iotlab-term: make tmux optional

[miri64]

This issue is two-fold:

1. I don't really understand the iotlab-term target in Makefile.iotlab anymore since the tmux logging feature was introduced in dist: make: iotlab: add logging to iotlab-term via tmux #5351 (main reason why I can't provide a fix myself). Considering that make term should be the simplest command of all that is a little disquieting.
2. Not everyone uses tmux and not everyone knows how to use it. The iotlab-* targets should simplify the usage of the IoT-Lab, so adding knowledge about another tool reduces the usability of these targets in my opinion.

[cgundogan]

Considering that make term should be the simplest command of all that is a little disquieting.

Why should term be the simplest command? The idea of this makefile is to abstract and hide complex command executions.

Not everyone uses tmux and not everyone knows how to use it.

See https://github.com/RIOT-OS/RIOT/blob/master/dist/testbed-support/README.iotlab.md#iotlab-term

One of the incentives of using the aggregator within tmux is that a user can now de-/attach from a running experiment. This was not possible before. I.e. you can start an experiment without the iotlab-term first, and just attach whenever desired and still see the full output (with or without logging enabled).

If you have discomfort with scrolling (I think we had an offline discussion about this once), then just put setw -g mode-mouse on in your .tmux.conf on the remote server. This could be put into the README as an improvement of the doc, but I don't see why we should drop tmux.

[OlegHahm]

While I mostly agree with @cgundogan here, I understand @miri64's concerns. How about offering a simple iotlab-term and an advanced iotlab-tmux target (maybe with different names)?

[miri64]

It's not like I don't know how to handle tmux, but as @OlegHahm states: it hightens the entry bar in my opinion.

[stale]

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