Make sure dotfiles path of fish is set up correctly

fish/config.fish

@@ -1,6 +1,8 @@
-if test "$SHLVL" -le 1
-  set -x DOTFILES {$HOME}/dotfiles
+set -x DOTFILES /Users/thomas/dotfiles
+# The definition of $DOTFILES MUST be the first line of this file
+# Don't change it!
 
+if test "$SHLVL" -le 1
   set -x PATH /usr/local/bin /usr/local/sbin $PATH
   set -x PATH $DOTFILES/bin $PATH
   if test -d $HOME/bin

fish/setup.sh

@@ -18,6 +18,10 @@ function main()
   # Install configuration files
   makedir ${HOME}/.config
 
+  if ! head -n 1 ${DOTFILES}/fish/config.fish | grep ${DOTFILES} >/dev/null; then
+    sed -i '' "1s;.*;set -x DOTFILES ${DOTFILES};" ${DOTFILES}/fish/config.fish
+  fi
+
   linkfile ${DOTFILES}/fish ${HOME}/.config/fish
 
   print_ok "Fish shell installed"