Ignore folders files (#651)

# Add .gitignore-Aware File Filtering to gemini-cli

This pull request introduces .gitignore-based file filtering to the gemini-cli, ensuring that git-ignored files are automatically excluded from file-related operations and suggestions throughout the CLI. The update enhances usability, reduces noise from build artifacts and dependencies, and provides new configuration options for fine-tuning file discovery.

Key Improvements
.gitignore File Filtering

All @ (at) commands, file completions, and core discovery tools now honor .gitignore patterns by default.
Git-ignored files (such as node_modules/, dist/, .env, and .git) are excluded from results unless explicitly overridden.
The behavior can be customized via a new fileFiltering section in settings.json, including options for:
Turning .gitignore respect on/off.
Adding custom ignore patterns.
Allowing or excluding build artifacts.
Configuration & Documentation Updates

settings.json schema extended with fileFiltering options.
Documentation updated to explain new filtering controls and usage patterns.
Testing

New and updated integration/unit tests for file filtering logic, configuration merging, and edge cases.
Test coverage ensures .gitignore filtering works as intended across different workflows.
Internal Refactoring

Core file discovery logic refactored for maintainability and extensibility.
Underlying tools (ls, glob, read-many-files) now support git-aware filtering out of the box.


Co-authored-by: N. Taylor Mullen <ntaylormullen@google.com>

packages/core/src/utils/gitIgnoreParser.ts

@@ -0,0 +1,116 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import * as fs from 'fs/promises';
+import * as path from 'path';
+import { minimatch } from 'minimatch';
+import { isGitRepository } from './gitUtils.js';
+
+export interface GitIgnoreFilter {
+  isIgnored(filePath: string): boolean;
+  getIgnoredPatterns(): string[];
+}
+
+export class GitIgnoreParser implements GitIgnoreFilter {
+  private ignorePatterns: string[] = [];
+  private projectRoot: string;
+  private isGitRepo: boolean = false;
+
+  constructor(projectRoot: string) {
+    this.projectRoot = path.resolve(projectRoot);
+  }
+
+  async initialize(): Promise<void> {
+    this.isGitRepo = isGitRepository(this.projectRoot);
+    if (this.isGitRepo) {
+      const gitIgnoreFiles = [
+        path.join(this.projectRoot, '.gitignore'),
+        path.join(this.projectRoot, '.git', 'info', 'exclude'),
+      ];
+
+      // Always ignore .git directory regardless of .gitignore content
+      this.ignorePatterns = ['.git/**', '.git'];
+
+      for (const gitIgnoreFile of gitIgnoreFiles) {
+        try {
+          const content = await fs.readFile(gitIgnoreFile, 'utf-8');
+          const patterns = this.parseGitIgnoreContent(content);
+          this.ignorePatterns.push(...patterns);
+        } catch (_error) {
+          // File doesn't exist or can't be read, continue silently
+        }
+      }
+    }
+  }
+
+  private parseGitIgnoreContent(content: string): string[] {
+    return content
+      .split('\n')
+      .map((line) => line.trim())
+      .filter((line) => line && !line.startsWith('#'))
+      .map((pattern) => {
+        // Handle negation patterns (!) - for now we'll skip them
+        if (pattern.startsWith('!')) {
+          return null;
+        }
+
+        // Convert gitignore patterns to minimatch-compatible patterns
+        if (pattern.endsWith('/')) {
+          // Directory pattern - match directory and all contents
+          const dirPattern = pattern.slice(0, -1); // Remove trailing slash
+          return [dirPattern, dirPattern + '/**'];
+        }
+
+        // If pattern doesn't contain /, it should match at any level
+        if (!pattern.includes('/') && !pattern.startsWith('**/')) {
+          return '**/' + pattern;
+        }
+
+        return pattern;
+      })
+      .filter((pattern) => pattern !== null)
+      .flat() as string[];
+  }
+
+  isIgnored(filePath: string): boolean {
+    // If not a git repository, nothing is ignored
+    if (!this.isGitRepo) {
+      return false;
+    }
+
+    // Normalize the input path (handle ./ prefixes)
+    let cleanPath = filePath;
+    if (cleanPath.startsWith('./')) {
+      cleanPath = cleanPath.slice(2);
+    }
+
+    // Convert to relative path from project root
+    const relativePath = path.relative(
+      this.projectRoot,
+      path.resolve(this.projectRoot, cleanPath),
+    );
+
+    // Handle paths that go outside project root
+    if (relativePath.startsWith('..')) {
+      return false;
+    }
+
+    // Normalize path separators for cross-platform compatibility
+    const normalizedPath = relativePath.replace(/\\/g, '/');
+
+    return this.ignorePatterns.some((pattern) =>
+      minimatch(normalizedPath, pattern, {
+        dot: true,
+        matchBase: false,
+        flipNegate: false,
+      }),
+    );
+  }
+
+  getIgnoredPatterns(): string[] {
+    return [...this.ignorePatterns];
+  }
+}