fail gracefully when dat share is already running fixes #561

[okdistribute]

fixes #561

[joehand]

Looks good to me! Thanks for putting those error functions in one place!

[max-mapper]

Nice and simple, do we need a test?

[okdistribute]

I tried adding a test but couldn't figure out how to trigger it, the simple stupid way of running a dat instance, not closing it, and opening another one with the same command was not working.

[juliangruber]

I tried adding a test but couldn't figure out how to trigger it, the simple stupid way of running a dat instance, not closing it, and opening another one with the same command was not working.

did you try with a child process too?

[joehand]

added a test

[okdistribute]

thanks @joehand ! I forgot the {end: false}!