Merge remote-tracking branch 'coreos/master' into merge

* coreos/master:
  scripts: build-docker tag and use ENTRYPOINT
  scripts: build-release add etcd-migrate
  create .godir
  raft: optimistically increase the next if the follower is already matched
  raft: add handleHeartbeat handleHeartbeat commits to the commit index in the message. It never decreases the commit index of the raft state machine.
  rafthttp: send takes raft message instead of bytes
  *: add rafthttp pkg into test list
  raft: include commitIndex in heartbeat
  rafthttp: move server stats in raftHandler to etcdserver
  *: etcdhttp.raftHandler -> rafthttp.RaftHandler
  etcdserver: rename sender.go -> sendhub.go
  *: etcdserver.sender -> rafthttp.Sender

Conflicts:
	raft/log.go
	raft/raft_paper_test.go

raft/log_test.go

@@ -400,6 +400,38 @@ func TestUnstableEnts(t *testing.T) {
 	}
 }
 
+func TestCommitTo(t *testing.T) {
+	previousEnts := []pb.Entry{{Term: 1, Index: 1}, {Term: 2, Index: 2}, {Term: 3, Index: 3}}
+	commit := uint64(2)
+	tests := []struct {
+		commit  uint64
+		wcommit uint64
+		wpanic  bool
+	}{
+		{3, 3, false},
+		{1, 2, false}, // never decrease
+		{4, 0, true},  // commit out of range -> panic
+	}
+	for i, tt := range tests {
+		func() {
+			defer func() {
+				if r := recover(); r != nil {
+					if tt.wpanic != true {
+						t.Errorf("%d: panic = %v, want %v", i, true, tt.wpanic)
+					}
+				}
+			}()
+			raftLog := newLog(NewMemoryStorage())
+			raftLog.append(0, previousEnts...)
+			raftLog.committed = commit
+			raftLog.commitTo(tt.commit)
+			if raftLog.committed != tt.wcommit {
+				t.Errorf("#%d: committed = %d, want %d", i, raftLog.committed, tt.wcommit)
+			}
+		}()
+	}
+}
+
 func TestStableTo(t *testing.T) {
 	tests := []struct {
 		stable    uint64