To load an image from a tar file, you can specify
the tar file in the -i/--input option:
docker load -i image_1.tar
or using stdin:
docker load < image_1.tar
cat image_1.tat | docker load
If the image file isn't given the `docker load`
command gets stuck.
To avoid that, the load makes sure the CLI input is
not a terminal or the `--input` option was set.
If not then an error message is shown.
Signed-off-by: Boaz Shuster <ripcurld.github@gmail.com>
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