feat(wpcarro/emacs): Package al, list, set, struct

Originally I set-out to package `al.el`, but as I started traversing the
dependencies, I needed to package increasingly more packages. I refactored some
of these to prune their dependencies to slay this hydra before it turned into a
never-ending project. I have mixed feelings about this.

I also introduced `ert` and unit tests into my Elisp packaging, so it'll be nice
to have build-time tests that run when Emacs updates land in depot.

Change-Id: I2756dc60888b80255a495e08ae61bd547e6b3db2
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5998
Reviewed-by: wpcarro <wpcarro@gmail.com>
Autosubmit: wpcarro <wpcarro@gmail.com>
Tested-by: BuildkiteCI

users/wpcarro/emacs/pkgs/struct/tests.el

@@ -0,0 +1,25 @@
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Dependencies
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(require 'ert)
+(require 'dash)
+(require 'struct)
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Tests
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(ert-deftest struct-set! ()
+  (cl-defstruct dummy name age)
+  (defvar struct--test-dummy (make-dummy :name "Roofus" :age 19))
+  (struct-set! dummy name "Doofus" struct--test-dummy)
+  (string= "Doofus" (dummy-name struct--test-dummy)))
+
+(ert-deftest struct-set ()
+  (cl-defstruct dummy name age)
+  (defvar struct--test-dummy (make-dummy :name "Roofus" :age 19))
+  (let ((result (struct-set dummy name "Shoofus" struct--test-dummy)))
+    (and
+     (string= "Roofus" (dummy-name struct--test-dummy))
+     (string= "Shoofus" (dummy-name result)))))