Fix massive memory allocation issue

Not exactly sure what was going on, other than cloning of the FileMatch
with its results, since it is recursive I believe this blew up the
stack/heap with unnecessary allocations. By using an iterator and filter
this seemed to greatly reduce memory use and improve speed.

src/main.rs

@@ -19,34 +19,40 @@ fn main() {
     }
 }
 
-fn traverse_dir(config: &config::Config, dir: &Path, operation: fn(&config::Config, &Path) -> io::Result<FileMatch>)
+fn traverse_dir(
-    -> io::Result<Vec<FileMatch>> {
+    config: &config::Config,
+    dir: &Path,
+    operation: fn(&config::Config, &Path) -> io::Result<FileMatch>,
+) -> io::Result<Vec<FileMatch>> {
+    let mut matches: Vec<FileMatch> = Vec::new();
+    for entry in fs::read_dir(dir)? {
+        let entry = entry?;
+        let file_type = entry.file_type()?;
 
-        let mut matches: Vec<FileMatch> = Vec::new();
+        if file_type.is_dir() {
-        for entry in fs::read_dir(dir)? {
+            let mut results = traverse_dir(&config, &entry.path(), operation)?;
-            let entry = entry?;
+            let has_results = results
-            let file_type = entry.file_type()?;
+                .iter()
+                .filter({ |mat| mat.matches.len() > 0 })
+                .count()
+                > 0;
 
-            if file_type.is_dir() {
+            if has_results {
-                let results = traverse_dir(&config, &entry.path(), operation)?;
+                matches.append(&mut results);
-                for mat in results.as_slice() {
+            }
-                    if mat.matches.len() > 0 {
+        } else {
-                        matches.append(&mut results.clone());
+            let result = operation(&config, &entry.path());
-                    }
+            match result {
-                }
+                Result::Ok(result) if result.matches.len() > 0 => matches.push(result),
-            } else {
+                _ => (),
-                let result = operation(&config, &entry.path());
-                match result {
-                    Result::Ok(result) if result.matches.len() > 0 => matches.push(result),
-                    _ => ()
-                }
             }
         }
-
-        Ok(matches)
     }
 
-#[derive(Debug, Clone)]
+    Ok(matches)
+}
+
+#[derive(Debug)]
 struct FileMatch {
     file_name: String,
     matches: Vec<Match>