To specify the version of SBT you want to use on your SBT project, specify the
sbt.version configuration parameter in the project/build.properties file in your SBT project:
sbt.version = 1.2.6
For example, if your project directory is named /Users/Al/Foo, the file would be here:
You can currently find more information about this setting on this scala-sbt.org page.