Change logic to support more port env use cases

The logic changes from strict overrides to a hybrid for merging os_env
and defaults, whereby defaults are chosen if they are not set in the
os_env or if the defaults contains substitutions (at which point os
environment is substituted).

This still means that rebar.config works as it did before, where it
overrides or substitutes based on the use of $VAR, but that default
and os environment merging works such that the common cases of
providing CC or LDFLAGS in the users environment or command line work
as you might expect.  In that CC is overriden by the os environment
unless rebar.config overrides it, and LDFLAGS from the user environment
is appended or prepended based on defaults and rebar.config.

Addresses problems with https://github.com/basho/rebar/pull/71
Also keeps the fix for bug 255.

0 files changed, 0 insertions, 0 deletions