refactor: deprecate letenv!

`letenv!` is a layover from the days before
`with-environment-variables` (introduced in 28.x), and it remained
afterwards because I preferred the shorter name. From v3 and onward,
Doom's core will be put on a diet which, among other things, will
include culling redundant or superfluous functions/macros like this one.

lisp/cli/packages.el

@@ -825,7 +825,8 @@ However, in batch mode, print to stdout instead of stderr."
 (defadvice! doom-cli--straight-ignore-gitconfig-a (fn &rest args)
   "Prevent user and system git configuration from interfering with git calls."
   :around #'straight--process-call
-  (letenv! (("GIT_CONFIG" nil)
+  (with-environment-variables
+      (("GIT_CONFIG" nil)
        ("GIT_CONFIG_NOSYSTEM" "1")
        ("GIT_CONFIG_GLOBAL" (or (getenv "DOOMGITCONFIG")
                                 "/dev/null")))

lisp/doom-lib.el

@@ -389,8 +389,7 @@ TRIGGER-HOOK is a list of quoted hooks and/or sharp-quoted functions."
   (let (file-name-handler-alist)
     (file-name-directory (macroexpand '(file!)))))
 
-;; REVIEW Should I deprecate this? The macro's name is so long...
-(defalias 'letenv! 'with-environment-variables)
+(define-obsolete-function-alias 'letenv! 'with-environment-variables "3.0.0")
 
 (put 'defun* 'lisp-indent-function 'defun)
 (defmacro letf! (bindings &rest body)

lisp/doom-straight.el

@@ -249,7 +249,8 @@ However, in batch mode, print to stdout instead of stderr."
 (defadvice! doom-straight--ignore-gitconfig-a (fn &rest args)
   "Prevent user and system git configuration from interfering with git calls."
   :around #'straight--process-call
-  (letenv! (("GIT_CONFIG" nil)
+  (with-environment-variables
+      (("GIT_CONFIG" nil)
        ("GIT_CONFIG_NOSYSTEM" "1")
        ("GIT_CONFIG_GLOBAL" (or (getenv "DOOMGITCONFIG")
                                 "/dev/null")))

lisp/lib/config.el

@@ -38,7 +38,8 @@
        (setq doom-bin "doom.ps1"))
      ;; Ensure the bin/doom operates with the same environment as this
      ;; running session.
-     (letenv! (("PATH" (string-join exec-path path-separator))
+     (with-environment-variables
+         (("PATH" (string-join exec-path path-separator))
           ("EMACS" (doom-path invocation-directory invocation-name))
           ("EMACSDIR" doom-emacs-dir)
           ("DOOMDIR" doom-user-dir)

lisp/lib/packages.el

@@ -58,7 +58,8 @@ package's name as a symbol, and whose CDR is the plist supplied to its
 ;;; Package management API
 
 (defun doom--ensure-straight (recipe pin)
-  (letenv! (("GIT_CONFIG" nil)
+  (with-environment-variables
+      (("GIT_CONFIG" nil)
        ("GIT_CONFIG_NOSYSTEM" "1")
        ("GIT_CONFIG_GLOBAL" (or (getenv "DOOMGITCONFIG")
                                 "/dev/null")))

lisp/lib/sandbox.el

@@ -49,7 +49,8 @@
 
 (defun doom--sandbox-run (&optional mode)
   "TODO"
-  (letenv! (("DOOMDIR" (if (eq mode 'vanilla-doom+)
+  (with-environment-variables
+      (("DOOMDIR" (if (eq mode 'vanilla-doom+)
                       (expand-file-name "___does_not_exist___" temporary-file-directory)
                     doom-user-dir)))
     (doom--sandbox-launch