Merge pull request #3223 from eed3si9n/fport/3153

[fport] Remove the "hit [ENTER] to switch to interactive mode" feature

main-command/src/main/scala/sbt/State.scala

@@ -229,15 +229,8 @@ object State {
                  currentCommand = Some(cmd),
                  history = cmd :: s.history))
       }
-      def isInteractive = System.console != null
-      def hasInput = Option(System.console) exists (_.reader.ready())
-      def hasShellCmd = s.definedCommands exists {
-        case c: SimpleCommand => c.name == Shell; case _ => false
-      }
       s.remainingCommands match {
-        case List() =>
-          if (isInteractive && hasInput && hasShellCmd) runCmd(Exec(Shell, s.source), Nil)
-          else exit(true)
+        case List()           => exit(true)
         case List(x, xs @ _*) => runCmd(x, xs.toList)
       }
     }

main/src/main/scala/sbt/Main.scala

@@ -759,15 +759,13 @@ object BuiltinCommands {
       writeSbtVersion(state); state
     }
 
-  private def isInteractive = System.console() != null
-
   private def intendsToInvokeCompile(state: State) =
     state.remainingCommands contains Keys.compile.key.label
 
   private def notifyUsersAboutShell(state: State): Unit = {
     val suppress = Project extract state getOpt Keys.suppressSbtShellNotification getOrElse false
-    if (!suppress && isInteractive && intendsToInvokeCompile(state))
-      state.log info "Executing in batch mode. For better performance use sbt's shell; hit [ENTER] to do so now"
+    if (!suppress && intendsToInvokeCompile(state))
+      state.log info "Executing in batch mode. For better performance use sbt's shell"
   }
 
   private def NotifyUsersAboutShell = "notify-users-about-shell"

notes/0.13.16.markdown

@@ -0,0 +1,93 @@
+### Fixes with compatibility implications
+
+- Removes the "hit \[ENTER\] to switch to interactive mode" feature. See below.
+
+### Improvements
+
+- Improves the new startup messages. See below.
+- Ports sbt-cross-building's `^` and `^^` commands for plugin cross building. See below.
+
+### Bug fixes
+
+- Fixes the new startup messages. See below.
+
+### Improvements and bug fixes to the new startup messages
+
+The two new startup messages introduced in sbt 0.13.15 are:
+
+- when writing out `sbt.version`, for build reproducability, and
+- when informing the user about sbt's shell, for the performance improvement
+
+When writing out `sbt.version` the messaging now:
+
+- correctly uses a logger rather than println
+- honours the log level set, for instance by `--error`
+- never executes when sbt "new" is being run
+
+When informing the user about sbt's shell the messaging now:
+
+- is a 1 line message, rather than 3
+- is at info level, rather than warn level
+- can be suppressed with `suppressSbtShellNotification := true`
+- only triggers when `compile` is being run
+- never shows when sbt `new` is being run
+
+[#3091][3091]/[#3097][3097]/[#3147][3147] by [@dwijnand][@dwijnand]
+
+### Remove the "hit \[ENTER\] to switch to interactive mode" feature
+
+In sbt 0.13.15, in addition to notifying the user about the existence of sbt's shell, a feature was added to
+allow the user to switch to sbt's shell - a more pro-active approach to just displaying a message.
+
+Unfortunately sbt is often unintentionally invoked in shell scripts in "interactive mode" when no interaction is
+expected by, for exmaple, invoking `sbt package` instead of `sbt package < /dev/null`. In that case hitting
+\[ENTER\] would silently trigger sbt to run its shell, easily wrecking the script. In addition to that I was
+unhappy with the implementation as it created a tight coupling between sbt's command processing abstraction to
+sbt's shell command.
+
+If you want to stay in sbt's shell after running a task like `package` then invoke sbt like so:
+
+    sbt package shell
+
+[#3091][3091]/[#3153][3153] by [@dwijnand][@dwijnand]
+
+### sbt-cross-building
+
+[@jrudolph][@jrudolph]'s sbt-cross-building is a plugin author's plugin.
+It adds cross command `^` and sbtVersion switch command `^^`, similar to `+` and `++`,
+but for switching between multiple sbt versions across major versions.
+sbt 0.13.16 merges these commands into sbt because the feature it provides is useful as we migrate plugins to sbt 1.0.
+
+To switch the `sbtVersion in pluginCrossBuild` from the shell use:
+
+```
+^^ 1.0.0-M5
+```
+
+Your plugin will now build with sbt 1.0.0-M5 (and its Scala version 2.12.2).
+
+If you need to make changes specific to a sbt version, you can now include them into `src/main/scala-sbt-0.13`,
+and `src/main/scala-sbt-1.0.0-M5`, where the binary sbt version number is used as postfix.
+
+To run a command across multiple sbt versions, set:
+
+```scala
+crossSbtVersions := Vector("0.13.15", "1.0.0-M5")
+```
+
+Then, run:
+
+```
+^ compile
+```
+
+[#3133][3133] by [@eed3si9n][@eed3si9n]
+
+  [3091]: https://github.com/sbt/sbt/issues/3091
+  [3097]: https://github.com/sbt/sbt/issues/3097
+  [3147]: https://github.com/sbt/sbt/pull/3147
+  [3133]: https://github.com/sbt/sbt/pull/3133
+  [3153]: https://github.com/sbt/sbt/pull/3153
+  [@jrudolph]: https://github.com/jrudolph
+  [@eed3si9n]: https://github.com/eed3si9n
+  [@dwijnand]: https://github.com/dwijnand