sstream-mirror outputs non-error output to stderr

[Jeff Lane ]

while trying to incorporate sstream-mirror into a shell script, I realised that the output is being dumped directly to stderr, rather than having normal output dumped to stdout with only error output being dumped to stderr.

Even when --progress is not used, and --log-file IS used, output like the following is still written to stderr, rather than stdout:

+ com.ubuntu.cloud.daily:server:14.04:arm64 20170619 disk1.img server/trusty/20170619/trusty-server-cloudimg-arm64-disk1.img 363 Mb
+ com.ubuntu.cloud.daily:server:14.04:arm64 20170619 lxd.tar.xz server/trusty/20170619/trusty-server-cloudimg-arm64-lxd.tar.xz 0 Mb
+ com.ubuntu.cloud.daily:server:14.04:arm64 20170619 uefi1.img server/trusty/20170619/trusty-server-cloudimg-arm64-uefi1.img 365 Mb
+ com.ubuntu.cloud.daily:server:14.04:arm64 20170619 root.tar.gz server/trusty/20170619/trusty-server-cloudimg-arm64-root.tar.gz 172 Mb
+ com.ubuntu.cloud.daily:server:14.04:arm64 20170619 root.tar.xz server/trusty/20170619/trusty-server-cloudimg-arm64-root.tar.xz 110 Mb
+ com.ubuntu.cloud.daily:server:14.04:arm64 20170619 tar.gz server/trusty/20170619/trusty-server-cloudimg-arm64.tar.gz 341 Mb

What should happen is ONLY error messaging is written to stderr, and information like the above is written quietly to LOG_FILE when specified OR stdout when --log-file is not.

Even better, NO output is generated at all to screen (except for error messaging) unless --verbose is used.

So behaviour would look something like this:

--verbose would trigger full console output.
--log-file LOG_FILE would dump all output to LOG_FILE (regardless of verbose or quiet selection)
--quiet would suppress console output (except for error messages)