Copy markdown from Emacs, paste formatted content directly into GMail

elisp.el

(defun formatted-copy (start end)
  "Export region to HTML, and copy it to the clipboard."
  (interactive "r")
  (let* ((region-string (buffer-substring-no-properties start end))
         (shell-command "pandoc -f gfm -t html5 | pbcopy_html")
         (output-buffer (generate-new-buffer "*Shell Command Output*")))
    (with-current-buffer output-buffer
      (erase-buffer)
      (insert region-string)
      (shell-command-on-region (point-min) (point-max) shell-command t t))
    (kill-buffer output-buffer)))

(global-set-key (kbd "C-M-c") 'formatted-copy)

pbcopy_html

#!/usr/bin/env swift

import Cocoa
import Darwin

let pasteboard = NSPasteboard.general

guard let data = try? FileHandle.standardInput.readToEnd() else {
    exit(1)
}

pasteboard.clearContents()
pasteboard.setData(data, forType: .html)