Add UV_OVERRIDE environment variable for --override (#4836)

Closes https://github.com/astral-sh/uv/issues/4827

README.md

@@ -574,6 +574,8 @@ uv accepts the following command-line arguments as environment variables:
   uv will require that all dependencies have a hash specified in the requirements file.
 - `UV_CONSTRAINT`: Equivalent to the `--constraint` command-line argument. If set, uv will use this
   file as the constraints file. Uses space-separated list of files.
+- `UV_OVERRIDE`: Equivalent to the `--override` command-line argument. If set, uv will use this
+  file as the overrides file. Uses space-separated list of files.
 - `UV_LINK_MODE`: Equivalent to the `--link-mode` command-line argument. If set, uv will use this
   as a link mode.
 - `UV_NO_BUILD_ISOLATION`: Equivalent to the `--no-build-isolation` command-line argument. If set,

crates/uv-cli/src/lib.rs

@@ -373,8 +373,8 @@ pub struct PipCompileArgs {
     /// While constraints are _additive_, in that they're combined with the requirements of the
     /// constituent packages, overrides are _absolute_, in that they completely replace the
     /// requirements of the constituent packages.
-    #[arg(long, value_parser = parse_file_path)]
+    #[arg(long, env = "UV_OVERRIDE", value_delimiter = ' ', value_parser = parse_maybe_file_path)]
-    pub r#override: Vec<PathBuf>,
+    pub r#override: Vec<Maybe<PathBuf>>,
 
     /// Include optional dependencies from the extra group name; may be provided more than once.
     /// Only applies to `pyproject.toml`, `setup.py`, and `setup.cfg` sources.
@@ -906,8 +906,8 @@ pub struct PipInstallArgs {
     /// While constraints are _additive_, in that they're combined with the requirements of the
     /// constituent packages, overrides are _absolute_, in that they completely replace the
     /// requirements of the constituent packages.
-    #[arg(long, value_parser = parse_file_path)]
+    #[arg(long, env = "UV_OVERRIDE", value_delimiter = ' ', value_parser = parse_maybe_file_path)]
-    pub r#override: Vec<PathBuf>,
+    pub r#override: Vec<Maybe<PathBuf>>,
 
     /// Include optional dependencies from the extra group name; may be provided more than once.
     /// Only applies to `pyproject.toml`, `setup.py`, and `setup.cfg` sources.

crates/uv/src/settings.rs

@@ -684,7 +684,10 @@ impl PipCompileSettings {
                 .into_iter()
                 .filter_map(Maybe::into_option)
                 .collect(),
-            r#override,
+            r#override: r#override
+                .into_iter()
+                .filter_map(Maybe::into_option)
+                .collect(),
             overrides_from_workspace,
             refresh: Refresh::from(refresh),
             settings: PipSettings::combine(
@@ -890,7 +893,10 @@ impl PipInstallSettings {
                 .into_iter()
                 .filter_map(Maybe::into_option)
                 .collect(),
-            r#override,
+            r#override: r#override
+                .into_iter()
+                .filter_map(Maybe::into_option)
+                .collect(),
             dry_run,
             overrides_from_workspace,
             refresh: Refresh::from(refresh),