Alexios Theodoros Brezas e3f480c217 Container restart policy specificiation.
Allow users to set container restart policy using environment variables.

RESIN_APP_RESTART_POLICY sets the name of the policy, and
if policy is "on-failure", optionally, RESIN_APP_RESTART_RETRIES
sets the maximum number of retries.

More information on docker docs:
https://docs.docker.com/engine/reference/run/#restart-policies-restart

One major change we introduce here is that the default policy is set
to always while we used to have the default "no".

We validate the arguments and pass retries parameter only for the case
of "on-failure" as specified in Docker API as of v1.19.
We could let docker handle the arguments directly, gaining
forwards-compatibility with any new features, but I opted
for an implementation that is as well-defined as possible.
2016-06-07 12:49:30 -03:00
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