Limit changing directories to only the run command.

This should reduce problems when using this module in more than one thread.

lib/Git/Wrapper.pm6

@@ -14,16 +14,14 @@ class Git::Wrapper {
 
     method run($subcommand, *@positionals, *%named) {
         my $old-dir = $*CWD;
-        chdir($.gitdir);
         my @optstr = map -> $k,$v {
             $v eqv Bool::True
                 ?? do { $k.chars > 1 ?? "--$k" !! "-$k" }
                 !! "--$k=$v"
         }, %named.kv;
         @positionals.unshift(|@optstr) if ?@optstr;
-        my $p = run :out, :err, $.git-executable, $subcommand, |@positionals;
+        my $p = run :out, :err, :cwd($.gitdir), $.git-executable, $subcommand, |@positionals;
         my @out = $p.out.slurp-rest;
-        chdir($old-dir);
         return @out;
     }