feat(init): show error and process tree if OMZ is loaded from non-zsh shells (#10234)

oh-my-zsh.sh

 # Protect against non-zsh execution of Oh My Zsh (use POSIX syntax here)
 [ -n "$ZSH_VERSION" ] || {
-  # ANSI (\033[<code>m): 0: reset, 1: bold, 4: underline, 22: no bold, 24: no underline, 31: red
-  printf "\033[1;31mERROR:\033[22m Oh My Zsh can't be loaded from: \033[1m${0#-}\033[22m. " >&2
-  printf "You need to run \033[1;4mzsh\033[22;24m instead.\033[0m\n" >&2
+  # ANSI formatting function (\033[<code>m)
+  # 0: reset, 1: bold, 4: underline, 22: no bold, 24: no underline, 31: red, 33: yellow
+  f() {
+    [ $# -gt 0 ] || return
+    IFS=";" printf "\033[%sm" $*
+  }
+  # If stdout is not a terminal ignore all formatting
+  [ -t 1 ] || f() { :; }
+
+  ptree() {
+    # Get process tree of the current process
+    pid=$$; pids="$pid"
+    while [ ${pid-0} -ne 1 ] && ppid=$(ps -e -o pid,ppid | awk "\$1 == $pid { print \$2 }"); do
+      pids="$pids $pid"; pid=$ppid
+    done
+
+    # Show process tree
+    case "$(uname)" in
+    Linux) ps -o ppid,pid,command -f -p $pids 2>/dev/null ;;
+    Darwin|*) ps -o ppid,pid,command -p $pids 2>/dev/null ;;
+    esac
+
+    # If ps command failed, try Busybox ps
+    [ $? -eq 0 ] || ps -o ppid,pid,comm | awk "NR == 1 || index(\"$pids\", \$2) != 0"
+  }
+
+  {
+    shell=$(ps -o pid,comm | awk "\$1 == $$ { print \$2 }")
+    printf "$(f 1 31)Error:$(f 22) Oh My Zsh can't be loaded from: $(f 1)${shell}$(f 22). "
+    printf "You need to run $(f 1)zsh$(f 22) instead.$(f 0)\n"
+    printf "$(f 33)Here's the process tree:$(f 22)\n\n"
+    ptree
+    printf "$(f 0)\n"
+  } >&2
+
   return 1
 }