peel_object(): give more specific information in return value
peel_object(): give more specific information in return value

Instead of just returning a success/failure bit, return an enumeration
value that explains the reason for any failure.  This will come in
handy shortly.

Signed-off-by: Michael Haggerty <c24c152f145c57791e809b126db9e61bd1c1782d@alum.mit.edu>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git