Improve file lock contention handlingThis commit improves the likelihood for lock requesters to acquire afile lock after it is released due to contention. After the lock hasbeen released, the former lock holder now sends a packet to the socketsof all requesters. While old clients will simply ignore the additionalpacket, new clients will interpret it as a signal that the file lock hasbeen released and will try to acquire it immediately.Issue: gradle/gradle-private#1412.
Provide an empty contended action instead of nullThis contention handling is already active for exclusive locks, butwithout an action it is ignoring requests from other parties.With this, it sends confirmation that the request was receivedand that lock releasing is in progress. Although the release itselfis not performed by the contended action, but manually after thelock is no longer needed (which is the contract for exclusive locks).