Use pub_semver package in pub.

sdk/lib/_internal/pub_generated/lib/src/global_packages.dart

 library pub.global_packages;
 import 'dart:async';
 import 'dart:io';
 import 'package:path/path.dart' as p;
 import 'package:barback/barback.dart';
+import 'package:pub_semver/pub_semver.dart';
 import 'barback/asset_environment.dart';
 import 'entrypoint.dart';
 import 'executable.dart' as exe;
 import 'io.dart';
 import 'lock_file.dart';
 import 'log.dart' as log;
 import 'package.dart';
 import 'pubspec.dart';
 import 'sdk.dart' as sdk;
 import 'solver/version_solver.dart';
 import 'source/cached.dart';
 import 'source/git.dart';
 import 'source/path.dart';
 import 'system_cache.dart';
 import 'utils.dart';
-import 'version.dart';
 final _binStubPackagePattern = new RegExp(r"Package: ([a-zA-Z0-9_-]+)");
 class GlobalPackages {
   final SystemCache cache;
   String get _directory => p.join(cache.rootDir, "global_packages");
   String get _binStubDir => p.join(cache.rootDir, "bin");
   GlobalPackages(this.cache);
   Future activateGit(String repo, List<String> executables,
       {bool overwriteBinStubs}) {
     final completer0 = new Completer();
     scheduleMicrotask(() {
@@ skipping 552 matching lines @@
       }
       log.warning(
           "${log.yellow('Warning:')} Pub installs executables into "
               "${log.bold(binDir)}, which is not on your path.\n"
               "You can fix that by adding this to your shell's config file "
               "(.bashrc, .bash_profile, etc.):\n" "\n"
               "  ${log.bold('export PATH="\$PATH":"$binDir"')}\n" "\n");
     }
   }
 }