fix: gitignore handling (#8177)

packages/core/src/utils/geminiIgnoreParser.ts

@@ -0,0 +1,81 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import * as fs from 'node:fs';
+import * as path from 'node:path';
+import ignore from 'ignore';
+
+export interface GeminiIgnoreFilter {
+  isIgnored(filePath: string): boolean;
+  getPatterns(): string[];
+}
+
+export class GeminiIgnoreParser implements GeminiIgnoreFilter {
+  private projectRoot: string;
+  private patterns: string[] = [];
+  private ig = ignore();
+
+  constructor(projectRoot: string) {
+    this.projectRoot = path.resolve(projectRoot);
+    this.loadPatterns();
+  }
+
+  private loadPatterns(): void {
+    const patternsFilePath = path.join(this.projectRoot, '.geminiignore');
+    let content: string;
+    try {
+      content = fs.readFileSync(patternsFilePath, 'utf-8');
+    } catch (_error) {
+      // ignore file not found
+      return;
+    }
+
+    this.patterns = (content ?? '')
+      .split('\n')
+      .map((p) => p.trim())
+      .filter((p) => p !== '' && !p.startsWith('#'));
+
+    this.ig.add(this.patterns);
+  }
+
+  isIgnored(filePath: string): boolean {
+    if (this.patterns.length === 0) {
+      return false;
+    }
+
+    if (!filePath || typeof filePath !== 'string') {
+      return false;
+    }
+
+    if (
+      filePath.startsWith('\\') ||
+      filePath === '/' ||
+      filePath.includes('\0')
+    ) {
+      return false;
+    }
+
+    const resolved = path.resolve(this.projectRoot, filePath);
+    const relativePath = path.relative(this.projectRoot, resolved);
+
+    if (relativePath === '' || relativePath.startsWith('..')) {
+      return false;
+    }
+
+    // Even in windows, Ignore expects forward slashes.
+    const normalizedPath = relativePath.replace(/\\/g, '/');
+
+    if (normalizedPath.startsWith('/') || normalizedPath === '') {
+      return false;
+    }
+
+    return this.ig.ignores(normalizedPath);
+  }
+
+  getPatterns(): string[] {
+    return this.patterns;
+  }
+}