Revert "Bump pub"

This reverts commit 633d4ace6b.

Reason for revert: breaks dependency resolution in some cases.

Original change's description:
> Bump pub
>
> New commits included:
> ```
> > git log --format="%C(auto) %h %s" 0e657414a472e74ca5dd76ae0db50cc060251dec..255a3091fc278b04be74d246a3bec8743ef4d0b7
>  255a3091 Vendor package:tar and package:chunked_stream (#2932)
>  86bf8b20 Handle relative git-url-paths correctly when --directory (#2919)
>  3716a681 Let `pub add` fail if extra arguments are passed (#2927)
>  a03ac729 Minor cleanup to reduce risk of using path.current (#2924)
>  e87b7b66 Added null check for name in UserInfo class (#2918)
>  056a8c9a pub deps --json (#2896)
>  53a69e27 Fix .packages entries of relative path deps when using --directory (#2916)
>  d6308efc pub upgrade command shows count of discontinued packages (#2908)
>  51744805 Upgrade to the null safe versions of all dependencies (#2913)
>  e0d538c7 Introduce .pubignore (#2787)
>  79f3a8b9 pub outdated: added clear message when no outdated packages. (#2898)
>  22463872 `cache clean` (#2904)
>  11e7b2ce `publish --dry-run` informs that the server might do more checks (#2883)
>  b6977d50 Remove untrue assert (#2884)
>  35841f8d Merge branch 'cherry_picks_for_2_12'
>  0db3255b Don't fail on failed status listing (#2877)
>  53e8ecca Don't allow outdated taking arguments (#2872)
>  e83a1dc1 Enable asserts when testing pub (#2754)
>  178f2edb Add --directory option (#2876)
>  5aadb70e Don't fail on failed status listing (#2877)
>  4bf8a927 Remove unused field (#2878)
>  73ad5426 Don't allow outdated taking arguments (#2872)
>  9a70949e Use Dart library to read and write tar files (#2817)
>  2f74230c Do not recommend decativating packages (#2871)
>  b1697a27 Use full error message string in CommandResolutionFailedException (#2870)
>  16a6210d Upgrade `downgrade --help`: `downgrade` actually updates `pubspec.lock` (#2859)
>  6e240ea9 Use cached version listings as heuristic when prefetching (#2851)
>  58152f7c Allow trailing slash in PUB_HOSTED_URL (#2856)
>  b1bf9a33 Handle poor package-listing responses robustly. (#2847)
>  d941bd24 Fix request metadata when overriding dependencyType (#2848)
>  ```
>
> Change-Id: Id6ed5698330fc0cdb507e024eabc34f925ca9208
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/192304
> Commit-Queue: Sigurd Meldgaard <sigurdm@google.com>
> Reviewed-by: Jonas Jensen <jonasfj@google.com>

TBR=sigurdm@google.com,jonasfj@google.com

Change-Id: I364a26468a36438bbbc887e613241030decef4d3
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/192748
Reviewed-by: Alexander Thomas <athom@google.com>
Commit-Queue: Alexander Thomas <athom@google.com>

CHANGELOG.md

@@ -40,34 +40,6 @@ Updated the Linter to `1.2.1`, which includes:
 - new lint: `use_named_constants`.
 - deprecation of `avoid_as`.
 
-### Pub
-
-* `dart pub publish` now respects `.pubignore` files with gitignore-style rules.
- `.gitignore` files in the repo are still respected if they are not
-  overridden by a `.pubignore` in the same directory.
-
-  pub no longer queries git for listing the files. This implies:
-  * Checked in files will now be ignored if they are included by a `.gitignore`
-    rule.
-  * Global ignores are no longer taken into account.
-  * Even packages that are not in git source control will have their
-    `.gitignore` files respected.
-
-* New flag `dart pub deps --json` gives a machine parsable overview of the
-  current dependencies.
-* New command: `dart pub cache clean`. Will delete everything in your current
-  pub cache.
-* Commands related to a single package now takes a `--directory` option to
-  operate on a package in the given directory instead of the working directory.
-* git dependencies with a relative repo url would previously be interpreted
-  relative to the current package, even for transitive dependencies. This now
-  fails instead.
-
-* Pub now uses a Dart library to read and write tar files.
-  This should fix several issues we had with incompatibilities between different
-  system `tar`s.
-* `PUB_HOSTED_URL` can now include a trailing slash.
-
 ## 2.12.2 - 2021-03-17
 
 This is a patch release that fixes crashes reported by Flutter 2 users (issue

DEPS

@@ -136,7 +136,7 @@ vars = {
   "pool_rev": "7abe634002a1ba8a0928eded086062f1307ccfae",
   "process_rev": "56ece43b53b64c63ae51ec184b76bd5360c28d0b",
   "protobuf_rev": "0d03fd588df69e9863e2a2efc0059dee8f18d5b2",
-  "pub_rev": "255a3091fc278b04be74d246a3bec8743ef4d0b7",
+  "pub_rev": "0e657414a472e74ca5dd76ae0db50cc060251dec",
   "pub_semver_rev": "f50d80ef10c4b2fa5f4c8878036a4d9342c0cc82",
   "resource_rev": "6b79867d0becf5395e5819a75720963b8298e9a7",
   "root_certificates_rev": "7e5ec82c99677a2e5b95ce296c4d68b0d3378ed8",