tmux: Mimic copy-mode -e when using the wheel

`copy-mode -e` annoyed me, as it happened sometimes that I would hold
down `C-d` to scroll down, only to close the shell and pane when
reaching the bottom.

But in principal I do like the idea of it and missed the feature when
reaching the bottom by using the scroll wheel.

Change the `WheelDownPane` in copy-mode to exit when the bottom is
reached.

.config/tmux/tmux.conf

@@ -11,15 +11,16 @@ bind -T copy-mode-vi MouseDragEnd1Pane send -X copy-pipe-no-clear "xclip -se p"
 # https://github.com/neovim/neovim/wiki/FAQ#cursor-shape-doesnt-change-in-tmux
 set -ga terminal-overrides '*:Ss=\E[%p1%d q:Se=\E[ q'
 
-# Do not exit automatically the copy-mode when reaching the bottom.  This was
-# especially annoying/dangerous when holding C-d down to scroll to the bottom.
-# (This is practically the default binding except for the `-e` flag for
-# `copy-mode`)
+# Scroll up one page when entering copy-mode through the mouse wheel. Also
+# discard the `-e` flag passed to copy-mode from the default binding (See below)
 bind -n WheelUpPane \
 	if -F "#{||:#{pane_in_mode},#{mouse_any_flag}}" { send -M } { copy-mode -u }
 # Scroll without selecting the pane
-bind -T copy-mode-vi WheelUpPane   send -XN5 scroll-up
-bind -T copy-mode-vi WheelDownPane send -XN5 scroll-down
+bind -T copy-mode-vi WheelUpPane send -XN5 scroll-up
+# Exit copy-mode when at the bottom. This practically mimics `copy-mode -e` but
+# only scrolling with the wheel (`-e` annoys me when scrolling down with `C-d`).
+bind -T copy-mode-vi WheelDownPane \
+	if -F "#{==:0,#{scroll_position}}" {send -X cancel} {send -XN5 scroll-down}
 
 # Set C-a as new prefix
 unbind C-b