tree 1876e03e4625931d15977f2a8030d4434f32edb0
parent 8d58a9ab17eafd6e8186d2cb7fe90430637c451a
author Dave Borowitz <dborowitz@google.com> 1542153507 -0800
committer Dave Borowitz <dborowitz@google.com> 1542222692 -0800

Factor out common code from RepoSequence

IntBlob is a simple value class encapsulating the results of reading an
integer blob from a given object ID in a repo. It includes factory
methods for reading/writing blobs to/from the repo, in an interface that
provides everything RepoSequence needs.

In the write case, RepoSequence needs two methods:
  * A tryStore method which returns a completed RefUpdate, which may or
    may not have succeeded. This return value is essentially an
    encapsulation of the RefUpdate.Result and the ref name; the latter
    is necessary for producing detailed error messages.
  * A checked store method which throws an exception if the result of
    tryStore was not success. This in turn delegates to a new
    RefUpdateUtil#checkResult method paralleling the existing
    checkResults.

Change-Id: Ibbe99972697cb4cb837673f19d7a6fac8b90fce0