More efficient way of finding files that may need to be formatted (#1778)

closes #1776

Author: belav

Src/CSharpier.Cli/CommandLineFormatter.cs

@@ -226,6 +226,27 @@ CancellationToken cancellationToken
                 }
             }
 
+            async IAsyncEnumerable<string> EnumerateNonignoredFiles(string directory)
+            {
+                foreach (var file in fileSystem.Directory.EnumerateFiles(directory))
+                {
+                    yield return file;
+                }
+
+                foreach (var subdirectory in fileSystem.Directory.EnumerateDirectories(directory))
+                {
+                    if (await optionsProvider.IsIgnoredAsync(subdirectory, cancellationToken))
+                    {
+                        continue;
+                    }
+
+                    await foreach (var file in EnumerateNonignoredFiles(subdirectory))
+                    {
+                        yield return file;
+                    }
+                }
+            }
+
             async Task FormatFile(
                 string actualFilePath,
                 string originalFilePath,
@@ -292,16 +313,16 @@ await FormatPhysicalFile(
                     return 1;
                 }
 
-                var tasks = fileSystem
-                    .Directory.EnumerateFiles(
-                        directoryOrFilePath,
-                        "*.*",
-                        SearchOption.AllDirectories
-                    )
-                    .Select(o =>
-                        FormatFile(o, o.Replace(directoryOrFilePath, originalDirectoryOrFile))
-                    )
-                    .ToArray();
+                var tasks = new List<Task>();
+                await foreach (
+                    var file in EnumerateNonignoredFiles(directoryOrFilePath)
+                        .WithCancellation(cancellationToken)
+                )
+                {
+                    var relativePath = file.Replace(directoryOrFilePath, originalDirectoryOrFile);
+                    tasks.Add(FormatFile(file, relativePath));
+                }
+
                 try
                 {
                     await Task.WhenAll(tasks).WaitAsync(cancellationToken);