sbt.sh -S-X option does nothing #6785
Description
steps
$ sbt --version
sbt version in this project: 1.5.6
sbt script version: 1.5.6
$ cat build.sbt
scalacOptions ++= Seq("-Ywarn-dead-code")
$ sbt 'show scalacOptions'
[info] welcome to sbt 1.5.6 (Oracle Corporation Java 11.0.13)
[info] loading global plugins from /home/lukas/.sbt/1.0/plugins
[info] loading project definition from /home/lukas/sbt-reproduce/project
[info] loading settings for project sbt-reproduce from build.sbt ...
[info] set current project to sbt-reproduce (in build file:/home/lukas/sbt-reproduce/)
[info] * -Ywarn-dead-code
[success] Total time: 0 s, completed Jan 10, 2022, 7:55:38 PM
$ sbt -S-Ywarn-value-discard 'show scalacOptions'
[info] welcome to sbt 1.5.6 (Oracle Corporation Java 11.0.13)
[info] loading global plugins from /home/lukas/.sbt/1.0/plugins
[info] loading project definition from /home/lukas/sbt-reproduce/project
[info] loading settings for project sbt-reproduce from build.sbt ...
[info] set current project to sbt-reproduce (in build file:/home/lukas/sbt-reproduce/)
[error] Expected symbol
[error] Not a valid command: -
[error] Expected end of input.
[error] Expected '--'
[error] Expected 'debug'
[error] Expected 'info'
[error] Expected 'warn'
[error] Expected 'error'
[error] Expected 'addPluginSbtFile'
[error] -S-Ywarn-value-discard
problem
CLI option -S-X add -X to sbt's scalacOptions (-S is stripped) defined here https://github.com/sbt/sbt/blob/develop/sbt#L583 does not work as expected.
expectation
Expected behavior is appended scalac option provided via CLI option:
$ sbt 'show scalacOptions'
[info] welcome to sbt 1.5.6 (Oracle Corporation Java 11.0.13)
[info] loading global plugins from /home/lukas/.sbt/1.0/plugins
[info] loading project definition from /home/lukas/sbt-reproduce/project
[info] loading settings for project sbt-reproduce from build.sbt ...
[info] set current project to sbt-reproduce (in build file:/home/lukas/sbt-reproduce/)
[info] * -Ywarn-dead-code
[info] * -Ywarn-value-discard
notes
Seems like it's not even being handled by the process_args function https://github.com/sbt/sbt/blob/develop/sbt#L655L686