Deduplicate PATH before exporting

Why:

* Remove dupes from PATH

How:

$PATH is a scalar composed of contents of $path, so it uses typeset -U
("U" as in Unique) to ensure there are no dupes. It preserves the first
occurrence in the array, since it would be searched first before others
when matching a command in the directories in the PATH anyway.

zsh/configs/post/path.zsh

@@ -1,5 +1,5 @@
 # ensure dotfiles bin directory is loaded first
-export PATH="$HOME/.bin:/usr/local/sbin:$PATH"
+PATH="$HOME/.bin:/usr/local/sbin:$PATH"
 
 # load rbenv if available
 if command -v rbenv >/dev/null; then
@@ -7,4 +7,8 @@ if command -v rbenv >/dev/null; then
 fi
 
 # mkdir .git/safe in the root of repositories you trust
-export PATH=".git/safe/../../bin:$PATH"
+PATH=".git/safe/../../bin:$PATH"
+
+typeset -U PATH
+
+export PATH

zsh/functions/move_to_front_of_path

@@ -0,0 +1,10 @@
+# Reorders existing entry in PATH to have it at the front
+#
+#   move_to_front_of_path "$HOME/.bin"
+#
+move_to_front_of_path() {
+  if [[ ":$PATH:" == *":$1:"* ]]; then
+    PATH=$(echo $PATH | sed 's#'$1'##g' | sed s/:://g | sed s/:$//g | sed s/^://g)
+    PATH="$1${PATH:+":$PATH"}"
+  fi
+}