doc: Clarify and expand descriptions of NonFiles

Discussed in:
#1730 (comment)

At least for now, they remain called `NonFile`s (and sometimes
referred to as "non-files" in text), but more specifically defined.

Author: EliahKagan

gix-dir/src/entry.rs

@@ -26,11 +26,13 @@ pub enum Property {
 /// The kind of the entry, seated in their kinds available on disk.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Ord, PartialOrd)]
 pub enum Kind {
-    /// Something that is not a file, like a named pipe or character device.
+    /// Something that is not a regular file, directory, or symbolic link.
     ///
-    /// These can only exist in the filesystem.
+    /// These can only exist in the filesystem, because Git repositories do not support them.
+    /// They do not appear as blobs in a repository, and their type is not specifiable in a tree object.
+    /// Examples include named pipes (FIFOs), character devices, block devices, and sockets.
     NonFile,
-    /// The entry is a blob, executable or not.
+    /// The entry is a blob, representing a regular file, executable or not.
     File,
     /// The entry is a symlink.
     Symlink,

gix-status/src/index_as_worktree/types.rs

@@ -103,7 +103,9 @@ impl Outcome {
 pub enum Change<T = (), U = ()> {
     /// This corresponding file does not exist in the worktree anymore.
     Removed,
-    /// The type of file changed compared to the worktree, i.e. a symlink is now a file, or a file was replaced with a named pipe.
+    /// The type of file changed compared to the worktree.
+    ///
+    /// Examples include when a symlink is now a regular file, or a regular file was replaced with a named pipe.
     ///
     /// ### Deviation
     ///