Add a flag to move-window to renumber the windows in a session (closing

any gaps) and add an option to do this automatically each time a window
is killed. From Thomas Adam.

tmux.1

@@ -1258,7 +1258,7 @@ and
 .Ar dst-pane
 may belong to the same window.
 .It Xo Ic move-window
-.Op Fl dk
+.Op Fl rdk
 .Op Fl s Ar src-window
 .Op Fl t Ar dst-window
 .Xc
@@ -1269,6 +1269,12 @@ except the window at
 .Ar src-window
 is moved to
 .Ar dst-window .
+With
+.Fl r ,
+all windows in the session are renumbered in sequential order, respecting
+the
+.Ic base-index
+option.
 .It Xo Ic new-window
 .Op Fl adkP
 .Op Fl c Ar start-directory
@@ -2122,6 +2128,15 @@ Set the pane border colour for panes aside from the active pane.
 Set the key accepted as a prefix key.
 .It Ic prefix2 Ar key
 Set a secondary key accepted as a prefix key.
+.It Xo Ic renumber-windows
+.Op Ic on | off
+.Xc
+If on, when a window is closed in a session, automatically renumber the other
+windows in numerical order.
+This respects the
+.Ic base-index
+option if it has been set.
+If off, do not renumber the windows.
 .It Ic repeat-time Ar time
 Allow multiple commands to be entered without pressing the prefix-key again
 in the specified