Support UV_WORKING_DIRECTORY for setting --directory (#16125)

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## Summary

<!-- What's the purpose of the change? What does it do, and why? -->

This pull request enables the `--directory` option to accept environment
variable: `UV_DIRECTORY`

### Motivation

Currently, the `--project` option already supports environment
variables, but --directory does not.

The motivation for this change is the same as for the --project option.
When using this option, it’s likely that the project root and the
directory containing the uv project differ. In such cases, allowing
environment variables makes it easier to avoid repeatedly specifying the
directory in commands or task runners.

### Other PRs

- PR for create `--project` option:
#12327

## Test Plan

<!-- How was it tested? -->

### no auto testing

As with the --project option, no auto tests are included for this
change.
This is because the implementation relies on Clap’s built-in attribute
functionality, and testing such behavior would effectively mean testing
a third-party crate, which would be redundant.

As long as the compiler accepts it, things should work as expected.

### testing manually

i tested manually like [previous pull
request](#12327)

```shell
$ cargo build --locked
./target/debug/uv init uv_directory

$ mkdir uv_directory

$ UV_DIRECTORY=uv_directory ./target/debug/uv sync
Using CPython 3.14.0rc3
Creating virtual environment at: .venv
Resolved 1 package in 15ms
Audited in 0.04ms

$ UV_DIRECTORY=uv_directory ./target/debug/uv run main.py
Hello from uv-directory!

$ ./target/debug/uv run main.py
error: Failed to spawn: `main.py`
  Caused by: No such file or directory (os error 2)
```

---------

Co-authored-by: Zanie Blue <[email protected]>

Author: shunsock

crates/uv-cli/src/lib.rs

@@ -339,7 +339,7 @@ pub struct GlobalArgs {
     /// Relative paths are resolved with the given directory as the base.
     ///
     /// See `--project` to only change the project root directory.
-    #[arg(global = true, long)]
+    #[arg(global = true, long, env = EnvVars::UV_WORKING_DIRECTORY)]
     pub directory: Option<PathBuf>,
 
     /// Run the command within the given project directory.

crates/uv-static/src/env_vars.rs

@@ -876,6 +876,9 @@ impl EnvVars {
     /// Equivalent to the `--project` command-line argument.
     pub const UV_PROJECT: &'static str = "UV_PROJECT";
 
+    /// Equivalent to the `--directory` command-line argument.
+    pub const UV_WORKING_DIRECTORY: &'static str = "UV_WORKING_DIRECTORY";
+
     /// Disable GitHub-specific requests that allow uv to skip `git fetch` in some circumstances.
     pub const UV_NO_GITHUB_FAST_PATH: &'static str = "UV_NO_GITHUB_FAST_PATH";
 

crates/uv/tests/it/help.rs

@@ -66,7 +66,7 @@ fn help() {
           --no-progress
               Hide all progress outputs [env: UV_NO_PROGRESS=]
           --directory <DIRECTORY>
-              Change to the given directory prior to running the command
+              Change to the given directory prior to running the command [env: UV_WORKING_DIRECTORY=]
           --project <PROJECT>
               Run the command within the given project directory [env: UV_PROJECT=]
           --config-file <CONFIG_FILE>
@@ -147,7 +147,7 @@ fn help_flag() {
           --no-progress
               Hide all progress outputs [env: UV_NO_PROGRESS=]
           --directory <DIRECTORY>
-              Change to the given directory prior to running the command
+              Change to the given directory prior to running the command [env: UV_WORKING_DIRECTORY=]
           --project <PROJECT>
               Run the command within the given project directory [env: UV_PROJECT=]
           --config-file <CONFIG_FILE>
@@ -227,7 +227,7 @@ fn help_short_flag() {
           --no-progress
               Hide all progress outputs [env: UV_NO_PROGRESS=]
           --directory <DIRECTORY>
-              Change to the given directory prior to running the command
+              Change to the given directory prior to running the command [env: UV_WORKING_DIRECTORY=]
           --project <PROJECT>
               Run the command within the given project directory [env: UV_PROJECT=]
           --config-file <CONFIG_FILE>
@@ -415,6 +415,8 @@ fn help_subcommand() {
               Relative paths are resolved with the given directory as the base.
               
               See `--project` to only change the project root directory.
+              
+              [env: UV_WORKING_DIRECTORY=]
 
           --project <PROJECT>
               Run the command within the given project directory.
@@ -676,6 +678,8 @@ fn help_subsubcommand() {
               Relative paths are resolved with the given directory as the base.
               
               See `--project` to only change the project root directory.
+              
+              [env: UV_WORKING_DIRECTORY=]
 
           --project <PROJECT>
               Run the command within the given project directory.
@@ -767,7 +771,7 @@ fn help_flag_subcommand() {
           --no-progress
               Hide all progress outputs [env: UV_NO_PROGRESS=]
           --directory <DIRECTORY>
-              Change to the given directory prior to running the command
+              Change to the given directory prior to running the command [env: UV_WORKING_DIRECTORY=]
           --project <PROJECT>
               Run the command within the given project directory [env: UV_PROJECT=]
           --config-file <CONFIG_FILE>
@@ -846,7 +850,7 @@ fn help_flag_subsubcommand() {
           --no-progress
               Hide all progress outputs [env: UV_NO_PROGRESS=]
           --directory <DIRECTORY>
-              Change to the given directory prior to running the command
+              Change to the given directory prior to running the command [env: UV_WORKING_DIRECTORY=]
           --project <PROJECT>
               Run the command within the given project directory [env: UV_PROJECT=]
           --config-file <CONFIG_FILE>
@@ -1008,7 +1012,7 @@ fn help_with_global_option() {
           --no-progress
               Hide all progress outputs [env: UV_NO_PROGRESS=]
           --directory <DIRECTORY>
-              Change to the given directory prior to running the command
+              Change to the given directory prior to running the command [env: UV_WORKING_DIRECTORY=]
           --project <PROJECT>
               Run the command within the given project directory [env: UV_PROJECT=]
           --config-file <CONFIG_FILE>
@@ -1131,7 +1135,7 @@ fn help_with_no_pager() {
           --no-progress
               Hide all progress outputs [env: UV_NO_PROGRESS=]
           --directory <DIRECTORY>
-              Change to the given directory prior to running the command
+              Change to the given directory prior to running the command [env: UV_WORKING_DIRECTORY=]
           --project <PROJECT>
               Run the command within the given project directory [env: UV_PROJECT=]
           --config-file <CONFIG_FILE>