Add docs for git authentication

Author: zanieb

README.md

@@ -172,6 +172,30 @@ Since uv has no dependency on Python, it can even install into virtual environme
 its own. For example, setting `VIRTUAL_ENV=/path/to/venv` will cause uv to install into
 `/path/to/venv`, no matter where uv is installed.
 
+### Git authentication
+
+uv allows packages to be installed from Git and supports the following schemes for authenticating with private
+repositories.
+
+Using SSH:
+
+- `git+ssh://git@<host>/...`
+
+uv supports hosts with additional identifiers e.g. `g.yxqyang.asia-repo-1`. 
+See the [GitHub SSH documentation](https://docs.github.com/en/authentication/connecting-to-github-with-ssh/about-ssh) for more details on how to configure SSH.
+
+Using a password, PAT, or OAuth token:
+
+- `git+https://<user>:<token>/...`
+- `git+https://<token>/...`
+- `git+https://<user>/...`
+
+When using a GitHub personal access token, the username is arbitrary. GitHub does not support logging in with password directly, although other Git hosts may.
+
+If a username is provided without a token, you will be prompted to enter a password.
+
+If there are no credentials present in the URL and authentication is needed, the [Git credential helper](https://git-scm.com/doc/credential-helpers)  will be queried.
+
 ### Dependency caching
 
 uv uses aggressive caching to avoid re-downloading (and re-building dependencies) that have