Eugene Yokota 06ffb4f440 warn about multiple instance once ... Fixes #3823 When you launch a second instance of sbt on a build, prior to this change it was displaying `java.io.IOException: sbt server is already running` on every command. This make it a bit less aggressive, and just display a warning once. ``` [warn] Is another instance of sbt is running on this build? [warn] Running multiple instances is unsupported ```		2017-12-20 10:09:03 -05:00
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contraband	IPC Unix domain socket for sbt server	2017-11-27 21:37:31 -05:00
contraband-scala	IPC Unix domain socket for sbt server	2017-11-27 21:37:31 -05:00
java/sbt/internal	Only the first session starts the server	2017-12-05 09:14:18 -05:00
scala	warn about multiple instance once	2017-12-20 10:09:03 -05:00