Improve dirname and basename filter doc (#80054)

lib/ansible/plugins/filter/basename.yml

@@ -5,6 +5,8 @@ DOCUMENTATION:
   short_description: get a path's base name
   description:
     - Returns the last name component of a path, what is left in the string that is not 'dirname'.
+  notes:
+    - The result of this filter is different from the Unix basename program; where basename for C(/foo/bar/) returns C(bar), the basename filter returns an empty string (C('')).
   options:
     _input:
       description: A path.
@@ -15,7 +17,7 @@ DOCUMENTATION:
       plugin: ansible.builtin.dirname
 EXAMPLES: |
 
-  # To get the last name of a file path, like 'foo.txt' out of '/etc/asdf/foo.txt'
+  # To get the last name of a file path, like 'foo.txt' out of '/etc/asdf/foo.txt'.
   {{ mypath | basename }}
 
 RETURN:

lib/ansible/plugins/filter/dirname.yml

@@ -5,6 +5,8 @@ DOCUMENTATION:
   short_description: get a path's directory name
   description:
     - Returns the 'head' component of a path, basically everything that is not the 'basename'.
+  notes:
+    - The result of this filter is different from the Unix dirname program; where dirname for C(/foo/bar/) returns C(/foo), the dirname filter returns the full path (C(/foo/bar/)).
   options:
     _input:
       description: A path.
@@ -15,7 +17,7 @@ DOCUMENTATION:
       plugin_type: filter
 EXAMPLES: |
 
-  # To get the dir name of a file path, like '/etc/asdf' out of '/etc/asdf/foo.txt'
+  # To get the dir name of a file path, like '/etc/asdf' out of '/etc/asdf/foo.txt'.
   {{ mypath | dirname }}
 
 RETURN: