commit: Fix specifier inheritance behavior

[Stephen J. Turnbull]

Michael Sperber writes:

 > I'm still not sure - does the hg command I posted give you the output
 > you want *for merges*?

I think I don't want to see merges at all.  As I wrote before, the
interesting thing is the conflict resolution changes, if they exist.
But that's actually a second order diff, and I doubt that any diff
program will produce readable output for that.