edition: Eliminate ref keyword

As described in:
https://doc.rust-lang.org/edition-guide/rust-2018/ownership-and-lifetimes/default-match-bindings.html
which also covers the new mental model that the Rust Book will use for
teaching binding modes and has been found to be more friendly for both
beginners and experienced users.

Before:

    match *opt {
        Some(ref v) => ...,
        None => ...,
    }

After:

    match opt {
        Some(v) => ...,
        None => ...,
    }

TEST=cargo check --all-features
TEST=local kokoro

Change-Id: I3c5800a9be36aaf5d3290ae3bd3116f699cb00b7
Reviewed-on: https://chromium-review.googlesource.com/1566669
Commit-Ready: David Tolnay <dtolnay@chromium.org>
Tested-by: David Tolnay <dtolnay@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>

3 files changed, 9 insertions, 9 deletions

diff --git a/src/argument.rs b/src/argument.rs
index 6b4cfe9..7cb56d6 100644
--- a/src/argument.rs
+++ b/src/argument.rs
@@ -324,7 +324,7 @@ pub fn print_help(program_name: &str, required_arg: &str, args: &[Argument]) {
     println!("Argument{}:", if args.len() > 1 { "s" } else { "" });
     for arg in args {
         match arg.short {
-            Some(ref s) => print!(" -{}, ", s),
+            Some(s) => print!(" -{}, ", s),
             None => print!("     "),
         }
         if arg.long.is_empty() {
diff --git a/src/linux.rs b/src/linux.rs
index 7ece6e3..977f7bf 100644
--- a/src/linux.rs
+++ b/src/linux.rs
@@ -164,8 +164,8 @@ impl Display for Error {
             Disk(e) => write!(f, "failed to load disk image: {}", e),
             DiskImageLock(e) => write!(f, "failed to lock disk image: {}", e),
             DropCapabilities(e) => write!(f, "failed to drop process capabilities: {}", e),
-            InputDeviceNew(ref e) => write!(f, "failed to set up input device: {}", e),
-            InputEventsOpen(ref e) => write!(f, "failed to open event device: {}", e),
+            InputDeviceNew(e) => write!(f, "failed to set up input device: {}", e),
+            InputEventsOpen(e) => write!(f, "failed to open event device: {}", e),
             InvalidFdPath => write!(f, "failed parsing a /proc/self/fd/*"),
             InvalidWaylandPath => write!(f, "wayland socket path has no parent or file name"),
             IoJail(e) => write!(f, "{}", e),
@@ -1275,7 +1275,7 @@ fn run_control(
 
     // Watch for low memory notifications and take memory back from the VM.
     let low_mem = File::open("/dev/chromeos-low-mem").ok();
-    if let Some(ref low_mem) = low_mem {
+    if let Some(low_mem) = &low_mem {
         poll_ctx
             .add(low_mem, Token::LowMemory)
             .map_err(Error::PollContextAdd)?;
@@ -1415,7 +1415,7 @@ fn run_control(
                     }
                 }
                 Token::LowMemory => {
-                    if let Some(ref low_mem) = low_mem {
+                    if let Some(low_mem) = &low_mem {
                         let old_balloon_memory = current_balloon_memory;
                         current_balloon_memory = min(
                             current_balloon_memory + balloon_memory_increment,
@@ -1453,7 +1453,7 @@ fn run_control(
                     // Acknowledge the timer.
                     lowmem_timer.wait().map_err(Error::TimerFd)?;
 
-                    if let Some(ref low_mem) = low_mem {
+                    if let Some(low_mem) = &low_mem {
                         // Start polling the lowmem device again.
                         poll_ctx
                             .add(low_mem, Token::LowMemory)
diff --git a/src/plugin/mod.rs b/src/plugin/mod.rs
index c01ff80..beedea4 100644
--- a/src/plugin/mod.rs
+++ b/src/plugin/mod.rs
@@ -467,8 +467,8 @@ pub fn run_config(cfg: Config) -> Result<()> {
 
     let jail = if cfg.sandbox {
         // An empty directory for jailed plugin pivot root.
-        let root_path = match cfg.plugin_root {
-            Some(ref dir) => Path::new(dir),
+        let root_path = match &cfg.plugin_root {
+            Some(dir) => dir,
             None => Path::new("/var/empty"),
         };
 
@@ -599,7 +599,7 @@ pub fn run_config(cfg: Config) -> Result<()> {
         let plugin_socket_count = plugin.sockets().len();
         let events = {
             let poll_res = match dying_instant {
-                Some(ref inst) => poll_ctx.wait_timeout(duration_to_die - inst.elapsed()),
+                Some(inst) => poll_ctx.wait_timeout(duration_to_die - inst.elapsed()),
                 None => poll_ctx.wait(),
             };
             match poll_res {