Right now, the quiet (-q, --quiet) flag ignores the output
generated from within the container.
However, it ought to be quiet in a way that all kind
of diagnostic output should be ignored, unless the build
process fails.
This patch makes the quiet flag behave in the following way:
1. If the build process succeeds, stdout contains the image ID
and stderr is empty.
2. If the build process fails, stdout is empty and stderr
has the error message and the diagnostic output of that process.
If the quiet flag is not set, then everything goes to stdout
and error messages, if there are any, go to stderr.
Signed-off-by: Boaz Shuster <ripcurld.github@gmail.com>
60b4db7eb1