emacs plugin tweak to open buffer from stdin (#5126)

plugins/emacs/emacsclient.sh

 #!/bin/sh
 
-# get list of available X windows.
-x=`emacsclient --alternate-editor '' --eval '(x-display-list)' 2>/dev/null`
+function _emacsfun
+{
+    # get list of available X windows.
+    x=`emacsclient --alternate-editor '' --eval '(x-display-list)' 2>/dev/null`
 
-if [ -z "$x" ] || [ "$x" = "nil" ] ;then
+    if [ -z "$x" ] || [ "$x" = "nil" ] ;then
         # Create one if there is no X window yet.
         emacsclient --alternate-editor "" --create-frame "$@"
-else
+    else
         # prevent creating another X frame if there is at least one present.
         emacsclient --alternate-editor "" "$@"
+    fi
+}
+
+
+# adopted from https://github.com/davidshepherd7/emacs-read-stdin/blob/master/emacs-read-stdin.sh
+# If the second argument is - then write stdin to a tempfile and open the
+# tempfile. (first argument will be `--no-wait` passed in by the plugin.zsh)
+if [[ $# -ge 2 ]] && [[ "$2" == - ]]; then
+    tempfile="$(mktemp emacs-stdin-$USER.XXXXXXX --tmpdir)"
+    cat - > "$tempfile"
+    _emacsfun --no-wait $tempfile
+else
+    _emacsfun "$@"
 fi