Respect UV_INDEX_ rather than UV_HTTP_BASIC_ (#8306)

The docs reference `UV_INDEX_`, but the code actually uses
UV_HTTP_BASIC_ as the prefix for environment variable credentials.

See PR #7741

Code is at
https://github.com/astral-sh/uv/blob/main/crates/uv-static/src/env_vars.rs#L163

```rust
    /// Generates the environment variable key for the HTTP Basic authentication username.
    pub fn http_basic_username(name: &str) -> String {
        format!("UV_HTTP_BASIC_{name}_USERNAME")
    }

    /// Generates the environment variable key for the HTTP Basic authentication password.
    pub fn http_basic_password(name: &str) -> String {
        format!("UV_HTTP_BASIC_{name}_PASSWORD")
    }
```

---------

Co-authored-by: Charlie Marsh <[email protected]>

Author: odie5533

crates/uv-auth/src/credentials.rs

@@ -147,8 +147,8 @@ impl Credentials {
     /// `UV_HTTP_BASIC_PYTORCH_PASSWORD`.
     pub fn from_env(name: &str) -> Option<Self> {
         let name = name.to_uppercase();
-        let username = std::env::var(EnvVars::http_basic_username(&name)).ok();
-        let password = std::env::var(EnvVars::http_basic_password(&name)).ok();
+        let username = std::env::var(EnvVars::index_username(&name)).ok();
+        let password = std::env::var(EnvVars::index_password(&name)).ok();
         if username.is_none() && password.is_none() {
             None
         } else {

crates/uv-static/src/env_vars.rs

@@ -160,13 +160,13 @@ impl EnvVars {
     pub const UV_STACK_SIZE: &'static str = "UV_STACK_SIZE";
 
     /// Generates the environment variable key for the HTTP Basic authentication username.
-    pub fn http_basic_username(name: &str) -> String {
-        format!("UV_HTTP_BASIC_{name}_USERNAME")
+    pub fn index_username(name: &str) -> String {
+        format!("UV_INDEX_{name}_USERNAME")
     }
 
     /// Generates the environment variable key for the HTTP Basic authentication password.
-    pub fn http_basic_password(name: &str) -> String {
-        format!("UV_HTTP_BASIC_{name}_PASSWORD")
+    pub fn index_password(name: &str) -> String {
+        format!("UV_INDEX_{name}_PASSWORD")
     }
 
     /// Used to set the uv commit hash at build time via `build.rs`.
@@ -184,12 +184,6 @@ impl EnvVars {
     /// Used to set the uv tag distance from head at build time via `build.rs`.
     pub const UV_LAST_TAG_DISTANCE: &'static str = "UV_LAST_TAG_DISTANCE";
 
-    /// Used in tests for testing providing credentials via environment variables.
-    pub const UV_HTTP_BASIC_PROXY_USERNAME: &'static str = "UV_HTTP_BASIC_PROXY_USERNAME";
-
-    /// Used in tests for testing providing credentials via environment variables.
-    pub const UV_HTTP_BASIC_PROXY_PASSWORD: &'static str = "UV_HTTP_BASIC_PROXY_PASSWORD";
-
     /// Used to set the spawning/parent interpreter when using --system in the test suite.
     pub const UV_INTERNAL__PARENT_INTERPRETER: &'static str = "UV_INTERNAL__PARENT_INTERPRETER";
 

crates/uv/tests/it/lock.rs

@@ -6678,8 +6678,8 @@ fn lock_env_credentials() -> Result<()> {
 
     // Provide credentials via environment variables.
     uv_snapshot!(context.filters(), context.lock()
-        .env(EnvVars::UV_HTTP_BASIC_PROXY_USERNAME, "public")
-        .env(EnvVars::UV_HTTP_BASIC_PROXY_PASSWORD, "heron"), @r###"
+        .env(EnvVars::index_username("PROXY"), "public")
+        .env(EnvVars::index_password("PROXY"), "heron"), @r###"
     success: true
     exit_code: 0
     ----- stdout -----