1 files changed, 116 insertions, 0 deletions
diff --git a/packages/core/src/utils/gitIgnoreParser.ts b/packages/core/src/utils/gitIgnoreParser.ts
new file mode 100644
index 00000000..098281ca
--- /dev/null
+++ b/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];
+  }
+}