JLine 3: resolve status of history and h? commands

[SethTisue]

commented-out code in the PR:

    // TODO maybe just drop these commands, as jline subsumes them -- before reenabling, finish scala.tools.nsc.interpreter.jline.HistoryAdaptor
     //historyCommand,
     //cmd("h?", "<string>", "search the history", searchHistory),

[SethTisue]

control-R already works for searching history. (this was true in JLine 2 as well.)

[hvesalai]

emacs-sbt-mode uses the history commands as well and also expects the commands run from emacs to be there (i.e. when jline is off, I guess)

[SethTisue]

I've made this ticket history-only, labeled it a blocker, and moved the edit stuff to a new ticket (#700)

[SethTisue]

now that I take a second, slower look at this I see that :history shows the history (optional numeric argument of how many entries to show) and :h? is for searching it:

scala 2.13.1> 2 + 2
res0: Int = 4

scala 2.13.1> 3 + 4
res1: Int = 7

scala 2.13.1> 5 + 6
res2: Int = 11

scala 2.13.1> :history
  1  2 + 2
  2  3 + 4
  3  5 + 6
  4  :history

scala 2.13.1> :h? 5
3 5 + 6
5 :h? 5

scala 2.13.1> :history 2
  5  :h? 5
  6  :history 2

[SethTisue]

@hvesalai I see that emacs-sbt-mode reads ~/.scala_history; note that we're changing it to ~/.scala_history_jline3

you write "uses the history commands as well" and I'm puzzled about that. I'm looking in the sbt-emacs-mode source code and I see that it uses :completions, but I do not see that it uses either :history or :h?

based on my observations, I'm removing the "blocker" label from this, but I can add it back if you can confirm that it's specifically :history and/or :h? that you want/need

[SethTisue]

Another thing I hadn't understood before: in JLine 3, history search is connected to up-arrow. So if you type e.g. pr and then hit up arrow, it starts cycling through previous entries that begin with pr. Dotty and Ammonite both support this. It doesn't make :h? useless, I guess, but the need for it to exist is now less.

It already works in our PR, too. (Perhaps not perfectly?)