Some explanatory comments

src/fs/fields.rs

@@ -135,6 +135,10 @@ pub enum Size {
     ///
     /// This is what ls does as well. Without it, the devices will just have
     /// file sizes of zero.
+    ///
+    /// You can see what these device numbers mean:
+    /// - http://www.lanana.org/docs/device-list/
+    /// - http://www.lanana.org/docs/device-list/devices-2.6+.txt
     DeviceIDs {
         major: u8,
         minor: u8,

src/fs/file.rs

@@ -259,11 +259,14 @@ impl<'dir> File<'dir> {
         f::Group(self.metadata.gid())
     }
 
-    /// This file's size, if it's a regular file.
+    /// This file’s size, if it’s a regular file.
     ///
     /// For directories, no size is given. Although they do have a size on
-    /// some filesystems, I've never looked at one of those numbers and gained
-    /// any information from it. So it's going to be hidden instead.
+    /// some filesystems, I’ve never looked at one of those numbers and gained
+    /// any information from it. So it’s going to be hidden instead.
+    ///
+    /// Block and character devices return their device IDs, because they
+    /// usually just have a file size of zero.
     pub fn size(&self) -> f::Size {
         if self.is_directory() {
             f::Size::None