Improve join-pane, move-pane and break-pane:

- There is no need for join-pane and move-pane to be different.
- break-pane can just behave like move-window if the source has only one
  pane, instead of failing.
- Add -a to break-pane like move-window.

Also add missing man page bits for previous window-tree.c changes.

GitHub issue 2176.

tmux.1

@@ -1714,7 +1714,7 @@ from which the layout was originally defined.
 Commands related to windows and panes are as follows:
 .Bl -tag -width Ds
 .It Xo Ic break-pane
-.Op Fl dP
+.Op Fl adP
 .Op Fl F Ar format
 .Op Fl n Ar window-name
 .Op Fl s Ar src-pane
@@ -1725,6 +1725,10 @@ Break
 .Ar src-pane
 off from its containing window to make it the only pane in
 .Ar dst-window .
+With
+.Fl a ,
+the window is moved to the next index up (following windows
+are moved if necessary).
 If
 .Fl d
 is given, the new window does not become the current window.
@@ -1873,12 +1877,15 @@ The following keys may be used in tree mode:
 .It Li "<" Ta "Scroll list of previews left"
 .It Li ">" Ta "Scroll list of previews right"
 .It Li "C-s" Ta "Search by name"
+.It Li "m" Ta "Set the marked pane"
+.It Li "M" Ta "Clear the marked pane"
 .It Li "n" Ta "Repeat last search"
 .It Li "t" Ta "Toggle if item is tagged"
 .It Li "T" Ta "Tag no items"
 .It Li "C-t" Ta "Tag all items"
 .It Li "\&:" Ta "Run a command for each tagged item"
 .It Li "f" Ta "Enter a format to filter items"
+.It Li "H" Ta "Jump to the starting pane"
 .It Li "O" Ta "Change sort field"
 .It Li "r" Ta "Reverse sort order"
 .It Li "v" Ta "Toggle preview"
@@ -2125,19 +2132,14 @@ See the
 .Sx FORMATS
 section.
 .It Xo Ic move-pane
-.Op Fl bdhv
+.Op Fl bdfhv
 .Op Fl l Ar size
 .Op Fl s Ar src-pane
 .Op Fl t Ar dst-pane
 .Xc
 .D1 (alias: Ic movep )
-Like
-.Ic join-pane ,
-but
-.Ar src-pane
-and
-.Ar dst-pane
-may belong to the same window.
+Does the same as
+.Ic join-pane .
 .It Xo Ic move-window
 .Op Fl ardk
 .Op Fl s Ar src-window