Re: Alternates and push

On Sat, Sep 06, 2008 at 11:06:49AM -0700, Junio C Hamano wrote:

We could instead redefine the semantics of the existing alternates
mechanism.  This technically *breaks* backward compatibility, but I
suspect it won't hurt many existing installations:

 - Declare that a freestanding object store is illegal.  In other words,
   if a directory "$D/objects" is (1) used as $GIT_OBJECT_DIRECTORY's
   value, (2) pointed by some repository's "alternates" file, or (3)
   listed in $GIT_ALTERNATE_OBJECT_DIRECTORIES's value, this change makes
   it illegal for "$D" not being a proper git repository.

   This will not break your example of your repository's object store
   borrowing from the object store inside Linus's repository.

 - When you have "$D/objects" in alternates, start relying on "$D/refs"
   being correct (i.e. repository $D is not corrupt).  This technically
   makes the system slightly less robust, as we are depending on _other
   people's_ good behaviour even more when you use alternates, but you are
   already depending on them having good objects in $D/objects anyway, so
   it is not a big deal.

One way that wouldn't break backwards compatibility would be to use
$D/refs if it exists, but if it isn't, fall back to existing behavior
(which is to say, only use the refs in the repository, not in the
borrowed repository/object store).  Is there a reason why this would
be problematic?

							- Ted