Add the documentation for the {update} keyword.
    
        | author | Steve Losh <steve@stevelosh.com> | 
    
        | date | Thu, 23 Jul 2009 02:38:15 -0400 | 
    
    
        | parents | 240e531b5fc7 | 
    
        | children | b2e16a4c2d46 | 
    
        | branches/tags | (none) | 
    
        | files | README prompt.py | 
Changes
    
--- a/README	Thu Jul 23 02:38:02 2009 -0400
+++ b/README	Thu Jul 23 02:38:15 2009 -0400
@@ -63,6 +63,7 @@
 * **root|basename:** the directory name of the root of the current repository.  For example, if the repository is in `/home/u/myrepo` then this keyword would expand to `myrepo`.
 * **status:**  `!` if the repository has any changed/added/removed files, otherwise `?` if it has any untracked (but not ignored) files, otherwise nothing.
 * **task:** the current task (requires the [tasks]() extension)
+* **update:** "^" if the current parent is not the tip of the current branch, otherwise nothing.  In effect, this lets you see if running `hg update` would do something.
 
 [bookmarks]: http://mercurial.selenic.com/wiki/BookmarksExtension
 [tasks]: http://bitbucket.org/alu/hgtasks/wiki/Home
--- a/prompt.py	Thu Jul 23 02:38:02 2009 -0400
+++ b/prompt.py	Thu Jul 23 02:38:15 2009 -0400
@@ -75,6 +75,9 @@
         modified, added, removed, or deleted, otherwise "?" if it contains
         untracked (and not ignored) files, otherwise nothing.
     - task: the current task (requires the tasks extension)
+    - update: "^" if the current parent is not the tip of the current branch,
+        otherwise nothing.  In effect, this lets you see if running 
+        'hg update' would do something.
     
     There are also several keywords that deal with the status of remote
     repositories.  They cache their results in .hg/prompt/cache/ and refresh