Append a comment at the end of new or modified lines.
+
If _<message>_ begins with one or more whitespaces followed
-by "#", it is used as-is. If it begins with "#", a space is
-prepended before it is used. Otherwise, a string " # " (a
+by `#`, it is used as-is. If it begins with `#`, a space is
+prepended before it is used. Otherwise, a string `" # "` (a
space followed by a hash followed by a space) is prepended
-to it. And the resulting string is placed immediately after
+to it. The resulting string is placed immediately after
the value defined for the variable. The _<message>_ must
not contain linefeed characters (no multi-line comments are
permitted).