Problem: Unable to configure message targets based on message kind.
Solution: Add cfg.msg.targets mapping message kinds to "cmd/msg/pager".
Check the configured target when writing the message.
cfg.msg = { target = 'cmd', targets = { progress = 'msg', list_cmd = 'pager' } }
will for example use the 'msg' target for progress messages,
immediately open the pager for 'list_cmd' and use the cmdline
for all other message kinds.
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