how to update the git repo?

[Bruno Haible]

Hi Jim, Eric, Ralf,

Sylvain Beucler writes in <http://savannah.gnu.org/>:
  We're reinstalling the system and restoring the data from a safe backup, 
November 24th.
  Please prepare to recommit your changes since that date.

When savannah is back online: Can we make this recommit of past changes in
such a way that existing checkouts continue to work?
  - Is it possible if one person who has a clean checkout does a "git push"?
    Or will the server reject that push because it contains commits from
    different authors?
  - Or do we have to recommit the changes person by person? Here's the list I
    have from "git log" (in reversed chronological order):

commit 84461c0af4d3be6ab62c4049c60c5170276c96db
Author: Bruno Haible <address@hidden>
Date:   Sat Nov 27 18:58:36 2010 +0100

commit 2cc246130b35ae6a35bc8328ee48a69b02b88d2a
Author: Bruno Haible <address@hidden>
Date:   Sat Nov 27 18:22:51 2010 +0100

commit 5ea438b5d354059846385a90f2f7f39e55d64bc4
Author: Bruno Haible <address@hidden>
Date:   Sat Nov 27 18:10:39 2010 +0100

commit 9fbfb9888f4ca4b7f74b900be4ebd6a8469f1613
Author: Bruno Haible <address@hidden>
Date:   Sat Nov 27 16:32:57 2010 +0100

commit 23e731fecc89375a6c00fa26f7f5489c3de03b2c
Author: Karl Berry <address@hidden>
Date:   Sat Nov 27 07:02:46 2010 -0800

commit 44d48c8524e2d7c7e2793f7bc0c2f4b5ed3b7be5
Author: Karl Berry <address@hidden>
Date:   Sat Nov 27 07:02:13 2010 -0800

commit 45ae3ef838307117d1cbea9b05b5db5e81e77f5e
Author: Bruno Haible <address@hidden>
Date:   Sat Nov 27 15:55:47 2010 +0100

commit fded1344e9babb1feddb8f32d9d2422052e4ce73
Author: Bruno Haible <address@hidden>
Date:   Sat Nov 27 15:43:57 2010 +0100

commit 4b731914f6c70e9c88b4a105787981ab85013947
Author: Bruno Haible <address@hidden>
Date:   Sat Nov 27 14:23:57 2010 +0100

commit f480581dc6834f060592a11c256b08068b518d42
Author: Bruno Haible <address@hidden>
Date:   Sat Nov 27 04:08:53 2010 +0100

commit b09cb6b027d3f97b34e3bb0308e337d161cc2ed3
Author: Paul Eggert <address@hidden>
Date:   Thu Nov 25 23:47:38 2010 -0800

commit ccd329f25cae690693c9589ec9bab59239464a5c
Author: Paul Eggert <address@hidden>
Date:   Wed Nov 24 12:05:43 2010 -0800

commit cae4370c3b21144791ace3432642970487385ecb
Author: Bruno Haible <address@hidden>
Date:   Wed Nov 24 13:10:19 2010 +0100

Bruno