warn on uncomitted changes (#30235)

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

@@ -72,6 +72,17 @@ class UpgradeCommandRunner {
         );
       }
     }
+    // If there are uncomitted changes we might be on the right commit but
+    // we should still warn.
+    if (!force && await hasUncomittedChanges()) {
+      throwToolExit(
+        'Your flutter checkout has local changes that would be erased by '
+        'upgrading. If you want to keep these changes, it is recommended that '
+        'you stash them via "git stash" or else commit the changes to a local '
+        'branch. If it is okay to remove local changes, then re-run this '
+        'command with --force.'
+      );
+    }
     await resetChanges(gitTagVersion);
     await upgradeChannel(flutterVersion);
     await attemptFastForward();
@@ -81,6 +92,18 @@ class UpgradeCommandRunner {
     return null;
   }
 
+  Future<bool> hasUncomittedChanges() async {
+    try {
+      final RunResult result = await runCheckedAsync(<String>[
+        'git', 'status', '-s'
+      ], workingDirectory: Cache.flutterRoot);
+      return result.stdout.trim().isNotEmpty;
+    } catch (e) {
+      throwToolExit('git status failed: $e');
+    }
+    return false;
+  }
+
   /// Check if there is an upstream repository configured.
   ///
   /// Exits tool if there is no upstream.

packages/flutter_tools/test/commands/upgrade_test.dart

@@ -29,6 +29,7 @@ void main() {
       fakeCommandRunner = FakeUpgradeCommandRunner();
       realCommandRunner = UpgradeCommandRunner();
       processManager = MockProcessManager();
+      fakeCommandRunner.willHaveUncomittedChanges = false;
     });
 
     test('throws on unknown tag, official branch,  noforce', () async {
@@ -49,6 +50,26 @@ void main() {
       expect(await result, null);
     });
 
+    test('throws tool exit with uncommited changes', () async {
+      fakeCommandRunner.willHaveUncomittedChanges = true;
+      final Future<FlutterCommandResult> result = fakeCommandRunner.runCommand(
+        false,
+        gitTagVersion,
+        flutterVersion,
+      );
+      expect(result, throwsA(isA<ToolExit>()));
+    });
+
+    test('does not throw tool exit with uncommited changes and force', () async {
+      fakeCommandRunner.willHaveUncomittedChanges = true;
+      final Future<FlutterCommandResult> result = fakeCommandRunner.runCommand(
+        true,
+        gitTagVersion,
+        flutterVersion,
+      );
+      expect(await result, null);
+    });
+
     test('Doesn\'t throw on known tag, dev branch, no force', () async {
       final Future<FlutterCommandResult> result = fakeCommandRunner.runCommand(
         false,
@@ -127,9 +148,14 @@ void main() {
 }
 
 class FakeUpgradeCommandRunner extends UpgradeCommandRunner {
+  bool willHaveUncomittedChanges = false;
+
   @override
   Future<void> verifyUpstreamConfigured() async {}
 
+  @override
+  Future<bool> hasUncomittedChanges() async => willHaveUncomittedChanges;
+
   @override
   Future<void> resetChanges(GitTagVersion gitTagVersion) async {}