zsh: Make nix-shell pretty and update ps1

users/hu/packages/zsh/config/conf.d/completions.zsh

@@ -1,17 +1,17 @@
 #!/usr/bin/env zsh
 
-if [ -z "$FZF_TAB_FILE" ]; then
+if [ -z "$FZF_TAB_PLUGIN" ]; then
     if [ ! -d "$HOME/.cache/fzf-tab" ]; then
         echo "Installing fzf-tab"
         git clone "https://github.com/Aloxaf/fzf-tab" "$HOME/.cache/fzf-tab" 
     fi
-    FZF_TAB_FILE="$HOME/.cache/fzf-tab/fzf-tab.plugin.zsh"
+    FZF_TAB_PLUGIN="$HOME/.cache/fzf-tab/fzf-tab.plugin.zsh"
 fi
 
 autoload -Uz compinit
 compinit
 
-source "$FZF_TAB_FILE"
+source "$FZF_TAB_PLUGIN"
 zstyle ':completion:*:git-checkout:*' sort false
 
 if [ -n "$TMUX" ]; then