[flutter_tools] fix version tag `v` stripping (#55385)

packages/flutter_tools/lib/src/commands/version.dart

@@ -87,7 +87,7 @@ class VersionCommand extends FlutterCommand {
       }
     }
 
-    final String version = argResults.rest[0].replaceFirst('v', '');
+    final String version = argResults.rest[0].replaceFirst(RegExp('^v'), '');
     final List<String> matchingTags = tags.where((String tag) => tag.contains(version)).toList();
     String matchingTag;
     // TODO(fujino): make this a tool exit and fix tests

packages/flutter_tools/test/commands.shard/hermetic/version_test.dart

@@ -71,6 +71,28 @@ void main() {
       FlutterVersion: () => mockVersion,
     });
 
+    testUsingContext('dev version switch prompt is accepted', () async {
+      when(mockStdio.stdinHasTerminal).thenReturn(true);
+      const String version = '30.0.0-dev.0.0';
+      final VersionCommand command = VersionCommand();
+      when(globals.terminal.promptForCharInput(<String>['y', 'n'],
+        logger: anyNamed('logger'),
+        prompt: 'Are you sure you want to proceed?')
+      ).thenAnswer((Invocation invocation) async => 'y');
+
+      await createTestCommandRunner(command).run(<String>[
+        'version',
+        '--no-pub',
+        version,
+      ]);
+      expect(testLogger.statusText, contains('Switching Flutter to version $version'));
+    }, overrides: <Type, Generator>{
+      ProcessManager: () => MockProcessManager(),
+      Stdio: () => mockStdio,
+      AnsiTerminal: () => MockTerminal(),
+      FlutterVersion: () => mockVersion,
+    });
+
     testUsingContext('version switch prompt is declined', () async {
       when(mockStdio.stdinHasTerminal).thenReturn(true);
       const String version = '10.0.0';
@@ -239,7 +261,7 @@ class MockProcessManager extends Mock implements ProcessManager {
       return ProcessResult(0, 0, 'v10.0.0\r\nv20.0.0\r\n30.0.0-dev.0.0', '');
     }
     if (command[0] == 'git' && command[1] == 'checkout') {
-      version = (command[2] as String).replaceFirst('v', '');
+      version = (command[2] as String).replaceFirst(RegExp('^v'), '');
     }
     return ProcessResult(0, 0, '', '');
   }