This isn't going to make it into -dev.4.0.

This will make it easier to add features to the pubspec and verify that
they're only published with appropriate SDK constraints.

It also simplifies the dependency validator logic around caret
constraints, since it's a lot less likely that anyone will want to
support an SDK older than 1.8.0 at this point.

This more clearly indicates the type of data the class contains. We
were already using in more places than just dependencies, so it makes
sense to have a name that reflects that.

These classes are largely independent of the Package class.

Fix #1560.

* Add metadata to requests to pub.dartlang.org.

This will help pub.dartlang.org better track how packages relate to one
another.

* Fix broken depenency tests.

Those unit tests import pub libraries directly without invoking a
command, so command was throwing an exception. Worse, the Pokemon
exception handler in DependencyValidator was then catching the
StateError, hiding the bug.

Also applied some other changes I suggested.

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//2184303002 .

We still need to verify that a Flutter SDK constraint is only
used with an appropriate Dart SDK constraint.

See #1432

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//2165423002 .

This allows PackageName equality to include description equality, and it
substantially cleans up other logic dealing with sources.

See #912

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//2079303003 .

This splits Source into two classes, Source and LiveSource. The former
is completely independent of the system cache directory, and mostly
contains source metadata and logic about manipulating descriptions.

SourceRegistry now deals strictly in Sources, with LiveSources being
handled by SystemCache. This means that classes like Pubspec and
LockFile no longer have transitive references to the system cache
directory.

This will also make it possible to clean up PackageName equality logic
by making PackageNames track their concrete Sources rather than just
their source names.

See #912

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//2044253003 .

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//1585513002 .

This folds the distinction between "resolved" and "unresolved"
descriptions into the distinction between PackageIds and PackageRefs. In
other words, all PackageIds now have resolved descriptions and all
PackageRefs now have unresolved descriptions. This makes it easier to
track which descriptions are resolved and express resolution constraints
via the type system.

This also restricts the creation of PackageRefs and PackageIds to source
classes, which helps ensure that the description format—which is an
implementation detail—doesn't leak into surrounding code.

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//1528523003 .

This allows getVersion() to return a list of package IDs rather than a
list of pubspecs, which in turn will allow the Git source to return
resolved IDs in #1335.

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//1459733002 .

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//1123323003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@45572 260f80e4-7a28-3924-810f-c04153c831b5

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//1113363004

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@45571 260f80e4-7a28-3924-810f-c04153c831b5

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//1101343004

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@45508 260f80e4-7a28-3924-810f-c04153c831b5

This gets rid of the suggested prerelease suffix for SDK constraints
for pubspecs using the ^ operator, since 1.8.0 itself is out now and
probably no one is using a prerelease version of it.

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//937503002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@43823 260f80e4-7a28-3924-810f-c04153c831b5

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//868463003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@43057 260f80e4-7a28-3924-810f-c04153c831b5

R=rnystrom@google.com
TBR

Review URL: https://codereview.chromium.org//702343002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@41542 260f80e4-7a28-3924-810f-c04153c831b5

R=rnystrom@google.com
BUG=17172

Review URL: https://codereview.chromium.org//686323002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@41538 260f80e4-7a28-3924-810f-c04153c831b5

R=nweiz@google.com

Review URL: https://codereview.chromium.org//602253002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@40849 260f80e4-7a28-3924-810f-c04153c831b5

BUG=https://code.google.com/p/dart/issues/detail?id=18538
R=nweiz@google.com

Review URL: https://codereview.chromium.org//354763006

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@37963 260f80e4-7a28-3924-810f-c04153c831b5

BUG=https://code.google.com/p/dart/issues/detail?id=10582
R=nweiz@google.com

Review URL: https://codereview.chromium.org//344493003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@37464 260f80e4-7a28-3924-810f-c04153c831b5

R=rnystrom@google.com
BUG=

Review URL: https://codereview.chromium.org//171523007

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@32877 260f80e4-7a28-3924-810f-c04153c831b5

This adds a warning for a constraint that only allows a single version
and warnings for constraints with no upper bound or no lower bound. It
also improves the upper bound on suggested pre-1.0 constraints to
follow the current Dart team practice and fixes a bug in
[VersionRange.isAny].

R=rnystrom@google.com
BUG=

Review URL: https://codereview.chromium.org//173113004

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@32867 260f80e4-7a28-3924-810f-c04153c831b5

BUG=https://code.google.com/p/dart/issues/detail?id=12300
R=nweiz@google.com

Review URL: https://codereview.chromium.org//22825024

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@26543 260f80e4-7a28-3924-810f-c04153c831b5

BUG=
R=nweiz@google.com

Review URL: https://codereview.chromium.org//22941002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@26040 260f80e4-7a28-3924-810f-c04153c831b5

R=nweiz@google.com

Review URL: https://codereview.chromium.org//18143002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@24555 260f80e4-7a28-3924-810f-c04153c831b5

BUG=https://code.google.com/p/dart/issues/detail?id=10190
R=nweiz@google.com

Review URL: https://codereview.chromium.org//15347004

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@22913 260f80e4-7a28-3924-810f-c04153c831b5

R=nweiz@google.com

Review URL: https://codereview.chromium.org//13952013

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@22187 260f80e4-7a28-3924-810f-c04153c831b5

BUG=

Review URL: https://codereview.chromium.org//14070010

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@21517 260f80e4-7a28-3924-810f-c04153c831b5

BUG=https://code.google.com/p/dart/issues/detail?id=6354

Review URL: https://codereview.chromium.org//12790006

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@20098 260f80e4-7a28-3924-810f-c04153c831b5

BUG=http://code.google.com/p/dart/issues/detail?id=3732

Review URL: https://codereview.chromium.org//12208138

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@18465 260f80e4-7a28-3924-810f-c04153c831b5

Review URL: https://codereview.chromium.org//12079112

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@18019 260f80e4-7a28-3924-810f-c04153c831b5

Optimize Future.forEach, Future.delay.

Review URL: https://codereview.chromium.org//11865005

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@16954 260f80e4-7a28-3924-810f-c04153c831b5

Pub is still all kinds of broken with this, but it's slightly
less broken. Some tests pass, and at least the code *parses*
after this.

Review URL: https://codereview.chromium.org//11785028

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@16763 260f80e4-7a28-3924-810f-c04153c831b5

BUG=7045

Review URL: https://codereview.chromium.org//11737013

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@16614 260f80e4-7a28-3924-810f-c04153c831b5

BUG=7045

Review URL: https://codereview.chromium.org//11635060

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@16415 260f80e4-7a28-3924-810f-c04153c831b5