This is a mess

I'm sorry.  I really wanted to improve my commit discipline.  I know.  I can't
be fucked to comb this diff and split it into 8 properly-ordered commits, like I
know I should.  I'm not having a good time right now.  We'll do better moving
forward.

users/crumb/programs/emacs/modules/syd-eshell.el

@@ -0,0 +1,110 @@
+;;; syd-eshell.el -*- lexical-binding: t; -*-
+
+(defvar eshell-buffer-name "*eshell*")
+
+(defvar syd-eshell-buffers (make-ring 25)
+  "List of open eshell buffers.")
+
+(defun syd-eshell-buffers ()
+  "TODO"
+  (ring-elements syd-eshell-buffers))
+
+;;;###autoload
+(defun syd-eshell-run-command (command &optional buffer)
+  "TODO"
+  (let ((buffer
+         (or buffer
+             (if (eq major-mode 'eshell-mode)
+                 (current-buffer)
+               (cl-find-if #'buffer-live-p (syd-eshell-buffers))))))
+    (unless buffer
+      (user-error "No living eshell buffers available"))
+    (unless (buffer-live-p buffer)
+      (user-error "Cannot operate on a dead buffer"))
+    (with-current-buffer buffer
+      (goto-char eshell-last-output-end)
+      (goto-char (line-end-position))
+      (insert command)
+      (eshell-send-input nil t))))
+
+;;;###autoload
+(defun syd-eshell/toggle (arg &optional command)
+  "Toggle eshell popup window."
+  (interactive "P")
+  (let ((eshell-buffer
+         (get-buffer-create
+          (format "*eshell-popup:%s*"
+                  (if (bound-and-true-p persp-mode)
+                      (safe-persp-name (get-current-persp))
+                    "main"))))
+        confirm-kill-processes
+        current-prefix-arg)
+    (when arg
+      (when-let* ((win (get-buffer-window eshell-buffer)))
+        (delete-window win))
+      (when (buffer-live-p eshell-buffer)
+        (with-current-buffer eshell-buffer
+          (fundamental-mode)
+          (erase-buffer))))
+    (if-let* ((win (get-buffer-window eshell-buffer)))
+        (let (confirm-kill-processes)
+          (delete-window win)
+          (ignore-errors (kill-buffer eshell-buffer)))
+      (with-current-buffer eshell-buffer
+        (syd-mark-buffer-as-real)
+        (if (eq major-mode 'eshell-mode)
+            (run-hooks 'eshell-mode-hook)
+          (eshell-mode))
+        (when command
+          (syd-eshell-run-command command eshell-buffer)))
+      (pop-to-buffer eshell-buffer))))
+
+(use-package eshell
+  :custom
+  ((eshell-banner-message
+    '(format "🦌 %s %s }:3\n"
+      (propertize (format " %s " (string-trim (buffer-name)))
+                  'face 'mode-line-highlight)
+      (propertize (current-time-string)
+                  'face 'font-lock-keyword-face)))
+   (eshell-scroll-to-bottom-on-input 'all)
+   (eshell-scroll-to-bottom-on-output 'all)
+   (eshell-kill-processes-on-exit t)
+   (eshell-hist-ignoredups t)
+   (eshell-glob-case-insensitive t)
+   (eshell-error-if-no-glob t))
+  :general
+  (:keymaps 'syd-leader-open-map
+            "e" #'syd-eshell/toggle)
+  (:keymaps 'eshell-mode-map
+   :states '(normal insert)
+   "C-j" #'eshell-next-matching-input-from-input
+   "C-k" #'eshell-previous-matching-input-from-input)
+  :config
+  (require 'syd-buffers)
+
+  (add-hook 'eshell-mode-hook #'syd-mark-buffer-as-real)
+
+  ;; UI enhancements.
+  (defun syd-eshell-remove-fringes-h ()
+    (set-window-fringes nil 0 0)
+    (set-window-margins nil 1 nil))
+  (defun syd-eshell-enable-text-wrapping-h ()
+    (visual-line-mode +1)
+    (set-display-table-slot standard-display-table 0 ?\ ))
+  (add-hook 'eshell-mode-hook #'syd-eshell-remove-fringes-h)
+  (add-hook 'eshell-mode-hook #'syd-eshell-enable-text-wrapping-h)
+
+  (with-eval-after-load 'hide-mode-line
+    (add-hook 'eshell-mode-hook #'hide-mode-line-mode))
+
+  ;; Remove hscroll-margin in shells, otherwise you get jumpiness when the
+  ;; cursor comes close to the left/right edges of the window.
+  (defun syd-eshell-disable-hscroll-margin ()
+    (setq hscroll-margin 0))
+  (add-hook 'eshell-mode-hook #'syd-eshell-disable-hscroll-margin))
+
+(set-popup-rule! "^\\*eshell-popup"
+       :vslot -5 :size 0.35 :select t :modeline nil :quit nil :ttl nil)
+
+(provide 'syd-eshell)