Minor changes to improve readability

This patch makes minor changes to make the code a little easier to
understand. For example, using the `?` operator in some fns that return
an `Option` type.

src/exec/command.rs

@@ -29,12 +29,11 @@ pub fn execute_command(mut cmd: Command, out_perm: Arc<Mutex<()>>) {
             let _ = stdout.lock().write_all(&output.stdout);
             let _ = stderr.lock().write_all(&output.stderr);
         }
+        Err(ref why) if why.kind() == io::ErrorKind::NotFound => {
+            eprintln!("fd: execution error: command not found");
+        }
         Err(why) => {
-            if why.kind() == io::ErrorKind::NotFound {
-                eprintln!("fd: execution error: command not found");
-            } else {
-                eprintln!("fd: execution error: {}", why);
-            }
+            eprintln!("fd: execution error: {}", why);
         }
     }
 }

src/fshelper/mod.rs

@@ -17,11 +17,11 @@ use ignore::DirEntry;
 
 pub fn path_absolute_form(path: &Path) -> io::Result<PathBuf> {
     if path.is_absolute() {
-        Ok(path.to_path_buf())
-    } else {
-        let path = path.strip_prefix(".").unwrap_or(path);
-        current_dir().map(|path_buf| path_buf.join(path))
+        return Ok(path.to_path_buf());
     }
+
+    let path = path.strip_prefix(".").unwrap_or(path);
+    current_dir().map(|path_buf| path_buf.join(path))
 }
 
 pub fn absolute_path(path: &Path) -> io::Result<PathBuf> {
@@ -42,11 +42,7 @@ pub fn absolute_path(path: &Path) -> io::Result<PathBuf> {
 // Path::is_dir() is not guaranteed to be intuitively correct for "." and ".."
 // See: https://github.com/rust-lang/rust/issues/45302
 pub fn is_dir(path: &Path) -> bool {
-    if path.file_name().is_some() {
-        path.is_dir()
-    } else {
-        path.is_dir() && path.canonicalize().is_ok()
-    }
+    path.is_dir() && (path.file_name().is_some() || path.canonicalize().is_ok())
 }
 
 #[cfg(any(unix, target_os = "redox"))]

src/internal.rs

@@ -66,20 +66,11 @@ impl SizeFilter {
             return None;
         }
 
-        let captures = match SIZE_CAPTURES.captures(s) {
-            Some(cap) => cap,
-            None => return None,
-        };
-
+        let captures = SIZE_CAPTURES.captures(s)?;
         let limit_kind = captures.get(1).map_or("+", |m| m.as_str());
-
-        let quantity = match captures.get(2) {
-            None => return None,
-            Some(v) => match v.as_str().parse::<u64>() {
-                Ok(val) => val,
-                _ => return None,
-            },
-        };
+        let quantity = captures
+            .get(2)
+            .and_then(|v| v.as_str().parse::<u64>().ok())?;
 
         let multiplier = match &captures.get(3).map_or("b", |m| m.as_str()).to_lowercase()[..] {
             v if v.starts_with("ki") => KIBI,