Document `.netrc` environment variable and path (#8511)

## Summary

Closes https://github.com/astral-sh/uv/issues/8482.

crates/uv-auth/src/middleware.rs

@@ -71,11 +71,11 @@ impl AuthMiddleware {
         }
     }
 
-    /// Configure the [`netrc::Netrc`] credential file to use.
+    /// Configure the [`Netrc`] credential file to use.
     ///
     /// `None` disables authentication via netrc.
     #[must_use]
-    pub fn with_netrc(mut self, netrc: Option<netrc::Netrc>) -> Self {
+    pub fn with_netrc(mut self, netrc: Option<Netrc>) -> Self {
         self.netrc = if let Some(netrc) = netrc {
             NetrcMode::Enabled(netrc)
         } else {

docs/configuration/authentication.md

@@ -35,15 +35,18 @@ uv supports credentials over HTTP when querying package registries.
 Authentication can come from the following sources, in order of precedence:
 
 - The URL, e.g., `https://<user>:<password>@<hostname>/...`
-- A [`netrc`](https://everything.curl.dev/usingcurl/netrc) configuration file
+- A [`.netrc`](https://everything.curl.dev/usingcurl/netrc) configuration file
 - A [keyring](https://github.com/jaraco/keyring) provider (requires opt-in)
 
 If authentication is found for a single net location (scheme, host, and port), it will be cached for
 the duration of the command and used for other queries to that net location. Authentication is not
 cached across invocations of uv.
 
-Note `--keyring-provider subprocess` or `UV_KEYRING_PROVIDER=subprocess` must be provided to enable
-keyring-based authentication.
+`.netc` authentication is enabled by default, and will respect the `NETRC` environment variable if
+defined, falling back to `~/.netrc` if not.
+
+To enable keyring-based authentication, pass the `--keyring-provider subprocess` command-line
+argument to uv, or set `UV_KEYRING_PROVIDER=subprocess`.
 
 Authentication may be used for hosts specified in the following contexts:
 

docs/configuration/environment.md

@@ -134,6 +134,7 @@ In addition, uv respects the following environment variables:
 - `HTTP_PROXY`, `HTTPS_PROXY`, `ALL_PROXY`: The proxy to use for all HTTP/HTTPS requests.
 - `HTTP_TIMEOUT` (or `UV_HTTP_TIMEOUT`): If set, uv will use this value (in seconds) as the timeout
   for HTTP reads (default: 30 s).
+- `NETRC`: If set, uv will read authentication information from this file instead of `~/.netrc`.
 - `PYC_INVALIDATION_MODE`: The validation modes to use when run with `--compile`. See:
   [`PycInvalidationMode`](https://docs.python.org/3/library/py_compile.html#py_compile.PycInvalidationMode).
 - `VIRTUAL_ENV`: Used to detect an activated virtual environment.