Scope local variable in anonymous function

so it does not leek into the shell.

Copied from zimfw/git@fea95a7655

modules/git/init.zsh

@@ -16,6 +16,7 @@ _git_log_oneline_medium_format='%C(bold yellow)%h%C(reset) %<(50,trunc)%s %C(bol
 # Aliases
 #
 
+() {
   local gprefix
   zstyle -s ':zim:git' aliases-prefix 'gprefix' || gprefix=g
 
@@ -188,3 +189,4 @@ alias ${gprefix}wX='git rm -rf'
 
   # Misc
   alias ${gprefix}..='cd "$(git-root || print .)"'
+}