Document the magic to make sequential inputTask

[devpts00]

Recently I had to make a composite inputTask that is a sequence of tasks and inputTasks. The composite inputTask was supposed to parse some input and then pass the parsed value to the nested inputTasks. There are some basic examples in documentation and googling did not offer much more than that. I had to literally perform a manual brute force attack trying to guess correct syntax that compiles and does what I wanted. The errors were cryptic. Macros expansions were unreadable. The result more or less is:

Keys.release := Def.inputTaskDyn {
  val bump = parserVersionBump.parsed.toString
  Def.sequential(
    Keys.buildNumberNext.toTask(bump),
    sbt.Keys.clean,
    Compile / sbt.Keys.compile,
    Compile / sbt.Keys.doc,
    Test / sbt.Keys.test,
    Keys.versioningTagNext.toTask(bump)
  )
}.evaluated

I confess I'm not a SBT guru, but still it must have been easier to understand what goes on behind the scene.