Make sure we refer to 'stable', and not 'release' branch. (#23745)

dev/bots/prepare_package.dart

diff --git a/dev/bots/prepare_package.dart b/dev/bots/prepare_package.dart
index 34464a9..e38e390 100644
--- a/dev/bots/prepare_package.dart
+++ b/dev/bots/prepare_package.dart
@@ -45,7 +45,7 @@
   }
 }
 
-enum Branch { dev, beta, release }
+enum Branch { dev, beta, stable }
 
 String getBranchName(Branch branch) {
   switch (branch) {
@@ -53,8 +53,8 @@
       return 'beta';
     case Branch.dev:
       return 'dev';
-    case Branch.release:
-      return 'release';
+    case Branch.stable:
+      return 'stable';
   }
   return null;
 }
@@ -65,8 +65,8 @@
       return Branch.beta;
     case 'dev':
       return Branch.dev;
-    case 'release':
-      return Branch.release;
+    case 'stable':
+      return Branch.stable;
     default:
       throw ArgumentError('Invalid branch name.');
   }

dev/bots/test/prepare_package_test.dart

diff --git a/dev/bots/test/prepare_package_test.dart b/dev/bots/test/prepare_package_test.dart
index 8e422d7..1b00996 100644
--- a/dev/bots/test/prepare_package_test.dart
+++ b/dev/bots/test/prepare_package_test.dart
@@ -221,7 +221,7 @@
         final String archiveName = platform.isLinux ? 'archive.tar.xz' : 'archive.zip';
         final String archiveMime = platform.isLinux ? 'application/x-gtar' : 'application/zip';
         final String archivePath = path.join(tempDir.absolute.path, archiveName);
-        final String gsArchivePath = 'gs://flutter_infra/releases/release/$platformName/$archiveName';
+        final String gsArchivePath = 'gs://flutter_infra/releases/stable/$platformName/$archiveName';
         final String jsonPath = path.join(tempDir.absolute.path, releasesName);
         final String gsJsonPath = 'gs://flutter_infra/releases/$releasesName';
         final String releasesJson = '''{
@@ -247,10 +247,10 @@
     },
     {
       "hash": "$testRef",
-      "channel": "release",
+      "channel": "stable",
       "version": "v0.0.0",
       "release_date": "2018-03-20T01:47:02.851729Z",
-      "archive": "release/$platformName/flutter_${platformName}_v0.0.0-dev.zip"
+      "archive": "stable/$platformName/flutter_${platformName}_v0.0.0-dev.zip"
     }
   ]
 }
@@ -269,7 +269,7 @@
         final ArchivePublisher publisher = ArchivePublisher(
           tempDir,
           testRef,
-          Branch.release,
+          Branch.stable,
           'v1.2.3',
           outputFile,
           processManager: processManager,
@@ -284,8 +284,8 @@
         final String contents = releaseFile.readAsStringSync();
         // Make sure new data is added.
         expect(contents, contains('"hash": "$testRef"'));
-        expect(contents, contains('"channel": "release"'));
-        expect(contents, contains('"archive": "release/$platformName/$archiveName"'));
+        expect(contents, contains('"channel": "stable"'));
+        expect(contents, contains('"archive": "stable/$platformName/$archiveName"'));
         // Make sure existing entries are preserved.
         expect(contents, contains('"hash": "5a58b36e36b8d7aace89d3950e6deb307956a6a0"'));
         expect(contents, contains('"hash": "b9bd51cc36b706215915711e580851901faebb40"'));

packages/flutter_tools/lib/src/version.dart

diff --git a/packages/flutter_tools/lib/src/version.dart b/packages/flutter_tools/lib/src/version.dart
index 1262c57..c8a39dc 100644
--- a/packages/flutter_tools/lib/src/version.dart
+++ b/packages/flutter_tools/lib/src/version.dart
@@ -47,7 +47,7 @@
     'master',
     'dev',
     'beta',
-    'release',
+    'stable',
   ]);
 
   /// This maps old branch names to the names of branches that replaced them.
@@ -63,7 +63,7 @@
 
   String _channel;
   /// The channel is the upstream branch.
-  /// `master`, `dev`, `beta`, `release`; or old ones, like `alpha`, `hackathon`, ...
+  /// `master`, `dev`, `beta`, `stable`; or old ones, like `alpha`, `hackathon`, ...
   String get channel => _channel;
 
   /// The name of the local branch.

packages/flutter_tools/test/channel_test.dart

diff --git a/packages/flutter_tools/test/channel_test.dart b/packages/flutter_tools/test/channel_test.dart
index 96c2e92..a7bdf64 100644
--- a/packages/flutter_tools/test/channel_test.dart
+++ b/packages/flutter_tools/test/channel_test.dart
@@ -56,8 +56,10 @@
       final Process process = createMockProcess(
           stdout: 'origin/dev\n'
                   'origin/beta\n'
+                  'origin/stable\n'
                   'upstream/dev\n'
-                  'upstream/beta\n');
+                  'upstream/beta\n'
+                  'upstream/stable\n');
       when(mockProcessManager.start(
         <String>['git', 'branch', '-r'],
         workingDirectory: anyNamed('workingDirectory'),
@@ -83,7 +85,7 @@
         .where((String line) => line?.isNotEmpty == true)
         .skip(1); // remove `Flutter channels:` line
 
-      expect(rows, <String>['dev', 'beta']);
+      expect(rows, <String>['dev', 'beta', 'stable']);
     }, overrides: <Type, Generator>{
       ProcessManager: () => mockProcessManager,
     });
@@ -127,6 +129,40 @@
 
       expect(testLogger.statusText, contains("Switching to flutter channel 'beta'..."));
       expect(testLogger.errorText, hasLength(0));
+
+      when(mockProcessManager.start(
+        <String>['git', 'fetch'],
+        workingDirectory: anyNamed('workingDirectory'),
+        environment: anyNamed('environment'),
+      )).thenAnswer((_) => Future<Process>.value(createMockProcess()));
+      when(mockProcessManager.start(
+        <String>['git', 'show-ref', '--verify', '--quiet', 'refs/heads/stable'],
+        workingDirectory: anyNamed('workingDirectory'),
+        environment: anyNamed('environment'),
+      )).thenAnswer((_) => Future<Process>.value(createMockProcess()));
+      when(mockProcessManager.start(
+        <String>['git', 'checkout', 'stable', '--'],
+        workingDirectory: anyNamed('workingDirectory'),
+        environment: anyNamed('environment'),
+      )).thenAnswer((_) => Future<Process>.value(createMockProcess()));
+
+      await runner.run(<String>['channel', 'stable']);
+
+      verify(mockProcessManager.start(
+        <String>['git', 'fetch'],
+        workingDirectory: anyNamed('workingDirectory'),
+        environment: anyNamed('environment'),
+      )).called(1);
+      verify(mockProcessManager.start(
+        <String>['git', 'show-ref', '--verify', '--quiet', 'refs/heads/stable'],
+        workingDirectory: anyNamed('workingDirectory'),
+        environment: anyNamed('environment'),
+      )).called(1);
+      verify(mockProcessManager.start(
+        <String>['git', 'checkout', 'stable', '--'],
+        workingDirectory: anyNamed('workingDirectory'),
+        environment: anyNamed('environment'),
+      )).called(1);
     }, overrides: <Type, Generator>{
       ProcessManager: () => mockProcessManager,
       FileSystem: () => MemoryFileSystem(),