When sending a build context to a remote server it may be
(significantly) advantageous to compress the build context. This commit
adds support for gz compression when constructing a build context
using a command like "docker build --compress ."
Signed-off-by: Paul Kehrer <paul.l.kehrer@gmail.com>
This fix tries to address the issue raised in 26453 where bad syntax
on dockerfile is not checked before building, thus user has to wait
before seeing error in dockerfile.
This fix fixes the issue by evaluating all the instructions and check
syntax before dockerfile is invoked actually.
All existing tests pass.
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
