Fix tab completion running `sbt console`

Fixes #3841

This fixes console task that internally uses JLine. When `console` is started from batch mode, the tab is printed as is. This is because JLine is not initialized yet.
Calling `usingTerminal` initializes and restores the terminal afterwards.

main/src/main/scala/sbt/Defaults.scala

@@ -1366,12 +1366,13 @@ object Defaults extends BuildCommon {
         (compilers in task).value.scalac match {
           case ac: AnalyzingCompiler => ac.onArgs(exported(s, "scala"))
         }
-      (new Console(compiler))(cpFiles,
-                              (scalacOptions in task).value,
-                              loader,
-                              (initialCommands in task).value,
-                              (cleanupCommands in task).value)()(s.log).get
-      println()
+      val sc = (scalacOptions in task).value
+      val ic = (initialCommands in task).value
+      val cc = (cleanupCommands in task).value
+      JLine.usingTerminal { _ =>
+        (new Console(compiler))(cpFiles, sc, loader, ic, cc)()(s.log).get
+        println()
+      }
     }
 
   private[this] def exported(w: PrintWriter, command: String): Seq[String] => Unit =

main/src/main/scala/sbt/internal/ConsoleProject.scala

@@ -9,6 +9,7 @@ package sbt
 package internal
 
 import sbt.util.Logger
+import sbt.internal.util.JLine
 import sbt.internal.inc.{ ScalaInstance, ZincUtil }
 import xsbti.compile.ClasspathOptionsUtil
 
@@ -42,13 +43,17 @@ object ConsoleProject {
     val imports = BuildUtil.getImports(unit.unit) ++ BuildUtil.importAll(bindings.map(_._1))
     val importString = imports.mkString("", ";\n", ";\n\n")
     val initCommands = importString + extra
-    // TODO - Hook up dsl classpath correctly...
-    (new Console(compiler))(
-      unit.classpath,
-      options,
-      initCommands,
-      cleanupCommands
-    )(Some(unit.loader), bindings)
+
+    JLine.usingTerminal { _ =>
+      // TODO - Hook up dsl classpath correctly...
+      (new Console(compiler))(
+        unit.classpath,
+        options,
+        initCommands,
+        cleanupCommands
+      )(Some(unit.loader), bindings)
+    }
+    ()
   }
 
   /** Conveniences for consoleProject that shouldn't normally be used for builds. */

notes/1.1.1/console_jline.md

@@ -0,0 +1,13 @@
+  [@eed3si9n]: https://github.com/eed3si9n
+
+  [3841]: https://github.com/sbt/sbt/issues/3841
+  [3876]: https://github.com/sbt/sbt/pull/3876
+
+### Fixes with compatibility implications
+
+### Improvements
+
+
+### Bug fixes
+
+- Fixes tab completion in `console` while running in batch mode as `sbt console`. [#3841][3841]/[#3876][3876] by [@eed3si9n][@eed3si9n]