[Feature Proposal] Add git controls tab in web UI (like GitHub Desktop) / 在 Web 端增加类 GitHub Desktop 风格的 Git 控制与仓库检查标签页

[rrb-rushikesh]

I put together a third tab for the web client to handle Git controls (view changes, commits history, diff viewer, and branch switching) styled like GitHub Desktop.

Links

• Branch: rrb-rushikesh/deepseek-harness @ feat/web-git-controls-tab
• Comparison: master...rrb-rushikesh:deepseek-harness:feat/web-git-controls-tab

Main things added

• Top bar: Repo name, branch selector, and sync/fetch button with status indicators
• Left sidebar: Dual sub-tabs for Changes (staged checkboxes, commit box) and History (commits log with search)
• Diff viewer: Side-by-side or unified diff view with syntax highlighting and hunk headers
• Branch modal: Dialog for switching branches and creating new branches

It uses the existing UI components and tokens, supports both en and zh, and passes all local checks (test:gui, typecheck, lint).

Since PRs are currently closed during pre-release, sharing the branch here. Let me know what you think or if you'd like to pull this in!

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中文说明 (Chinese)

我在 Web 客户端（Chat 与 Trajectory 旁）新增了第三个标签页，用于提供类似 GitHub Desktop 风格的 Git 控制功能（查看工作区变更、提交历史、代码差异查看器和分支切换）。

相关链接

• 分支: rrb-rushikesh/deepseek-harness @ feat/web-git-controls-tab
• 对比 Diff: master...rrb-rushikesh:deepseek-harness:feat/web-git-controls-tab

主要功能

• 顶部工具栏: 显示仓库名、分支选择器、同步/拉取按钮（带状态指示和时间戳）
• 左侧面板: 支持 Changes（文件暂存多选框、提交输入框）与 History（带搜索的提交记录）双子标签切换
• 代码差异对比器: 支持并排/合并模式（Split / Unified）、行增删高亮与 hunk 头部显示
• 分支管理弹窗: 支持切换现有分支与创建新分支

该功能完全遵循 Harness 现有的 UI 基础组件和设计系统 Token，支持中英双语，并通过了全部本地质量检查（test:gui、typecheck、lint）。

由于预发布阶段 PR 暂未开放，在此先行分享该分支。欢迎核心团队提供反馈或在适当时机合入主干！

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[tianhao8687]

The UI direction is useful, but the integration should not execute Git commands directly from the browser or hide mutations behind an unreviewed Host endpoint. Git is workspace-scoped, not conversation-scoped, so this also fits better as a root/workspace page (and would be a strong consumer for the extension point proposed in #2873).

A safe delivery sequence would be:

1. Ship a read-only capability first: repository identity, status, log, refs, and bounded diff. Every call takes an explicit validated repository root under the selected Workspace, supports cancellation/timeouts, and returns structured data rather than shell text.
2. Add mutations separately: stage/unstage, commit, checkout/create branch, fetch/push. They must use the same permission/approval policy as shell operations, with the exact repo, ref, paths and commit message shown before execution.
3. Never background-fetch without an explicit user setting, and never allow an interactive credential prompt to hang the Host process.
4. Log model-visible Git state and mutation results through the Session event path; keep credentials out of events and client responses.

The test matrix should include a non-repo directory, dirty tree, detached HEAD, renames/deletes, binary and very large diffs, submodules, checkout conflicts, cancellation, and unavailable credentials. A branch switch must fail without modifying the tree when local changes would be lost.

The screenshots and bilingual UI are a good prototype. Separating the Git capability/service from the tab now will make the UI reusable and keep it inside the repository's plugin + approval architecture.