Auto merge of rust-lang#37754 - frewsxcv:path-push, r=GuillaumeGomez

Minor rewriting of `std::path::Path::push` doc example.

None

Author: bors

src/libstd/path.rs

@@ -983,17 +983,24 @@ impl PathBuf {
     ///
     /// # Examples
     ///
+    /// Pushing a relative path extends the existing path:
+    ///
     /// ```
     /// use std::path::PathBuf;
     ///
-    /// let mut path = PathBuf::new();
-    /// path.push("/tmp");
+    /// let mut path = PathBuf::from("/tmp");
     /// path.push("file.bk");
     /// assert_eq!(path, PathBuf::from("/tmp/file.bk"));
+    /// ```
+    ///
+    /// Pushing an absolute path replaces the existing path:
+    ///
+    /// ```
+    /// use std::path::PathBuf;
     ///
-    /// // Pushing an absolute path replaces the current path
-    /// path.push("/etc/passwd");
-    /// assert_eq!(path, PathBuf::from("/etc/passwd"));
+    /// let mut path = PathBuf::from("/tmp");
+    /// path.push("/etc");
+    /// assert_eq!(path, PathBuf::from("/etc"));
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn push<P: AsRef<Path>>(&mut self, path: P) {