dotcloud/docker — pull request #1112 by cespare (2013-07-02 23:01:48+00:00)
Title: Mutex style change.

For structs protected by a single mutex, embed the mutex for more
concise usage.

Also use a sync.Mutex directly, rather than a pointer, to avoid the
need for initialization (because a Mutex's zero-value is valid and
ready to be used).