This adds support for Dockerfile commands to have options - e.g:
COPY --user=john foo /tmp/
COPY --ignore-mtime foo /tmp/
Supports both booleans and strings.
Signed-off-by: Doug Davis <dug@us.ibm.com>
Upstream-commit: a8e871b0bbbb63310f372332176875ffcc01aaf6
Component: engine