Create README.md for Git-Xet (#529)

Added a README file for Git-Xet, detailing installation and
functionality.

---------

Co-authored-by: Jared Sulzdorf <[email protected]>

Author: seanses

git_xet/README.md

@@ -0,0 +1,61 @@
+Git-Xet is a Git LFS custom transfer agent that implements upload and download of files using the Xet protocol. Install `git-xet`, follow your regular workflow to `git lfs track ...` & `git add ...` & `git commit ...` & `git push`, and your files are uploaded to Hugging Face repos using the Xet protocol. Enjoy the dedupe!
+
+## Installation
+### Prerequisite
+Make sure you have [git](https://git-scm.com/downloads) and [git-lfs](https://git-lfs.com/) installed and configured correctly.
+### macOS or Linux (amd64 or aarch64)
+ To install using Homebrew:
+   ```
+   brew tap huggingface/tap
+   brew install git-xet
+   ```
+ Or, using an installation script, run the following in your terminal (requires `curl` and `unzip`):
+   ```
+   curl --proto '=https' --tlsv1.2 -sSf https://raw.githubusercontent.com/huggingface/xet-core/refs/heads/main/git_xet/install.sh | sh
+   ```
+  To verify the installation, run:
+   ```
+   git-xet --version
+   ```
+
+### Windows (amd64)
+ Using an installer: 
+ - Download `git-xet-windows-installer-x86_64.zip` ([available here](https://github.com/huggingface/xet-core/releases/download/git-xet-v0.1.0/git-xet-windows-installer-x86_64.zip)) and unzip. 
+ - Run the `msi` installer file and follow the prompts.
+   
+ Manual installation:
+ - Download `git-xet-windows-x86_64.zip` ([available here](https://github.com/huggingface/xet-core/releases/download/git-xet-v0.1.0/git-xet-windows-x86_64.zip)) and unzip. 
+ - Place the extracted `git-xet.exe` under a `PATH` directory.
+ - Run `git-xet install` in a terminal.
+
+To verity the installation, run:
+  ```
+  git-xet --version
+  ```
+
+## Uninstall
+### macOS or Linux
+Using Homebrew:
+   ```
+   git-xet uninstall
+   brew uninstall git-xet
+   ```
+If you used the installation script (for MacOS or Linux), run the following in your terminal:
+   ```
+   git-xet uninstall
+   sudo rm $(which git-xet)
+   ```
+### Windows
+If you used the installer:
+-  Navigate to Settings -> Apps -> Installed apps
+- Find "Git-Xet".
+- Select the "Uninstall" option available in the context menu.
+
+If you manually installed:
+- Run `git-xet uninstall` in a terminal. 
+- Delete the `git-xet.exe` file from the location where it was originally placed.
+
+## How It Works
+Git-Xet works by registering itself as a custom transfer agent to Git LFS by name "xet". On `git push`, `git fetch` or `git pull`, `git-lfs` negotiates with the remote server to determine the transfer agent to use. During this process, `git-lfs` sends to the server all locally registered agent names in the Batch API request, and the server replies with exactly one agent name in the response. Should "xet" be picked, `git-lfs` delegates the uploading or downloading operation to `git-xet` through a sequential protocol.
+
+For more details, see the Git LFS [Batch API](https://github.com/git-lfs/git-lfs/blob/main/docs/api/batch.md) and [Custom Transfer Agent](https://github.com/git-lfs/git-lfs/blob/main/docs/custom-transfers.md) documentation.