* Extend .dockerignore integration test with copies in later stages
.dockerignore should continue to apply when copying from the build context in later stages, but it currently doesn't
* Replace excluded global with passed along FileContext struct
This new FileContext struct allows much cleaner handling of context specific file exclusions.
The global excluded file state is no longer needed.
Additionally this also fixes the issue where excluded files aren't being applied for build context copies in later build stages.
Cached COPY layers are expensive in that they both need to be retrieved
over the network and occupy space in the layer cache.
They are unnecessary in that we already have all resources needed to
execute the COPY locally, and doing so is a trivial file-system
operation. This is in contrast to RUN layers, which can do
arbitrary and unbounded work.
The end result is that cached COPY commands were more expensive when
cached, not less. Remove them.
Resolves#1357
* Update cached copy command to return the same result for
files used from context so that cached and uncached copy
commands produce the same cache key
* Update tests for fix
* Add test for cached run command key consistency
Tejal Desai
Tinjo Schöni
Ian Kerins
Yoan Blanc
Dani Raznikov
Cole Wippern
ohchang-kwon
Don McCasland