Bump pub to a949b329b1b51f5f3973a790e0a0a45897d837de
Bump pub to a949b329b1b51f5f3973a790e0a0a45897d837de

Changes:
```
> git log --format="%C(auto) %h %s" a3a102a..a949b32
 https://dart.googlesource.com/pub.git/+/a949b329 Fix handling of 'git@github.com:dart-lang/pub.git' style urls in git source (#3381)
 https://dart.googlesource.com/pub.git/+/c6cd3758 Always use forward slash for relative paths in lockfile (#3379)
 https://dart.googlesource.com/pub.git/+/7d48f902 Remove unused function (#3370)
 https://dart.googlesource.com/pub.git/+/b1373d4c Fix import prefix (#3369)

```

Diff: https://dart.googlesource.com/pub.git/+/a3a102a549388a6dbfecc9252fabb618f9a2f5f7~..a949b329b1b51f5f3973a790e0a0a45897d837de/

A bunch of bugfixes.

Change-Id: I1f791cad27194359091f489f36dcc3ad2b78bb31
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/240052
Reviewed-by: Jonas Jensen <c9327fa216ae2ef84df7c55b809d4ba270141b48@google.com>
Commit-Queue: Sigurd Meldgaard <3f12f2c0f1efe4fd67753fcd55cd7bc21e5b85cf@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk