fix(tmux): macOS clipboard, C-a passthrough, vim detection

- y/p use pbcopy/pbpaste (xsel is X11, absent on macOS); xsel kept as the Linux variant in a comment
- bind C-a send-prefix: C-a C-a sends a literal C-a to the shell
- is_vim reads #{pane_current_command}; the @tmux_vim_<pane> variable was never set, so C-h/j/k/l never reached vim

tmux.conf

@@ -43,12 +43,11 @@ set -g set-titles-string '#S :: #W :: #F#P #{pane_current_command}'
 # Variables:                                                                {{{
 # ---------
 
-is_vim='tmux show -v "@tmux_vim_#{pane_id}" | grep yes' # check if is vim
+is_vim='echo "#{pane_current_command}" | grep -iqE "(^|\/)g?(view|n?vim?)(diff)?$"'
 # is_vim Note: {{{
-#   vim is actually changing values of a variable to make it visible by tmux.
-#   Without this, tmux would have to grep the current pane to see what is
-#   running. ex:
-#   echo "#{pane_current_command}" | grep -iqE "(^|\/)g?(view|n?vim?)(diff)?$"
+#   The pane's foreground command, as tmux sees it. The older variant read a
+#   "@tmux_vim_<pane>" variable that a vim plugin had to set; nothing sets it
+#   here, so C-h/j/k/l never reached vim.
 # }}}
 
 resurrect_root_dir="$XDG_CACHE_HOME/tmux/resurect"
@@ -114,6 +113,7 @@ unbind-key -T copy-mode-vi MouseDragEnd1Pane # (mouse setting) {{{
 # }}}
 
 set -g prefix C-a                               # bind screen like prefix
+bind C-a send-prefix                            # C-a C-a = literal C-a (shell home)
 
 # specific commands
 bind-key C-o command-prompt "new-session -s %1 -c ~"
@@ -136,16 +136,13 @@ bind -n C-l if-shell "$is_vim" "send-keys C-l" "select-pane -R"
 
 bind Escape copy-mode                              # bind vi-like 'normal' mode
 bind -Tcopy-mode-vi 'v' send -X begin-selection    # bind vi-like visual mode
-bind -Tcopy-mode-vi 'y' send -X copy-pipe-and-cancel "xsel -b -i"  # xsel copy
-bind p run "xsel -b -o | tmux load-buffer - ; tmux paste-buffer"   # xsel paste
+bind -Tcopy-mode-vi 'y' send -X copy-pipe-and-cancel "pbcopy"       # macOS copy
+bind p run "pbpaste | tmux load-buffer - ; tmux paste-buffer"      # macOS paste
 # bind vi-like copy/paste through 'normal' mode, (Note) {{{
-#   It is encouraged to use xsel instead of xclip, because xclip does not close
-#   STDOUT after it has read from tmux's buffer. As such, tmux doesn't know
-#   that the copy task has completed, and continues to wait for xclip's
-#   termination, thereby rendering tmux unresponsive.
-# Here an example of copy paste with pbcopy/pbpaste (macos)
-#  bind -Tcopy-mode-vi 'y' send -X copy-pipe-and-cancel "pbcopy"
-#  bind p run "pbpaste | tmux load-buffer - ; tmux paste-buffer"
+#   Linux (X11) variant, xsel rather than xclip: xclip does not close STDOUT
+#   after reading tmux's buffer, so tmux waits for it and hangs.
+#  bind -Tcopy-mode-vi 'y' send -X copy-pipe-and-cancel "xsel -b -i"
+#  bind p run "xsel -b -o | tmux load-buffer - ; tmux paste-buffer"
 # }}}
 bind-key -Tcopy-mode-vi Escape send -X cancel                  # cancel v mode
 bind-key -Tcopy-mode-vi ^v send -X rectangle-toggle            # cancel v mode