Allow creating symbolic references with link, and deleting them or
switching to ObjectId with unlink. How this happens is up to the
individual RefDatabase.
The default implementation detaches RefUpdate if a symbolic reference
is involved, supporting these command instances on RefDirectory.
Unfortunately the packed-refs file does not support storing symrefs,
so atomic transactions involving more than one symref command are
failed early.
Updating InMemoryRepository is deferred until reftable lands, as I
plan to switch InMemoryRepository to use reftable for its internal
storage representation.
Change-Id: Ibcae068b17a2fc6d958f767f402a570ad88d9151
Signed-off-by: Minh Thai <mthai@google.com>
Signed-off-by: Terry Parker <tparker@google.com>
7f59cfe143