add gitdesk to detect updates

README.md

@@ -4,9 +4,18 @@ A GitHub Desktop-style git client that runs in your terminal. Use the mouse or t
 
 ## Setup
 
-1. Install Python 3.9+ and git (2.25 or newer).
+1. Install Python 3.9+. That's not needed if you use the built exe.
 2. Install the one dependency: `python -m pip install -r requirements.txt`
    (or just run gitdesk once and say yes when it offers to install it).
+3. **git:** if it isn't installed, gitdesk offers to install it for you when it starts.
+   It does the same if your git is older than 2.25.
+   - **Windows:** installs Git for Windows (which includes Git LFS) with `winget`, after
+     the usual permission prompt. gitdesk picks it up straight away. Without winget, it opens
+     the download page.
+   - **Linux:** installs `git` and `git-lfs` with apt, dnf, yum, pacman, zypper or apk, using sudo.
+   - **macOS:** uses Homebrew, or Apple's command line tools.
+4. **Your name and email:** the first time you commit or create a repository, gitdesk asks
+   for them if git doesn't know them yet. They're saved for all your repositories.
 
 ## Build a standalone executable (optional)