[zsh] Reimplement loading of custom scripts.

zsh/functions.zsh

@@ -6,6 +6,10 @@ bytecount() { wc -c "$@" | numfmt --to=iec-i; }
 
 mkcd() { mkdir -p "$@" && cd "${@[-1]}"; }
 
+# Re-added from:
+# https://github.com/dmitmel/dotfiles/blob/16f0a1cf32ec97355da2e17de1c4bb458431767b/zsh/functions.zsh#L19
+source_if_exists() { [[ -f "$1" ]] && source "$1" }
+
 silence() { $1 &>/dev/null }
 
 viscd() {

zsh/zshrc

@@ -52,11 +52,13 @@ for script in functions options path env plugins aliases completion zle prompt c
   _perf_timer_stop "$script.zsh"
 done
 
-for script in $ZSH_DOTFILES/custom/**; do
-  _perf_timer_start "$script"
-  source "$script"
-  _perf_timer_stop "$script"
-done
+if [[ -d "$ZSH_DOTFILES/custom" ]]; then
+  for script in $ZSH_DOTFILES/custom/*.zsh; do
+    _perf_timer_start "custom/${script##*/}"
+    source "$script"
+    _perf_timer_stop "custom/${script##*/}"
+  done
+fi
 
 command_exists rbenv && eval "$(rbenv init -)"