Optimize "extends" without file specification
Optimize "extends" without file specification

Loading the same config file add about 100ms per each extension
service, which results in painfully slow CLI calls when a config
consists of a couple of dozens of services.

This patch makes Compose re-use config files.

Signed-off-by: Vadim Semenov <5bf054062aa1a7593f9145c1839647c7914c6580@gmail.com>

shin-/compose,vdemeester/compose,dnephin/compose,funkyfuture/docker-compose,shin-/compose,thaJeztah/compose,thaJeztah/compose,vdemeester/compose,dnephin/compose,funkyfuture/docker-compose