How to specify the output directory for Dart's "pub deploy"?

How to specify the output directory for Dart's "pub deploy"?

With Dart's "pub" tool and its "deploy" command, you can create a
deployable version of your Dart web application. The output is written to
the "deploy" directory. I want to know if there's a way to specify a
different output directory?
I looked search the internet for a command-line option, but found no
mention of it. Running "pub help deploy" shows no options for the deploy
command.
If "pub deploy" has no output directory option, I want to find the
pub.dart source code. I create my own version of it that accepts an output
directory option. Unfortunately, I can't find pub.dart in the SDK. I found
the pub shell script. It calls pub.dart.snapshot, which is 100 thousand
lines of unintelligible Dart bytecode. Is there a human readable pub.dart
file? Is it in the SDK?
Your help is appreciated.