diff -r f2c3fd21fa63 -r d48aae167b9d hgext/evolve.py
--- a/hgext/evolve.py	Mon Feb 04 22:05:03 2013 +0100
+++ b/hgext/evolve.py	Mon Feb 04 19:02:19 2013 +0100
@@ -1243,14 +1243,20 @@
      ('r', 'rev', [], _("revisions to prune"))],
     _('[OPTION] [-r] REV...'))
 def cmdprune(ui, repo, *revs, **opts):
-    """mark a changeset as obsolete
+    """get rid of changesets by marking them obsolete
+
+    Obsolete changesets becomes invisible to all commands.
+
+    Non-pruned descendant of pruned changesets becomes "unstable". Use the
+    :hg:`evolve` to handle such situation.
 
-    This update the parent directory to a not-killed parent if the current
-    working directory parent are killed.
+    When the working directory parent is pruned the repository is updated to a
+    non obsolete parents.
 
-    XXX bookmark support
-    XXX handle merge
-    XXX check immutable first
+    you can use the ``--succ`` option to informs mercurial that a newer version
+    of the pruned changeset exists.
+
+    XXX this commands needs bookmarks support.
     """
     revs = list(revs)
     revs.extend(opts['rev'])