Document the "jump" command in pdb.__doc__, and add a version tag for "until X".
diff --git a/Lib/pdb.py b/Lib/pdb.py
index 7c6b848..cedd17e 100755
--- a/Lib/pdb.py
+++ b/Lib/pdb.py
@@ -147,6 +147,16 @@
         or equal to that is reached.  In both cases, also stop when
         the current frame returns.
 
+j(ump) lineno
+        Set the next line that will be executed.  Only available in
+        the bottom-most frame.  This lets you jump back and execute
+        code again, or jump forward to skip code that you don't want
+        to run.
+
+        It should be noted that not all jumps are allowed -- for
+        instance it is not possible to jump into the middle of a
+        for loop or out of a finally clause.
+
 r(eturn)
         Continue execution until the current function returns.