shell: have, path_(append|prepend|remove)

- have: command -v shorthand
- path_append: appends dir to PATH
- path_prepend: prepends dir to PATH
- path_remove: removes dir from PATH

config/exports-shell

@@ -1,6 +1,7 @@
 #!/usr/bin/env bash
 # shellcheck shell=bash
 # vim: filetype=zsh
+source "$DOTFILES/scripts/shared.sh"
 
 export LC_ALL=fi_FI.utf8
 
@@ -39,10 +40,7 @@ hash shopt 2> /dev/null && shopt -s checkwinsize
   && source "$XDG_BIN_HOME/iterm2_shell_integration.zsh"
 
 # Set dircolors based on the file, if it exists
-if command -v dircolors &> /dev/null; then
-  # shellcheck disable=SC2046
-  eval $(dircolors "$XDG_CONFIG_HOME/dircolors")
-fi
+have dircolors && eval $(dircolors "$XDG_CONFIG_HOME/dircolors")
 
 # If we are using zsh, color our dir lists and such
 if [ "$SHELL" = "$(which zsh)" ]; then
@@ -52,4 +50,3 @@ if [ "$SHELL" = "$(which zsh)" ]; then
   zstyle ':completion:*' cache-path "$XDG_CACHE_HOME/zsh/zcompcache"
   zstyle ':completion:*' list-colors "$LS_COLORS"
 fi
-