make mq and tags hardlink safe
The code didn't check for modes like "r+" or "rb+".
Many thanks to agriffis for noticing it.
#!/bin/shhg initecho a > ahg ci -Am thg mv a bhg ci -Am t1hg debugrename bhg mv b ahg ci -Am t2hg debugrename aecho % test with --revhg debugrename --rev 1 b