Add a "global activate" command to pub.

sdk/lib/_internal/pub/lib/src/utils.dart

Index: sdk/lib/_internal/pub/lib/src/utils.dart
diff --git a/sdk/lib/_internal/pub/lib/src/utils.dart b/sdk/lib/_internal/pub/lib/src/utils.dart
index 24c9ecfc76ed0d6f42d327540f52cd139e2ab65e..1c447c24142ddbb342cd40c55ce57f25d24f3d9c 100644
--- a/sdk/lib/_internal/pub/lib/src/utils.dart
+++ b/sdk/lib/_internal/pub/lib/src/utils.dart
@@ -819,3 +819,11 @@ void fail(String message, [innerError, StackTrace innerTrace]) {
     throw new ApplicationException(message);
   }
 }
+
+/// Throw a [DataException] with [message] to indicate that the command has
+/// failed because of invalid input data.
+///
+/// This will report the error and cause pub to exit with [exit_codes.DATA].
+void dataError(String message) {
+  throw new DataException(message);

[nweiz, 2014/06/26 22:43:26]

Is this really worth having a custom function for? It's not used very often and
it doesn't do any extra processing.

[Bob Nystrom, 2014/06/27 00:30:23]

I like having it mainly because it mirrors usageError(), which is used pretty
frequently. However, usageError() has to be on Command (since it accesses the
help stuff from there) and this doesn't. They're conceptually siblings even
though they're defined in different places.

[nweiz, 2014/06/30 19:42:28]

I don't think this parallel will be clear to people reading the code, but keep
it if you want.

[Bob Nystrom, 2014/06/30 20:36:01]

In a later patch, usageError() ends up getting moved too, so I think it will
make a bit more sense.

+}