Track eshell sessions dwim-style

track-eshell.el

  (defvar eshell-previous-buffer nil)
  (defvar eshell-session-alist nil)

  (defun dwc-switch-to-terminal (arg)
    (interactive "p")
    (if (eq arg 4)
        (progn
          (let ((sesh (alist-get (current-buffer) eshell-session-alist)))
            (if sesh
                (progn
                  (setq eshell-previous-buffer (current-buffer))
                  (eshell sesh)) 
              (let ((len (length eshell-session-alist)))
                (push (cons (current-buffer) len) eshell-session-alist)
                (eshell len)))))
      (if (string-match-p (regexp-quote eshell-buffer-name)
                          (buffer-name (current-buffer)))
          (if eshell-previous-buffer
              (switch-to-buffer eshell-previous-buffer)
            (previous-buffer))
        (setq eshell-previous-buffer (current-buffer))
        (eshell))))

  (define-key global-map (kbd "C-x j") 'dwc-switch-to-terminal)