lockfile.c: document the various states of lock_file objects
lockfile.c: document the various states of lock_file objects

Document the valid states of lock_file objects, how they get into each
state, and how the state is encoded in the object's fields.

Signed-off-by: Michael Haggerty <c24c152f145c57791e809b126db9e61bd1c1782d@alum.mit.edu>
Reviewed-by: Ronnie Sahlberg <2cb6c6c4ccf58d41468189c2307f7a4ebf120324@google.com>
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