package/homebrew: extract the SHA1 from the version instead of duplicating.

Co-authored-by: Dora "cat" <cat@thenight.club>

package/homebrew/magnum-bindings.rb

@@ -4,7 +4,7 @@ class MagnumBindings < Formula
   # git describe origin/master, except the `v` prefix
   version "2020.06-421-g439945c"
   # Clone instead of getting an archive to have tags for version.h generation
-  url "https://github.com/mosra/magnum-bindings.git", revision: "439945c"
+  url "https://github.com/mosra/magnum-bindings.git", revision: version.to_str().rpartition('g')[2]
   head "https://github.com/mosra/magnum-bindings.git"
 
   depends_on "cmake" => :build