Don’t wrap stdin in a BufReader when prompting

stdin() is already buffered.

stdin().read_line() calls stdin().lock() behind the hood (see
https://doc.rust-lang.org/src/std/io/stdio.rs.html#274)
Here we are reading user input, prompting them to confirm their action:
it seems useless to handle mutex locking/unlocking explicitely and
beforehand to avoid its overhead.

This commit is related to issue #1103.

src/cp/cp.rs

@@ -42,7 +42,7 @@ use clap::{App, Arg, ArgMatches};
 use quick_error::ResultExt;
 use std::collections::HashSet;
 use std::fs;
-use std::io::{stdin, stdout, BufRead, BufReader, Write};
+use std::io::{stdin, stdout, Write};
 use std::io;
 use std::path::{Path, PathBuf, StripPrefixError};
 use std::str::FromStr;
@@ -123,7 +123,7 @@ macro_rules! prompt_yes(
         print!(" [y/N]: ");
         crash_if_err!(1, stdout().flush());
         let mut s = String::new();
-        match BufReader::new(stdin()).read_line(&mut s) {
+        match stdin().read_line(&mut s) {
             Ok(_) => match s.char_indices().nth(0) {
                 Some((_, x)) => x == 'y' || x == 'Y',
                 _ => false

src/ln/ln.rs

@@ -13,7 +13,7 @@
 extern crate uucore;
 
 use std::fs;
-use std::io::{stdin, BufRead, BufReader, Result};
+use std::io::{stdin, Result};
 #[cfg(any(unix, target_os = "redox"))]
 use std::os::unix::fs::symlink;
 #[cfg(windows)]
@@ -303,7 +303,7 @@ fn link(src: &PathBuf, dst: &PathBuf, settings: &Settings) -> Result<()> {
 
 fn read_yes() -> bool {
     let mut s = String::new();
-    match BufReader::new(stdin()).read_line(&mut s) {
+    match stdin().read_line(&mut s) {
         Ok(_) => match s.char_indices().nth(0) {
             Some((_, x)) => x == 'y' || x == 'Y',
             _ => false,

src/mv/mv.rs

@@ -16,7 +16,7 @@ extern crate uucore;
 
 use std::fs;
 use std::env;
-use std::io::{stdin, BufRead, BufReader, Result};
+use std::io::{stdin, Result};
 use std::path::{Path, PathBuf};
 
 static NAME: &str = "mv";
@@ -374,7 +374,7 @@ fn rename(from: &PathBuf, to: &PathBuf, b: &Behaviour) -> Result<()> {
 
 fn read_yes() -> bool {
     let mut s = String::new();
-    match BufReader::new(stdin()).read_line(&mut s) {
+    match stdin().read_line(&mut s) {
         Ok(_) => match s.chars().nth(0) {
             Some(x) => x == 'y' || x == 'Y',
             _ => false,