Re: Ambiguous sha-1 during a rebase

From: Matthieu Moy <matthieu.moy@grenoble-inp.fr>
Date: Apr 14, 2016, 09:09 UTC
Message-ID: <vpqr3e8wo99.fsf@anie.imag.fr>
In-Reply-To: <20160413225234.GA21602@glandium.org>

Mike Hommey <mh@glandium.org> writes:

Show 9 quoted lines

> On Wed, Apr 13, 2016 at 03:42:44PM -0700, Junio C Hamano wrote:
>> Mike Hommey <mh@glandium.org> writes:
>> 
>> > Should git-rebase use full sha-1s under the hood to avoid these type of
>> > races?
>> 
>> It already should be doing so since Aug 2013, IIRC.
>
> I'm using 2.8.1. Would there have been a regression?

I guess you managed to get into a corner-case which isn't managed properly. With my git version 2.8.1.53.g7ee34ab, I just checked the normal use-case:

$ git rebase -i HEAD^^

The editor pops up with short sha1. I insert a "exec false" like this:

,----[ git-rebase-todo ]
| pick 0c722f9 foo
| exec false
| pick 6305d56 commited
`----

The execution goes on like this:

  Executing: false
  Execution failed: false
  You can fix the problem, and then run
  
          git rebase --continue

And I can check:

$ cat .git/rebase-merge/git-rebase-todo pick 6305d56f7218b6f04451bab3ff27adb80dd6dad4 commited ...

I suspect you did:

$ git rebase -i # editor pops up # switch to another terminal and fetch from elsewhere # close editor

Then only, git turns short sha1s into long ones, and does not have the information to resolve ambiguities.

We could save a map (short -> long) before poping the editor and use this map in priority when normalizing the todo-list to use long sha1s, but we currently don't.

But I'm tempted to say that you just went very, very unlucky, and it's not worth fixing ...

-- 
Matthieu Moy
http://www-verimag.imag.fr/~moy/