feat: update depot version to 0.12.0 and refactor environment variable handling in tests

src/test_support.rs

@@ -0,0 +1,50 @@
+use std::collections::BTreeMap;
+use std::env;
+use std::ffi::{OsStr, OsString};
+use std::sync::{Mutex, MutexGuard, OnceLock};
+
+fn env_lock() -> &'static Mutex<()> {
+    static ENV_LOCK: OnceLock<Mutex<()>> = OnceLock::new();
+    ENV_LOCK.get_or_init(|| Mutex::new(()))
+}
+
+pub(crate) struct TestEnv {
+    _guard: MutexGuard<'static, ()>,
+    saved: BTreeMap<String, Option<OsString>>,
+}
+
+impl TestEnv {
+    pub(crate) fn new() -> Self {
+        Self {
+            _guard: env_lock().lock().expect("test env lock poisoned"),
+            saved: BTreeMap::new(),
+        }
+    }
+
+    pub(crate) fn set_var(&mut self, key: &str, value: impl AsRef<OsStr>) {
+        self.snapshot(key);
+        unsafe {
+            env::set_var(key, value);
+        }
+    }
+
+    fn snapshot(&mut self, key: &str) {
+        self.saved
+            .entry(key.to_string())
+            .or_insert_with(|| env::var_os(key));
+    }
+}
+
+impl Drop for TestEnv {
+    fn drop(&mut self) {
+        for (key, value) in &self.saved {
+            unsafe {
+                if let Some(value) = value {
+                    env::set_var(key, value);
+                } else {
+                    env::remove_var(key);
+                }
+            }
+        }
+    }
+}