VS Code扩展：通过文件系统监控检测Git分支变更

npm install chokidar
# 或者 yarn add chokidar

import * as vscode from 'vscode';
import * as path from 'path';
import * as fs from 'fs';
import * as chokidar from 'chokidar';

let watcher: chokidar.FSWatcher | undefined;

export function activate(context: vscode.ExtensionContext) {
    console.log('Congratulations, your extension "my-git-branch-watcher" is now active!');

    // 获取当前工作区的根目录
    const workspaceRoot = vscode.workspace.workspaceFolders?.[0]?.uri.fsPath;

    if (!workspaceRoot) {
        vscode.window.showWarningMessage('No workspace folder found. Cannot monitor Git HEAD.');
        return;
    }

    const gitHeadPath = path.join(workspaceRoot, '.git', 'HEAD');

    // 检查 .git/HEAD 文件是否存在
    if (!fs.existsSync(gitHeadPath)) {
        vscode.window.showWarningMessage(`Git repository not found at ${workspaceRoot}. Cannot monitor Git HEAD.`);
        return;
    }

    // 3. 设置文件系统观察器
    watcher = chokidar.watch(gitHeadPath, {
        persistent: true, // 保持进程活跃
        ignoreInitial: true, // 忽略初始化时的文件状态，只监听后续变化
        awaitWriteFinish: { // 等待文件写入完成，避免读取到不完整的内容
            stabilityThreshold: 50,
            pollInterval: 10
        }
    });

    // 4. 监听 'change' 事件
    watcher.on('change', async (filePath) => {
        console.log(`Git HEAD file changed: ${filePath}`);
        try {
            // 5. 读取新的分支名称
            const headContent = await fs.promises.readFile(filePath, 'utf8');
            const currentBranch = parseGitHeadContent(headContent);

            if (currentBranch) {
                vscode.window.showInformationMessage(`Git branch switched to: ${currentBranch}`);
                // 在这里触发你的扩展逻辑
                triggerMyExtensionLogic(currentBranch);
            } else {
                vscode.window.showWarningMessage('Could not determine current branch from .git/HEAD.');
            }
        } catch (error: any) {
            console.error('Error reading .git/HEAD:', error.message);
        }
    });

    watcher.on('error', (error) => console.error('Watcher error:', error));

    console.log(`Monitoring Git HEAD at: ${gitHeadPath}`);
}

// 解析 .git/HEAD 文件内容以获取当前分支名
function parseGitHeadContent(content: string): string | null {
    const match = content.match(/^ref: refs\/heads\/(.*)$/m);
    if (match && match[1]) {
        return match[1].trim();
    }
    // 处理分离头指针（detached HEAD）的情况，直接返回SHA值或提示
    if (content.match(/^[0-9a-f]{40}$/i)) {
        return `(detached HEAD: ${content.substring(0, 7)})`;
    }
    return null;
}

// 示例：触发你的扩展逻辑
function triggerMyExtensionLogic(branchName: string) {
    // 你的自定义功能代码
    console.log(`Extension logic triggered for branch: ${branchName}`);
    // 例如：更新状态栏、刷新某个视图、执行其他Git操作等
}

export function deactivate() {
    // 资源清理：在扩展停用时关闭观察器
    if (watcher) {
        watcher.close();
        console.log('Git HEAD watcher closed.');
    }
}