviously we do eventually turn the index into a tree, which is used
by the commit. Would it be possible to simply somehow store these
trees, and have commands which blow the tree away simply instead, save
it? I'm not sure how costly that is.

Thanks,
Jake