indexedlog: address clippy warnings

Summary:
These were from a wide variety of warnings. The only one I haven't addressed is
that clippy complains that Pin<Box<Vec<u8>>> can be replaced by Pin<Vec<u8>>. I
haven't investigated too much into it, someone more familiar with this code can
probably figure out if this is buggy or not :)

Reviewed By: DurhamG

Differential Revision: D20469647

fbshipit-source-id: d42891d95c1d21b625230234994ab49bbc45b961

eden/scm/lib/indexedlog/src/index.rs

@@ -1637,7 +1637,7 @@ impl MemChecksum {
         // See the comment in `read_from` for `start_chunk_index`.
         // It is the starting index for
         let start_chunk_index = (self.start >> self.chunk_size_logarithm) as usize;
-        return &self.xxhash_list[start_chunk_index..];
+        &self.xxhash_list[start_chunk_index..]
     }
 
     /// Reset the `chunk_size_logarithm`.

eden/scm/lib/indexedlog/src/log/mod.rs

@@ -694,8 +694,7 @@ impl Log {
     pub(crate) fn finalize_indexes(&mut self) -> crate::Result<()> {
         let result: crate::Result<_> = (|| {
             let dir = self.dir.clone();
-            if let Some(ref dir) = dir.as_opt_path() {
-                let dir = dir.clone();
+            if let Some(dir) = dir.as_opt_path() {
                 if !self.mem_buf.is_empty() {
                     return Err(crate::Error::programming(
                         "sync() should be called before finalize_indexes()",

eden/scm/lib/indexedlog/src/multi.rs

@@ -83,12 +83,11 @@ impl OpenOptions {
         let result: crate::Result<_> = (|| {
             let meta_path = multi_meta_path(path);
             let mut multimeta = MultiMeta::default();
-            match multimeta.read_file(&meta_path) {
-                Err(e) => match e.kind() {
+            if let Err(e) = multimeta.read_file(&meta_path) {
+                match e.kind() {
                     io::ErrorKind::NotFound => (), // not fatal.
                     _ => return Err(e).context(&meta_path, "when opening MultiLog"),
-                },
-                Ok(_) => (),
+                }
             };
 
             let locked = if self
@@ -107,7 +106,7 @@ impl OpenOptions {
             let mut logs = Vec::with_capacity(self.name_open_options.len());
             for (name, opts) in self.name_open_options.iter() {
                 let fspath = path.join(name);
-                let name_ref: &str = name.as_ref();
+                let name_ref: &str = name;
                 if !multimeta.metas.contains_key(name_ref) {
                     // Create a new Log if it does not exist in MultiMeta.
                     utils::mkdir_p(&fspath)?;
@@ -160,7 +159,7 @@ impl MultiLog {
     /// A lock must be provided to prove that there is no race condition.
     /// The lock is usually obtained via `lock()`.
     pub fn write_meta(&mut self, lock: &LockGuard) -> crate::Result<()> {
-        if lock.0.path() != &self.path {
+        if lock.0.path() != self.path {
             let msg = format!(
                 "Invalid lock used to write_meta (Lock path = {:?}, MultiLog path = {:?})",
                 lock.0.path(),

eden/scm/lib/indexedlog/src/rotate.rs

@@ -392,7 +392,7 @@ impl RotateLog {
                 return Ok(0);
             }
 
-            if self.writable_log().iter_dirty().nth(0).is_none() {
+            if self.writable_log().iter_dirty().next().is_none() {
                 // Read-only path, no need to take directory lock.
                 if let Ok(latest) = read_latest(self.dir.as_ref().unwrap()) {
                     if latest != self.latest {

eden/scm/lib/indexedlog/src/utils.rs

@@ -81,9 +81,7 @@ pub fn mmap_path(path: &Path, len: u64) -> crate::Result<Bytes> {
                     Err(err).context(path, "cannot open for mmap")
                 }
             })?;
-        Ok(Bytes::from(
-            mmap_bytes(&file, Some(len)).context(path, "cannot mmap")?,
-        ))
+        Ok(mmap_bytes(&file, Some(len)).context(path, "cannot mmap")?)
     }
 }
 
@@ -141,7 +139,7 @@ pub fn atomic_write(
         // should also result in a non-empty file. However, we have seen empty
         // files sometimes without OS crashes (see https://fburl.com/bky2zu9e).
         if SYMLINK_ATOMIC_WRITE.load(atomic::Ordering::SeqCst) {
-            if let Ok(_) = atomic_write_symlink(path, content) {
+            if atomic_write_symlink(path, content).is_ok() {
                 return Ok(());
             }
         }