Add UV_INIT_BARE environment variable for uv init (#18210)

Resolves https://github.com/astral-sh/uv/issues/18202

This diff adds a `UV_INIT_BARE` environment variable that makes `--bare`
the default behavior for `uv init`. The command-line flag takes
precedence over the environment variable, following the same pattern
used by `UV_FROZEN`, `UV_LOCKED`, and other boolean environment
variables.

crates/uv-settings/src/lib.rs

@@ -657,6 +657,7 @@ pub struct EnvironmentOptions {
     pub no_env_file: EnvFlag,
     pub venv_seed: EnvFlag,
     pub venv_clear: EnvFlag,
+    pub init_bare: EnvFlag,
 }
 
 impl EnvironmentOptions {
@@ -749,6 +750,7 @@ impl EnvironmentOptions {
             no_env_file: EnvFlag::new(EnvVars::UV_NO_ENV_FILE)?,
             venv_seed: EnvFlag::new(EnvVars::UV_VENV_SEED)?,
             venv_clear: EnvFlag::new(EnvVars::UV_VENV_CLEAR)?,
+            init_bare: EnvFlag::new(EnvVars::UV_INIT_BARE)?,
         })
     }
 }

crates/uv-static/src/env_vars.rs

@@ -380,6 +380,11 @@ impl EnvVars {
     #[attr_added_in("0.3.0")]
     pub const UV_TOOL_BIN_DIR: &'static str = "UV_TOOL_BIN_DIR";
 
+    /// Equivalent to the `--bare` argument for `uv init`. If set, uv will only create a
+    /// `pyproject.toml`.
+    #[attr_added_in("0.10.7")]
+    pub const UV_INIT_BARE: &'static str = "UV_INIT_BARE";
+
     /// Equivalent to the `--build-backend` argument for `uv init`. Determines the default backend
     /// to use when creating a new project.
     #[attr_added_in("0.8.2")]

crates/uv/src/settings.rs

@@ -431,6 +431,8 @@ impl InitSettings {
         )
         .unwrap_or(kind.packaged_by_default());
 
+        let bare = resolve_flag(bare, "bare", environment.init_bare).is_enabled();
+
         let filesystem_install_mirrors = filesystem
             .map(|fs| fs.install_mirrors.clone())
             .unwrap_or_default();

crates/uv/tests/it/init.rs

@@ -647,6 +647,52 @@ fn init_bare_opt_in() {
     });
 }
 
+#[test]
+fn init_bare_env_var() {
+    let context = uv_test::test_context!("3.12");
+
+    uv_snapshot!(context.filters(), context.init().arg("foo").env(EnvVars::UV_INIT_BARE, "true"), @"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Initialized project `foo` at `[TEMP_DIR]/foo`
+    ");
+
+    context
+        .temp_dir
+        .child("foo/README.md")
+        .assert(predicate::path::missing());
+    context
+        .temp_dir
+        .child("foo/hello.py")
+        .assert(predicate::path::missing());
+    context
+        .temp_dir
+        .child("foo/.python-version")
+        .assert(predicate::path::missing());
+    context
+        .temp_dir
+        .child("foo/.git")
+        .assert(predicate::path::missing());
+
+    let pyproject = context.read("foo/pyproject.toml");
+    insta::with_settings!({
+        filters => context.filters(),
+    }, {
+        assert_snapshot!(
+            pyproject, @r#"
+        [project]
+        name = "foo"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = []
+        "#
+        );
+    });
+}
+
 // General init --script correctness test
 #[test]
 fn init_script() -> Result<()> {