Add `-error` etc for log levels with one hyphen

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

@@ -52,7 +52,7 @@ object BasicCommandStrings {
 	This will be used as the default level for logging from commands, settings, and tasks.
 	Any explicit `logLevel` configuration in a project overrides this setting.
 
-${runEarly(level.toString)}
+-$level
 
 	Sets the global logging level as described above, but does so before any other commands are executed on startup, including project loading.
 	This is useful as a startup option:
@@ -62,7 +62,9 @@ ${runEarly(level.toString)}
 
   def runEarly(command: String) = s"$EarlyCommand($command)"
   private[sbt] def isEarlyCommand(s: String): Boolean = {
-    s.startsWith(EarlyCommand + "(") && s.endsWith(")")
+    val levelOptions = Level.values.toSeq map { "-" + _ }
+    (s.startsWith(EarlyCommand + "(") && s.endsWith(")")) ||
+      (levelOptions contains s)
   }
 
   val EarlyCommand = "early"

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

@@ -1,5 +1,6 @@
 package sbt
 
+import sbt.util.Level
 import sbt.internal.util.{ AttributeKey, FullReader }
 import sbt.internal.util.complete.{ Completion, Completions, DefaultParsers, History => CHistory, HistoryCommands, Parser, TokenCompletions }
 import sbt.internal.util.Types.{ const, idFun }
@@ -24,10 +25,15 @@ object BasicCommands {
   def ignore = Command.command(FailureWall)(idFun)
 
   def early = Command.arb(earlyParser, earlyHelp) { (s, other) => other :: s }
-  private[this] def earlyParser = (s: State) =>
-    token(EarlyCommand + "(") flatMap { _ =>
+  private[this] def levelParser: Parser[String] =
+    token(Level.Debug.toString) | token(Level.Info.toString) | token(Level.Warn.toString) | token(Level.Error.toString)
+  private[this] def earlyParser: State => Parser[String] = (s: State) =>
+    (token(EarlyCommand + "(") flatMap { _ =>
       otherCommandParser(s) <~ token(")")
-    }
+    }) |
+      (token("-") flatMap { _ =>
+        levelParser
+      })
   private[this] def earlyHelp = Help(EarlyCommand, EarlyCommandBrief, EarlyCommandDetailed)
 
   def help = Command.make(HelpCommand, helpBrief, helpDetailed)(helpParser)

sbt/src/sbt-test/actions/early-command/test

@@ -1 +1,2 @@
+> -error
 > early(error)