Simplification suggested by @nickelc

in e169da7#r109077300

This also restores an unrelated change in the order of imports in a test
that did not need to be reverted.

Signed-off-by: Daira Emma Hopwood <daira@jacaranda.org>

src/xdg_user_dirs.rs

@@ -32,7 +32,7 @@ fn parse_user_dirs(home_dir: &Path, user_dir: Option<&str>, bytes: &[u8]) -> Has
         let key = if key.starts_with(b"XDG_") && key.ends_with(b"_DIR") {
             match str::from_utf8(&key[4..key.len()-4]) {
                 Ok(key) =>
-                    if user_dir.is_some() && option_contains(user_dir, key) {
+                    if user_dir == Some(key) {
                         single_dir_found = true;
                         key
                     } else if user_dir.is_none() {
@@ -137,18 +137,12 @@ fn shell_unescape(escaped: &[u8]) -> Vec<u8> {
     unescaped
 }
 
-fn option_contains<T : PartialEq>(option: Option<T>, value: T) -> bool {
-    match option {
-        Some(val) => val == value,
-        None => false
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use std::collections::HashMap;
     use std::path::{Path, PathBuf};
-    use super::{trim_blank, shell_unescape, split_once, parse_user_dirs};
+
+    use super::{parse_user_dirs, shell_unescape, split_once, trim_blank};
 
     #[test]
     fn test_trim_blank() {