feat(emacs): add script for loading lean mode and its dependencies

src/emacs/load-lean.el

@@ -0,0 +1,49 @@
+(setq inhibit-startup-screen t)
+
+(if (getenv "LEAN_ROOTDIR")
+    (setq lean-rootdir (getenv "LEAN_ROOTDIR"))
+    (error "LEAN_ROOTDIR environment variable must be set"))
+
+(if (getenv "LEAN_EMACS_PATH")
+    (setq-local lean-emacs-path (getenv "LEAN_EMACS_PATH"))
+    (error "LEAN_EMACS_PATH environment variable must be set"))
+
+(setq lean-emacs-dependencies-path (format "%s/dependencies") lean-emacs-path)
+
+(setq lean-logo (create-image (format "%s/lean.png" lean-emacs-path)))
+(setq lean-required-packages '(company dash dash-functional f fill-column-indicator flycheck lua-mode mmm-mode s))
+
+(setq load-path
+      (append
+       (list lean-emacs-path)
+       (mapcar (lambda (p) (format "%s/%s" lean-emacs-dependencies-path p)) lean-required-packages)
+       load-path))
+
+(require 'package)
+(require 'lean-mode)
+
+(defun lean-welcome ()
+  (let ((cbuf (current-buffer))
+        (buf (get-buffer-create "Lean Welcome"))
+        (cpoint (point-min)))
+    (set-buffer buf)
+    (setq fill-column (window-width))
+    (if buffer-read-only (toggle-read-only))
+    (erase-buffer)
+    (insert "\n\n")
+    (insert "           ")
+    (insert-image lean-logo)
+    (setq cpoint (1+ (point)))
+    (insert "\n")
+    (insert "\n\nPlease check our website periodically for news of later versions")
+    (insert "\nat http://leanprover.github.io")
+    (insert "\n\nBug reports and suggestions for improvement should be posted at\nhttps://github.com/leanprover/lean/issues")
+    (set-buffer-modified-p nil)
+    (text-mode)
+    (toggle-read-only)
+    (goto-char (point-min))
+    (switch-to-buffer buf)
+    (set-buffer cbuf)
+    buf))
+
+(lean-welcome)