help: change a message to be more precise

When the user tries to use '--help' option on an aliased command
information about the alias is printed as sshown below,

    $ git co --help
    `git co' is aliased to `checkout'

This doesn't seem correct as the user has aliased only 'co' and not
'git co'. This might even be incorrect in cases in which the user has
used an alias like 'tgit'.

    $ tgit co --help
    `git co' is aliased to `checkout'

So, make the message more precise.

Signed-off-by: Kaartic Sivaraam <kaarticsivaraam91196@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/help.c

@@ -438,7 +438,7 @@ static const char *check_git_cmd(const char* cmd)
 
 	alias = alias_lookup(cmd);
 	if (alias) {
-		printf_ln(_("`git %s' is aliased to `%s'"), cmd, alias);
+		printf_ln(_("'%s' is aliased to '%s'"), cmd, alias);
 		free(alias);
 		exit(0);
 	}