feat: add Windows Git Bash support to bash tool

Add platform detection and Git Bash integration for Windows:
- Detect Windows platform using process.platform
- Search for Git Bash in common installation paths
- Use taskkill for process tree termination on Windows
- Maintain backward compatibility with Unix/Linux/Mac systems
- Add helpful error message if Git Bash not found on Windows

packages/coding-agent/src/tools/bash.ts

@@ -1,6 +1,83 @@
 import type { AgentTool } from "@mariozechner/pi-ai";
 import { Type } from "@sinclair/typebox";
 import { spawn } from "child_process";
+import { existsSync } from "fs";
+
+/**
+ * Find Git Bash installation on Windows
+ * Searches common installation paths
+ */
+function findGitBash(): string | null {
+	if (process.platform !== "win32") {
+		return null;
+	}
+
+	const paths = ["C:\\Program Files\\Git\\bin\\bash.exe", "C:\\Program Files (x86)\\Git\\bin\\bash.exe"];
+
+	// Also check ProgramFiles environment variables
+	const programFiles = process.env.ProgramFiles;
+	if (programFiles) {
+		paths.push(`${programFiles}\\Git\\bin\\bash.exe`);
+	}
+
+	const programFilesX86 = process.env["ProgramFiles(x86)"];
+	if (programFilesX86) {
+		paths.push(`${programFilesX86}\\Git\\bin\\bash.exe`);
+	}
+
+	for (const path of paths) {
+		if (existsSync(path)) {
+			return path;
+		}
+	}
+
+	return null;
+}
+
+/**
+ * Get shell configuration based on platform
+ */
+function getShellConfig(): { shell: string; args: string[] } {
+	if (process.platform === "win32") {
+		const gitBash = findGitBash();
+		if (!gitBash) {
+			throw new Error(
+				"Git Bash not found. Please install Git for Windows from https://git-scm.com/download/win and ensure it's installed with Git Bash support.",
+			);
+		}
+		return { shell: gitBash, args: ["-c"] };
+	}
+	return { shell: "sh", args: ["-c"] };
+}
+
+/**
+ * Kill a process and all its children
+ */
+function killProcessTree(pid: number): void {
+	if (process.platform === "win32") {
+		// Use taskkill on Windows to kill process tree
+		try {
+			spawn("taskkill", ["/F", "/T", "/PID", String(pid)], {
+				stdio: "ignore",
+				detached: true,
+			});
+		} catch (e) {
+			// Ignore errors if taskkill fails
+		}
+	} else {
+		// Use SIGKILL on Unix/Linux/Mac
+		try {
+			process.kill(-pid, "SIGKILL");
+		} catch (e) {
+			// Fallback to killing just the child if process group kill fails
+			try {
+				process.kill(pid, "SIGKILL");
+			} catch (e2) {
+				// Process already dead
+			}
+		}
+	}
+}
 
 const bashSchema = Type.Object({
 	command: Type.String({ description: "Bash command to execute" }),
@@ -19,7 +96,8 @@ export const bashTool: AgentTool<typeof bashSchema> = {
 		signal?: AbortSignal,
 	) => {
 		return new Promise((resolve, _reject) => {
-			const child = spawn("sh", ["-c", command], {
+			const { shell, args } = getShellConfig();
+			const child = spawn(shell, [...args, command], {
 				detached: true,
 				stdio: ["ignore", "pipe", "pipe"],
 			});
@@ -115,17 +193,7 @@ export const bashTool: AgentTool<typeof bashSchema> = {
 			// Handle abort signal - kill entire process tree
 			const onAbort = () => {
 				if (child.pid) {
-					// Kill the entire process group (negative PID kills all processes in the group)
-					try {
-						process.kill(-child.pid, "SIGKILL");
-					} catch (e) {
-						// Fallback to killing just the child if process group kill fails
-						try {
-							child.kill("SIGKILL");
-						} catch (e2) {
-							// Process already dead
-						}
-					}
+					killProcessTree(child.pid);
 				}
 			};