Use rayon to parallelize walk, this speeds up access over NFS.

src/bin/cleanupdupes.rs

@@ -1,6 +1,7 @@
 use std::{collections::HashMap, fs::remove_file};
 
 use email::hash_file;
+use rayon::{iter::ParallelBridge, prelude::ParallelIterator};
 use walkdir::WalkDir;
 const ENV_VAR_TO_DELETE: &str = "DELETE_DUPES";
 
@@ -11,6 +12,7 @@ fn main() -> anyhow::Result<()> {
         .map(|dir| {
             WalkDir::new(dir)
                 .into_iter()
+                .par_bridge()
                 .filter_map(|entry| entry.ok())
                 .filter_map(|entry| {
                     if entry.file_type().is_dir() {
@@ -26,12 +28,25 @@ fn main() -> anyhow::Result<()> {
                         }
                     }
                 })
-                .fold(HashMap::new(), |mut m, (h, arg)| {
-                    m.entry(h).or_insert(Vec::new()).push(arg);
-                    m
-                })
+                .fold(
+                    || HashMap::new(),
+                    |mut m, (h, arg)| {
+                        m.entry(h).or_insert(Vec::new()).push(arg);
+                        m
+                    },
+                )
         })
-        .unwrap();
+        .unwrap()
+        // Merge maps created by parallel iteration.
+        .reduce(
+            || HashMap::new(),
+            |mut acc, m| {
+                for (k, v) in m {
+                    acc.entry(k).or_insert(Vec::new()).extend(v);
+                }
+                acc
+            },
+        );
 
     for (hash, mut paths) in map {
         if paths.len() == 1 {