Use sbt native thin client for sbt >= 1.4

[steinybot]

I saw this tweet by Eugene and didn't realise that this was a thing. I thought it would be a cool default for sbt-github-actions.

[steinybot]

Woops. olafurpg/setup-scala@v10 doesn't install sbtn yet.

[steinybot]

Arghh this doesn't work as expected either.

It ends up doing:

Run sbt --client ++2.12.13 scalafmtCheckAll scalastyle
[info] entering *experimental* thin client - BEEP WHIRR
[info] terminate the server with `shutdown`
> ++2.12.13 scalafmtCheckAll scalastyle
[error] Expected ';'
[error] ++2.12.13 scalafmtCheckAll scalastyle
[error]                                      ^
[error] Total time: 0 s, completed Mar 24, 2021, 9:35:06 AM

Which returns a 0 exit code and doesn't fail the GitHub step.

[steinybot]

Multi-command handling issue: sbt/sbt#5969
Exit code zero issue: sbt/sbt#6196

[steinybot]

Latest commit works around sbt/sbt#5969.

Should probably hold off merging this until sbt/sbt#6196 is fixed otherwise builds will have false positives. We can exclude the buggy 1.4.x versions from using sbtn.

[djspiewak]

Hmm, this is interesting! I think we should probably make it configurable as a separate setting. Maybe something like githubWorkflowUseSbtThinClient? And then we can set that to false for anything which is < 1.4 or in the set of buggy versions. What do you think?

[steinybot]

Yeah sure that sounds good.

It doesn't look like it is a bug in sbt but in sbt-extras. I haven't succeeded in getting that recognised as a bug yet. I also raised olafurpg/setup-scala#36 to get sbtn support (I mistakenly thought sbt --client was the same thing but it's not).

[steinybot]

Huh maybe I was right after all. The sbt docs seem to say that sbt --client does run the native thin client but only when using the official launcher.