💥 Replace exec-path-from-shell w/ 'bin/doom env'

IMPORTANT: This is a breaking update for Mac users, as your shell
environment will no longer be inherited correctly (with the removal of
exec-path-from-shell). The quick fix is: 'bin/doom env refresh'. Also,
the set-env! autodef now does nothing (and is deprecated), be sure to
remove calls to it in your config.

Smaller changes:
+ This update also adds --no-* switches to doom quickstart
+ Includes general improvements to the documentation of several bin/doom
  commands.
+ Moves doom/reload* commands to core/autoload/config.el
+ doom/reload-project has been removed (it didn't actually do anything)

The breaking change:
This update adds an "envvar file" to Doom Emacs. This file is generated
by `doom env refresh`, populated with variables scraped from your shell
environment (from both non-interactive and interactive sessions). This
file is then (inexpensively) loaded at startup, if it exists.

+ The file is manually generated with `doom env refresh`.
+ It can be regenerated automatically whenever `doom refresh` is run by
  running `doom env enable` (`doom env clear` will reverse this and
  delete the env file).
+ `doom quickstart` will ask if you want to auto-generate this envvar
  file. You won't need it if you're confident Emacs will always be
  started from the correct environment, however.
+ Your env file can be reloaded from a running Emacs session with `M-x
  doom/reload-env`. Note: this won't work if the Emacs session you're
  running it in doesn't have a correct SHELL set. i.e. don't use this to
  create your first env file!

The idea isn't mine -- it's borrowed from Spacemacs -- and was
introduced to me in #1053 by @yurimx. I was impressed with it. Prior to
this, I was unhappy with exec-path-from-shell (no hate to the dev, I
understand its necessity), and 'doom patch-macos' wasn't ideal for mac
users (needed to be reapplied every time you update Emacs). What's more,
many users (even Linux users) had to install exec-path-from-shell
anyway.

This solution suffers from none of their shortcomings. More reliable
than patch-macos, more performant and complete than
exec-path-from-shell, and easily handled by bin/doom.

core/core-os.el

@@ -1,5 +1,8 @@
 ;;; core-os.el -*- lexical-binding: t; -*-
 
+;; TODO Remove me later (deprecated)
+(defmacro set-env! (&rest _))
+
 ;; clipboard
 (setq x-select-request-type '(UTF8_STRING COMPOUND_TEXT TEXT STRING))
 
@@ -19,35 +22,6 @@
 ;; grokked from: http://stackoverflow.com/questions/15873346/elisp-rename-macro
 (advice-add #'evil-visual-update-x-selection :override #'ignore)
 
-;; In case it is never defined:
-(defmacro set-env! (&rest _vars)
-  "Inject VARS from your shell environment into Emacs.")
-
-(when (or (daemonp) (display-graphic-p))
-  ;; Syncs ns frame parameters with theme (and fixes mismatching text
-  ;; colr in the frame title)
-  (when (and IS-MAC (require 'ns-auto-titlebar nil t))
-    (add-hook 'doom-load-theme-hook #'ns-auto-titlebar-mode))
-
-  ;; If you launch GUI Emacs from the wrong shell environment, Emacs will be
-  ;; gimped. This regularly happens on MacOS (or daemons started via launchctl
-  ;; or brew services): it runs in an isolated environment, so envvars will be
-  ;; wrong. That includes the PATH Emacs picks up.
-  ;;
-  ;; `exec-path-from-shell' tries to address this, but it is only set up to run
-  ;; for mac users.
-  (when (require 'exec-path-from-shell nil t)
-    (defun set-env! (&rest vars)
-      "Inject VARS from your shell environment into Emacs."
-      (exec-path-from-shell-copy-envs vars))
-    (setq exec-path-from-shell-check-startup-files nil
-          exec-path-from-shell-arguments (delete "-i" exec-path-from-shell-arguments)
-          exec-path-from-shell-debug doom-debug-mode
-          exec-path-from-shell-variables
-          (nconc exec-path-from-shell-variables '("LC_CTYPE" "LC_ALL" "LANG")))
-    (exec-path-from-shell-initialize)))
-
-
 (cond (IS-MAC
        (setq mac-command-modifier 'super
              mac-option-modifier  'meta
@@ -61,7 +35,14 @@
              ns-use-native-fullscreen nil
              ;; Visit files opened outside of Emacs in existing frame, rather
              ;; than a new one
-             ns-pop-up-frames nil))
+             ns-pop-up-frames nil)
+
+       ;; Syncs ns frame parameters with theme (and fixes mismatching text color
+       ;; in the frame title)
+       (when (and (or (daemonp)
+                      (display-graphic-p))
+                  (require 'ns-auto-titlebar nil t))
+         (add-hook 'doom-load-theme-hook #'ns-auto-titlebar-mode)))
 
       (IS-LINUX
        (setq x-gtk-use-system-tooltips nil    ; native tooltips are ugly!