zsh: Load ASDF if it exists

etc/profile

@@ -1,3 +1,7 @@
+has() {
+    command -V "$1" > /dev/null
+}
+
 source_if() {
     if [ -e "$1" ]; then
         source "$1"
@@ -17,13 +21,17 @@ path_if() {
 
 source_if "${HOME}/.nix-profile/etc/profile.d/nix.sh"
 
+if has brew; then
+    source_if "$(brew --prefix asdf)/libexec/asdf.sh"
+fi
+
 path_if "$HOME/bin"
 path_if "$HOME/.local/bin"
 
 unset -f source_if
 unset -f path_if
 
-if command -V gnome-keyring-daemon > /dev/null; then
+if has gnome-keyring-daemon; then
     eval "$(gnome-keyring-daemon --start)"
     export SSH_AUTH_SOCK
 fi