update docs for insertbefore/insertafter

lib/ansible/modules/files/lineinfile.py

@@ -85,8 +85,9 @@ options:
     default: EOF
     description:
       - Used with C(state=present). If specified, the line will be inserted
-        after the specified regular expression. A special value is
+        after the last match of specified regular expression. A special value is
         available; C(EOF) for inserting the line at the end of the file. 
+        If specified regular expresion has no matches, EOF will be used instead.
         May not be used with C(backrefs).
     choices: [ 'EOF', '*regex*' ]
   insertbefore:
@@ -94,9 +95,10 @@ options:
     version_added: "1.1"
     description:
       - Used with C(state=present). If specified, the line will be inserted
-        before the specified regular expression. A value is available;
+        before the last match of specified regular expression. A value is 
-        C(BOF) for inserting the line at the beginning of the file.
+        available; C(BOF) for inserting the line at the beginning of the file.
-        May not be used with C(backrefs).
+        If specified regular expresion has no matches, C(insertbefore) will be 
+        ignored. May not be used with C(backrefs).
     choices: [ 'BOF', '*regex*' ]
   create:
     required: false