Thanks, @amitz... That should be doable on OS X -- I'll give that a whirl!
OMG - with a little tweak for tmux 2.5 (I'm running on HEAD from brew) that worked -- something I've been struggling with for quite some time.
First, there's a breaking change in later versions of tmux (starting with 2.4, I believe): a "Fundamental change to how copy mode key bindings work" is described here.
In short, vi-copy (and emacs-copy) tables are "gone" and now referenced simply as 'copy-mode'. Also the
bind -t xxx becomes
bind -T xxx. Not sure exactly how that works as my existing
bind -t vi-copy xxx commands are not causing errors? So your command be becomes
bind-key -T copymode MouseDragEnd1Pane copy-pipe "reattach-to-user-namespace pbcopy"
on my system.
For a moment I thought it was broken until I realized that the selection goes immediately into the clipboard, without to follow the selection with
<Cmd-v> to copy the selection: as soon as you let go of the mouse -- poof -- it's there in the clipboard.
Awesome -- thanks so much for the comment; really made my day (week? month?)
UPDATE - YMMV: This stuff seems to be changing quite a bit (or I'm copy/paste-challenged:). The above command worked on my personal system (compiled/installed from tmux master in Jan/2017 on either V2.3 or V2.4). When I ported the command to my Client system (home brew HEAD version just updated), it didn't work and I had to change it to:
bind-key -T copy-mode-vi MouseDragEnd1Pane send -X copy-pipe "reattach-to-user-namespace pbcopy"
send -X changes. I plan to port this back to my personal system and see if this one works both places.