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From:   Junio C Hamano <gitster@pobox.com>
To:     Anthony Sottile <asottile@umich.edu>
Cc:     Duy Nguyen <pclouds@gmail.com>, Ben Peart <peartben@gmail.com>,
        Git Mailing List <git@vger.kernel.org>
Subject: Re: Regression `git checkout $rev -b branch` while in a `--no-checkout` clone does not check out files
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Date:   Thu, 03 Jan 2019 13:51:11 -0800
In-Reply-To: <CA+dzEB=+ROLVjp36SQjucouc8YUWTvYBrN4QyS5fsStMPtbw_w@mail.gmail.com>
        (Anthony Sottile's message of "Thu, 3 Jan 2019 12:35:24 -0800")
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Anthony Sottile <asottile@umich.edu> writes:

> On Thu, Jan 3, 2019 at 12:26 PM Junio C Hamano <gitster@pobox.com> wrote:
>> A "fix" to Ben's optimization for this particular case should be
>> fairly straight-forward.  I think we have a special case in the
>> checkout codepath for an initial checkout and disable "carry forward
>> the fact that the user wanted all the paths removed", so it would be
>> the matter of adding yet another condition (is_cache_unborn(), which
>> is used to set topts.initial_checkout) to the large collection of
>> conditions in skip_merge_working_tree().
>
> I think it might be simpler than that even -- the optimization treats
> the following as equivalent when the current checked out revision is
> deadbeef (even if the index / worktree differ), when before they were
> not:
>
> - git checkout -b newbranch
> - git checkout deadbeef -b newbranch
>
> If a revision is specified on the commandline it should be checked out.

If it were to be a "fix", the exact same command line as people used
to be able to use, i.e. "git checkout -b newbranch", should be made
to do what it used to do.

Forcing users to use a different command to workaround the bug is
not a usable "fix".  If we want a working workaround, you can tell
your users to use 

    git reset --hard HEAD && git checkout -b newbranch

and that would already work without any code change ;-).