“did you want benchable6 or committable6?”

[AlexDaniel]

When the message starts with HEAD, releases, 2015.12, etc. it is clear that somebody wanted to use committable or benchable, not bisectable.

I think bisectable can detect that and print a useful error message.

[AlexDaniel]

Or maybe it should simply ignore the first word

[AlexDaniel]

By the way, this syntax is now also supported:

<AlexDaniel> bisect: 2015.12,2016.01 say rand <bisectable6> AlexDaniel, Using old=2015.12 new=2016.01 in an attempt to DWIM <bisectable6> AlexDaniel, Bisecting by output (old=2015.12 new=2016.01) because on both starting points the exit code is 0 … … …

But it doesn't understand a single revision because IIRC there are cases when it would be ambiguous.