Accept multiple `.env` files in `UV_ENV_FILE` (#11665)

According to the [UV
documentation](https://docs.astral.sh/uv/configuration/files/#env), the
UV_ENV_FILE environment variable should support multiple .env files,
separated by spaces. However, when I tried using this feature in my
repository, it didn’t work as expected.

To investigate, I checked the UV repository for relevant tests and found
`run_with_multiple_env_files`.
This test asserts the following `error: No environment file found at:
.env1 .env2.`

This discrepancy could indicate either a mismatch between the
documentation and the implementation or a bug in the code.

I decided to fix the issue in the code since the ability to pass
multiple `.env` files is a valuable feature.
If my fix isn’t appropriate, I’d be happy to make any necessary
adjustments.

---------

Co-authored-by: Yaroslav Limanskiy <yaroslav.limanskiy@pandadoc.com>
Co-authored-by: Charlie Marsh <charlie.r.marsh@gmail.com>

crates/uv-cli/src/lib.rs

@@ -2784,7 +2784,7 @@ pub struct RunArgs {
     ///
     /// Can be provided multiple times, with subsequent files overriding values defined in previous
     /// files.
-    #[arg(long, env = EnvVars::UV_ENV_FILE)]
+    #[arg(long, value_delimiter = ' ', env = EnvVars::UV_ENV_FILE)]
     pub env_file: Vec<PathBuf>,
 
     /// Avoid reading environment variables from a `.env` file.

crates/uv/tests/it/run.rs

@@ -3974,12 +3974,14 @@ fn run_with_multiple_env_files() -> Result<()> {
     "###);
 
     uv_snapshot!(context.filters(), context.run().arg("test.py").env(EnvVars::UV_ENV_FILE, ".env1 .env2"), @r###"
-    success: false
-    exit_code: 2
+    success: true
+    exit_code: 0
     ----- stdout -----
+    palpatine
+    obi_wan_kenobi
+    C3PO
 
     ----- stderr -----
-    error: No environment file found at: `.env1 .env2`
     "###);
 
     Ok(())