Auto merge of #49460 - kennytm:rollup, r=kennytm

Rollup of 12 pull requests

- Successful merges: #49243, #49329, #49364, #49400, #49405, #49427, #49428, #49429, #49439, #49442, #49444, #49452
- Failed merges:

1 files changed, 29 insertions, 3 deletions

diff --git a/src/liballoc/string.rs b/src/liballoc/string.rs
index e253122ffd6..23c12bef3aa 100644
--- a/src/liballoc/string.rs
+++ b/src/liballoc/string.rs
@@ -1015,6 +1015,34 @@ impl String {
         self.vec.shrink_to_fit()
     }
 
+    /// Shrinks the capacity of this `String` with a lower bound.
+    ///
+    /// The capacity will remain at least as large as both the length
+    /// and the supplied value.
+    ///
+    /// Panics if the current capacity is smaller than the supplied
+    /// minimum capacity.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(shrink_to)]
+    /// let mut s = String::from("foo");
+    ///
+    /// s.reserve(100);
+    /// assert!(s.capacity() >= 100);
+    ///
+    /// s.shrink_to(10);
+    /// assert!(s.capacity() >= 10);
+    /// s.shrink_to(0);
+    /// assert!(s.capacity() >= 3);
+    /// ```
+    #[inline]
+    #[unstable(feature = "shrink_to", reason = "new API", issue="0")]
+    pub fn shrink_to(&mut self, min_capacity: usize) {
+        self.vec.shrink_to(min_capacity)
+    }
+
     /// Appends the given [`char`] to the end of this `String`.
     ///
     /// [`char`]: ../../std/primitive.char.html
@@ -1177,8 +1205,6 @@ impl String {
     /// # Examples
     ///
     /// ```
-    /// #![feature(string_retain)]
-    ///
     /// let mut s = String::from("f_o_ob_ar");
     ///
     /// s.retain(|c| c != '_');
@@ -1186,7 +1212,7 @@ impl String {
     /// assert_eq!(s, "foobar");
     /// ```
     #[inline]
-    #[unstable(feature = "string_retain", issue = "43874")]
+    #[stable(feature = "string_retain", since = "1.26.0")]
     pub fn retain<F>(&mut self, mut f: F)
         where F: FnMut(char) -> bool
     {