Explain why directory-abbrev-alist should be anchored (Bug#7777).

* files.texi (Directory Names): Explain why directory-abbrev-alist
elements should be anchored (Bug#7777).

doc/lispref/ChangeLog

+2011-01-08  Chong Yidong  <cyd@stupidchicken.com>
+
+	* files.texi (Directory Names): Explain why directory-abbrev-alist
+	elements should be anchored (Bug#7777).
+
 2011-01-07  Eli Zaretskii  <eliz@gnu.org>
 
 	* files.texi (Directory Names): Explain why FROM in

doc/lispref/files.texi

@@ -1932,14 +1932,15 @@ abbreviation instead.
 The variable @code{directory-abbrev-alist} contains an alist of
 abbreviations to use for file directories.  Each element has the form
 @code{(@var{from} . @var{to})}, and says to replace @var{from} with
-@var{to} when it appears in a directory name.  The @var{from} string is
-actually a regular expression; it is matched against directory names
-anchored at the first character, so it should start with @samp{\`}, to
-support directory names with embedded newlines (which will defeat
-@samp{^}).  The @var{to} string should be an ordinary absolute
-directory name.  Do not use @samp{~} to stand for a home directory in
-that string.  The function @code{abbreviate-file-name} performs these
-substitutions.
+@var{to} when it appears in a directory name.
+
+The @var{from} string is actually a regular expression.  It ought to
+always start with @samp{\`}, to avoid incorrectly matching to a
+relative portion of the supplied directory name.
+
+The @var{to} string should be an ordinary absolute directory name.
+Do not use @samp{~} to stand for a home directory in that string; the
+function @code{abbreviate-file-name} performs these substitutions.
 
 You can set this variable in @file{site-init.el} to describe the
 abbreviations appropriate for your site.