Add sync-all new-workdir

[tibbe]

The attached patch implements a new sync-all command, which calls git-new-workdir. git-new-workdir lets you create separate working directories, all connected to the same repository. Separate working directories can be used to:

• Store repos on NFS, where they can be easily backed up, but store the checked out code on local disk, speeding up builds and many git operations (e.g. git status.)
• Implement separate build trees. While full clones can be used to implement build trees, they are somewhat more heavyweight to use (e.g. you need to shuffle patches between them.)

Usage:
  sync-all new-workdir <new_workdir> [<branch>]

Example:
  sync-all ~/src/ghc-validate

Note: git-new-workdir is typically not on the user's PATH after a standard git installation. It can be found in the contrib directory in most git distributions.

Feel free to edit the patch. My perl-fu is weak.

[simonmar]

I'm doing a validate run, so I'll get this one in too.

[simonmar]

Pushed:

commit 4bac993e3d00edc0ceac99f4b44ade477ae9aa90

Author: Johan Tibell <johan.tibell@gmail.com>
Date:   Thu Feb 16 19:09:55 2012 -0800

    Add sync-all new-workdir
    
    This command calls git-new-workdir (a separate script in git's contrib
    directory) on all repos.  Useful to create multiple build trees, without
    cloning the repos.
    
    Usage:
      sync-all new-workdir <new_workdir> [<branch>]

[simonmar]

On second thoughts, we don't need to merge this.