fix: fix diff functionality

packages/melos/lib/src/common/git.dart

@@ -276,23 +276,8 @@ Future<List<GitCommit>> gitCommitsForPackage(
   String? diff,
   required MelosLogger logger,
 }) async {
-  var revisionRange = diff?.trim();
-  if (revisionRange != null) {
-    if (revisionRange.isEmpty) {
-      revisionRange = null;
-    } else if (!_gitVersionRangeShortHandRegExp.hasMatch(revisionRange)) {
-      // If the revision range is not a valid revision range short hand then we
-      // assume it's a commit or tag and default to the range from that
-      // commit/tag to HEAD.
-      revisionRange = '$revisionRange...HEAD';
-    }
-  }
-
-  if (revisionRange == null) {
-    final latestTag = await gitLatestTagForPackage(package, logger: logger);
-    // If no latest tag is found then we default to the entire git history.
-    revisionRange = latestTag != null ? '$latestTag...HEAD' : 'HEAD';
-  }
+  final revisionRange =
+      await _resolveRevisionRange(package, diff: diff, logger: logger);
 
   logger.trace(
     '[GIT] Getting commits for package ${package.name} for revision range '
@@ -328,6 +313,34 @@ Future<List<GitCommit>> gitCommitsForPackage(
   }).toList();
 }
 
+Future<bool> gitHasDiffInPackage(
+  Package package, {
+  required String? diff,
+  required MelosLogger logger,
+}) async {
+  final revisionRange =
+      await _resolveRevisionRange(package, diff: diff, logger: logger);
+
+  logger.trace(
+    '[GIT] Getting $diff diff for package ${package.name}.',
+  );
+
+  final processResult = await gitExecuteCommand(
+    arguments: [
+      '--no-pager',
+      'diff',
+      '--name-status',
+      revisionRange,
+      '--',
+      '.',
+    ],
+    workingDirectory: package.path,
+    logger: logger,
+  );
+
+  return (processResult.stdout as String).isNotEmpty;
+}
+
 /// Returns the current branch name of the local git repository.
 Future<String> gitGetCurrentBranchName({
   required String workingDirectory,
@@ -396,3 +409,29 @@ Future<bool> gitIsBehindUpstream({
 
   return isBehind;
 }
+
+Future<String> _resolveRevisionRange(
+  Package package, {
+  required String? diff,
+  required MelosLogger logger,
+}) async {
+  var revisionRange = diff?.trim();
+  if (revisionRange != null) {
+    if (revisionRange.isEmpty) {
+      revisionRange = null;
+    } else if (!_gitVersionRangeShortHandRegExp.hasMatch(revisionRange)) {
+      // If the revision range is not a valid revision range short hand then we
+      // assume it's a commit or tag and default to the range from that
+      // commit/tag to HEAD.
+      return '$revisionRange...HEAD';
+    }
+  }
+
+  if (revisionRange == null) {
+    final latestTag = await gitLatestTagForPackage(package, logger: logger);
+    // If no latest tag is found then we default to the entire git history.
+    return latestTag != null ? '$latestTag...HEAD' : 'HEAD';
+  }
+
+  return 'HEAD';
+}

packages/melos/lib/src/package.dart

@@ -689,9 +689,9 @@ extension on Iterable<Package> {
 
     return Pool(10)
         .forEach(this, (package) async {
-          final commits =
-              await gitCommitsForPackage(package, diff: diff, logger: logger);
-          return MapEntry(package, commits.isNotEmpty);
+          final hasDiff =
+              await gitHasDiffInPackage(package, diff: diff, logger: logger);
+          return MapEntry(package, hasDiff);
         })
         .where((event) => event.value)
         .map((event) => event.key)