ls: implement --color flag

GNU coreutils ls command implements the --color option as follow:
  --color[=WHEN]
          colorize the output; WHEN can be 'always' (default if omitted),
          'auto', or 'never'

With --color=auto, ls emits color codes only when standard output is connected
to a terminal.

Also, add support for the following aliases:
  - ‘always’, ‘yes’, ‘force’
  - ‘never’, ‘no’, ‘none’
  - ‘auto’, ‘tty’, ‘if-tty’

Signed-off-by: Gabriel Ganne <gabriel.ganne@gmail.com>

src/ls/ls.rs

@@ -158,7 +158,7 @@ pub fn uumain(args: Vec<String>) -> i32 {
              directory.  This is especially useful when listing very large directories, \
              since not doing any sorting can be noticeably faster.",
         )
-        .optflag("", "color", "Color output based on file type.")
+        .optflagopt("", "color", "Color output based on file type.", "always|auto|never")
         .parse(args);
 
     list(matches);
@@ -611,7 +611,14 @@ fn display_file_name(
     }
     let mut width = UnicodeWidthStr::width(&*name);
 
-    let color = options.opt_present("color");
+    let color = match options.opt_str("color") {
+        None => true,
+        Some(val) => match val.as_ref() {
+            "always" | "yes" | "force" => true,
+            "auto" | "tty" | "if-tty" => true, /* TODO */
+            "never" | "no" | "none" | _ => false,
+        },
+    };
     let classify = options.opt_present("classify");
     let ext;
 

tests/test_ls.rs

@@ -11,3 +11,10 @@ fn test_ls_ls_i() {
     new_ucmd!().arg("-i").succeeds();
     new_ucmd!().arg("-il").succeeds();
 }
+
+#[test]
+fn test_ls_ls_color() {
+    new_ucmd!().arg("--color").succeeds();
+    new_ucmd!().arg("--color=always").succeeds();
+    new_ucmd!().arg("--color=never").succeeds();
+}