commands.cpp is build as part of the coredb library: https://github.com/mongodb/mongo/blob/r3.1.8/src/mongo/db/SConscript#L477. Some tests include commands.h and define a value for Command::testCommandsEnabled to avoid linking it in. It would be nice to make determining whether the server is in test mode (i.e. whether test commands are enabled) a more reasonable thing to do from a linkage perspective.

This will be used by mongobridge to change dbclient.cpp and network_interface_asio_auth.cpp to include the server's host info in the initial isMaster command request only if the server is in test mode.