Rollup merge of rust-lang#135176 - kornelski:env-example, r=cuviper

More compelling env_clear() examples

`ls` isn't a command that people usually set env vars for, and `PATH` in particular isn't even used by `ls`.

Author: jhpratt

std/src/process.rs

@@ -868,13 +868,17 @@ impl Command {
     ///
     /// # Examples
     ///
+    /// Prevent any inherited `GIT_DIR` variable from changing the target of the `git` command,
+    /// while allowing all other variables, like `GIT_AUTHOR_NAME`.
+    ///
     /// ```no_run
     /// use std::process::Command;
     ///
-    /// Command::new("ls")
-    ///     .env_remove("PATH")
-    ///     .spawn()
-    ///     .expect("ls command failed to start");
+    /// Command::new("git")
+    ///     .arg("commit")
+    ///     .env_remove("GIT_DIR")
+    ///     .spawn()?;
+    /// # std::io::Result::Ok(())
     /// ```
     #[stable(feature = "process", since = "1.0.0")]
     pub fn env_remove<K: AsRef<OsStr>>(&mut self, key: K) -> &mut Command {
@@ -896,13 +900,17 @@ impl Command {
     ///
     /// # Examples
     ///
+    /// The behavior of `sort` is affected by `LANG` and `LC_*` environment variables.
+    /// Clearing the environment makes `sort`'s behavior independent of the parent processes' language.
+    ///
     /// ```no_run
     /// use std::process::Command;
     ///
-    /// Command::new("ls")
+    /// Command::new("sort")
+    ///     .arg("file.txt")
     ///     .env_clear()
-    ///     .spawn()
-    ///     .expect("ls command failed to start");
+    ///     .spawn()?;
+    /// # std::io::Result::Ok(())
     /// ```
     #[stable(feature = "process", since = "1.0.0")]
     pub fn env_clear(&mut self) -> &mut Command {