Allow passing in an existing ArgParser for a command.

Allow passing in an existing ArgParser for a command.

R=gram@google.com

Committed: https://code.google.com/p/dart/source/detail?r=22973

[Bob Nystrom, 2013-05-21 22:43:39]

I'm working on making pub use the args package's command support and this will
help.

[gram, 2013-05-21 23:11:07]

The specific change lgtm but the feature needs more explanation.

https://codereview.chromium.org/15621002/diff/1/pkg/args/lib/args.dart
File pkg/args/lib/args.dart (right):

https://codereview.chromium.org/15621002/diff/1/pkg/args/lib/args.dart#newcod...
pkg/args/lib/args.dart:185: * entered and what options were provided for it.
Can you elaborate more here? Can an argparser have more than one command? Can a
command line have more than one command? How are the arguments then split
between multiple commands? What if there is ambiguity?

It's cool that we have this feature but there is a lot left out in this
description.

[Bob Nystrom, 2013-05-21 23:20:15]

https://codereview.chromium.org/15621002/diff/1/pkg/args/lib/args.dart
File pkg/args/lib/args.dart (right):

https://codereview.chromium.org/15621002/diff/1/pkg/args/lib/args.dart#newcod...
pkg/args/lib/args.dart:185: * entered and what options were provided for it.
On 2013/05/21 23:11:07, gram wrote:
> Can you elaborate more here? Can an argparser have more than one command? Can
a
> command line have more than one command? How are the arguments then split
> between multiple commands? What if there is ambiguity?

There's lots of tests for these cases, but little docs.

> 
> It's cool that we have this feature but there is a lot left out in this
> description.

Added some more docs.

[Bob Nystrom, 2013-05-21 23:20:38]

Committed patchset #2 manually as r22973 (presubmit successful).