Fix cursor shape change bug in tmux

Sending escape sequences directly from zsh and bypassing tmux results in
the wrong cursor shape when switching between panes which no longer
reflect the current zsh vi mode.

When using ZTE compatible terminals tmux supports tracking cursor shape
changes on a per pane basis using a suitable `terminal-override`, this
allows zsh and vim to behave as if they are not operating in tmux and
everything works as expected. However, so far I've not been able to
reproduce this behaviour in iTerm2.

zshrc

@@ -77,21 +77,23 @@ autoload -U edit-command-line
 zle -N edit-command-line
 bindkey -M vicmd '^V' edit-command-line
 
+# Get the shells parent process name.
+ppid_name() { echo $(ps -p $(ps -p $(echo $$) -o ppid=) -o comm=) }
+
 # Enable changing cursor shape based on vi mode
-if [ "$TMUX" != "" ]; then
-  tmux_before="\EPtmux;\E"
-  tmux_after="\E\\"
+if [ "$ITERM_PROFILE" != "" ]; then
+  # TODO: This only works outside tmux, unlike VTE compatible terminals I've
+  # not found a tmux terminal-override which works with iTerm2's CursorShape
+  # escape sequences.
+  # iTerm2 cursor shape escape sequences
+  cursor_block="\E]50;CursorShape=0\C-G"
+  cursor_line="\E]50;CursorShape=1\C-G"
+elif [ "$(ppid_name)" != "python2" ]; then
+  # VTE compatible cursor shape escape sequences, excluding Guake even though
+  # it is VTE based it doesn't seem to handle these properly
+  cursor_block="\e[2 q"
+  cursor_line="\e[6 q"
 fi
-if [ "$ITERM_SESSION_ID" != "" ]; then
-  # iterm2 cursor shape escape sequences
-  cursor_block="$tmux_before\E]50;CursorShape=0\C-G$tmux_after"
-  cursor_line="$tmux_before\E]50;CursorShape=1\C-G$tmux_after"
-else
-  # VTE compatible cursor shape escape sequences
-  cursor_block="$tmux_before\E[2 q$tmux_after"
-  cursor_line="$tmux_before\E[6 q$tmux_after"
-fi
-unset tmux_before tmux_after
 
 if [[ ! -z "$cursor_block" && ! -z "$cursor_line" ]]; then
   # Change cursor shape when vi mode changes