Derive Default for CachePolicy

Thanks to `cargo clippy` for the suggestion.

See
https://rust-lang.github.io/rust-clippy/master/index.html#derivable_impls
for background.

Author: matthiasgoergens

src/passthrough/mod.rs

@@ -342,7 +342,7 @@ unsafe impl ByteValued for LinuxDirent64 {}
 /// The caching policy that the file system should report to the FUSE client. By default the FUSE
 /// protocol uses close-to-open consistency. This means that any cached contents of the file are
 /// invalidated the next time that file is opened.
-#[derive(Debug, Clone, Eq, PartialEq)]
+#[derive(Debug, Default, Clone, Eq, PartialEq)]
 pub enum CachePolicy {
     /// The client should never cache file data and all I/O should be directly forwarded to the
     /// server. This policy must be selected when file contents may change without the knowledge of
@@ -351,6 +351,7 @@ pub enum CachePolicy {
 
     /// The client is free to choose when and how to cache file data. This is the default policy and
     /// uses close-to-open consistency as described in the enum documentation.
+    #[default]
     Auto,
 
     /// The client should always cache file data. This means that the FUSE client will not
@@ -373,12 +374,6 @@ impl FromStr for CachePolicy {
     }
 }
 
-impl Default for CachePolicy {
-    fn default() -> Self {
-        CachePolicy::Auto
-    }
-}
-
 /// Options that configure the behavior of the passthrough fuse file system.
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub struct Config {