This has no real impact on performance[1] but should
make it clear which application can run the broker
and/or publish to Hex.pm. In particular, applications
that we can't run the broker from will now give up
early if we try to.
Note that while the broker can't normally run from the
amqp_client application's directory, it can run from
tests and some of the tests start the broker.
[1] on my machine
This variable should remain unset so that the top-level version obtained from git is used for dependencies like rabbit_common
With this line in place, the following reports the wrong version for rabbit_common, for instance:
rabbitmq_aws: rabbit_common git_rmq https://github.com/rabbitmq/rabbitmq-common master /home/lbakken/development/rabbitmq/umbrella/deps/rabbit_common
even if rabbitmq_aws is checked out to tag v3.8.7